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Dynamics of shoot and fruit growth following fruit thinning in olive trees: Same season and subsequent season responses
Abstract
The need to understand how the balance between vegetative and reproductive growth in olive trees is modified by different crop loads has become more important over the last 20 years due to increasing planting densities and the greater use of irrigation. The objectives of this study conducted in a well-irrigated olive orchard were to: (1) evaluate shoot and fruit growth dynamics following fruit thinning during the same growing season in which thinning was applied and during the next growing season; and to (2) determine crop load effects on bloom, fruit set, and fruit yield over three growing seasons. Hand-thinning of fruit 35 days after full bloom on 9-year-old cv. ‘Arauco’ trees in an “on” year led to thinning treatments of 24, 48, and 87% with respect to an unthinned control. Apical and lateral shoot elongation were measured every two weeks throughout the growing season, and fruit were sampled to determine fruit weight at the same interval. Apical shoot elongation occurred only early in the season when crop load was medium or high, while apical elongation continued for most of the season when crop load was low. Elongation of laterals contributed significantly to total shoot elongation on fruit-bearing branches in trees with low crop loads after thinning the first season. Individual fruit dry weight was reduced about 40% by high crop loads in both seasons. Differences in relative growth rates of both the shoots and the fruit due to crop load suggest fruit growth was limited by photoassimilate availability early in the season, but shoot growth was limited most of the season under medium and high crop loads. Inflorescence number per shoot was reduced by crop load in the two seasons following the thinning event. Fresh fruit yield was only reduced in one of the two biennia (i.e., periods of 2 years) in the trees that were heavily thinned (87%) the first season. The trees in which about one-half (48%) of the fruit were thinned the first season did not show biennia yield reductions and maintained a low alternate bearing index over three seasons. Thus, chemical thinning could be applied in growing seasons with high flowering. Further studies are needed to better assess competition for resources between shoots and fruit with the ultimate goal of reducing alternate bearing.
... As the fruit number increases, the assimilates available during the post-fruit set are distributed and shared by more fruits, resulting in reduced assimilate availability per fruit (Trentacoste et al. 2010). Experiments aimed at studying fruit mass and fruit oil concentration determination and their environmental influence usually focus on the post-flowering period (Dag et al. 2010;Fernández et al. 2015). The assumption that fruit mass is determined exclusively after flowering needs to be reviewed. ...
... In other words, the production of inflorescences per tree was extremely reduced by severe shading during the fruit set to harvest (post-fruit set) period and not affected by severe shading from winter to early spring (pre-fruit set). Most of the shoot growth occurs during the post-fruit set period, determining the total number of axillary buds, i.e., the "number of potential flower sites" (Fernández et al. 2015). The majority of olive research has focused on crop load effects on vegetative growth, which has been widely described as the importance of assimilates on vegetative growth increasing flowering sites the following season (e.g., Dag et al. 2010;Fernández et al. 2015). ...
... Most of the shoot growth occurs during the post-fruit set period, determining the total number of axillary buds, i.e., the "number of potential flower sites" (Fernández et al. 2015). The majority of olive research has focused on crop load effects on vegetative growth, which has been widely described as the importance of assimilates on vegetative growth increasing flowering sites the following season (e.g., Dag et al. 2010;Fernández et al. 2015). ...
Olive yield components are first determined during flowering, ovary growth, and fruit set. However, variations of the assimilates available during these important processes have been little studied. The aims of this study were to evaluate the effects of source-sink alterations on (i) production of flowers and their structure, (ii) sink responsiveness source activity, and (iii) the relationship between final fruit mass and flower ovary size. Two levels of shading at 50% and 80% were applied in an orchard cv. Arbequina over three seasons, with two durations: short-period (SP, from harvest up to 20 days after flowering) and long-period (LP, continuous shading from beginning to end of the experimental period). An unshaded Control was included. Control presented the highest fruit yield and was 50% greater than both SP50-LP50, and 80% greater than both SP80-LP80. Fruit number was highly responsive to source-sink alterations. The control and both SP50-LP50 treatments presented similar fruit loads, whereas both SP80-LP80 produced 80% less fruits. Source activity alteration during pre-fruit set affected inflorescence structure. By contrast, during the post-fruit set, it drastically reduced inflorescence production. Fruit mass increased mainly due to fruit growth rate in relation to the assimilate. Reduction in ovary mass due to low source activity during pre-fruit set had a slight influence on final fruit mass when source activity was not limited during the post-fruit set period. Fruit oil concentration was highly conservative across a wide range of source-sink ratios.
... Shoot growth starts in spring and potentially extends until the middle of fall depending on crop load, climate, and crop management (Connor and Fereres, 2005). In northwestern Argentina, a pronounced growth peak most often occurs early in the season and a secondary peak may occur after harvest in late summer or autumn (Fernández et al., 2015). Flowering also occurs in the spring, and flowering intensity depends on several factors including the number of buds formed on shoot growth from the previous season and the accumulation of chilling hours during the fall and winter (Lavee, 1996;Aybar et al., 2015;Haberman et al., 2017). ...
... In other fruit species such as loquat and peach, several studies have shown that severe water stress can improve return flowering over several seasons (Larson et al., 1988;Johnson et al., 1992;Cuevas et al., 2012). The T0 treatment in the present study may not of had greater flowering (− 19%) after the second post-harvest RDI application due to the greater fruit number and yield than in the other irrigation treatments the previous season (Fernández et al., 2015). Of course, it cannot be discounted that the greater S Ψ during the second RDI application ...
... This likely contributed to cumulative yield being unaffected over the three seasons. Other studies from the same region and the Mediterranean Basin have also reported that shoot growth in autumn is much lower than in the spring (Correa-Tedesco et al., 2010;Fernández et al., 2015;Girón et al., 2015). In contrast to shoot growth, trunk growth was substantial in postharvest and was sensitive to post-harvest RDI. ...
Olive trees are harvested in late summer or during the fall in the Mediterranean Basin with considerable rainfall often occurring after harvest, which largely eliminates the need to irrigate at that time. As olive cultivation has expanded to new regions, it has become necessary to develop new water management strategies to account for non-Mediterranean climate conditions. In northwestern Argentina, olive cultivars are harvested as early as mid-summer for green table olive processing, but rainfall is low and temperatures remain high after harvest. Thus, we evaluated the responses of yield determinants and components, crop water productivity, and vegetative growth of olive trees (cv. Manzanilla fina) to different post-harvest irrigation levels in three growing seasons. A fully irrigated control (100% crop evapotranspiration; ETc) and three regulated deficit irrigation treatments (RDI; T66 = 66% ETc, T33 = 33% ETc, T0 = 0% ETc) were applied for 75 days after harvest from mid-summer to mid-fall. The RDI treatments received irrigation equivalent to the control during the rest of the year. The return flowering in the spring after the first season of RDI tended to be greater in T0 than in the well-watered control and other RDI treatments. Despite some decrease in fruit set, this led to a significant increase in fruit number and yield in T0 compared to the control and the other RDI treatments. In contrast, flowering tended to be lower in T0 than in the irrigated control, T66, and T33 following the second season of RDI, but fruit number and yield were not different at harvest. Similarly, no differences in fruit number and yield were observed after the third RDI season. Cumulative total yield over the three seasons was not significantly affected by applying post-harvest RDI. Crop water productivity expressed as fruit yield per amount of annual irrigation plus effective rainfall was significantly higher in T0 than in the control after the first and second seasons of RDI. Shoot growth during the RDI period was very low, and only reduced significantly during the third RDI period. The results suggest that alternative irrigation strategies that adapt to regional climatic conditions should be further developed in non-Mediterranean climates. Water savings up to 20% per year appear feasible with post-harvest RDI in northwestern Argentina without significant losses in yield.
... In other words, fruit size is affected by the ratio between leaves (source) that provide photoassimilates for growth and the number of fruit and other organs (sinks) that compete for photoassimilates ( Grossman and DeJong, 1994). A recent study has shown that the sink activity of individual olive fruit (i.e., relative growth rate) is limited by high crop load during the first 30-60 days after flowering, while shoot growth is limited most of the growing season ( Fernández et al., 2015). Such limitations on fruit growth due to lack of photoassimilate availability https://doi.org/10.1016/j.scienta ...
... The growth of these two tissues is closely interrelated due to their common origin in the ovary pericarp ( Gucci et al., 2009), yet they also appear to compete as sinks, as long proposed in interpreting the double sigmoid growth pattern in which the slowdown of overall fruit growth has been associated with pit hardening ( Hartmann, 1949;Barabé and Jean, 1995). Furthermore, endocarp growth occurs early, whereas mesocarp growth occurs throughout olive fruit development ( Hammami et al., 2011;García-Inza et al., 2016), suggesting possible sink competition in early fruit growth ( Fernández et al., 2015). Also, during reduced growth under early water deficits, endocarp development often extends over a longer period and successfully competes for assimilates to the detriment of the mesocarp ( Rapoport et al., 2004;Gucci et al., 2009). ...
... Yearly crop reference evapotranspiration in this arid region is approximately 1600 mm with a rainfall of about 100 mm ( Searles et al., 2011). Further orchard management and climate details can be found in Fernández et al. (2015), and some preliminary results from one growing season were presented in Fernández et al. (2014). Fruit thinning was performed the first growing season on uniform trees with a high initial crop load four weeks after full bloom on November 13-14, 2007 to obtain a broad range of crop loads. ...
The annual fluctuations in olive crop load due to alternate bearing and other factors often lead to large differences in fruit size and oil content between years at harvest. A better understanding of how fruit parameters respond to the different leaf: fruit (i.e., source: sink) ratios that occur with contrasting crop loads would provide important information for crop management. Thus, the primary objectives of this study conducted with the cv. Arauco in three growing seasons were to: 1) determine the weight and size responses of the fruit and its main tissues, mesocarp (pulp) and endocarp (pit), to crop load; and 2) obtain relationships between different estimates of the source: sink ratio versus various fruit and oil parameters. Fruit thinning was performed by hand on uniform trees with high initial crop loads four weeks after full bloom the first season to obtain different crop loads at harvest. The thinning percentages the first season were 24%, 48% and 87%, along with an unthinned control. The same trees were then monitored the following two seasons without any further thinning. Fruit were sampled at harvest each season to determine fruit and tissue weights and diameters, oil weight per fruit, and oil concentration (%). Fruit weight was reduced 30–40% by high crop loads in each growing season with the mesocarp being much more affected than the endocarp. Oil weight per fruit (−50%) showed a somewhat greater reduction than fruit weight to crop load due to both fruit diameters and fruit oil concentration being decreased at high crop loads. Fruit and tissue weights and oil weight per fruit all displayed bilinear functions versus source: sink ratio when the source was expressed as canopy volume (a surrogate for leaf area) and sink on both a fruit number and glucose equivalent (GE) basis. Source limited fruit growth at both medium and high crop loads due to limited photoassimilate availability based on the bilinear functions, and the slope of the endocarp response to source: sink ratio was 15 times less than that of the mesocarp when expressed on a GE basis. A quantitative comparison with previously published studies indicated that maximum fruit weight appears to be obtained in olive between 1–2 m² of leaf area per kg of GE. The bilinear relationships of source: sink ratio versus fruit weight observed in this study could contribute to crop modelling, and further research concerning how and when the mesocarp and endocarp respond to crop load is needed to aid crop management in obtaining sufficient fruit size and quality for table olive cultivars.
... If a tree spends more of the available resources into producing fruits, it can only grow less as a result (Grossman and DeJong, 1994). Competition between vegetative and reproductive growth is well established in several tree species (Berman and DeJong, 2003;Costes et al., 2000;Lauri and T erouanne, 1999;Salazar-García et al., 1998;Stevenson and Shackel, 1998) including olive (Castillo-Llanque and Rapoport, 2011;Connor and Fereres, 2005;Dag et al., 2010;Fern andez et al., 2015;Monselise and Goldschmidt, 1982;Rallo and Su arez, 1989). However, very few studies considered young trees and no relationship between tree initial growth and cumulative yield was found (Moutier, 2006). ...
... However, several previous findings also suggest that reduced growth might be indeed the consequence of early and abundant fruiting. In fact, in olive, it is well established that vegetative growth is more abundant in off (i.e., with low yield) years (Castillo-Llanque and Rapoport, 2011;Fern andez et al., 2015;Lavee, 2007). Trees that spend more energy on production are expected to grow less vegetation because reproductive and vegetative growth compete for the same sources within a tree (Grossman and DeJong, 1994). ...
... Trees that spend more energy on production are expected to grow less vegetation because reproductive and vegetative growth compete for the same sources within a tree (Grossman and DeJong, 1994). This competition is well established in several tree species (Berman and DeJong, 2003; Costes et al., 2000;Lauri and T erouanne, 1999;Salazar-García et al., 1998;Stevenson and Shackel, 1998) including olive (Castillo-Llanque and Rapoport, 2011;Connor and Fereres, 2005;Dag et al., 2010;Fern andez et al., 2015;Monselise and Goldschmidt, 1982;Rallo and Su arez, 1989). Most of these studies have focused on mature trees during 1 year. ...
The modern olive industry is increasingly interested in olive cultivars that start producing early and remain relatively small, because they are suitable for super highdensity orchards. Some cultivars are better suited to this than others but it is not clear why. Understanding the mechanisms that lead to early production and reduced canopy size is therefore important. The object of this study was to investigate whether differences in vigor across olive cultivars are related to earliness and abundance of bearing. We analyzed tree growth and productivity in young coetaneous trees of 12 olive cultivars, grown together in the same orchard. Trunk diameter increased over the observation period, reaching significantly different values across cultivars. Canopy volume also increased, reaching 2-fold differences between the minimum and the maximum values. Cumulative yield increased, reaching up to 3-fold differences. When the cumulative yield at the end of the experiment was plotted against the final trunk diameter, no correlation was found. A significant correlation was found when cumulative yield was plotted against the increment in trunk diameter during the observation period for which yield data were collected. This relationship improved (i.e., R² rose from 0.57 to 0.83) when yield efficiency [i.e., cumulative yield per unit of final trunk cross-sectional area (TCSA) or per unit of canopy volume] was used instead of yield. These results clearly showed that trees that produced proportionally more (i.e., higher yield efficiencies) grew less. We conclude that, in young olive trees, vigor is inversely related to early bearing efficiency, which differs significantly across cultivars. The results support the hypothesis that early and abundant bearing is a major factor in explaining differences in vigor across olive cultivars. © 2017, American Society for Horticultural Science. All rights reserved.
... It was observed that, below the inflection point (point at which the slope changes), about 18 kg/tree, the oil yield 8. Relative fruit yield, expressed as maximum yield potential between two consecutive seasons, "n" and "n + 1". A single model (solid line) fitted the data pooling several cultivars and studies (Conde et al., 2013;Dag et al., 2009;Fernández et al., 2015;Fichet, 2013;Lavee, 2007;Tous et al., 1998); 'Frantoio' cultivar data are from this research. increased abruptly as the fruit production increased; once the point was reached, the oil gain per kg of fruit produced fell from 0.09 to 0.035 kg. ...
... We suggest this range can be found in adult trees with strong alternate bearing by calculating the average two-year production or observing a uniform production between seasons (Tree 9; Fig. 7). Previous studies endorse this approach (Fig. 8) (Conde et al., 2013;Dag et al., 2009;Fernández et al., 2015;Fichet, 2013;Lavee, 2007;Tous et al., 1998). However, is necessary a long-term study to confirm this hypothesis. ...
... It was observed that, below the inflection point (point at which the slope changes), about 18 kg/tree, the oil yield 8. Relative fruit yield, expressed as maximum yield potential between two consecutive seasons, "n" and "n + 1". A single model (solid line) fitted the data pooling several cultivars and studies (Conde et al., 2013;Dag et al., 2009;Fernández et al., 2015;Fichet, 2013;Lavee, 2007;Tous et al., 1998); 'Frantoio' cultivar data are from this research. increased abruptly as the fruit production increased; once the point was reached, the oil gain per kg of fruit produced fell from 0.09 to 0.035 kg. ...
... We suggest this range can be found in adult trees with strong alternate bearing by calculating the average two-year production or observing a uniform production between seasons (Tree 9; Fig. 7). Previous studies endorse this approach (Fig. 8) (Conde et al., 2013;Dag et al., 2009;Fernández et al., 2015;Fichet, 2013;Lavee, 2007;Tous et al., 1998). However, is necessary a long-term study to confirm this hypothesis. ...
The aim of this study was to examine the influence of crop load on the next season’s crop potential of Frantoio olive trees and its effect on some production variables. To do this, a follow-up was made of oil
accumulation in the final period of fruit growth during the 2012 −2013 vegetative seasons, with low and high crop loads, respectively. At harvest, the following fruit traits were evaluated: concentration and content of pulp oil, pulp/pit ratio, fruit and mesocarp weight, crop load and oil yield. The main results show crop load heavily influences the variables assessed. It was observed that the average production of a tree over two consecutive seasons with low and high crop loads remains constant, regardless of the production level of the trees, suggesting an optimal yield potential where subsequent crop is not reduced. This potential, in turn, seems to be related to the rate of maximum gain of oil yield per kg of fruit produced. Thus, when the production optimum is exceeded in a year with a high crop load, this rate falls.
... Once the cultivar starts to bear, the yield will compete with and reduce vegetative growth and, therefore, vigour [55,82]. Moreover, reduced growth might be the consequence of early and abundant fruiting: in mature olive trees, it is well established that vegetative growth is more abundant in off (i.e., with low yield) years [83]. The general assumption indicates that trees that spend more energy on production are expected to grow less in terms of vegetative growth because both reproductive and vegetative growth competes for the same sources within a tree [82]. ...
Until today, only Leccino and Fs-17 (=Favolosa®) olive cultivars proved resistant to Xylella fastidiosa subsp. pauca (Xfp) due to a low presence of bacteria in the xylem. Integrated disease management in olive growing areas threatened by the spread of Xfp is crucial to overcoming the environmental, economic and social crisis. Since the EU Decision allows for the plantation of resistant olive cultivars in infected areas, there is a need to define a suitable plantation system for these cultivars. The adoption of new planting systems, such as intensive and super-intensive (SHD), could compensate for the economic losses and restore the olive agroecosystem. The aim is to ascertain the suitability of the available Xfp-resistant cultivars to SHD planting systems that demonstrate the best economic and environmental sustainability. Hence, a five-year study was established in an experimental SHD olive orchard (Southern Italy) in order to analyse the main vegetative and productive traits of Leccino and Fs-17, together with four other Italian cultivars (Cipressino, Coratina, Frantoio and Urano), compared with the well-adapted cultivars to SHD orchards (Arbequina and Arbosana), by means of the von Bertalanffy function. The results indicated that cv. Fs-17 showed sufficient suitability for SHD planting systems, giving the best-accumulated yield despite some canopy growth limitations, whereas cv. Leccino did not show satisfactory results in terms of both vegetative and yield parameters, confirming its suitability for intensive planting systems. These results are useful for optimizing integrated resistance management in Xfp-infected areas by planting resistant host plants.
... Indeed, it has been observed that once reproduction starts, the crop will compete with and reduce vegetative growth [15]. This competition has been well recognized in mature trees of several species [16][17][18], including olive [19][20][21][22][23][24]. It is especially prominent in young fruit trees, where the removal of all blossoms or fruit results in dramatic increases in growth with respect to the fruiting trees [25][26][27][28][29]. ...
In 2019–2020, trials were carried out in both intensive (cultivar Moraiolo) and super-high-density (cultivar Sikitita) young olive orchards to drastically reduce early production and, consequently, accelerate tree growth. Different concentrations of naphthaleneacetic acid (NAA) (0 ppm–control, 20 ppm, 40 ppm, 80 ppm, 160 ppm and 250 ppm) were applied at full bloom (open flowers > 80%), using a shoulder sprayer, and their effects on vegetative growth and reproductive behavior were evaluated, also compared to manually deflowered trees. The treatments with NAA reduced fruit set (down to values close to zero) compared to the control, and the reduction was correlated with the NAA concentration. In particular, 160 ppm virtually eliminated fruit set and thus production in both Moraiolo and Sikitita cultivars. In Moraiolo, 160 ppm NAA and manual deflowering determined similar shoot and trunk growths, which were greater than in control trees. Application of 160 ppm NAA for two consecutive years gave a progressively higher increase in trunk growth compared to the control. In conclusion, in young olive trees, the treatment with 160 ppm NAA at full bloom practically eliminated fruit set and production, with a parallel great increase in vegetative growth. This can be exploited as a powerful technique to accelerate the growth of young olive trees in both intensive and super-high-density orchards, as well as in nurseries. A more rapid transition to the adult stage/size of the trees and to full production of the orchard allows us to anticipate the use of mechanical harvesting and the recovery of the planting investment.
... Nos primeiros pomares o espaçamento entre árvores foi inferior a 1,2 m (RIUS;LACARTE, 2015), embora não houvesse informações experimentais para frutos, cujo momento também depende do vigor da cultivar, das condições climáticas e do solo e do manejo do pomar (principalmente irrigação e adubação nitrogenada). O vigor do cultivo também é afetado pela carga de frutos, pois a frutificação precoce reduz o crescimento vegetativo e o desenvolvimento da sebe(CASTILLO- LLANQUE;RAPOPORT, 2011;FERNÁNDEZ et al., 2015). Sob condições de alto vigor (cultivar vigorosa, temperatura ótima e teor de água no solo) as árvores podem ser plantadas em espaçamento mais amplo do que sob condições de baixo vigor e ainda preencher a sebe ao mesmo tempo.As características genéticas da cultivar determinam não só o vigor, mas também o hábito de crescimento e, portanto, o melhor preparo e espaçamento entrelinhas. ...
oliveira é uma das frutíferas mais antigas utilizadas pelo homem. Seu cultivo remonta a 6.000 anos. É originária de vasta grande área, que abrange desde o Sul do Cáucaso até os planaltos do Irã, Palestina e a zona costeira da Síria, estendendo-se pelo Chipre até o Egito, povoando posteriormente para todos os países que margeiam o Mediterrâneo. O cultivo em sebe representa a grande revolução na cultura do olival, porque permite obter em 10 anos de cultivo a mesma produção acumulada de um olival tradicional de sequeiro em 70 anos. Para os cultivos de superintensivo têm sido propostos inicialmente as variedades de alto rendimento como Arbosana, Arbequina e Koroneiki, que apresentam desenvolvimento limitado (porte médio). Posteriormente, foram lançadas novas variedades de porte baixo mais apropriadas ao cultivo em sebe. São recomendados espaçamentos de 3-4 m x 1,0-1,5 m ao longo das linhas. As árvores prontas para o plantio são pequenas, com cerca de 18 meses, 40-50 cm de altura e um bom sistema radicular. Elas devem ser manejadas com cuidado para mantê-las no tamanho certo para a colheita mecanizada ao longo da linha e para garantir um equilíbrio entre a atividade vegetativa e reprodutiva. A grande vantagem que este sistema apresenta reside no fato das cultivares utilizadas terem uma entrada em produção ultraprecoce, permitindo obter logo elevadas produções entre o 3º e o 5º ano após a plantação. No olival superintensivo, sua colheita mecanizada recorre a máquinas de vindimar cavalgantes automotrizes, possibilitando capacidades de trabalho de 2-3h/h. Também o cultivo em sebe permitir ser podado mecanicamente, visando manter uma copa reduzida. Em razão do exposto, há uma redução significativamente nos custos de produção, pois este sistema em sebe facilmente atinge os 12.000 kg/ha. Vale lembrar que no passado ocorreu a domesticação dessa árvore de porte alto para de porte médio e recentemente para de porte baixo, mas por meio do desenvolvimento de novas cultivares com características de baixo vigor e, ao mesmo tempo, de pouca exigência em frio (fatos parecidos sucederam com a outras espécies vegetais) é possível futuramente ampliar o cultivo em sebe para outras regiões fora de climas subtropical e temperado. Portanto, aquele que decidir cultivar essa cultura de forma superintensiva e conhecê-la em maior profundidade, o livro Tecnologias utilizadas no cultivo em sebe da oliveira (Olea europaea, L.) mecanizada, será de grande interesse e ajuda para o produtor que necessita pôr em prática as várias tecnologias abordadas no mesmo.
... To resolve this imbalance, agronomic practices have attempted to better balance fruit production and vegetative growth either by manually or chemically thinning fruit or by increasing vegetative growth through fertilization, irrigation or pruning [6][7][8]. However, research on how to increase fruit yield and quality and constrain excessive vegetative growth of branches and roots, especially under poor environmental conditions, remains insufficient [9,10]. ...
Persian or common walnut (Juglans regia L.) is a fruit tree of significant agricultural importance and is considered highly drought-resistant. However, the effects of different irrigation treatments and tree height on the physiology, growth and fruit quality of the walnut tree remain largely elusive. In the presently study, we selected ‘Wen 185’, one of the main walnut cultivars, as the target plant species. We established three irrigation treatments (deficit (DI), conventional (CI) and excess irrigation (EI)) from April to September of 2020 and measured leaf hydraulic traits, photosynthetic characteristics, soluble sugar (SS) content, leaf area, branch growth, fruit morphology and the no and deflated kernel (NDK) rate of walnut trees in each treatment. Our results showed that: (1) midday leaf water potential (Ψmd) decreased significantly under the DI treatment and declined significantly with increasing tree height; upper canopy Ψmd in the DI group decreased by 18.40% compared to the lower canopy; (2) the light compensation point, light saturation point, maximum net photosynthetic rate, maximum photochemical efficiency and chlorophyll SPAD values of trees in the DI group decreased slightly but did not differ significantly from the CI and EI treatments; (3) reduced irrigation did not significantly affect the soluble sugar content of leaves (LSs) and fine roots (RSs), but the soluble sugar content of walnut kernels (FSs) was significantly higher in the DI treatment than under the CI and EI treatments and also increased with tree height; the average soluble sugar content across heights was 6.61% in the EI group, 7.19% in the CI group and 9.52% in the DI group; (4) branch terminal leaf area (LA) was significantly reduced at the end of new branches, and Huber values (HV) were significantly higher under the DI treatment; compared to the EI group, LA was reduced by 52.30% in the DI group and 32.50% in the CI group; HV increased by 79.00% in the DI group and 15.70% in the CI group; (5) reduced irrigation did not significantly affect fruit morphology but did increase the NDK rate of walnuts, which also increased with tree height; the average NDK rate across all heights was 4.63% in the EI group, 5.04% in the CI group, and 8.70% in the DI group; the NDK rate was 41.75% higher in the upper part of the canopy compared to the lower part in the DI group. Our results indicate that walnut trees suffer greater water stress in the upper canopy than in the middle and low parts of the canopy. By increasing HV, walnut trees maintained relatively stable photosynthetic capacity under drought. However, water deficit had a significant effect on NDK rates, particularly at greater tree heights.
... For example, the fruit dry weight, longitudinal diameter, transverse diameter, and kernel dry weight of fruits on branches with bigger leaf numbers (5NPCL: 1NF, 5NPCL: 2NF, and 5NPCL: 3NF) were higher than on branches with lower leaf numbers (1NPCL: 3NF) (Figure 2A-D), but soluble sugar content and starch content in the kernel were the opposite ( Figure 2G,H). At the same time, the accumulation of carbohydrates in the fruit is related to the comprehensive influence of both the source-sink relationship and the saturation of carbohydrate demand on the fruit itself, which is regulated by carbohydrate supply capacity [11,29]. For instance, the number of fruits did not significantly affect the dry matter accumulation of fruits at the level of 3NPCL and 5NPCL and had significant differences at the level of 1NPCL (Figure 2A). ...
Fruit quality is known to be regulated by the balance between leaf number/area and fruit number, but less is known about the effects of fruit–bearing branch agronomic traits, particularly for walnuts (Juglans regia L.). We assessed nut quality, physiological and biochemical indexes of leaves, and microstructure of leaves and fruit stalks at various leaf–to–fruit ratios to gain insight into the relationships between branch agronomic traits and nut quality, to identify those traits that made a better contribution to nut quality and to find out the range of the leaf–to–fruit ratio and the object of fruit to be removed for thinning. We found that the top fruit on the fruit stalk had a higher longitudinal diameter and kernel weight than the bottom at the low leaf–to–fruit level, and branches with more pinnate compound leaves had a better capacity for carbohydrate assimilation and transportation to produce better quality fruits. Specifically, with the increasing leaf number, the branch diameter, total leaf area, net photosynthetic rate, chlorophyll content, fruit weight, fruit diameters, and kernel protein content also increased. Moreover, at the microscopic level, the fruit stalk vascular bundle, leaf thickness, palisade mesophyll thickness, and ratios of palisade mesophyll to spongy mesophyll thickness in the leaf also showed the same trend. Therefore, when the ratio of leaf area to the fruit number was less than 181.5 square centimeters per fruit on the branches, reducing the fruit number could improve the size and the crude fat content of fruits. While the ratio was more than 247.8 square centimeters per fruit, the fruit number had no significant effect on fruit quality, but increasing leaf area and branch diameter could improve the fruit size and yield.
... During "on" years, shoot elongation ceased around the flowering or maximum rate of the pit hardening stage. This was most likely due to the assimilate demand for flower formation and fruit growth, as described for well-watered 4-year-old 'Barnea' and 'Coratina' trees grown in Israel [29,45] and 9-year-old 'Arauco' trees grown in Argentina [46], where fruits were manually thinned. [43] found that the pattern of fruit growth was similar in fully irrigated 44-year-old 'Manzanillo' trees and trees where irrigation was withdrawn at the maximum rate of pit hardening in Spain, even though their Ψ s values after the treatments began were significantly different. ...
Climate change is affecting water resources in the Mediterranean region. In olive orchards, irrigation water use efficiency could be increased by accounting for trees’ alternate bearing behaviour and growth-stage sensitivity to drought. The main objective of this study is to examine olive tree phenology, morphology and physiology in “on” and “off” productive years for the improvement of irrigation scheduling. A regulated (RDI) and a sustained (SDI) deficit irrigation treatment were applied in a ‘Koroneiki’ olive orchard in Cyprus. Flowering occurred on 11 May 2019 and on 27 April 2021, which was caused by the lower temperatures in 2019. The Kc for the irrigation season, computed from daily water balance observations, was 0.37 in 2019 (38% canopy cover) and 0.41 in 2021 (62% canopy cover). Irrigation treatments did not significantly affect plant morphology and stem water potentials. In “on” years, shoot elongation ceased early in the season and stem water potential towards the end of September (−4.0 MPa) was lower than in the “off” year. Stem water potential recovery in the September of the “off” year indicated that irrigation could be less than 35% ETc in early fall. Water savings in RDI were 24–32% in “on” and 48% in “off” years relative to SDI, with no statistically significant effects on olive yields.
... Vegetative and reproductive growth in olive trees occur simultaneously for several months during the growing season with competition for carbohydrates between plant organs often occurring. Fruit are considered to be a stronger sink than vegetative shoots, but a reduction in both vegetative and reproductive growth has been observed when fruit load is high (Dag et al., 2010;Fernández et al., 2015;Rosati et al., 2018). The warming study of whole olive trees mentioned earlier using OTCs in southern Spain found that a 4 • C increase in air temperature increased trunk growth and pruning weight over three years, although individual shoot length appeared to be less sensitive to warming (Benlloch--González et al., 2019). ...
Global warming and olive expansion to new regions have increased interest in understanding how air temperature affects olive production. Thus, the objective of this study was to evaluate the responses of oil yield components, total biomass production, and its partitioning to a moderate temperature increase (3–4 °C) during the oil accumulation phase in young olive trees of two olive cultivars (cvs. Arbequina, Coratina). Young, potted olive trees were actively heated by 3–4 °C in open top chambers under outdoor conditions compared to near-ambient temperature in similar control chambers. The trees were warmed from final fruit set to the end of the oil accumulation phase (5 months) in one (2014–15 or 2015–16) or in two consecutive seasons. Oil yield and its components were obtained from fruit harvested at the end of the season, while the vegetative dry biomass produced was estimated from destructive harvests of entire trees before and after a warming period. Glucose equivalents (GE) were also calculated for both oil yield and vegetative growth. Warming during the oil accumulation phase in one season led to some significant temperature x cultivar interactions for oil components. Individual fruit dry weight was reduced by warming to a greater extent in cv. Coratina than in cv. Arbequina, while fruit oil concentration was decreased more in cv. Arbequina. Significant decreases in oil yield were also observed for both cultivars. Warmed trees had a greater net leaf area increase than control trees when heated during the oil accumulation phase for one season (2014–15 or 2015–16), and allocated more GE to vegetative organs than to fruit in 2015–16. However, total tree biomass was not affected by warming. Warming trees the first season led to reduced flowering the following spring, and directly contributed to a temperature x cultivar interaction for fruit number during the second warming period with a 66% reduction in fruit number in warmed trees of cv. Arbequina and very low fruit number in all cv. Coratina trees. In contrast to warming during one season, total tree biomass GE decreased across cultivars when warming was performed in the oil accumulation phase for two consecutive seasons. The results suggest that cultivars should be carefully selected for new, warmer growing regions and that global warming may ultimately reduce oil yields and affect cultivar selection.
... Increments in TCSA (and thus for whole-tree biomass) were lower for fruiting than non-fruiting treatments (Figure 2A and Figure 3), in line with previous findings in olive trees (Fern andez et al., 2015;Rosati et al., 2018a). The TCSA of Arbequina NF was comparable to that of Frantoio NF up to the first three years of observation, confirming that the low vigor generally observed in Arbequina is due to its early and abundant fruiting (up to 159 g of fruit þ flower dry matter per tree in the first and second year after transplanting Rosati et al., 2018a;2018b). ...
This study investigated the effects of cultivar, fruit presence and tree age on whole-plant partitioning of dry matter and energy equivalents (i.e., glucose equivalents). Young trees of two cultivars characterized by different vigor (i.e., Arbequina, low vigor and Frantoio, high vigor) were either completely deflowered from 2014 to 2017 or never, providing two contrasting levels of cumulated reproductive growth over the following 4 years. Total vegetative dry matter growth over the 4 years was assessed by destructive samplings (whole tree). Plant growth was inversely correlated to reproductive efforts, with Arbequina producing more and growing less than Frantoio. Deflowered trees grew similarly across cultivars, although deflowered Arbequina grew statistically less than deflowered Frantoio by the fourth year, due to abundant flower production. Total reproductive (flowers + fruit) and vegetative biomass production were the same for all cultivars and treatments. Arbequina had a greater distribution of dry matter in directly productive structures (current and one-year-old shoots) and in leaves. This allows it to increase the number of current and following-year production sites, and to save in the resources invested in non-productive sinks (roots, trunk and branches), thus liberating resources for reproductive growth. Greater investments in leaves allow it to intercept more light and thus to increase assimilation. Increased assimilation and increased partitioning towards productive structures, and decreased competition by non-productive structures might contribute to explain the greater early bearing attitude of this cultivar.
... Fruit oil content (mg of oil per fruit), which is a function of both fruit weight and oil concentration, displayed a sigmoidal increase over the course of the season (Fig. 3). Similar patterns have also been observed previously for both fruit transversal area and weight (Hammami et al., 2011;Fernández et al., 2015) and oil concentration (Bodoira et al., 2015). In our study, fruit oil content increased at a low rate during the first 60 days after full bloom with maximum rates occurring after endocarp sclerification until towards the end of the growing season (200 DAFB). ...
The fatty acid composition of olive oil is greatly affected by geographical origin, and olive oil is often promoted by health experts because of its high oleic acid concentration. Unfortunately, recent evidence has shown that oleic acid (%) can be low in many non-Mediterranean regions due to high temperatures. Thus, management tools related to irrigation, fertilization, and canopy management are being sought that might improve fatty acid composition in such regions. The objectives here were to: 1) evaluate the relationships between fatty acid composition in fruit at different canopy positions and both the photosynthetically active radiation (PAR) and red-to-far red ratio (R/FR) measured at these same positions; and 2) determine the response functions of the fatty acid concentrations to PAR using multiple shading levels applied at different fruit growth phases. Fruit samples were taken from 60 canopy positions in a large olive hedgerow (cv. Arbequina) to achieve the first objective, and different shading levels (3, 20, 40, 70% PAR) were applied using shade cloth over the northern portion of large individual trees (cv. Arbequina) for the second objective. The oleic acid concentration (%) showed a significant exponential decay with increasing daily PAR values obtained from the different canopy positions. Maximum values of about 60% oleic acid were observed at low PAR and minimum values of 50% occurred at high PAR. Based on the artificial shading treatments, the high oleic acid at shaded canopy positions appeared to be related to less fruit maturation. The other main fatty acids did not differ by canopy position, and no significant relationships between individual fatty acids and R/FR ratio were found. However, severe artificial shading under shade cloth did increase stearic and linolenic acid concentrations. Despite oleic acid being about 10% higher in the more shaded parts of the canopy, cultivating olive trees at low PAR values in order to meet international olive oil trade standards would likely not be commercially feasible due to low flowering and yields. Careful cultivar selection, early harvesting when fruit are less mature and oleic acid is higher, and blending of oils from different cultivars are recommended to improve fatty acid composition in warm regions.
... For the same pruning intensity, summer pruning resulted in a greater proportion of low vigor shoots compared to watersprouts than with winter pruning (Fig. 2). It is likely that a shift towards less vigorous shoot types occurred with summer pruning due to the well-known reduction in vigorous vegetative growth during fruit growth and olive oil accumulation in the summer months (Dag et al. 2010;Fernández et al. 2015). The timing of pruning had less affect than shoot type on return flowering, and the percentage of flowering base branches was similar on trees pruned in the winter or in the summer for the 3 years after simulated mechanical pruning (Fig. 4). ...
Key message
More vigorous watersprouts and fewer low vigor shoots form as wood age increases at the cutting points with greater canopy pruning depth in olive trees, which reduces return flowering. Such information is relevant to long-term olive orchard pruning strategies in hedgerows.
Abstract
Demographic analysis of growth responses to pruning in fruit trees seeks the quantification of the typology of new shoots originating from the remaining branches. Pruning of hedgerows using mechanical discs is becoming increasingly common in orchards, but little information is available as to how such pruning, which does not discriminate between branch size, wood age at the cutting point, branch type, or position, modifies subsequent new shoot demography. Hence, the experiment described in this study in young olive trees (cv. Arbequina) assessed the following questions: (1) Is the type and growth of new shoots associated with the intensity of mechanical pruning and/or the wood age on which they grow? (2) How many growing seasons does it take for new shoots formed after pruning to flower? The principal hypothesis was that a greater proportion of vigorous watersprouts form compared to low vigor shoots as wood age at the cutting points increases with canopy pruning depth, and that the watersprouts have low flowering potential. Both new shoot growth and return flowering were monitored on exposed supporting wood over several growing seasons after implementing three winter (25W, 50W, and 75W) pruning levels of increasing intensity and one summer pruning (75S) treatment along with an unpruned control (CON). As hypothesized, a greater number and elongation of vigorous watersprouts were found as wood age increased at the cutting points with greater winter pruning intensity, and the watersprouts had low levels of return flowering even 3 full years after pruning compared to the CON. Growth of low vigor shoots was relatively more important than watersprout growth in the severe summer pruning treatment, although 3 years after the summer pruning flowering was not fully recovered. In contrast, the more lightly pruned winter treatments (25W, 50W) did not show significant differences in flowering with the CON at the end of 3 years. Thus, mechanical hedge pruning in olive trees should be light-to-moderate to avoid the formation of watersprouts on older wood, which leads to long-term reductions in flowering.
... It is likely that much of the overall tree shoot elongation and leaf area expansion occurred early in the season during fruit set and early fruit growth before heating was started. In our experiment, fruit load was high considering tree size, and likely limited photoassimilate availability for shoot growth in the latter part of the season (Fernández et al., 2015). Greater vegetative responses to heating would be anticipated if the heating was done early in the season as has been described in grapes (Keller and Tarara, 2010). ...
... The experimental tree canopy volume was of 25 m 3 in average and each tree yielded 80 kg on average (fresh weight). Fruit load was 400 fruit m −3 , intermediate for cultivar Arauco (Fernández et al., 2015). Flowering was recorded on October 19, 2012 and endocarp hardening (defined as the date at which it was no longer possible to cut the pit with a knife) occurred on December 22, 2012. ...
Olive fruit dry weight, oil concentration and the proportions of individual fatty acids in the oil are influenced by environmental variables, such as ambient temperatures, between flowering and harvest. An increase in mean daily temperature above 25 °C has been shown to have a negative effect on fruit dry weight, and to produce a linear decrease both in fruit oil concentration and oleic acid proportion in the oil over the range of 16–32 °C. Under natural conditions or in experiments in which mean daily temperatures are manipulated following the natural daily oscillation in temperature, mean daily maximum and minimum temperatures covary with mean daily temperature. However, variations in temperature associated with altitude, location and climate change can affect maximum and minimum temperatures differently and modify thermal amplitude. The objectives of the present study were to assess associations between changes in: i) yield variables (fruit dry weight and oil concentration) and ii) the proportions of major fatty acids in the oil, with the different dimensions of the daily temperature oscillation (mean daily minimum and maximum temperatures, mean daily thermal amplitude) experienced by the fruit during its growth from the pit-hardening stage to maturity. Five branch-level temperature treatments were applied: a control (T0) that followed the daily dynamics of ambient temperature, two levels of daytime (8–20 h) heating that increased temperature 5 and 10 °C relative to T0 during the day, and two levels of nighttime (20–8 h) heating to 5 and 10 °C more than T0. Treatments were applied for 76 days during the oil accumulation phase using transparent chambers with individualized temperature control to enclose fruiting branches of cultivar Arauco trees. The treatments successfully broke the natural covariance between the different dimensions of daily temperature variation, and achieved a broad range in mean daily temperature (∼6 °C) which covered the natural range of this variable for the region. Fruit dry weight showed a tendency to decrease with increasing mean temperature, while the proportion of oil in the fruit exhibited a significant relationship (R² = 0.70) with mean daily thermal amplitude, and weaker −but significant- ones with mean daily maximum and minimum temperatures. The proportion of the main fatty acid in the oil, oleic acid, showed significant negative associations with mean daily minimum temperature (R² = 0.45) and with mean daily temperature (R² = 0.32), and a significant curvilinear relationship with mean daily thermal amplitude, but was not significantly associated with mean maximum temperature. Mean daily thermal amplitude in our experiment was determined mainly by mean daily minimum temperatures, a feature also found in an analysis of meteorological data for five sites and five years in the olive producing areas of La Rioja province, Argentina. Our results highlight the need to broaden studies on the temperature responses of olive fruit size, oil content and oleic acid content of the oil to include the effects of minimum temperature and thermal amplitude.
... The main objective of close intra-row spacing is to obtain rapid canopy development for early high fruit production, the timing of which also depends on cultivar vigor, climatic and soil conditions and orchard management (mainly irrigation and N fertilization). Cultivar vigor is also affected by fruit load since early fruiting reduces vegetative growth and hedgerow development (Castillo-Llanque and Rapoport, 2011;Fernández et al., 2015). Under high-vigor conditions (vigorous cultivar, optimum temperature and soil water content) trees can be planted at wider spacing than under low-vigor conditions and yet fill the hedgerow at the same time. ...
Intra-row spacing is known to determine early productivity of super-high density olive orchards depending on growing conditions, cultivar growth characteristics, planting geometry and subsequent pruning management but few experiments have been carried out in this olive hedgerow orchard design. In 2008 an experiment of 4-m spaced hedgerows was established with 8 intra-row spacings (from 1.0 to 2.5 m) in Toledo (Spain) resulting in orchards of density ranging from 2,500 to 1,000 trees ha−1. Tree growth was evaluated as height, trunk diameter and leaf area during the first 4 years. Hedgerow porosity was calculated from the 4th until the 9th year. In the 8th year hedgerow height, width, leaf area and branch angles were measured. Olives were harvested from 3rd to 9th year for measurements of fruit characteristics and productivity. Tree growth was not affected by intra-row spacing during the first 4 years. In the 8th year leaf area, external surface area and volume per tree were significantly greater in the more spaced trees; but hedgerow characteristics of leaf area per hectare, number of effective leaf layers horizontally through the hedgerow, and leaf density were not affected. In the more spaced trees insertion angles of branches to the vertical were significantly greater, mainly in the lower canopy. Intra-row spacing did not affect fruit characteristics. Oil production ha−1 decreased linearly with spacing during the first 4 harvests while production per tree increased significantly with spacing after the 3rd harvest. As a result, oil production ha−1 from the seven harvests combined only increased for tree spacing less than 1.2 m; wider spacing had no effect. Annual oil production ha−1 increased linearly as porosity was reduced by greater tree density and canopy development along the seasons.
... Such a pattern is common in most olive cultivars (Lavee, 2007). This often occurs because in the "on" year there is low shoot growth, which leads to few potentially reproductive buds for the next year; when crop load is high there is inhibition of floral induction (Dag et al., 2010;Fernández et al., 2015). Consequently, the year-to-year variations in yield are directly related with fruit number per tree of each year (Martín-Vertedor et al., 2011;Trentacoste et al., 2015). ...
An increase in the land area dedicated to super-high density olive orchards has occurred in Chile in recent years. Such modern orchards have high irrigation requirements, and optimizing water use is a priority. Moreover, this region presents low water availability, which makes necessary to establish irrigation strategies to improve water productivity. An experiment was conducted during four consecutive growing seasons (2010-2011 to 2013-2014) to evaluate the responses of yield and water productivity to irrigation cut-off strategies. These strategies were applied after fruit set using midday stem water potential (Ψstem) thresholds in a super-high density olive orchard (cv. Arbequina), located in the Pencahue Valley, Maule Region, Chile. The experimental design was completely randomized with four irrigation cut-off treatments based on the Ψstem thresholds and four replicate plots per treatment (five trees per plot). Similar to commercial growing conditions in our region, the Ψstem in the T1 treatment was maintained between -1.4 and -2.2 MPa (100% of actual evapotranspiration), while T2, T3 and T4 treatments did not receive irrigation from fruit set until they reached a Ψstem threshold of approximately -3.5, -5.0, and -6.0 MPa, respectively. Once the specific thresholds were reached, irrigation was restored and maintained as T1 in all treatments until fruits were harvested. Yield and its components were not significantly different between T1 and T2, but fruit yield and total oil yield, fruit weight, and fruit diameter were decreased by the T3 and T4 treatments. Moreover, yield showed a linear response with water stress integral (SΨ), which was strongly influenced by fruit load. Total oil content (%) and pulp/stone ratio were not affected by the different irrigation strategies. Also, fruit and oil water productivities were significantly greater in T1 and T2 than in the T3 and T4. Moreover, the T2, T3 and T4 treatments averaged 37, 51 and 72 days without irrigation which represented 75-83, 62-76 and 56-70% of applied water compared with T1, respectively. These results suggest that using the T2 irrigation cut-off strategy could be applied in a super-high density olive orchard (cv. Arbequina) because it maintained yields, saving 20% of the applied water.
... In Years 2 and 3, fruit number and yield in unpruned trees were influenced by the previous year fruit load with some tradeoff between fruit number and fruit weight and oil content (Fig. 6). There are indications that the vegetative growth of the unpruned, control trees was also regulated by the fruit load as has been seen in previous studies (e.g., Dag et al., 2010;Fernández et al., 2015). Both trunk and branch growth (Figs. ...
Mechanical pruning has become increasingly common in olive orchards, particularly under high tree densities. Large cutting disks make heading cuts at a single canopy depth without discriminating between branch thickness, size, or type of branch. The objectives of this study were to: (i) quantify the responses of vegetative growth over two growing seasons and yield components over three seasons following different intensities and moments of application of mechanical pruning; and (ii) evaluate some leaf morphology and gas-exchange characteristics of the remaining leaves after pruning. Five year-old olive trees with high crop load (cv. Arbequina) were pruned towards the end of the winter (W) or early summer (S). Three intensities of winter pruning representing different distances (0.25, 0.50, 0.75 m) from the outer canopy surface were applied, while there was only a single summer pruning treatment (0.75 m). The vegetative growth variables measured after pruning included new branch number and length, new leaf number, and increase in trunk cross sectional area. Reproductive variables included fruit and oil yield, fruit number, fruit weight, and oil content per fruit. Growth of new branches increased significantly with winter pruning intensity while delaying pruning to early summer reduced regrowth to the level of the unpruned control. Despite differences in yield in individual years between the unpruned control and the winter pruning treatments, the average yield over the three years after the winter pruning event was similar between all trees. Delaying the intense pruning to summer was associated with some reduction in yield, and moderate winter pruning (0.50 m) appeared to partially reduce alternate bearing. When measured shortly after winter pruning, specific leaf mass of the remaining leaves decreased steadily as the level of winter pruning increased, which is consistent with prior shading within the tree. The leaf net photosynthetic rate per unit mass was also different between pruning treatments. In conclusion, our results contribute to filling the gaps in knowledge related to important aspects of olive tree responses to the intensity and timing of mechanical pruning.
... In addition, a marked inter-annual variability with respect to the PI (mean = 20 045; standard deviation = 21 752; coefficient of variation = 109%), was observed for the Salerno station when taking into account a greater number of years (period 1999-2011). This alternating behavior might be influenced by less developed agricultural techniques that favor the alternate bearing (Fernández-Escobar et al., 2004;Bustan et al., 2011;Fernández et al., 2015) when compared with other Italian regions where olive growing is more relevant. This might also reflect that the pollen recorded in Salerno is originated in a reduced geographical area with homogeneous environmental conditions, thus favoring the year-to-year synchrony of the olive groves (Monselise and Goldschmidt, 1982). ...
A sufficient and mature vegetative growth is an essential condition for production in the following season and consequently affects the alternate bearing (AB) behavior. However, little is known about its interaction with the crop load and water supply. Herein, we studied the effect of different water regimes and bearing status on the vegetative intensity and flush and its consequence on the flowering parameters of the following season. Rainfed (RF) and fully irrigated (FI) treatments were applied for bearing (ON) and non-bearing (OFF) trees of the ‘Zalmati’ olive orchard in south Tunisia during 2018. The water deficit condition (RF) and the high crop load (ON) have caused a similar decrease in the total node number and shoots length by about 65%. Furthermore, the flowering parameters in 2019, especially the percentage of floral buds (i.e., floral induction intensity), were differentially affected by water supply according to the bearing status of the previous season. FI reduced the percentage of floral buds in 2019 by about 37% for OFF trees, while it increased it by more than four times for the ON trees. Concerning the growth flush, the second (i.e., autumnal) flush seems to respond better to water supply than the first (i.e., spring) one, for both vegetative and flowering parameters. The second flush of growth provided 28% of the total vegetative growth but contributed about 35% to the total number of floral buds for RF OFF trees. Besides, FI makes the first and the second flushes contribute equally to total vegetative growth and to the flowering parameters of the following season. On the other hand, the bearing status of the trees does not affect the contribution of each flush to the total vegetative growth.
Yearly yield fluctuations are normal in fruit trees. Yield alternation might be induced by environmental stresses, but in many fruit tree species yield alternation is an inherent characteristic, resulting in perpetual biennial cycling. Endogenous cues are thought to be the major players in determining the phenomenon, although the genetic basis, if it exists, is still enigmatic. In most cases, alternate bearing is due to inhibition of floral induction, following a heavy fruit load ON year. Understanding of flowering control in model plants has made great progress during recent decades. Due to conservation of many molecular components of the flowering‐control pathways among higher plants, there has also been considerable progress in the identification of these components and in the understanding of their role in fruit trees. In this review, flowering control by exogenous and endogenous cues in Arabidopsis along with updated findings in fruit trees are summarized. The effect of fruit load on flowering‐control genes is also examined. Along with these fundamental traits, more practical aspects, namely mitigation strategies of alternate bearing, are also reviewed. Recent developments in mitigation practices of six representative fruit trees are also summarized. Finally, some basic questions, including the genetic and epigenetic background of alternate bearing, an evolutionary perspective, and possible common mechanisms among various fruit trees, are thoroughly discussed.
Harvest timing in olive orchards has a strong effect on the quality and quantity of oil yield, but many farmers still lack simple and affordable quantitative tools for rationally deciding appropriate harvest dates. This study presents and tests a conceptual model for predicting fruit oil content (Of, g oil fruit⁻¹) from inexpensive measurements of fruit dry weight (wf). The model presents two physiologically relevant parameters, the fruit dry weight at the onset of the oil accumulation phase (wf0) and the ratio of accumulated oil per unit of fruit dry weight increase during the oil accumulation period (β), the latter assumed invariable throughout ripening. A compilation of data on wf and Of dynamics collected from four experiments including six olive cultivars and contrasting conditions of water supply and crop load was used to test the model. Our results suggest that β could be fairly independent of crop load or watering regime and, probably, genetically controlled. By contrast, wf0 is clearly affected by both the cultivar and the availability of assimilates for fruit growth preceding oil accumulation, which makes it orchard- and year-specific. According to those premises, once cultivar-specific β values are available wf0 could be easily calibrated by either a single determination of Of and wf at any time during the oil accumulation phase (Approach A) or by directly measuring wf0 if the date for the onset of oil accumulation can be estimated (Approach B). Validation tests with an independently calibrated β showed an excellent performance for reproducing Of patterns from wf data using Approach A. Approach B satisfactory predicted oil accumulation rates, but absolute estimates of Of were less reliable. Regardless of the calibration approach, the model is easy to implement and has a minimal cost, which satisfies the demand for inexpensive tools for monitoring oil accumulation dynamics.
In 1993 and 1994, fruit thinning, defoliation and shading were carried out on shoots and on tertiary, secondary and primary branches in olive trees, cv. Maurino. Fruit thinning increased shoot growth and the different sized branches showed a similar increase. Leaf removal and shading drastically reduced the vegetative growth without differences between the different sized units. In relation to vegetative activity, the shoot can be considered an independent unit. In conditions of high assimilate availability (fruit thinning), the fruit weight increased without differences between the different sized units. Whereas, leaf removal one month after fruit set reduced fruit growth in the shoot and greater reductions were noted as branch size increased. In conditions of reduced assimilate supply, the fruit attracted substances close to or at short distances from the crown parts. Fruit thinning on the shoots increased the number of inflorescences in the following season, with a further increase when thinning was applied to the tertiary branches, then it remained constant. Leaf removal on the shoots reduced flower formation by 50%; a continuous increased reduction was observed with increased treatment of the different sized units. This indicates that flower formation is influenced by the translocation of some substances. Shading reduced flower formation to the same extent on the shoot as in the larger branches. This indicates that some substances, the formation of which is light dependent, are not translocated. In general the treatments did not influence the reducing sugar and starch contents of shoot, leaves and stems. Leaf removal and shading of the main branch reduced the starch content in root tissues.
GA 3 scaffold injections applied between May and November to nonbearing olive (Olea europea L.) trees inhibited flowering the following year, increased shoot width when applied in May, June, and July, and increased inflorescence length when applied in November and February. Fruit removal and seed destruction were effective in improving the return bloom in `Manzanillo' olives when done before endocarp sclerification. Depending on-the year, endocarp sclerification takes place 7 to 8 weeks after full bloom (AFB), usually about 1 July. Fruit removal had no effect on flowering when done after this time. Scaffold injection of paclobutrazol applied to bearing trees between May and September did not affect flowering the following year. The results of our research supports the hypothesis that olive flower induction occurs around the time of endocarp sclerification. Chemical names used: gibberellic acid (GA 3 ), (2RS,3RS)-1-(4-chlorophenyl)-4-dimethyl-2-1,2-4-triazol-1-yl) pentan-3-ol(paclobutrazol).
Peach [Prunus persica (L.) Batsch] fruit thinning was used to reduce the competition for assimilates among peach fruits and to identify periods of source- and sink-limited growth during development. Individual fruit size, based on diameter or calculated dry matter accumulation, increased in trees with lower crop loads compared to fruits of unthinned trees in three peach cultivars. Relative growth rate analysis indicated that peach fruit growth was apparently limited by the assimilate supply (source-limited) or by its genetic growth potential (sink-limited) during specific growth periods. In stage I and at the beginning of stage III of the double-sigmoid growth curve, periods of source-limited growth occurred in the later-maturing cultivars Flamecrest and Cal Red. Peach fruit growth was apparently sink-limited during stage II of the growth curve when fruit relative growth rates were similar for the thinning treatments. Fruit growth in `Spring Lady', an early maturing cultivar, appeared to be primarily source-limited during the season. Although total fruit dry matter production was reduced by thinning, individual fruit dry weight on thinned trees was higher than that on trees with a heavy crop load. This typical thinning response was apparently caused by the differences in the amount of time that fruits grew under sink-vs. source-limited conditions with different crop loads. Final crop yield depended on fruit count per tree and on the available assimilate supply, and was affected by the individual fruit growth potential.
Under semi-arid climate, olive trees suffer periodically from water shortage, which may reduce consistently the plant growth and fruit yield, depending on variety and how long the dry period is. To assure suitable growth and regular yields, complementary irrigation is nowadays applied to olive orchards, with however, variable water amounts which may not meet the crop water needs. The present work was carried out in order to study the behaviour of local and foreigner varieties like Chetoui, Chemlali, Coratina, Picholine and Manzanilla under climatic conditions of central Tunisia. Plants were planted in 2002 with a density of 204 tree ha−1. Three irrigation treatments were applied during two consecutive growing seasons (2008–2009) with water amounts of 20% ETc, 50% ETc and 100% ETc, where ETc is the crop evapotranspiration. Growth parameters (length, metamer number and diameter) were measured regularly on representative shoots, which were previously tagged. Flowering and fruit set were monitored on the same trees. Yield, fruit characteristics and water use efficiency (ratio between yield/irrigation amounts) were determined for both seasons then for the overall growing cycle. Irrigation regime affects differently the shoot length and shoot thickness, flowering and fruit set, fruit characteristics (length, width and weight) and olive production depending mainly on trees’ fruit load, which was apparently the main factor controlling shoot growth dynamic. All varieties showed rhythmic growth and weak primary growth intensity during the On year, while primary growth was continuous with a higher intensity on the Off year. Basal diameter showed continuous growth. Linear relationship was found between basal diameter and length increment. Maximum productions recorded through the growing season cycle (an On year followed by Off year) were given by Picholine and Coratina irrigated with 100% ETc (23.0 kg tree−1 and 18.0 kg tree−1, respectively), by Manzanilla and Chetoui cultivated at 20% ETc (33.3 kg tree−1 and 27.1 kg tree−1) and finally by Chemlali at 50% ETc (26.4 kg tree−1). Most varieties showed higher water use efficiency at 20% ETc. To conclude we can say that, under the conditions of semi-arid climate of central Tunisia, with average annual rainfall of about 250 mm, olive trees Chetoui, Chemlali, Coratina, Picholine and Manzanilla cultivated at 7 m × 7 m spacing, can vegetate and produce properly with an irrigation amount ranging between 80 mm and 200 mm (20–50% ETc). The irrigation volume can be adjusted following the expected fruit crop load. Particularly, the smallest irrigation amount (80 mm) is recommended for low fruit load years.
Biennial bearing is a major horticultural and economic drawback of olive (Olea europaea L.) cultivation, which particularly affects the olive oil industry under intensive production systems. The number of fruits per tree in an on-year is a primary determinant of the biennial cycle. While fruit thinning using NAA shortly after full bloom is commonly practiced to increase fruit size in table olives, the extent of its influence on biennial bearing is unknown. In the present study, the ability of that common naphthaleneacetic acid (NAA) treatment (100mg/L, 10 days after full bloom) to alleviate biennial bearing in two oil olive cultivars, Picual and Barnea, was poor, although significant influence on the number of fruit was evident solely in Barnea. Picual seemed less susceptible than Barnea to biennial bearing. Consequently, the effect of a broad range of NAA concentrations (0-320mg/L, 10 days after full bloom) on various yield parameters was investigated during a biennial cycle of Barnea trees. There was a gradual proportional decline in the on-year number of fruits from ∼50000 to 10000/tree in response to increasing NAA concentrations. The number of return fruits in the off-year was reciprocal to the on-year fruit load, but remained relatively small, below 15000/tree. The dynamic relationship between fruit load and fruit size in both on- and off-years was a significant compensation factor in fruit and oil yields. In both cultivars, an on-year fruit load smaller than 20000/tree is likely to provide consistent yearly oil yields ranging from 10 to 12kg/tree. The results demonstrate the possibility of using NAA post-bloom spraying to balance biennial bearing in oil olives.
In Argentina, the proposed expansion of olive growing into areas ecologically different from areas where commercial plantations now exist, carries a high probability of failure. Temperatures in the Chaco ecosystem may not be conducive to olive production. Thus, the effects of temperatures on flowering and fruiting on olive trees were investigated using a model of thermal adaptability. The model evaluated vernalization periods for 19 sites of Argentina, Italy, Mexico, Peru, Spain and USA, using maximum mean temperatures of 12.5°C and minimum mean temperatures of 0.0°C. The probability of obtaining temperatures included within limits for each 10-day period during the vernalization interval was calculated. Daily probability and the number of days within each period were taken as binomial parameters and outlined as binomial modes. To determine the probability of high temperature damage during flowering within each region, temperatures equal to or higher than 37.8°C were considered. To determine damage produced by late frost, temperature equal to or below 0°C that occurred during flowering within each region was considered. Analysis of thermal information for olive sites proposed for the Arid Chaco indicates important differences from traditional olive growing sites.
SUMMARY The influence of individual plant yield on olive fruit ripening. oil accumulation pattern and oil quality was investigated on plants of cv. Cassanese. at full yield (100% = 26.2 kg tree'). partially reduced yield (70% = 18,4 kg tree-I) and halved yield (50% = 12.5 kg tree 1). Fruits of trees with halved yield were bigger and reached full black maturation stage 30 d earlier than those of the more heavily loaded trees while oil accumulated faster and reached higher final amounts. No differences in acidity, peroxides, alcohol and sterol content were recorded between treatments, but polyphenols, palmitic and linoleic acid contents were highest when the crop load was halved.
Temperature is one of the most important factors controlling plant growth and development. Knowledge of the effects of temperature on plants is vital if crop management strategies are to be optimised and the best varieties chosen for local conditions. As the effects of global warming are now becoming patent, it is even more critical that we should understand how temperature affects crop growth. In this study, degree-day (DD) accumulation was used to establish the influence of temperature on flowering, vegetative growth, and fruit growth in olive. The results show that the timing of olive flowering in the study region can be predicted from mean April and May temperatures, although this can be improved by taking into account the maximum March, and even February, temperatures. With respect to heat accumulation and flowering, the lower threshold temperature (LTT) was 4.7 degrees C, with 890 degrees Cd necessary. The LTT for trunk. growth was 7 degrees C, while that for shoot and crown volume growth was 13 degrees - 14 degrees C. The LTT for fruit growth was 15 degrees C with respect to fresh weight, and 24 degrees- 26 degrees C with respect to cross-sectional diameter. The increase in the longitudinal diameter of fruit was more rapid than the increase in the cross-sectional diameter, which was more dependent on temperature. Increasing temperatures in the study area would cause olive trees to flower earlier and their growth period to be lengthened.
The influence of different leaf-to-fruit (l-t-f) ratios on leaf net photosynthetic rate (P
N) and fruit characteristics in Olea europaea L. cv. Frantoio was evaluated in 2001 and 2002. In both years, at the end of June, at the end of July, and in mid-September (first, second, and third time of treatment, respectively), defoliation or fruit thinning were performed to give l-t-f ratios of 1/1, 3/1, 5/1, and 7/1 (about 5.1, 15.3, 25.6, and 35.8 cm2 of leaf area per fruit, respectively) on girdled and ungirdled peripheral shoots. P
N showed substantial seasonal and diurnal variations. In ungirdled shoots, no differences due to the different l-t-f ratios were observed, whereas in girdled shoots P
N tended to be lower in shoots with a high l-t-f ratio. In general, the values of leaf transpiration rate (E), stomatal conductance (g
s), sub-stomatal CO2 concentration (C
i), and dark respiration rate (R
D) were associated with those of P
N. The starch and reducing sugar contents and area leaf dry mass (ADM) tended to be higher in leaves on girdled shoots with high l-t-f ratio, whereas in ungirdled shoots no differences related to the different l-t-f ratios were observed. The higher saccharide content in the leaves and the lower P
N, in the presence of a high C
i, observed in girdled shoots with a high l-t-f ratio suggests that the depression in P
N in these shoots may be the result of a feedback inhibition of the photosynthetic mechanism that regulates such a process. The l-t-f ratio did not have a substantial effect on fruit drop. In ungirdled shoots, the different l-t-f ratios did not produce significant differences in terms of fruit growth and leaf dry matter and saccharide contents, whereas in girdled shoots fruit growth increased as the l-t-f ratio increased, particularly when treatments were applied at the initial stage of fruit development. The percentage of oil in the pulp, on a dry matter basis, was not substantially influenced by girdling and l-t-f ratio. The abundant availability of assimilates seemed to cause earlier fruit ripening and, at the same time, retard fruit senescence (fruit detachment force). Shoot growth was slightly reduced by girdling. The abundant availability of assimilates, induced by girdling associated with high l-t-f ratio, stimulated flower induction.
The development of new shoots plays a central role in the complex interactions determining vegetative and reproductive growth
in woody plants. To explore this role we evaluated the new shoots in the olive tree, Olea europaea L., and the effect of fruiting on new shoot growth and subsequent flowering. Five-year-old branches served as canopy subunits
in order to obtain a global, whole-tree view of new shoot number, size and morphological origin. The non-bearing trees had
many more shoots than the fruit-bearing trees, and a greater number of longer shoots. In both bearing conditions, however,
the majority of shoots were less than 4cm long, with shoots of progressively longer lengths present in successively decreasing
frequencies. Six major shoot types were defined on the basis of apical or lateral bud origin and of parent shoot age. On fruit-bearing
trees, the new shoots originated predominantly from the shoot apex, while on non-fruiting trees, they formed mainly from axillary
buds, but in both cases, they tended to develop on younger parent shoots. The previous bearing condition of the tree was the
main determinant for subsequent inflorescence development, which was independent of both shoot type and length. Thus, reproductive
behavior strongly affected both the amount and type of new branching, but subsequent flowering level was more influenced by
previous bearing than by the potential flowering sites on new shoots.
KeywordsAlternate bearing–Axillary bud–Flowering intensity–Reproductive shoot–Shoot origin
Olive (Olea europaea) has a very high tendency for year-to-year deviation in yield (alternate bearing), which has a negative economic impact on the olive oil industry. Among possible reasons for alternate bearing, depletion of stored carbohydrates (CHO) during the On-year (high yield) has often been mentioned. The objective of the present study was to verify the role of CHO reserves, as a cause or effect, in the alternate bearing of intensively cultivated olives. A monthly survey of soluble sugar and starch concentrations in the leaves, branches, bark and roots of On- and Off-trees (cv. Barnea) was carried out during a complete reproductive cycle from November 2005 to October 2006. Carbohydrate concentration in the sapwood was determined in January, as well as an estimate of whole-tree biomass. The trunk and limbs possess the largest portion of CHO reserves. The influence of reduced fruit load on CHO reserves was also investigated. Starch, mannitol and sucrose concentrations increased from December to March in all tissues, and then declined along with fruit development. Leaves, branches and bark have a significant role in CHO storage, whereas roots accumulated the lowest CHO concentrations. However, fluctuations in reserve content suggested considerable involvement of roots in the CHO budget. Nevertheless, there were no meaningful differences in the annual pattern of CHO concentration between On- and Off-trees. Even a 75-100% reduction in fruit number brought about only a minor, sluggish increase in CHO content, though this was more pronounced in the roots. Carbohydrate reserves were not depleted, even under maximum demands for fruit and oil production. It is concluded that in olives, the status of CHO reserves is not a yield determinant. However, they may play a significant role in the olive's survival strategy, ensuring tree recovery in the unpredictable semiarid Mediterranean environment. This suggests that CHO reserves in olive act like an active sink, challenging the common concept regarding the regulation of CHO reserves in plants.
The hypothesis that carbohydrate partitioning is driven by competition among individual plant organs, based on each organ's growth potential, was used to develop a simulation model of the carbon supply and demand for reproductive and vegetative growth in peach trees. In the model, photosynthetic carbon assimilation is simulated using daily minimum and maximum temperature and solar radiation as inputs. Carbohydrate is first partitioned to maintenance respiration, then to leaves, fruits, stems and branches, then to the trunk. Root activity is supported by residual carbohydrate after aboveground growth.
Verification of the model was carried out with field data from trees that were thinned at different times. In general, the model predictions corresponded to field data for fruit and vegetative growth. The model predicted that resource availability limited fruit and stem growth during two periods of fruit growth, periods that had been identified in earlier experimental studies as resource-limited growth periods. The model also predicted that there were two periods of high carbohydrate availability for root activity. The fit between model predictions and field data supports the initial hypothesis that plants function as collections of semiautonomous, interacting organs that compete for resources based on their growth potentials.
We investigated relationships between tree water status, vegetative growth and leaf gas exchange of peach trees growing on different rootstocks under field conditions. Tree water status was manipulated by partially covering (0, approximately 30 and approximately 60%) the tree canopies on individual days and then evaluating the effects of tree water status on vegetative growth and leaf gas exchange. Early morning stem water potentials were approximately -0.4 MPa for trees in all treatments, but mean midday values ranged from -1.1 to -1.7 MPa depending on rootstock and canopy coverage treatment. Relative shoot extension growth rate, leaf conductance, transpiration rate and net CO2 exchange rate differed significantly among trees in the different rootstocks and canopy coverage treatments. Shoot extension growth rate, leaf conductance, leaf transpiration rate and leaf net CO2 exchange rate were linearly correlated with midday stem water potential. These relationships were independent of the rootstock and canopy coverage treatments, indicating that tree water relations are probably directly involved in the mechanism that imparts vegetative growth control by selected peach rootstocks.
Olive growing is expanding rapidly in many countries around the world in which olives have not previously been widely cultivated. Pruning olive trees is quite different from pruning other fruit trees of the temperate zone, because of their biological peculiarities. Errors in pruning may result in yield losses or higher cultivation costs. Pruning also determines the training system which, in turn, is one of the major factors for successful tree performance and orchard profitability. Pruning and Training Systems for Modern Olive Growing summarises the information available on current pruning techniques and training systems. It specifically addresses the problems faced by growers, professionals and students who are new to olive growing and provides information previously not available in English. The fundamental aim of this book is to explain the basic concepts at a practical level. It will allow the reader, whether experienced horticulturalist or beginner, to develop his or her own skills and pruning strategy.
For the last several years, research in my laboratory has been focused on studying the developmental and environmental control of dry matter partitioning in peach trees based on the concept that plants grow as collections of semi-autonomous, but interacting, organs. This concept assumes that plant genotype, triggered by developmental and environmental signals, determines current organ specific growth potentials and that environmental conditions dictate conditional growth capacity and respiration (both growth and maintenance) requirements of each organ at any specific time. Dry matter partitioning at any given time is then determined by the availability of resources to be partitioned, the conditional growth capacity and maintenance requirements of each organ, and the relative ability of each organ to compete for the resources. In this presentation, I will demonstrate how developmental patterns of various organs influence dry-matter partitioning within the tree over time, how organ number can influence the amount of dry-matter partitioned collectively to an organ type, and propose an hypothesis for how environmental conditions may influence partitioning on a diurnal basis.
In the last 20 years, there has been a great expansion in the land area planted with olive trees (Olea europaea L.) in the Northwest of Argentina (NWA). Nevertheless, most of the information utilized in management decisions in the region concerning crop water use comes from the Mediterranean Basin. This review discusses: 1) differences in climate between the Mediterranean Basin and the olive production areas in the NWA, 2) water use by olive in the Mediterranean and ecophysiological responses to water stress, and 3) experimental results from the NWA using Aimogasta (La Rioja) as a case study. Meteorological data indicate that the air temperature (primarily in the winter and spring) and the annual potential evapotranspiration (ETo) are higher in the NWA than in the Mediterranean, while precipitation is less. Differences in temperature have been shown to result in lack of chilling hours for flowering in some varieties, advances in phenological stages, and changes in oil quality and quantity in NWA relative to the Mediterranean. Experimental results from the Mediterranean show that transpiration, yield, and other variables respond strongly to irrigation although olive is a species with a high tolerance to water stress in comparison to other fruit trees. Similar to the Mediterranean, olive water use in Aimogasta was estimated to be 70-75% of ETo under optimally irrigated conditions. Considering the differences in the ETo values in the two regions, water use is 1100-1200 mm/year in the NWA and 900-1000 in the Mediterranean. Additionally, the required irrigation is more than double due to the lack of precipitation in many areas. An unanticipated result in Aimogasta based on the studies from the Mediterranean was the excessive vegetative growth under high irrigation conditions. The excessive vigour was potentially a response to the irrigation in interaction with the high spring temperatures that occur in the region. The development of regulated deficit irrigation strategies in the spring (or in other time periods) could save water and improve the ratio of vegetative to reproductive growth.
Table olives are being accepted as a more intensive crop than oil olives, and produce better returns to the grower. This crop receives more inputs such as additional irrigations and fertilizers in order to improve fruit yield and quality. A problem occurs at years when fruit load is quite high, forcing a decrease of the fruit size. Thus, when the offering to the industry is high, the industry puts a bottom line on accepted fruit size (e.g. 15 mm). Undersized fruit is rejected at a total loss to the grower as oil content is too low for oil. On the other hand, increasing premiums are paid for higher fruit sizes according to size grouping by the industry (e.g. 15-16, 17-18, 19-20 mm etc). Field trials were laid out in Israel during the years 2002 and 2003, looking for alternative ways to solve this problem. The target was to increase the partial part of the large fruits, without losing yield. Trials were done with the Manzanillo cv. for table olives, grown under intensive cultivation. Beside the known techniques of using pruning or fruit thinning (NAA), some new methods were tried such as spraying the canopy with plant hormones such as cytokinines (CPPU) or auxin (2-4:DP), or a special designed foliar fertilizer "SON" (Summer Olive NutriVant) 8-16-40+FV, to young fruitlets at various timing and concentrations, either as separate or combined treatments. The best results were obtained with the "SON" 3% fertilizer treatment, applied one time at 2 weeks after full bloom.
The expolinear growth model of Goudriaan and Monteith (1990) is proposed as a new model for the inherent growth pattern of fruit of apple (Malus domestica Borkh.), defined as growth pattern under apparently non–limiting conditions This function has three parameters: maximum relative growth rate, maximum absolute growth rate, and “lost time” (x intercept of the linear growth phase). Apple fruit growth (weight basis) at very low crop loads and apparently optimum environmental conditions, displays an early positive curvilinear growth followed by linear growth to harvest, and is described well by the expolinear function. The model also fits growth patterns of ‘Empire’ and ‘Golden Delicious’ apple fruit differing in the rate of growth in the exponential phase due to differences in the crop load. Estimates of cortical cell numbers in ‘Empire’ fruit from related studies suggest that during the linear phase in mid–season, different growth rates among crop load treatments were apparently controlled by differences in numbers of cells in the fruit, since estimated growth rates per cortical cell were essentially constant over several treatments.
To determine relative dry-matter partitioning to early-season growth of extension shoots vs. fruits under competitive conditions in the shade, heavily cropping branch sections of 'Empire' apple (Malus xdomestica Borkh.) were girdled and shaded to 15%, 40%, and 60% of available light for 9 days, while control branches were girdled and fully exposed. Treatments were applied at both 17 and 27 days after bloom, when fruit diameters averaged 13 and 23 mm, and the number of unfolded leaves on extension shoots averaged 13 and 19, respectively. Fruit diameters, extension shoot lengths, and numbers of unfolded leaves were monitored on the treated branches. Shoot growth was not affected by shading at either growth stage. Fruit growth rate was similar at 100% and 60% available light, but declined 25% at 40% available light and 50% at 15% available light. These results indicate that shoot growth has priority over fruit growth for partitioning in light-limiting conditions early in the season.
Shading for short periods during potentially critical phenological phases can improve our understanding of the processes underlying the reductions in crop performance when solar radiation is limiting in high density orchards. Our objective was to evaluate the effects of three separate 30 day-long shade periods imposed during fruit set (FS), endocarp sclerification (ES), and early oil accumulation (OA) on some oil yield determinants and components in olive. Four shading levels (3, 20, 40, and 70% of incident photosynthetically active radiation; PAR) were applied in each period using shade cloths that surrounded one-half of large individual trees. Individual fruit dry weight, oil concentration (%) on a dry weight basis, and non-fruiting branch growth were determined at the end of each shading period, 45 days after their completion, and at the end of the season. The previously shaded- and the unshaded-halves of each tree were also harvested at the end of the season to obtain fruit number and oil yield for each half-tree. Individual fruit dry weight and oil concentration at the end of all three shading periods were decreased by shading due to reduced absolute rates of fruit growth and oil accumulation, respectively. However, at final harvest, there were no statistically significant treatment differences in individual fruit weight. By contrast, a small reduction in oil concentration persisted in the fruit from trees subjected to heavy shading during the OA period. Oil yield per half-tree at end of the season was decreased by shading applied during FS and OA periods, principally due to decreases in fruit number and oil concentration, respectively. Final oil yield was not affected by shading during the ES period. Elongation of non-fruiting branches was only decreased by shading during the early spring FS period, when vegetative growth was somewhat more sensitive to shading than fruit growth. Lastly, no consistent response of return bloom to the shading periods was detected the following spring. Our results suggest that the FS period when fruit number is defined and the OA period are more critical for determining final oil yield than the ES period. This information could provide guidance for the design of more effective management strategies in high density orchards where shading can play a key role.
Maximizing productivity in super high density and intensive olive orchards requires proper management of illumination of the canopy walls and their interior. Currently, this is difficult to achieve due to the limited knowledge about the responses to incident photosynthetically active radiation (PAR) of yield determinants and components. We determined the response functions for PAR during the oil synthesis phase of yield components (fruit dry weight and oil concentration) of fruit at a height of 2 m on the canopy periphery by applying several radiation levels (3, 20, 40, and 70% of incident PAR) to the north side (S hemisphere) of well-illuminated trees. The experiment was initiated after endocarp hardening as fruit number had already been established at that time. This avoided possible confounding effects due compensation between fruit number and size. Absence of differential fruit fall in response to treatments and of changes in (endocarp + seed) dry weight after application of treatment confirmed the achievement of this objective. Fruit dry weight, oil concentration, and, consequently, yield increased linearly with mean daily PAR receipt up to a threshold of 15 mol PAR m−2 d−1 (i.e., 40% of PAR). In treatments with irradiance levels below this threshold the fruit became the priority sinks for assimilates, although their growth rate and oil concentration were reduced. Increments in length of non-fruiting branches and of trunk cross-sectional areas were substantially reduced in response to shading. We conclude that manipulation of PAR levels during the oil synthesis phase can reduce final fruit dry weight and oil concentration, confirms the existence of upper thresholds to PAR responses for these variables, and provides evidence that fruit growth has priority in the partitioning of photosynthate over vegetative growth under low to moderate levels of PAR.
A field experiment was performed in Tuscany, Italy, whereby fruit growth and development of irrigated olive trees (Olea europaea L. cv. Frantoio) was compared, at two stages of fruit development, with that of trees cultivated under rainfed conditions. The fresh weight of fruits from irrigated trees was significantly higher than that from rainfed trees at 21 weeks AFB sampling date, whereas there were no differences at 8 weeks AFB or in fruit dry weight at both dates. Mesocarp transverse equatorial areas were 15.6 and 13.5% greater for the irrigated treatment than rainfed cultivated trees at 8 and 21 weeks AFB, respectively. Endocarp transverse area did not increase between 8 and 21 weeks AFB, indicating that endocarp expansion had occurred completely by 8 weeks AFB. The endocarp area of irrigated trees was greater than that of unirrigated trees. For both treatments mesocarp area increased about 2.5-fold from 8 to 21 weeks AFB. Growth of the mesocarp between sampling dates was mainly due to the more than 2-fold increase in mesocarp cell size for both treatments, whereas the cell number increased only slightly between dates. Irrigation appeared to increase mesocarp cell size rather than mesocarp cell number at both sampling dates.
Olive oil yield and its components (fruit number, average fruit weight and fruit oil concentration) depend on crop load and source–sink ratios as affected by environmental conditions, management and the alternate bearing typical of the species. The aims of this work were to: (i) establish quantitative relationships between oil yield and its components as affected by fruit load in a high-yielding production system, (ii) analyse the dynamics of fruit weight and fruit oil concentration in terms of rates and durations, and (iii) explore the relationships between the dynamics of oil and water in fruit. In a fully irrigated olive orchard in Mendoza (32° S), Argentina, cv. Arbequina trees with similar crown volume and three fruit loads (3-fold range) were monitored during two seasons. Oil yield was positively associated with both fruit number and fruit fresh weight, but not with fruit oil concentration. Across seasons and fruit loads, fruit yield increased linearly with fruit number at ∼1.5kg per thousand fruit and reached a maximum ∼60kgtree−1 (or 25tha−1) at a fruit load of 32,700 fruit tree−1. The fruit filling rate was affected by fruit load, while the duration of fruit growth and the dynamics of oil and water concentration were unaffected by fruit load. Fruit water concentration reached a minimum at the onset of Stage III of fruit growth, which was marked by a rapid increase in oil concentration. Fruit fresh weight and oil weight increased with source–sink ratio from ∼0.5 up to a threshold ∼2m3 crown per thousand fruit. In contrast, a 8-fold range of source–sink ratio did not affect fruit oil concentration.
IntroductionDefinition of AlternationRepresentative Cases of AlternationHorticultural TraitsCauses of AlternationHorticultural Control of AlternationConclusions
Literature Cited
Introduction Seasonal Growth Pattern of Apple Trees Factors Affecting Vegetative Growth Factors Affecting Flowering and Fruiting Vigor Vegetative Growth—Fruiting Interactions Effective Management Literature Cited
To understand the relations between water use and yield in response to crop load, two experiments were conducted in olive (cv. Morisca), during six consecutive years (2002-2007) in an experimental orchard located in Badajoz, Southwest Spain. Experiment 1, assessed the responses during the early years of the orchard (2002-2004) using four irrigation treatments that applied fractions of the estimated crop evapotranspiration (ETc) (125%, 100%, 75% and 0%) and three crop load levels (100%, 50% and 0% of fruit removal, termed Off, Medium and On treatments). Experiment 2 assessed the response of more mature trees (2005-2007) to three irrigation treatments (115%, 100%, and 60% of ETc) and the natural crop load which were Off, On, and Medium in 2005, 2006 and 2007, respectively. Yield was reduced by water deficits and so did the estimated tree transpiration which was linearly related to yield (y = 1.2302x - 21.15, R2 = 0.8864), showing the high sensitivity of cultivar Morisca to water deficits. The relations between fruit number and fruit weight showed that high crop loads had lower fruit weights and oil yield, a decrease that was more pronounced as water deficits increased. The yield response to water supply in the control and excess treatments, and the observations on the water relations of these two treatments suggest that the calculations made using the FAO method (Doorenbos and Pruit, 1974) with the crop coefficient proposed by Pastor et al. (1998) and the reduction coefficient (Fereres et al., 1982) to apply 100% of ETc in the control treatment, underestimated the ETc of the orchard. The results indicate that, although the absence of fruits lead to reduced water use as compared to situations of medium and high crop loads, canopy size was much more determinant of orchard water requirements than crop load.
To characterize the interactions between variable water supply and crop load on vegetative growth and water relations of an olive orchard (cv. Morisca) planted in 1998 at 417 trees ha-1, two different experiments were conducted over a six-year period (2002-2007) in Badajoz, Southwest of Spain. Experiment 1, assessed the responses during the early years of the orchard (2002-2004) using four irrigation treatments that applied fractions of the estimated crop evapotranspiration (ETc) (125%, 100%, 75% and 0%) and three crop load levels (100%, 50% and 0% of fruit removal, termed off, medium and on treatments). Experiment 2, assessed the response of more mature trees (2005-2007) to three irrigation treatments (115%, 100%, and 60% of ETc) and the natural crop load which were off, on, and medium in 2005, 2006 and 2007, respectively. Although vegetative growth was mainly affected by the level of water supply, crop load also influenced vegetative parameters, especially the interaction between high loads and water deficit. Trunk growth was more sensitive to water deficits than ground cover, and at the branch scale, water deficits reduced branch length and node numbers but only reduced internode length in on trees. Water relations were more affected by the level of water supply than by crop load. Nevertheless, the presence of fruits affected olive tree water status and, particularly, increased the stomatal conductance of on trees during late summer and early fall under all levels of water supply. Interactions between water stress and crop load levels were not very strong, and were more evident in mature than in young olive trees.
Over the last two decades, a significant increase in intensively managed olive orchards has occurred in the northwest of Argentina where climatic conditions differ greatly from the Mediterranean Basin. Annual amounts of applied irrigation are generally high due to low rainfall, access to deep ground water, and little information about water use by the crop in the region. The objectives of this study were to: (1) assess the responses of plant growth, yield components, and several physiological parameters to five different irrigation levels and (2) determine an optimum crop coefficient (Kc) for the entire growing season considering both fruit yield and vegetative growth. Five irrigation treatments (Kc = 0.50, 0.70, 0.85, 1.0, 1.15) were employed from late winter to the fall over 2 years in a 6-year-old cv. 'Manzanilla fina' olive orchard. Tree canopy volume was approximately 15 m3 with a leaf area of about 40 m2 at the beginning of the experiment. During much of each year, the volumetric soil water content was lower in the Kc = 0.50 treatment than in the other irrigation levels evaluated (Kc = 0.85 and 1.15). Although differences in midday stem water potential ([Psi]s) were not always apparent between treatments during the first year, there were lower [Psi]s values in Kc = 0.50 and 0.70 relative to the higher irrigation levels during the second year. Shoot elongation in Kc = 0.50 was about 50% of that in Kc = 1.0 and 1.15 during both years leading to significant differences in the increase of tree canopy volume by the end of the first year. Fruit yield was similar among irrigation levels the first year, but yield reached a maximum value the second year between Kc = 0.70 and 0.85 above which no increase was apparent. The somewhat lower fruit yield values in Kc = 0.50 and 0.70 were associated with decreased fruit number rather than reductions in individual fruit weight. The water productivity on a yield basis (fruit yield per mm of applied irrigation) decreased as irrigation increased in the second year, while similar calculations based on trunk cross-sectional area growth indicated that vegetative growth was proportional to the amount of irrigation. This suggests that the warm climate of northwest Argentina (28° S) can induce excessive vegetative growth when very high irrigation levels are applied. A Kc value of approximately 0.70 over the course of the growing season should be sufficient to maintain both fruit yield and vegetative growth at adequate levels. An evaluation of regulated deficit irrigation strategies for table olives in this region could be beneficial to further reduce irrigation.
Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.
Plant age and size, seasonal growth patters and crop load, among other factors, have been reported to decrease the usefulness of trunk diameter variation (TDV) derived indices as water stress indicators in olive trees. Our hypothesis, however, is that indices derived from TDV records in old, big olive trees are sensitive enough to detect levels of water stress in trees of orchards under deficit irrigation that, although severe, are below the threshold for fruit shrivelling. This is of importance for the production of good quality oils, since fruit shrivelling may affect oil quality. The aim of this work was to assess different TDV-derived indices as water stress indicators in 40-year-old 'Manzanilla' olive trees with heavy crop load. We derived the maximum daily shrinkage (MDS), daily growth (DG) and daily recovery (DR) from TDV records taken during the 2008 dry season both in well-irrigated FAO trees and in deficit-irrigated RI trees. Measurements of volumetric soil water content ([theta]v), leaf water potential ([Psi]l), stomatal conductance (gs), net CO2 assimilation rate (A), water and oil accumulation in the fruits and yield parameters were made for both treatments. The trunks did not grow during the experimental season, either in the FAO or RI trees, likely because of the heavy crop load. Therefore, DG was useless as water stress indicator. For MDS and DR, which were responsive to the increase of the trees' water stress, we calculated the variability, quantified by the coefficient of variation (CV), the signal intensity (SI) and the sensitivity (SI/CV) values. In addition, we derived reference equations for irrigation scheduling from the relationships between MDS values in the FAO trees and main meteorological variables. Values both of SI-MDS and SI-DR were steady until September 9, despite of increasing differences in [theta]v between treatments from early in the dry season. The [Psi]l vs [theta]v values showed an outstanding capacity of the RI trees to take up water from the drying soil, and the [Psi]l vs gs values showed a near-isohydric behaviour of those deficit-irrigated trees. These results explain, at least in part, the lack of response of MDS and DR on that period. Both SI-MDS and SI-DR peaked for the first time on September 9, 16 days before the appearance of fruit shrivelling. Our results suggest that using TDV-derived indices as water stress indicators for irrigation scheduling in old olive orchards with medium to low plant densities, i.e. with large root zones, may be useless in case the irrigation strategy is aimed at keeping the soil close to field capacity. Nevertheless, the MDS and DR indices may be useful indicators for the avoidance of fruit shrivelling in deficit irrigated olive orchards for the production of good quality oil. Reliable reference equations for scheduling irrigation with the signal intensity approach were obtained from the regression of MDS values vs the daily maximum values of both the air temperature and the vapour pressure deficit of the air.
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To achieve its maximum organ growth potential, an organ must grow at its potential relative growth rate (RGR) throughout development. When resource availability limits growth, the RGR is reduced below the potential RGR. This study examines whether, following a period of resource-limited growth, the RGR is able to increase to the potential RGR when sufficient resources are available. Fruit RGRs of a late maturing peach cultivar were examined following removal of most of the fruits (heavy thinning) from previously unthinned trees in Apr., May, and Jun. The fruit RGRs after imposition of the thinning treatments were higher than those on unthinned trees during source-limited periods of the growing season, suggesting that fruit RGR can increase in response to increased resource availability. In general, the RGRs of fruits of trees thinned in Apr., May, and Jun. did not exceed those of fruits on trees thinned at bloom, suggesting that heavy thinning at bloom provides a reasonable estimate of the potential RGR. There were times, however, when the effects of competition with vegetative sinks were apparent, suggesting that the RGR of fruits on trees that were heavily thinned at bloom may underestimate the potential RGR during these times. The absolute growth rates of fruits on thinned trees were greater than those on unthinned trees, but generally were not greater than those on trees that were thinned at bloom, suggesting that peach fruits are unable to recover potential growth lost during resource-limited growth periods. Copyright 1995, 1999 Academic Press
Maximum fruit growth potential, the growth attained by fruits when they are grown under optimal environmental conditions in the presence of a non-limiting supply of resources, was estimated for two peach [Prunus persica (L.) Batsch] cultivars that differ in the timing of resource demand for reproductive growth. Maximum potential fruit growth was estimated on trees that were heavily thinned at bloom. On these trees, resource availability exceeded resource demand for fruit growth.
For both cultivars, the mean dry weights of fruits grown on unthinned trees were approximately half the mean dry weights of fruits grown on trees that were heavily thinned at bloom, indicating that fruit growth was source-limited on unthinned trees. Comparison of the seasonal patterns of relative growth rate of fruits on unthinned and heavily thinned trees indicated the source-limited fruit growth occurred during distinct periods of the growing season. On the early maturing cultivar, source-limited fruit growth occurred from 300 degree-days after bloom until harvest (4·5-10 weeks after bloom). On the late maturing cultivar, source-limited fruit growth occurred from 200-900 and 1600-1900 degree-days (3·5-12 and 18-20 weeks) after bloom.
Although the final dry weight of fruits on the early maturing cultivar was only half that of fruits on the late maturing cultivar, the potential net sink strength of fruits was significantly higher on the early than the late maturing cultivar throughout the entire growth period of the early maturing cultivar. Resource availability for fruit growth was similar on the early and late maturing cultivars, indicating that selection for early maturing fruits has not changed the patterns of resource availability for fruit growth.Copyright 1995, 1999 Academic Press
The maximum vegetative growth potential of two peach [Prunus persica (L.) Batsch] cultivars that differ in the timing of resource demand for reproductive growth was determined in terms of stem extension, stem and leaf dry weight accumulation, and trunk radial increment on defruited trees. The maximum vegetative growth potentials were similar on the two cultivars indicating that the greater partitioning of dry weight to vegetative growth frequently observed on early maturing cultivars compared to late maturing cultivars is the result of a shorter period of competition between reproductive and vegetative growth, rather than a genetic difference in vegetative growth potential. On both cultivars, stem extension and leaf dry weight accumulation ceased in mid-summer, however stem dry weight accumulation and trunk radial increment increase continued through the autumn.
The presence of fruit did not have a detectable effect on the final stem length, stem dry weight or leaf dry weight on the early maturing cultivar, but it reduced final stem length and dry weight by 43 and 56%, respectively on the late maturing cultivar. The presence of fruit did decrease stem length, stem dry weight and leaf dry weight on the early maturing cultivar for 1 month prior to and 1 month after fruit harvest. Fruit decreased final trunk radial increment by 42 and 77% on the early and late maturing cultivars, respectively. These reductions in vegetative growth indicate that resource partitioning to vegetative growth was reduced by competition with fruit growth.
Comparison of stem relative extension rates and stem and leaf relative growth rates on fruited and defruited trees indicated that vegetative growth was resource-limited shortly after vegetative bud break on fruited trees of both cultivars. This period of resource-limited vegetative growth corresponded to a period of resource-limited fruit growth identified in an earlier study. During the period of resource-limited vegetative growth, assimilate supply was low due to low leaf area index, and carbohydrate demand was relatively high due to high vegetative and reproductive growth potentials, creating resource-limited growth conditions.Copyright 1995, 1999 Academic Press