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Effects of irradiance and spectral quality on seedling development of two Southeast Asian Hopea species
Abstract
Seedling developmental responses to understory shade combine the effects of reductions in irradiance and changes in spectral
quality. We studied the seedling development of two Southeast Asian dipterocarp trees in response to differences in irradiance
(photosynthetic photon flux density, PPFD) and spectral quality (red to far-red ratio, R:FR). The two species, Hopea helferei and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferei is more drought-tolerant and typically grows in more open habitats. Seedlings were grown in six different replicated shadehouse
treatments varying in percentage of solar PPFD and R:FR. The two species differed in the influence of light variables on most
seedling characters, particularly for final height, internode distance, branch/trunk internodes, stem length/mass, leaf area/stem
length, petiole length, and growth/mol of photons received. Most of the characters in both taxa were primarily influenced
by PPFD, but spectral quality also influenced some characters – more so for H. odorata. The latter species grew more rapidly, particularly in the low PPFD treatments, and its leaves were capable of higher photosynthesis
rates. However, growth in H. helferei was not reduced in direct sunlight. The growth of this taxon may be constrained by adaptations, particularly in leaves, for
drought tolerance.
... H. odorata is a late successional tree species of the Dipterocarpaceae that requires shade and high soil moisture content for its natural regeneration (Bunyavejchewin et al. 2003). In a glasshouse experiment, seedling growth and photosynthetic rates responded positively to treatments up to 42% of ambient incident photosynthetically active radiation (PAR) (Lee et al. 1997). The demand of H. odorata for light increases with age (Kamaluddin and Grace 1993;Appanah 1998) and there is evidence that H. odorata can adapt to ambient light conditions by changing its foliar chemistry and structure (Lee et al. 2000). ...
... While sunadapted plants tend to allocate photosynthate to height growth, shade-adapted plants allocate more photosynthate to lateral growth to capture more light (Tilman 1988;Oliver and Larson 1990;Chen et al. 1996;Chen 1997). Under different shading levels in a glasshouse, leaves of H. odorata and Hopea helferi in deeper shade were thinner; this was associated with significantly thinner leaf mesophyll (Lee et al. 2000), lower stomatal density (Lee et al. 1997), and higher chlorophyll content per unit area, particularly chlorophyll b for capturing light at low intensities (Lee et al. 2000;Phonguodume et al. 2012). There is also evidence that photosynthetic capacity is positively related to leaf mesophyll structure (Kenzo et al. 2004). ...
... In the current study, light saturation at age 1 year in the G-1 treatment occurred at~600 μmol m −2 s −1 and~1500 μmol m −2 s −1 in the G9 treatment, providing strong evidence that H. odorata has the ability to develop physiological capacities associated with sun-adapted species that were fully consolidated by age 2 years when A sat occurred at >1000 μmol m −2 s −1 in all treatments. This adaptation to higher irradiance was accompanied by greater A max (8-13 µmol m −2 s −1 ) than in studies where dipterocarp leaves were saturated at lower PAR (5-6 µmol m −2 s −1 (Eschenbach et al. 1998) and 4-6 µmol m −2 s −1 (Lee et al. 1997)). Adaptation to higher incident levels of light at age 1 year was also associated with an increase in quantum yield; saplings at the GC also had a higher light-use efficiency (Dong et al. ...
Background: Mixtures of tropical acacia nurse crops and understorey native species have been established to aid forest restoration in Vietnam, but with partial success. Knowledge of physiological mechanisms underlying competitive interactions remains limited.
Aim: To examine growth and physiological responses of Hopea odorata, a shade-tolerant dipterocarp, established within an Acacia hybrid (Acacia mangium × A. auriculiformis) nurse-crop plantation.
Method: Hopea odorata seedlings were planted within three 22-m diameter gaps in a 3-year-old Acacia hybrid plantation in Central Vietnam. Responses to an environmental gradient in gaps were examined over two years.
Results: Growth rate, and maximum rates of photosynthesis and stomatal conductance of H. odorata saplings increased significantly with increases in relative daily incident photosynthetically active radiation (PAR) from 24% at the gap perimeter to 61% at the gap centre. Leaf N, P and chlorophyll concentration were unaffected by position. At the end of dry season, there were significant reductions in leaf water potential for saplings close to the gap perimeter suggesting interspecific competition for water.
Conclusions: Despite naturally regenerating in shade, the strong ability of H. odorata to acclimate to higher light environments suggests that its re-establishment on degraded sites using Acacia hybrid as a nurse crop should be possible, provided that competition for light and water are managed.
... Under natural conditions, regeneration occurs where there is shade, suggesting that seedlings are adapted to shady conditions (Sakai et al., 2009). Shade-house experiments showed that growth rate and physiological performance of seedlings were highest in between 10 -40% of incident photosynthetically active radiation (PAR) (Lee et al., 1997;Lee et al., 2000). In plantations, previous studies found that shading benefits settlement and early growth of H. odorata seedlings, which leads to high survival rates and avoidance of photoinhibition with sudden changes to high irradiation conditions . ...
... Although H. odorata seedlings are considered as shade-tolerant, it can acclimatise to high light conditions (Lee et al., 1997;Lee et al., 2000). Under full sunlight, photosynthetic rate of H. odorata was not significantly different compared to shading treatments (Lee et al., 1997), but biomass production was highest because of higher receipt of radiation (Phonguodume et al., 2012).. ...
... Although H. odorata seedlings are considered as shade-tolerant, it can acclimatise to high light conditions (Lee et al., 1997;Lee et al., 2000). Under full sunlight, photosynthetic rate of H. odorata was not significantly different compared to shading treatments (Lee et al., 1997), but biomass production was highest because of higher receipt of radiation (Phonguodume et al., 2012).. Such acclimatisation indicates that the physiological traits of leaves change to adapt to high irradiation, and leaf traits become closer to those of sun plants e.g. ...
... Such alterations are mediated by pigments, known as phytochromes, which have absorption peaks in the red and blue/ultraviolet regions of the spectrum (LI et al., 2000). These photoreceptors are able to detect variations in light composition and induce photomorphogenetic responses, either in vivo or in vitro (KIM et al., 2004;MACEDO et al., 2004) that influence growth and development (LEE et al., 1997;LI et al., 2000), morphology (STUEFER and HUBER, 1998), leaf and stem anatomy (SCHUERGER et al., 1997;LEE et al., 2000), distribution of photosynthetic products (KASPERBBAUER, 1987;BROWN et al., 1995), photosynthetic efficiency (KASPERBBAUER and PEASLEE, 1973) and chemical composition (MACEDO et al., 2004). ...
... Moreover, the management of light intensity had no effect on the diameter of stems or the length of petioles. Since the stem is characterized by house the vascular tissue, stem diameter is correlated directly with the capacity for transporting water and carbohydrates (STUEFER and HUBER, 1998), and indirectly with the capacity for storing these metabolites (LEE et al., 1997). ...
... Total dry biomass (exception inflorescences) of plants cultivated under full sunlight was significantly greater than that of those maintained under red or blue shading (Table 1). The response of a plant to shading conditions depends on the complex interaction between quality and quantity of the incident light (LEE et al., 1997). Typically, growth and biomass production are influenced by light intensity, whilst development and morphogenesis are influenced by alterations in light composition (STUEFER and HUBER, 1998 ...
The objective of this work was to investigate the effects of shading on the growth and development of the medicinal plant Ocimum selloi after 90 days. Seedlings were maintained under three different light treatments, namely, full sunlight vs coloured shade treatments provided by red and blue ChromatiNet® 50% coloured netting. After 90 days of cultivation, height, stem diameter, petiole length, total leaf area (TLA), specific leaf area (SLA), leaf area ratio (LAR) and leaf weight ratio (LWR) of each plant hare measured. Microscopic examination of leaf sections were conducted in order to determine the leaf blade thicknesses, together with the size and density of the stomata, the number and area of chloroplasts, and chloroplast starch grains present in the palisade parenchyma cells. Although coloured shade-grown plants were taller in comparison with those grown in full sunlight, total dry biomass together with root, stem and leaf tissue biomasses were lower. Plants exhibited phenotypic plasticity, as demonstrated by the different TLA, SLA, LAR and LWR values that were recorded under the various light treatments. Stomatal density and leaf thickness was increased in plants maintained in full sunlight owing to the expansion of the abaxial epidermis and the spongy parenchyma. Chloroplasts were more numerous and larger in plants grown under shading, whilst the accumulation of chloroplastic starch grains was greater in plants grown under red shading or in full sunlight.
... Such alterations are mediated by pigments, known as phytochromes, which have absorption peaks in the red and blue/ultraviolet regions of the spectrum (LI et al., 2000). These photoreceptors are able to detect variations in light composition and induce photomorphogenetic responses, either in vivo or in vitro (KIM et al., 2004;MACEDO et al., 2004) that influence growth and development (LEE et al., 1997;LI et al., 2000), morphology (STUEFER and HUBER, 1998), leaf and stem anatomy (SCHUERGER et al., 1997;LEE et al., 2000), distribution of photosynthetic products (KASPERBBAUER, 1987;BROWN et al., 1995), photosynthetic efficiency (KASPERBBAUER and PEASLEE, 1973) and chemical composition (MACEDO et al., 2004). ...
... Moreover, the management of light intensity had no effect on the diameter of stems or the length of petioles. Since the stem is characterized by house the vascular tissue, stem diameter is correlated directly with the capacity for transporting water and carbohydrates (STUEFER and HUBER, 1998), and indirectly with the capacity for storing these metabolites (LEE et al., 1997). ...
... Total dry biomass (exception inflorescences) of plants cultivated under full sunlight was significantly greater than that of those maintained under red or blue shading (Table 1). The response of a plant to shading conditions depends on the complex interaction between quality and quantity of the incident light (LEE et al., 1997). Typically, growth and biomass production are influenced by light intensity, whilst development and morphogenesis are influenced by alterations in light composition (STUEFER and HUBER, 1998 ...
O objetivo deste trabalho foi verificar o efeito do sombreamento de Ocimum selloi com telas coloridas do tipo Cromatinet® (50%) vermelha, azul e a condição natural de pleno sol (sem tela) sobre as características biométricas, fisiológicas, anatômicas e ultraestruturais da planta após 90 dias. As plantas nas telas coloridas tiveram maior crescimento em altura, mas o maior acúmulo de biomassa seca total e particionada e relação raiz: parte aérea (R:PA) ocorreram na condição de pleno sol. A espécie proporcionou plasticidade fenotípica, verificada pelos ajustes das variáveis área foliar total (AFT), área foliar específica (AFE), razão de área foliar (RAF) e razão de massa foliar (RPF) em função dos tratamentos. Ocorreu maior espessamento foliar na condição de pleno sol pelo somatório do maior espessamento da epiderme abaxial e do parênquima esponjoso. A densidade estomática foi maior nas plantas a pleno sol. O número de cloroplastos e seu tamanho foi maior nas telas coloridas, enquanto o maior acúmulo de amido ocorreu a pleno sol e tela vermelha.
... We have discussed the effects of thinning on the soil environment and understory herbaceous diversity before (Choe et al., 2021), but the changes in light environment and shrub diversity were still unclear. Based on the "Niche Partitioning Theory" (NPT), which indicates that abiotic factors have essential roles in regulating species diversity (Austin, 1989;Pacala et al., 1996;Sterck et al., 2011), we constructed our conceptual model guided by the theory and related previous studies (Supplementary Figure 1) (Gerhardt, 1996;Lee et al., 1997;Nicotra et al., 1999;Wetzel and Burgess, 2001;Ediriweera et al., 2008). The data were analyzed using a structural equation model (SEM) to explore (1) the response of both light and soil environment in the mixed broadleaf-conifer forest to different thinning intensities, as well as (2) the influencing mechanism of light and soil environment on the species diversity of understory vegetation after thinning. ...
... The amount of light reaching the understory is one of the most important limiting factors affecting the species of understory plants (Kirby, 1988;Van Calster et al., 2008;Márialigeti et al., 2016;Shi et al., 2021), which determines the coverage, diversity and species composition of undergrowth vegetation. Many studies have shown that improved understory light conditions caused by increased canopy openness can improve plant diversity, especially in the herbaceous layer (Lee et al., 1997;Beaudet and Messier, 2002;Vesala et al., 2005;Ligot et al., 2014;Wang et al., 2017;Ádám et al., 2018;Wan and He, 2020;Shi et al., 2021;Zhang et al., 2021;Su et al., 2022). Theoretically, the effects of light on vegetation are complex because the abundance or diversity of understory vegetation does not necessarily correlate positively with light availability. ...
Tree thinning affects the light environment, which in turn affects the growth and survival of understory vegetation, thus improving species diversity and nutrient cycling, as well as the ecological habitat factors. However, the response of understory vegetation to the thinning intensity and short-time effects in the temperate broadleaf-conifer mixed forest is not completely clear. In this study, four permanent plots with a total area of 4 hm² were established in a mixed broadleaf-conifer forest in northeast China, with thinning intensities of 20% (light thinning, LT), 35% (medium thinning, MT), 55% (heavy thinning, HT) and the unthinned plot (CK), respectively, in accordance with the basal area. The responses of species diversity to changes in understory vegetation were conducted by a structural equation model (SEM). The results showed that compared with CK, thinning significantly increased the photosynthetically active radiation (PAR) and the light quality (R/FR) (p < 0.05), while decreased the contents of soil total nitrogen (TN), total phosphorous (TP), organic matter (OM), nitrate nitrogen (NN), ammonia nitrogen (AN) and pH. The degree of fragmentation of light factors among the treatment plots gradually decreased as thinning intensity increased. Among all the thinning treatments, PAR and R/FR were found to be the optimal light condition when the forest thinning intensity was 55%. The light condition was found to have a significant negative correlation with soil TN, TP, OM, and AN. While the soil nutrients were positively correlated with herbaceous layer diversity but negatively correlated with shrub layer diversity. The soil nutrients were lost after thinning in a short time and herb diversity decreased, but shrub diversity increased significantly compared with unthinned plots. For the understory vegetation, the species diversity of shrub and herb layer were showed to be more sensitive to soil nutrients than light environment.
... A degree of drought tolerance in A. hirta may contribute to its survival in ridge habitats, which often experience drought stress caused by soil water deficits during periods of low rainfall (Ishizuka et al. 1998). Similar habitat-associated drought tolerance has been inferred based on leaf morphology and gas exchange traits in several dipterocarp species in tropical rainforests in Sri Lanka (Ashton and Berlyn 1992) and Malaysia (Lee et al. 1997;Kenzo et al. 2007a). ...
... Consequently, A. subintegra is expected to have the lowest survival rate after transfer to open conditions with low air humidity and high temperature. Lee et al. (1997) reported similar mechanisms of drought intolerance in Hopea odrata (Dipterocarpaceae), which had a relatively high growth rate, P max , and gs max , and relatively low WUE, compared to the drought-tolerant species Hopea helferei, which is found on ridge habitats in Malaysia. ...
The genus Aquilaria (Thymelaeaceae) is widely used for the production of agarwood, and includes several valuable plantation species in Southeast Asia. To understand appropriate planting conditions, it is necessary to characterize species-specific ecological traits such as photosynthesis and drought tolerance among Aquilaria species. To this end, we measured leaf morphological and photosynthetic traits among three Aquilaria seedlings (A. hirta, A. malaccensis, A. subintegra) in Malaysia. We also monitored changes in growth and survival in a shaded nursery and 7 and 18 months after transfer to open conditions. To avoid transplant stress, the seedlings were kept in polybags. The highest leaf cuticle and epidermis layer ratio, leaf mass per area, and long-term water use efficiency indicated by δ¹³C were recorded in A. hirta, suggesting that this species had relatively high drought tolerance. By contrast, the high maximum photosynthetic rate and high stomatal conductance observed in A. subintegra explained their high growth rate, although their drought tolerance was the lowest among the studied species. A. malaccensis was considered an intermediate species in terms of photosynthesis and drought tolerance. Interspecific differences in growth and survival were present after transfer to open conditions. A. hirta had the lowest growth rate and highest survival rate (50% survival after 18 months), whereas A. subintegra had the highest growth rate and lowest survival rate (9% survival after 18 months). A. malaccensis was intermediate between the two. In summary, the studied Aquilaria species were susceptible to stress under the open and dry conditions of our study. This includes Aquilaria hirta, the most drought-tolerant species in this group, and A. subintegra, the most vulnerable species to drought, which may require careful management when planted in open conditions.
... Petiole samples of 0.2 cm in length were also taken from the middle region for cross sections. Samples were immediately fixed in glutaraldehyde (Kraus and Arduin 1997), transversely sectioned with a rotary microtome and stained with toluidine blue (O'Brien et al. 1964). For epidermis dissociation, samples were placed in a 1:1 glacial acetic acid and hydrogen peroxide solution (modified from Franklin 1945). ...
... Increased stomatal density and Stomate Area Index in high-light treatments seem to be characteristic of these high-light conditions (Lee et al. 1997). Higher light intensity is associated with higher photosynthetic capacity (Björkman 1981). ...
Leaf light responses, especially structural aspects, are well studied in adult tropical tree species. However, there is still a gap in the knowledge of these plastic responses on first developed leaves, which may be important to seedling survival in variable environments. An experimental approach was used to test the hypothesis that phenotypic plasticity is expressed in first leaves in response to different light intensities. This study was conducted in the Upper Paraná River floodplain, near Porto Rico city (22°55′S, 53°10′W), Southeast Brazil. We quantified the responses of 40 morphological and anatomical traits in first leaves of Eugenia hiemalis Cambess. (Myrtaceae), a riparian shrub that occurs in deep shade and full sun exposure. Seedlings were grown under four treatments: 100, 50, 30, and 0.3 % of full sunlight. Lamina and petiole size was larger in leaves exposed to 0.3 % of full sunlight than in full sun leaves, which have greater leaf thickness, palisade parenchyma, stomatal density, xylem area, and vascular density. Intermediate values were found in 50 and 30 % of full sunlight. The morphological and anatomical variability of E. hiemalis first leaves results from plasticity onset and is regarded as an advantage to seedlings exposed to different light conditions.
... A luz é um dos fatores físicos mais importantes no controle do desenvolvimento de plântulas de espécies arbóreas em florestas tropicais úmidas (Lee et al. 1997). As condições de luz para as plântulas, no nível do chão da floresta, são extremamente variáveis. ...
... (Ackerly & Bazzaz 1995) e em Stokesia laevis Hill (Callan & Kennedy 1995), sendo relacionada à diminuição da transpiração, já que esse comportamento evita que os raios solares atinjam perpendicularmente a folha (Callan & Kennedy 1995). Densidade dos estômatos -A densidade estomática costuma aumentar em plantas submetidas a altas irradiâncias (Lee et al. 1997), podendo resultar tanto em um aumento na absorção de CO 2 (Abrans et al. 1992), quanto em uma diminuição na transpiração, este último fato devido à sobreposição da área de difusão do vapor d'água em virtude da maior proximidade dos estômatos (Larcher 1995). As três espécies estudadas foram capazes de aumentar a densidade estomática com aumento da irradiância, pelo menos até 30% de luz. ...
The growth response of seedlings of three woody species from the Tropical Atlantic rain forest to changing light conditions was studied. The species were the early successional Cecropia glazioui Sneth., the intermediary in succession Cedrela fissilis Vell. and the late successional Bathysa australis (A. St.-Hil.) Hook. ex Sch. These species showed, within the range of light gradient, plasticity to increase light interception at lower light levels (through increasing leaf area ratio - LAR, and decreasing root/shoot ratio - R/SH); and plasticity to increase carbon gain and decreasing transpiration at high light levels (through increasing stomatal density and R/SH, and decreasing LAR). Species responses to irradiance varied with position along the light gradient. Plants at the lower end of the light gradient were more responsive than plants at the higher end of the light gradient. C. glazioui seemed to be more plastic than C. fissilis to alter several features. The behavior showed by the three species in response to changing light was consistent with their environmental occurrence.
... A luz é um dos fatores físicos mais importantes no controle do desenvolvimento de plântulas de espécies arbóreas em florestas tropicais úmidas (Lee et al. 1997). As condições de luz para as plântulas, no nível do chão da floresta, são extremamente variáveis. ...
... (Ackerly & Bazzaz 1995) e em Stokesia laevis Hill (Callan & Kennedy 1995), sendo relacionada à diminuição da transpiração, já que esse comportamento evita que os raios solares atinjam perpendicularmente a folha (Callan & Kennedy 1995). Densidade dos estômatos – A densidade estomática costuma aumentar em plantas submetidas a altas irradiâncias (Lee et al. 1997), podendo resultar tanto em um aumento na absorção de CO 2 (Abrans et al. 1992), quanto em uma diminuição na transpiração, este último fato devido à sobreposição da área de difusão do vapor d'água em virtude da maior proximidade dos estômatos (Larcher 1995). As três espécies estudadas foram capazes de aumentar a densidade estomática com aumento da irradiância, pelo menos até 30% de luz. ...
The growth response of seedlings of three woody species from the Tropical Atlantic rain forest to changing light
conditions was studied. The species were the early successional Cecropia glazioui Sneth., the intermediary in succession
Cedrela fissilis Vell. and the late successional Bathysa australis (A. St.-Hil.) Hook. ex Sch. These species showed, within the
range of light gradient, plasticity to increase light interception at lower light levels (through increasing leaf area ratio - LAR,
and decreasing root/shoot ratio - R/SH); and plasticity to increase carbon gain and decreasing transpiration at high light levels
(through increasing stomatal density and R/SH, and decreasing LAR). Species responses to irradiance varied with position
along the light gradient. Plants at the lower end of the light gradient were more responsive than plants at the higher end of the
light gradient. C. glazioui seemed to be more plastic than C. fissilis to alter several features. The behavior showed by the three
species in response to changing light was consistent with their environmental occurrence.
... Chlorophyll a (C a ) As observed by Kitajima (1994) and Lee et al. (1997), biomass accumulation responses across species and treatments were not proportional to CO 2 assimilation rates. Diurnal net CO 2 assimilation in clear days was much higher in T. micrantha than H. courbaril under HL as well as maximum assimilation rates, mainly on an area basis (A max ). ...
... These characteristics seem to bring benefits by increasing light capture and, consequently, increasing the ratio between photosynthesis and respiration of the whole plant. This may contribute to the maintenance of a positive carbon balance and survival by optimizing growth under these conditions (Givnish 1988, Kitajima 1994, Lee et al. 1997. It is interesting to note, however, that T. micrantha presented higher SLA, LA and lower root:shoot ratio than H. courbaril under low light. ...
In this study we evaluated photosynthetic characteristics and patterns of biomass accumulation in seedlings of two tree species from a Semideciduous Tropical Forest of Brazil. Seedlings of Trema micrantha (L.) Blum. (pioneer) and Hymenaea courbaril (L.) var. stilbocarpa (Hayne) Lee & Langenh. (climax) were grown for 4 months under low light (LL) (5%-8% of sunlight) and high light (HL) (100% of sunlight). Under HL, T. micrantha showed higher CO 2 assimilation rates (A CO2) and light saturation than H. courbaril. Under LL, A CO2 were higher in H. courbaril. Under LL, total chlorophyll and carotenoid contents per unit leaf area were higher in H. courbaril. Chlorophyll a/b ratio was higher in T. micrantha under both light regimes. A CO2 and F v/F m ratio at both pre-dawn and midday in H. coubaril were lower in HL indicating chronic photoinhibition. Thus, the climax species was more susceptible to photoinhibition than the pioneer. However, H. courbaril produced higher total biomass under both treatments showing high efficiency in the maintenance of a positive carbon balance. Thus, both species expressed characteristics that favor growth under conditions that resemble their natural microenvironments, but H. courbaril also grew under HL. The ecophysiological range of responses to contrasting light levels of this climax plant seems to be broader than generally observed for other rainforest climax species. We propose that this could be related to the particular spatio-temporal light regime of the semideciduous forests.
... As it is characterized by a high degree of stability [11,12] , and Benzyl adenine BA is one of the types of cytokinins, as it was found that the synthetic form of cytokinin is represented by the growth regulator Benzyl adenine (BA), which is more effective than the natural cytokinins as it has a high degree of stability [13] . And that organic fertilizer are known as materials originally produced from plant residues and animal waste, and these fertilizers are rich in water and carbon compounds [14,15], so spraying with organic fertilizers for seedlings has a role in improving vegetative characteristics through the nutrients that enter into the formation of amino acids And nuclear and important enzymes in increasing vegetative growth and the emergence of the chlorophyll molecule, which is the basis for photosynthesis, which increases the processed carbohydrates and increases growth rates [16,17]. ...
The study was conducted in the fields of the Department of Horticulture and Garden Engineering / College of Agriculture / University of Kirkuk / Shwaro District, located at latitude (35.53°) and longitude (44.38°) for the city of Kirkuk for a period of ten months from June 2021 until April 2022, for seedlings of myrtle plant of the age The seedlings were homogeneous in size and height (2 ± 42 cm), and the study included the effect of three factors on the myrtle plant, the first factor was the percentage of shading (50% inside the wooden canopy and shading with green saran clip 75%), and the second factor was three levels of benzyl growth regulator Adenine at concentrations (0, 35, 70) mg.l ⁻¹ , by two sprays, the first in October and the second in November, and the third factor was three levels of Horti boost10 organic fertilizer at concentrations (0, 1, 2) ml. Liter ⁻¹ , the implementation of this study followed the design of randomized complete blocks RCBD with a factorial experiment with three replications and the number of seedlings was (2 x 3 x 3 x 3 x 2 = 108) seedlings. The results were analyzed using the SAS program and the averages were compared using the test Duncan’s polynomial at the 5% probability level, and the results showed that the effect of shading ratio at the intensity was 50% It led to a significant increase in the leaves content of nitrogen 2.76%, potassium 1.95%, protein 1.55%, respectively, and there were no significant differences between the averages when using benzyl adenine at different concentrations in the experiment. And when spraying with organic fertilizer, a significant increase was observed in most of the chemical elements, where the spraying at a concentration of 2 ml.l ⁻¹ was significantly superior to the leaf content of nitrogen, phosphorous, potassium, protein, and carbohydrate (3.18%, 0.134%, 1.93%, 1.80%, and 10.60 %) Straight.
... Plants from unshaded plots recorded the highest fresh biomass (762.1 g/plant) followed by white shade net treatments (533.6 g/plant), with the lowest fresh biomass (391.9 g/plant) being recorded in plants grown under black shade nets (Table 1). The complex interaction between quantity and quality of incident radiation determines the response of plant to shading conditions (Lee et al., 1997). The significant decrease of fresh weight on plants grown under black shade net might be due to insufficient light the plants had received, which resulted in stunting growth that clearly demonstrates the importance of a favorable environment in determining plant growth and yield of bush tea in any region. ...
Additional index words. herbal tea, quality control, protected environment, light intensity, quality index Abstract. Horticultural practices and quality of bush tea (Athrixia phylicoides DC.) are critical for herbal tea industrialization. The objective of the current study was to determine the effect of selected shade nets and seasonal variation on plant growth and development, and hydroxycinnamic acid content of field-grown bush tea. The trial was laid out in a ran-domized complete block design consisting of three shade nets (black, green, and white) and control or full sunlight with three different light intensities (40%, 50%, and 80%) repli-cated three times. Proportion of intercepted radiation by the canopy, chlorophyll content, plant height, and fresh and dry mass were measured, and hydroxycinnamic acid accumulation was determined. In addition, hydroxycinnamic acid composition was determined using liquid chromatography linked to mass spectrometry (LC-MS). The application of shade nets resulted in plant growth and yield reduction as compared with the plants exposed to full sunlight during summer followed by white shade net. The accumulation of hydroxycinnamic acid was higher in 80% white shade net plots compared with unshaded plants (control) and the other shade nets. Therefore, lack of shading provides a conducive environment to enhance plant growth and development of bush tea. The white shade net (80%) was an effective microclimate tool to enhance accumulation of caffeoylquinic acid (m/z 353), p-coumaric acids (m/z 337), dicaffeoylquinic acid (m/z 515), and tricaffeoylquinic acids of bush tea. This study is the first to demonstrate light as a determining factor for production of chlorogenates in bush tea plants. Future studies will be conducted to determine the effect of light on extracts of the bush tea using different solvents.
... Reduction in 40 % light cause reduction in PAR and incident solar radiation (SR) by 48.3 and 46.3 %, respectively, (Ferreira et al., 2014). Lesser PAR with increased shade intensity was observed in rose cultivar (Rosa hybridL.) and clary sage (Salvia officinalis L.) (Hatamian and Salehi, 2017;Rezai et al., 2018), however, higher PAR was observed in open sunny conditions (Lee et al., 1997). Color of shade net also affect the intensity of light which was lower under the black net (20-27 %) followed by grey (18 %) and white net (12-15 %) (Middleton and McWaters, 2002). ...
In recent years, the demand for herbs and aromatic products has increased worldwide in the herbal, flavor, and fragrance industry. Studies suggest that rapidly increasing anthropogenic activities have put a lot of pressure on energy and water use, especially in the dry land areas. To meet the burgeoning demand of medicinal and aromatic plants (MAPs), long-term use of agrochemicals and poor farming techniques reduced the quality of produce as per industrialist grade and can cause public health challenges and environmental pollution. Sustainable crops, higher productivity, and quality are typically assured by microclimate modification, which in turn contributes to sustainability and livelihood generation for people. Modification of climatic conditions in a relatively small area, at a height of 3–6 m over the surface of the earth, affect the growth and development of plants by altering different physical parameters such as light intensity and wavelength. Morphology, growth, yield, and secondary metabolites production in MAPs are affected by microclimate modification. These parameters influence plant photosynthesis which plays an important role in plant vegetative, reproductive, and developmental stages, yield, and secondary metabolite accumulation. Different crops behave differently to microclimate modifications. In some crops, shade levels significantly reduce the yield and quality of seed, while in some others, higher amount of light is required to enhance productivity and quality. Therefore, it is indispensable to evaluate the threshold light intensity to ensure the sustainable production of MAPs. This study provides an understanding of plant acclimation to light intensity from the vegetative phase to the reproductive phase of the MAPs. So, from the current study we have concluded that in the climate change era and as per the need of the herbs, aromatic products and perfumery industry, substitution of synthetic fertilizers and poor agronomic techniques with microclimate modification can be considered to enhance the quality of products. This technique can be recommended to industrialist and farmers as sustainable culture techniques by eliminating the additional need of chemical fertilizers, however, more studies are required to fill the information gaps with morphology, physiology, quality and soil properties of MAPs in different light conditions along with other agronomic techniques.
... Overall, colored shade-nets had the highest impact on this trait when compared to control that was not shaded. We also found that the highest leaf and flower fresh and dry weights were obtained from the colored shade nets.Plant response to shade nets varies with light quality and quantity (Lee et al., 1997). Typically, growth and biomass production is determined by light intensity whereas growth, development, and morphogenesis are dictated by light composition (quality) (Stuefer & Huber, 1998). ...
A new group of colored shade net has been developed that can influence the quality and quantity of the light intercepted by the plants. To explore the effect of applying colored shade nets on physiological traits of marigold and violet plants, a split-plot experiment was carried out. The trial was done with two factors including colored shade net at four levels (no net, green, yellow and red net) and two plant species (marigold and violet). The results showed that yellow shade net increased the vegetative growth of the plants. However, the highest leaf area was related to the red shade net. Chlorophyll content, Brix°, and carotenoid content were significantly higher in plants grown under the yellow net. The highest peroxidase was obtained from green and red shade nets. The plants grown under the green shade net had higher anthocyanin and antioxidant activities than other shade nets. The interaction of ‘shade net × plant species’ showed that the highest root and flower fresh weights were related to ‘yellow net × marigold’, the highest plant growth rate, total chlorophyll, and carotenoid contents was related to ‘yellow net × violet’. The results revealed that yellow shade nets outperformed the other nets in improving plant growth.
... At 240 days, plants in full sun had a higher number of leaves and lower leaf area compared with plants grown under shade (Dalmolin et al., 2015), in agreement with our results for both number of leaves and leaf area. Rev. Ceres, Viçosa, v. 65, n.1, p. 044-055, jan/fev, 2018 For some species, stem diameter is a highly plastic trait, and this is desirable because it ensures a greater support to shoots (Lee et al., 1997). With increased shade, stem diameter linearly increased by 0.0369 mm per shade unit, representing gains of 7.12, 6.22, and 17.78% for plants under shade levels of 18, 30, and 50%, respectively, compared with stem growth of plants in full sunlight ( Figure 1C). ...
Talinum triangulare (Jacq.) Willd, known as Ceylon spinach, Surinam purslane, or waterleaf, is cultivated for medicinal and food purposes. Among environmental factors, light is an important regulator of primary production, contributing to plant growth. However, the success of each plant species depends on its morphoanatomical responses to light. The aim of this study was to determine whether T. triangulare leaf micromorphometry is affected when grown in full sun and under shade, and if so, which plant biometric variables are affected. T. triangulare cultivation was tested in beds arranged in blocks under shade levels of 0, 18, 30, and 50%. Each bed was considered a basic experimental unit, totaling four replications per treatment. Plant height, stem diameter, leaf area, leaf fresh weight, stem fresh weight, specific leaf area, leaf area ratio, abaxial epidermis, and mesophyll thickness were higher as shade levels increased. However, there was a decrease in the number of leaves, root to shoot ratio, stomatal density on abaxial and adaxial surfaces, and palisade parenchyma thickness. Nevertheless, root length, leaf and stem dry weights, leaf weight ratio, adaxial stomatal index, adaxial epidermis, and spongy parenchyma thickness remained constant. Plants responded differently to shade, with morphological and anatomical changes, suggesting a phenotypic plasticity and raising the possibility of being grown both in shaded environments and in full sunlight.
... The average values of light intensity obtained during the study time were 1500 μ mol m -2 s -1 (full sunlight), 650μ mol m -2 s -1 (under 50% blue shading) and 690μmol m -2 s -1 (under 50% red shading) (Lee et al. 1997 (Buisson and Lee, 1993) and is usually associated with extra layers of mesophyll cells. ...
Cut greens are an important component of the horticulture industry, largely used
for decoration as filler in floral compositions. They provide freshness, colour and variety
to arrangements and bouquets. The commercial value of cut greens depends on
vegetative characters, such as stem length, leaf colour and density, and side-branching.
Most of the cut greens have a different natural habitat compared to the conditions under
which they are commercially grown. Each plant has its individual requirements for
sunlight and shade under which it flourishes at its best. To create optimum climatic
conditions, selection of the correct percentage of shade level is a crucial factor to
enhance plant's productivity to its highest. Colour shade nets provide physical protection
(birds, hail, insects, excessive radiation) modify environment (humidity, shade,
temperature), and increase the relative proportion of diffuse (scattered) light as well as
absorb various spectral bands, thereby affecting light quality. The effects of coloured
nets are varied.
The research programme was formulated to standardize the shade levels and
coloured nets for Cordyline terminalis and Dracaena fragrans. In the first experiment,
plants were raised under green shade net with different shade level viz. 35%, 50%, 75%,
90% and control (open condition) while in the second experiment, green, black, red and
white coloured net were used along with outdoor environment (Control). Different
weather parameters (temperature, relative humidity), light intensity, photosynthetically
active radiation, transmittance, canopy temperature, gas exchange properties
(photosynthetic rate, stomatal conductance, transpiration rate), crop growth parameters
(plant height, number of leaves, petiole, length, internode length, leaf chlorophyll
content, leaf area, fresh leaf weight, dry leaf weight, vase life and harvest index) were
observed during different stages of growth.
Shade nets significantly modified the microenvironment. The air temperature,
light intensity, canopy temperature, photosynthetically active radiation and transmittance
were found to be lower under shade nets. The relative humidity increased with shading
intensity. The plant height, number of leaves, leaf area, fresh leaf weight, dry leaf
59
weight, Specific Leaf Area, leaf chlorophyll content, photosynthetic rate were higher
under shade nets when compared to control. In cordyline, 50% shade level produced
plants with highest plant height, number of leaves and petiole length with good harvest
index and vase life. 50% shade level was also found optimal for dracaena as the plants in
this environment recorded higher number of leaves, higher leaf area, fresh weight, leaf
chlorophyll content and harvest index.The shade levels of 50% were optimal for both the
cut greens and as a result recorded better chlorophyll content and photosynthetic rate at
this level. Among coloured shade net, white shade net has been found to be best for
Cordyline terminalis as plant height, inter-node length, photosynthesis rate, PS 2
efficiency and other important characteristics were superior while same can be said for
red coloured net in case of Dracaena fragrans. Shade nets can be used improve
vegetative growth, yield, vase life and quality of cut foliage while colour shade nets
provide a new, multi-benefit tool for crop protection. It changes the light intensity
and radiation, which influence microenvironment and production. So it can be concluded
that red or white coloured net with 50% intensity provide optimal conditions for superior
performance of cut greens
... However, despite their contrasting physiological and chemical propertiesshade intolerant vs. shade tolerant and N-fixing vs. non-Nfixinglarge differences in growth rate between the acacia nurse crop and H. odorata resulted in suppression of the H. odorata in mixed-species plantations in Vietnam (Tam 2007). In addition, high light intensity affected the leaf structure, function and growth of H. odorata saplings (Lee et al. 1997(Lee et al. , 2000. These findings highlight the importance of achieving a balance between shading H. odorata to protect it from high light intensities and not shading it so much that it dies or its growth stagnates. ...
Background: Young saplings of Hopea odorata, a native dipterocarp in Vietnam, require shading to prevent photoinhibition but they must avoid competition that stagnates their growth.
Aims: To develop a silvicultural regime by examining how the biomass production of H. odorata changes along a light gradient in gaps within Acacia hybrid plantations.
Methods: Hopea odorata saplings were planted in 22-m-diameter circular gaps within a 3-year-old Acacia hybrid plantation and in 5-m and 7.5-m-wide strip gaps within a 2.5-year-old Acacia hybrid plantation.
Results: In the circular gap, biomass growth increased nearly tenfold from the gap perimeter (GP) to about 9 m from the perimeter, and then decreased. This was associated with a fivefold increase in the absorption of photosynthetically active radiation (APAR) and a nearly twofold increase in light-use efficiency (LUE). The increasing APAR was primarily related to increasing H. odorata crown sizes and a reduction in shading from the Acacia hybrid. In the strip gaps, the APAR was similar to that at the GP in the circular gap, however LUE was about threefold higher.
Conclusions: Hopea odorata expressed plasticity in crown structure in response to incident light. While it grows under a wide range of availability of photosynthetically active radiation, growth increases strongly to a certain level of PAR. The best conditions for H. odorata growth were near the centre of the circular gaps, where PAR was 60% of full sunlight, while the strip gaps, where PAR was 20%, were too narrow owing to shading from the Acacia hybrid.
... This effect of water stress on biomass allocation to roots indicates that the combination of shade and drought could impair plant development under long-term exposure to shade. The decreased biomass allocation to roots could also be caused by faulty translocation of photoassimilates from leaves to roots in shaded plants (Lee et al. 1997). This indicates that J. curcas is adapted to dry conditions; however, this vegetative growth was not associated with production Table 2. Biometric indices in physic nut plants (Jatropha curcas L.) during January and June 2011. ...
Jatropha curcas (physic nut) is a plant with economic and pharmaceutical uses. Basic studies on the influence of environmental factors on the early development of J. curcas are important for improving farming techniques and increasing productivity. This study investigated the adjustments of J. curcas to the environmental factors of drought and light stress in order to determine which factors most strongly affect the allocation of biomass during early growth. Leaves, stems, and roots of young plants were sampled and leaf area was measured during January and June in 2011. Plants of J. curcas that were grown in shade and subjected to water stress showed higher biomass allocation to aerial parts (mainly stems), which can be explained as a strategy for maximizing carbon assimilation. The pattern of biomass allocation between aerial components and the root system changed in plants grown in shade. During June 2011, biomass in shade-grown J. curcas was preferentially allocated to stems, indicating long-term adjustment. The lower biomass allocation to the root system suggests reduced exploitation of soil water even when this resource is scarce. Thus, over the long term, growth of J. curcas may be compromised by the combined effects of light stress and water deficit.
... Como conseqüência, o crescimento de muitas plântulas nestas florestas pode ser limitado pela quantidade de luz disponível e muitas desenvolvem estratégias para sobreviverem e se estabelecerem neste ambiente de pouca luz (Osunkoya et al. 1994, Claussen 1996. Por outro lado, plântulas crescendo no interior de uma floresta tropical passam por mudanças bruscas na quantidade de luz, estando sujeitas a incidências de luz que variam com as horas do dia, com as estações do ano, com a movimentação de copas, ou devido à queda de outros vegetais ao redor (Osunkoya & Ash 1991, Lee et al. 1997. ...
... O ambiente de restinga, além da alta insolação apresenta também menor disponibilidade hídrica que o ambiente de florestas (Scarano 2002) e folhas pequenas podem minimizar os prejuízos fisiológicos de estresse de água que seriam causados por uma grande área de transpiração (Poorter 1999). Na floresta, maiores áreas foliares aumentam as superfícies receptoras de luz, proporcionando aumento na captação da luz solar, como ocorre em plantas de locais sombreados (Lee et al. 1997). ...
Enviado em julho de 2010. Aceito em novembro de 2010. RESUMO Guapira opposita é uma espécie arbórea encontrada em ambiente sombreado e úmido da Floresta Ombrófila Densa e em áreas abertas ensolaradas e com baixa disponibilidade hídrica como as de restinga. Este trabalho teve como objetivo comparar as folhas de plantas da floresta e da restinga, buscando conhecer as carcterísticas morfoanatômicas que favorecem a sobrevivência da espécie em ambientes tão distintos. Os resultados mostraram que variação de algumas características entre folhas de floresta e restinga ajuda a explicar a adaptação da espécie a estes ambientes tão diferentes, como área foliar, densidade estomática, espessura das células epidérmicas, espessura da membrana cuticular, espessura da lâmina foliar, em especial do parênquima paliçádico, e teor de clorofilas. Entretanto, a variação na forma e nas dimensões das células-guarda e do poro estomático ocorrida, parece não favorecer a adaptação das plantas aos diferentes ambientes. ABSTRACT Guapira opposita is a tree species that occurs in the shaded and humid environment of the Floresta Ombrófila Densa and in sunny and dry sandbank areas. This work had as objective to compare the anatomical characteristics of the leaves from forest and Este artigo é de Acesso Livre, disponibilizado sob os termos da Creative Commons Attribution 3.0 Unported License (h t t p : / / c r e a t i v e c o m mo n s. o r g / l i c e n s e s / b y / 3. 0 /) que permite uso não-comercial, distribuição e reprodução em qualquer meio, desde que este trabalho original seja devidamente citado.
... Chez certaines espèces, la diminution du ratio rouge clair : rouge sombre (RC:RS) et/ou la diminution de l'intensité de la lumière bleu au sein de la couronne se tradui(sen)t par des modifications morphologiques et anatomiques. Lee et al. (1997), par exemple, ont mis en évidence expérimentalement un effet du ratio RC:RS sur la longueur des pousses et le nombre d'entre-noeuds chez deux espèces d'arbres du genre Hopea. Aphalo et Letho (2001) ont montré un effet positif d'un éclairage enrichi en rayonnement rouge sombre sur la croissance des pousses de Betula pendula. ...
Modelling tree architectural development according to environmental factors is an emerging field of
research thanks to the development of adequate computational methods. However, modelling virtual
plants is greatly constrained by the difficulty in collecting the architectural and geometric data of woody
architecture and foliage. Moreover, partial understanding of functional processes that drive shoot growth
limits the analysis and the modelling of the processes involved. Cross-fertilization of insights into
architectural and morphological variability of Walnut tree on the one hand, and into growth physiology on
the other hand, enables to better understand crown development. Thanks to 3-dimensional measurements
of topology and geometry made on 7 to 9 years-old Walnut trees, we have analysed the impact on light
interception of variables required for virtual plant modelling that are tedious to measure and that render
extrapolation methods necessary. Secondly, we quantified the part of variance of growth variables which
can be explained by radiation intercepted by comparison with other factors such as topological position.
Our results point out the limitations of using allometric relationships and statistical laws for the
reconstruction of 3D canopies. Leaf clumping inside the crown, including the clumping of leaflets at leaf
scale, strongly determines the radiative properties of reconstructed crowns. Thanks to an approach based
on correlations and statistics, an effect of light intercepted by mother shoots on the growth of daughter
shoots was established. Strong correlations between shoot vigour (quantified by an index) and the length
of the pathway between the collar and shoots on the one hand and shoot growth on the other hand
suggest an effect of hydraulic architecture.
... Chez certaines espèces, la diminution du ratio rouge clair : rouge sombre (RC:RS) et/ou la diminution de l'intensité de la lumière bleu au sein de la couronne se tradui(sen)t par des modifications morphologiques et anatomiques. Lee et al. (1997), par exemple, ont mis en évidence expérimentalement un effet du ratio RC:RS sur la longueur des pousses et le nombre d'entre-noeuds chez deux espèces d'arbres du genre Hopea. Aphalo et Letho (2001) ont montré un effet positif d'un éclairage enrichi en rayonnement rouge sombre sur la croissance des pousses de Betula pendula. ...
... Um dos aspectos mais importantes de se conhecer sobre a ecofisiologia das espécies florestais é sua capacidade em responder à variação de luz. A luz é um dos fatores físicos mais importantes no controle do desenvolvimento de plântulas de espécies arbóreas em florestas tropicais úmidas (Lee et al. 1997). As condições de luz para as plantas, ao nível do chão da floresta, são extremamente heterogêneas: a radiação incidente nas folhas próximas ao chão da floresta, devido à atenuação da radiação através dos vários estratos da cobertura vegetal, pode ser cerca de 1 a 2% da radiação incidente nas folhas do dossel, enquanto que em clareiras provocadas pela queda ou retirada de árvores a quantidade de luz pode ser similar à incidente sobre o dossel (Lee et al. 1996). ...
RESUMO Estudo prévio com plantas jovens de Cecropia glazioui crescidas sob tela de polietileno mostrou a resposta destas plantas à variação de luz entre 2% a 50% de luz solar. O presente trabalho pretendeu responder às seguintes questões em relação à resposta de plantas jovens desta espécie à variação de luz entre 50% a 100% de luz solar e sob sombreamento dado por cobertura florestal vegetal em relação aos seguintes aspectos: 1) As plantas apresentam ajuste quando a quantidade de luz varia acima de 50% de luz solar total? 2) Intensidades de luz acima de 50% da luz solar plena, inibem ainda mais o crescimento de plantas? 3) Que alterações no crescimento são verificadas por plantas à variação na quantidade de luz dada? 4) As plantas respondem da mesma maneira ao sombreamento dado por tela de polietileno e ao sombreamento dado por cobertura florestal? Para a verificação destes aspectos as plantas foram colocadas em sacos plásticos de 18 x 13cm, contendo solo de mata e compostagem termofílica, na proporção de 1:1. As plantas foram colocadas a 100%, 70% de luz solar e 50% de luz solar e em borda de mata, clareira pequena e mata fechada. Os resultados obtidos mostraram que a espécie estudada responde da mesma maneira em sombreamentos dado por tela de polietileno e sombreamento florestal. A espécie não apresentou ajuste morfológico ou fisiológico, quando a intensidade luz variou acima de 50% de luz solar. Também a intensidade de luz acima de 50% da luz solar não inibiu o crescimento da espécie. As principais alterações significativas, verificadas no crescimento, de acordo com o aumento na quantidade de luz foram: diminuição da razão raiz/ parte aérea (R/PA), da área foliar específica (AFE), da razão de área foliar (RAF) e da altura do caule e do aumento da capacidade fotossintética. Este artigo é de Acesso Livre, disponibilizado sob os termos da Creative Commons Attribution 3.0 Unported License (h t t p : / / c r e a t i v e c o m m o n s . o r g / l i c e n s e s / b y / 3 . 0 /) que permite uso não-comercial, distribuição e reprodução em qualquer meio, desde que este trabalho original seja devidamente citado.
... O ambiente de restinga, além da alta insolação apresenta também menor disponibilidade hídrica que o ambiente de florestas (Scarano 2002) e folhas pequenas podem minimizar os prejuízos fisiológicos de estresse de água que seriam causados por uma grande área de transpiração (Poorter 1999). Na floresta, maiores áreas foliares aumentam as superfícies receptoras de luz, proporcionando aumento na captação da luz solar, como ocorre em plantas de locais sombreados (Lee et al. 1997). ...
Guapira opposita is a tree species that occurs in the shaded and humid environment
of the Floresta Ombrófila Densa and in sunny and dry sandbank areas. This work had
as objective to compare the anatomical characteristics of the leaves from forest and sandbank, looking for differences that can favor the survival of the species in such
different environments. The results showed that the variation of some characteristics
between forest and sandbank leaves help to explain the adaptation of the species to
these environments, as leaf area, stomatal density, chlorophyll contents and thickness
of epidermal cells, cuticle membrane and leaf blade. The form of leaves, the guard
cell dimensions and stomatal pore size, on the other hand, did not show clear
behaviour related to the variation in the light intensity.
... In between 1950-2450 nm range there was no significant difference, hence 720-1360 nm range can be used for identification of different colour shade nets. The response of a plant to shading conditions depends on the complex interaction between quality and quantity of the incident light (Lee et al., 1997). Percentage reflectance as observed in our study had higher value in colour shade nets than control except in white shade nets. ...
Field experiment was undertaken at research farm of IARI, New Delhi to study the effect of
change in the microenvironment under different colour shade nets during summer and rainy season, of
2012 on yield of spinach. Spinach crop was sown under different colour shade nets such as red, green,
black, white along with control (without shade net) during summer and rainy season. Crop duration from
sowing to harvesting was 62 days in summer and 58 days in rainy season. Different weather parameters
were measured at regular interval in each treatment. Results showed that the light intensity, incoming
radiation, canopy temperature, air temperature, soil temperature were found to be lower under different
colour shade nets compared to the control. However the relative humidity, soil moisture were found to be
higher under colour shade nets compared to control.
... In a shade-house experiment, Lee et al. (1997) found that H. odorata seedling growth and photosynthetic rate can respond positively up to PAR levels of 40% of that experienced in an open area. Thus while H. odorata requires a relative incident PAR of around 11% to initiate active growth in its natural environment, greater levels of disturbance may lead to its more rapid development. ...
Matching species to suitable sites is important in reforestation. This study investigated the site conditions that support regeneration of Hopea odorata, a valuable timber species, in a secondary evergreen natural forest. Stand structure, light intensity at seedling level and soil condition were examined in three representative 50 × 50 m plots. The upper canopy was dominated by four dipterocarps: H. odorata, Shorea roxburghii, Anisoptera costata and Dipterocarpus alatus. The prevailing stand structure supported vigorous germination but not development of seedlings of all four species. Low light levels near the forest floor were the major constraint on seedling development of H. odorata. There was no regeneration when the mean per cent transmitted incident daily photosynthetic active radiation (PAR) was 2.2%; seedling germination but not development was supported when PAR was 6.6%; regeneration and development occurred when PAR was 11.4%. The soils were slightly acidic with low clay and high sand contents and low nutrient concentration, but this was apparently not a constraint on growth given adequate light conditions. The results suggest that the re-establishment of H. odorata on degraded sites using nurse crops should be possible provided that high levels of shading are avoided.
... In between 1950-2450 nm range there was no significant difference, hence 720-1360 nm range can be used for identification of different colour shade nets. The response of a plant to shading conditions depends on the complex interaction between quality and quantity of the incident light (Lee et al., 1997). Percentage reflectance as observed in our study had higher value in colour shade nets than control except in white shade nets. ...
Field experiment was undertaken at research farm of IARI, New Delhi to study the effect of
change in the microenvironment under different colour shade nets during summer and rainy season, of
2012 on yield of spinach. Spinach crop was sown under different colour shade nets such as red, green,
black, white along with control (without shade net) during summer and rainy season. Crop duration from
sowing to harvesting was 62 days in summer and 58 days in rainy season. Different weather parameters
were measured at regular interval in each treatment. Results showed that the light intensity, incoming
radiation, canopy temperature, air temperature, soil temperature were found to be lower under different
colour shade nets compared to the control. However the relative humidity, soil moisture were found to be
higher under colour shade nets compared to control.
... However, the prevalence of each one of these changes is highly variable depending on the characteristics of each species, and the quantification thereof may help to improve conditions for growing plants. Based on the widely-known susceptibility of the leaves and morphological/anatomical variations in the plant-environment relation (Lee et al., 1997), this study was aimed at characterizing and analyzing the leaf anatomical plasticity of African oil palm seedlings formed from the rescue and cultivation of zygotic embryos in vitro and the germination of pre-germinated seeds in greenhouse. ...
Changes in the leaf structure of plants grown in different conditions have been reported, such as increase in size and density of stomata and reduction in stomatal control, amount of epicuticular wax, and mesophyll thickness, with a high diversity of intercellular spaces. However, these changes are highly variable depending on the physiological and morphological characteristics of each species. The objective of this work was to analyze the adaptability and anatomical plasticity of oil palm seedlings produced after embryo rescue and pre-germinated seeds. Expanded leaves were prepared for evaluation of morphometric data and anatomical structures. It was verified that the environmental conditions in vitro negatively influenced the stomata density, epidermal and hypodermal thickness, and the values for the expansion cells and leaf mesophile. Anatomically, the oil palm leaves present the same tissues composition in both growth conditions, with uniseriate epidermal cells, and tetracitic stomata occurring in both epidermal surfaces. Epidermal cells from in vitro plants are thinner than ones from greenhouse. The midrib of leaves from greenhouse plants are more developed and is composed by only one central vascular bundle, while plants from in vitro cultivation developed three to four collateral vascular bundles.
... Diferenças no comprimento da ráquis e no número de pinas foram detectadas entre os indivíduos adultos e jovens dessa espécie. O maior comprimento da ráquis nos indivíduos jovens pode estar indicando a influência da baixa razão vermelho/vermelho distante que predomina no sub-bosque (LEE et al., 1997). O aumento em extensão de caule e, ou, pecíolo tem sido considerado típica resposta morfogênica que ocorre em condições de sombra natural (APHALO e BALLARÉ, 1995), resultando em maior probabilidade de captura de radiação luminosa. ...
Caesalpinia echinata Lam. (Caesalpiniaceae) is a tree species that naturally regenerates in the forest understory and reaches the upper canopy through small gaps. We conducted a study with the objective of comparing some aspects of leaf morphology of adult individuals, in which the leaves were exposed to full sunlight, and saplings, grown in the forest understory. The study was conducted in a semidecidual forest in Jussari, southern Bahia, Brazil. Initially, eight adult and eight sapling individuals were selected and marked. In September/October, 2004 and April, 2005 eight leaves for each adult and three leaves for each sapling individual were collected and analyzed. In general, the area of leaves, rachis and leaflets, the length of rachis, the width of leaves, the number of pinnes and the dried mass of leaves were significantly higher in young individuals. Notwithstanding, the specific mass of leaves and leaflets were significantly higher in the adults. For both, adults and saplings, strong relationships were observed between the leaf dried mass and leaf area. Based on the results, we conclude that the leaves of C. echinata present characteristics that allow the maximization of light absorption in environments in which light radiation is a limiting factor, at the same time allocating carbon to the support tissues. The results obtained in the present study were in accordance with the successional status of this tree species and its strategies to occupy small canopy gaps of the semidecidual forest environments.
... Como conseqüência, o crescimento de muitas plântulas nestas florestas pode ser limitado pela quantidade de luz disponível e muitas desenvolvem estratégias para sobreviverem e se estabelecerem neste ambiente de pouca luz (Osunkoya et al. 1994, Claussen 1996. Por outro lado, plântulas crescendo no interior de uma floresta tropical passam por mudanças bruscas na quantidade de luz, estando sujeitas a incidências de luz que variam com as horas do dia, com as estações do ano, com a movimentação de copas, ou devido à queda de outros vegetais ao redor (Osunkoya & Ash 1991, Lee et al. 1997. ...
Plantas sob forte sombreamento (2% ou 6% da luz solar direta) apresentaram, em relação às plantas sob maior nível de luz, menor biomassa, menores taxas de crescimento, menor razão raiz/parte aérea, menor massa foliar específica (MFE), menor razão clorofila a/b e maior razão de área foliar (RAF). Com o aumento da irradiância as plantas apresentaram três tipos de comportamento, dependendo da quantidade de luz dada: 1) até cerca de 20% da luz solar direta as plantas apresentaram, com aumento da luz, aumento de biomassa, das taxas de crescimento relativo (TCR) e de assimilação líquida (TAL), maior alocação de biomassa para a raiz, maior número de folhas, maior MFE, maior razão clorofila a/b e menor razão de peso foliar (RPF) e RAF; 2) entre 20% e 70% de luz as plantas não mostraram alterações morfológicas ou fisiológicas com aumento na quantidade de luz, à exceção de um aumento na razão clorofila a/b; e 3) plantas crescendo em luz solar plena apresentaram uma redução do crescimento em massa seca. As plantas transferidas de 4% para 20 ou 30% de luz mostraram respostas similares àquelas das plantas crescidas sempre em mais luz. A densidade de estômatos mostrou uma leve tendência ao aumento em plantas transferidas para maior quantidade de luz. O menor crescimento em níveis mais fortes de sombreamento e o maior crescimento com aumento de irradiância até 20-30% da luz solar total sugere que a espécie possa se beneficiar do aparecimento de clareiras para sua regeneração. O menor desempenho das plantas em condições de luz plena ou forte sombreamento sugere menor capacidade competitiva da espécie em grandes clareiras ou sob dossel fechado.
... Levels of light required to saturate photosynthesis increased from the gap edge where saturation occurred at PAR levels of about 500 µmol m -2 s -1 , to the trees at 9 m from gap edge (Figure 1b). Lee et al. (1997) also found that H. odorata seedling growth and photosynthetic rate respond positively up to PAR levels of 40% of incident light. Thus, while H. odorata has a minimum light requirement for active growth to be initiated in its natural environment, greater levels of light lead to more rapid seedling growth and adaptation to higher light conditions. ...
... However, its influence on seedling growth varied according to the species and the growing season. Seedling growth and morphology depended not only on light availability (GSF), but also on its spectral quality (R:FR), which highlights the importance of this factor as a mediator of seedling performance in tree species (Lee et al. 1997; Ammer 2003; Tegelberg et al. 2004 ). In shade conditions (i.e. in microsites with lower values of R:FR and GSF), seedlings of the three studied species were taller, sometimes at the expense of increased thinness of their stems (higher SSL). ...
Question: What is the relative importance of seed mass and abiotic factors in species-specific seedling growth and morphology during the first and the second growing season? How do oak species respond along gradients of these factors?
Location: Mediterranean oak forest in southern Spain.
Methods: We analysed seedling growth components and morphology of three co-occurring Quercus species (two deciduous and one evergreen). Oak seeds with a wide variety of sizes were sown along broad gradients of abiotic conditions. Intra- and inter-specific differences were evaluated by calibrating maximum likelihood estimators of seedling growth during the first two years of life.
Results: We found multiple resources and conditions affecting seedling morphology and biomass allocation. However, the integrative variables of seedling growth – total aboveground biomass and relative growth rate (RGR) – were affected by two main factors: seed mass and light conditions. The relative contribution of these two factors depended strongly on seedling age. Seed mass explained most of the growth and morphological variables during the first year, while light conditions were the best predictor in the second growing season. In contrast, soil factors did not play an important role in seedling growth. We found some evidence of regeneration niche partitioning between oak species along the light gradient, a reflection of their distribution patterns as adults at the study site.
Conclusions: We conclude that inter-specific differences in seedling growth, arising from seed size variability and microsite heterogeneity, could be of paramount importance in oak species niche segregation, driving stand dynamics and composition along environmental gradients.
... One half of each shade-house was exposed to low light (1.5% full sun and a red:far red ratio of 0.28), mimicking conditions within a typical hemlock stand (Kozlowski et al. 1991; Canham et al. 1994), and the other half was exposed to high light (60% full sun and a red:far red ratio of 1.1), simulating conditions in a multiple tree-fall forest gap (Bazzaz & Wayne 1994). Light quantity was manipulated using dierent grades of neutral shade-cloth, while light quality was simultaneously altered with coloured ®lter plastic placed beneath the shade-cloth (Lee et al. 1997). We placed vertical slits in sections of the shade-cloth not receiving direct sunlight to ensure adequate ventilation within the shade-houses and prevent temperatures from climbing much above ambient air temperature. ...
1 When a species influences conditions at a site to promote recruitment of conspecifics, the community may remain dominated by that species until the next major disturbance. We examined the occurrence of possible mechanisms for such a positive feedback in one community where it may be important: forests dominated by eastern hemlock (Tsuga canadensis).
2 Intact soil divots were collected from a hemlock stand in central Massachusetts, USA, and placed in shade-houses at either 1.5% or 60% full sun. Soil was amended with nitrogen (5 g m−2 year−1), lime (1 kg m−2 year−1; to increase soil pH) or left untreated. Emergence, survival and growth of seedlings arising from the soil seed bank were subsequently monitored.
3 Light availability had a very large influence on seedling regeneration dynamics. Birch (Betula spp.) seedlings were most sensitive of all species to light availability, with low light reducing emergence by 43% and substantially decreasing seedling growth (by 99%) and survival (by 94%). In contrast, light treatments had smaller effects on performance of other species [hemlock and white pine (Pinus strobus)]. Birch survival was also increased by nitrogen addition, but only in low light. Liming had only marginal effects on seedling performance.
4 Differential seedling responses to resource availability led to dominance of final seedling communities by hemlock in low light, unamended soils (i.e., under conditions naturally found in hemlock stands), but by birch in high light, as well as in low light, nitrogen-amended soils.
5 Positive feedbacks in hemlock stands are mediated both by availability of light and nitrogen, and by species’ life-history strategies.
... Changes in radiation quality, in terms of the ratio of red radiation (RR) to far red radiation (FR), occur naturally within the forest canopy, as the transmitted radiation and reflected radiation on a forest floor have lower ratios of red to far-red photons than does incident radiation on the forest canopy (Kozlowski et al. 1991, Chazdon et al. 1996. The influence of RR:FR ratio on the photosynthetic characteristics of plants is relatively small, compared with that of radiation quantity (Schmitt and Wulff 1993, Hinsberg and Tienderen 1997, Lee et al. 1997. The perception of radiation quality, in terms of RR:FR, by phytochromes provides plants with a sensitive mean of detecting and responding to vegetation shade, and allows them to sense future competition, thus triggering morphological and physiological responses to avoid shading (Ballaré et al. 1987, 1990, Kendrick and Kronenberg 1994, Smith and Whitelam 1997. ...
Radiation quality was an important environmental cue to stimulate seed germination in Acacia mangium. The photo-synthetic CO2 assimilation rate, dark respiration rate, total biomass, and relative growth rate of seedlings grown under monochromatic radiation were significantly lower than those of seedlings grown under full spectrum radiation. Blue and red radiation induced shade-avoidance and shade-tolerant responses of A. mangium seedlings, respectively.
... The ratio of stem mass per length, which documents the robustness of the stem, was greater under the canopy for almost the species studied. Similar results were obtained by Lee (1988) with three Asian tropical leguminous vines species as well as for Asian tropical rain forest tree (Lee et al. 1996(Lee et al. , 1997. ...
Species composition and forest structure change with topography.However, mechanisms for topographical vegetation changes are still not wellunderstood, because a topographical gradient is a complex environmentalgradientinclusive of many factors. The foot of Mt. Kinabalu is covered with three typesof geological substrates, i.e. Quaternary and Tertiary sedimentary rocks andultrabasic (serpentine) rock. Quaternary and Tertiary sedimentaryrocks are different in site age, but controlled in primary minerals. Tertiarysedimentary and ultrabasic rocks are contrasting in primary minerals, but arecomparable in age. This setting provides an opportunity to examine thevegetation differentiation along topographical gradients that are contrastinginmajor-nutrient supply due to the difference in site age and parent rock.We established a total of nine study plots by choosing three topographicalunits(ridge, middle- and lower-slope) on each substrate inthe tropical lower montane forest. Pool size and supply of soil N and Pdecreased upslope on each substrate, and the magnitude of the reduction fromslope to ridge decreased in the order of Quaternary sedimentary > Tertiarysedimentary > ultrabasic rock. Between-substrate difference in soilnutrient condition was greater on the lower-slopes than the ridges.Maximum tree size decreased and stem density increased upslope on eachsubstrate. Detrended correspondence analysis demonstrated that speciescomposition also changed along topographical gradients on all substrates.However, the magnitude of topographical changes in forest structure and speciescomposition varied with substrate and decreased from Quaternary sedimentary>Tertiary sedimentary > ultrabasic rock. The greatest between-substratedifference in vegetation occurred on the lower-slopes. Accordingly, ourresults suggest that the magnitude of vegetation changes due to topographybecomes smaller with decreasing pool size and supply of nutrients.
... This photoinhibition is associated with reductions in quantum yield, photochemical efficiency, and capacity of photosynthesis, and acceleration of nonphotochemical quenching (Demmig et al. 1987). The morphological and physiological acclimation of plants to different I (Lee et al. 1997, Logan et al. 1998, Smith et al. 1998, Poorter 1999 ) and short-term acclimation after a sudden change in I over a duration of several h or d (Langenheim et al. 1984, Öquist et al. 1992, Kitao et al. 2000) have often been studied. After gap formation, acclimation of the understorey plants to the new environment may take much longer time (several weeks or even months). ...
We investigated the acclimation of seedlings of three tropical rain forest sub-canopy Garcinia species (G. xanthochymus, G. cowa, and G. bracteata) after transfer from 4.5 (LI) to 40 % (HI) sunlight and 12.5 (MI) sunlight to HI (LH1 and LH2 denoting transfer from LI to HI and MI to HI transfer, respectively). The changes of chlorophyll (Chl) fluorescence, net photosynthetic rate (P
N), dark respiration rate (R
D), Chl content per unit area (Chlarea), leaf mass per unit area (LMA), and seedling mortality were monitored over two months after transfer. These parameters together with leaf anatomy of transferred and control seedlings (kept in LI, MI, and HI) were also examined after two months. No seedlings died during the two months. Fv/Fm, P
N, and Chlarea of the transferred seedlings decreased in the first 3 to 12 d. LH1 leaves showed larger reduction in Fv/Fm (>23 % vs. <16 %) and slower recovery of Fv/Fm than LH2 leaves. P
N started to recover after about one week of I transfer and approached higher values in all G. cowa seedlings and G. xanthochymus LH1 seedlings than those before the transfer. However, P
N of G. bracteata seedlings approached the values before transfer. The final P
N values in leaves of transferred G. xanthochymus and G. cowa seedlings approached that of leaves kept in HI, while the final P
N values of transferred leaves of G. bracteata were significantly lower than that of leaves grown under HI (p<0.05). R
D of G. xanthochymus LH1 seedlings and all G. cowa seedlings increased and approached the value of the seedlings in HI. The final Chlarea of both G. xanthochymus and G. cowa approached the values before transfer, but that of G. bracteata did not recover to the level before transfer. The final Chlarea of all transferred seedlings was not significantly different from that of seedlings in HI except that G. cowa LH1 seedlings had higher Chlarea than that in HI. LMA decreased within 2 d and then increased continuously until about 30 d and approached the value under HI. Spongy/palisade mesophyll ratio decreased after transfer because of the increase in palisade thickness. Leaf thickness did not change, so LMA increase of transferred seedlings was mainly due to the increase of leaf density. Thus the mature leaves under LI and MI of G. xanthochymus and G. cowa are able to acclimate to HI by leaf physiological and anatomical adjustment, while G. bracteata had limited ability to acclimate to HI.
Understanding the requirements and tolerances of the seedlings of climax species is fundamental for tropical forest restoration. This study investigates how the presence and abundance of seedlings of a previously dominant, now threatened species (Dipterocapus dyeri Pierre), varies across a range of environmental conditions. Dipterocapus dyeri seedling abundance and site characteristics were recorded at 122 observation points (4 m²) at nine clusters from two sites. Seedling presence (p = 0.065) and abundance varied significantly (p = 0.001) between the two sites, and was strongly correlated with adult D. dyeri dominance and lower soil pH, and weakly correlated with canopy openness and total stand basal area. Dipterocarpus dyeri seedlings were also grown in shade houses with three light levels on two soils. Seedling survival was significantly lower at the lowest light level (<10% full irradiance) at 13% for the forest soil and 25% for degraded soil. At higher irradiance the seedling survival rates were greater than 99%. Moisture levels remained high at the lowest light level and many seedlings died from fungal infection. We concluded that secondary forests which contain adequate numbers of adult D. dyeri as seed sources, light availability, soil pH of < 5.0, and good drainage strongly favour survival and growth of D. dyeri seedlings. Historically, D. dyeri was dominant in moist deciduous tropical forest across south-eastern Vietnam, but today it is rare. Active management of these recovering forests is essential in order to recover this high-value, climax forest species.
By means of meta‐analyses we determined how 70 traits related to plant anatomy, morphology, chemistry, physiology, growth and reproduction are affected by daily light integral (DLI; mol photons m⁻² d⁻¹). A large database including 500 experiments with 760 plant species enabled us to determine generalized dose–response curves. Many traits increase with DLI in a saturating fashion. Some showed a more than 10‐fold increase over the DLI range of 1–50 mol m⁻² d⁻¹, such as the number of seeds produced per plant and the actual rate of photosynthesis. Strong decreases with DLI (up to three‐fold) were observed for leaf area ratio and leaf payback time. Plasticity differences among species groups were generally small compared with the overall responses to DLI. However, for a number of traits, including photosynthetic capacity and realized growth, we found woody and shade‐tolerant species to have lower plasticity. We further conclude that the direction and degree of trait changes adheres with responses to plant density and to vertical light gradients within plant canopies. This synthesis provides a strong quantitative basis for understanding plant acclimation to light, from molecular to whole plant responses, but also identifies the variables that currently form weak spots in our knowledge, such as respiration and reproductive characteristics.
Although all the trees that compose a mature forest originate as seedlings on the forest floor, the composition of a seedling or sapling community of ten differs from that of the adult trees. While this discrepancy may signal a shift or fluctuation in the forest (see Chapter 6), it can be attributed to demographic behaviors of each species (e.g., Harcombe 1987; Aiba and Kohyama 1997). To understand the maintenance mechanisms of a forest community, or to predict the forest dynamics, we must consider the seedling and sapling stages, since they, as well as the seed stage, are the stages subject to drastic demographic changes (see Chapter 1). Following on the previous chapters of this volume on seed production (Chapter 9), dispersal (Chapter 10), and dormancy and germination (Chapter 11), I describe the young tree community in Ogawa Forest Reserve (OFR) in this chapter, especially as it relates to forest disturbances.
Introduction This chapter focuses on phylogenetically diverse groups of plants that do not have typical life history strategies as seedlings, juveniles, and mature individuals. Plants that live on other plants are classified as epiphytes, and they include both vascular and nonvascular species (Benzing, 1990). Tropical orchids and bromeliads comprise the vast majority of epiphytic flowering plants. However, orchids are global in their distribution and many are terrestrial (Dixon et al., 2003). Carnivorous plants are also globally distributed, occurring in many types of ecosystems (Lloyd, 1976), as are parasitic plants (Press & Graves, 1995). The ability of seedlings to establish in habitats with extreme limiting resources is one of the few factors that links the diverse plants covered in this chapter. Epiphytes, for example, must initially become established on structures (i.e. branches) where resources are scarce. Once established, epiphytes may have to deal with combinations of stresses, including aridity, few available nutrients, and either high or low light conditions. Carnivorous plant species and many terrestrial orchids occur in habitats where nutrients or light are limiting. Many parasitic plants (e.g. mistletoes) also occur in resource-limited environments. One of our approaches to organizing this chapter is to determine if seedlings differ in their physical or ecological characteristics in a manner similar to mature plants. The literature has few examples of investigations focusing specifically on seedlings. As an example, in the seminal book on Bromeliaceae, Benzing (2000) did not consider seedlings as a separate heading.
A part of the Pasoh Forest Reserve (Pasoh FR) was once logged under a logging regime called the Malayan Uniform System (MUS) in the 1950s. The core area of the reserve is a residual unlogged (primary) forest that shows the typical structure and species composition of lowland dipterocarp forest; the logged area of the reserve is also a relict area of regenerating lowland forest. In this chapter, we review and summarize previous studies of logging impacts on the forest structure and total aboveground biomass by comparing the primary and regenerating forests of this reserve. We also studied landscape changes in the Pasoh Forest Region in order to discuss the relationship between logging history in this region and its impacts on the forest. From a chronological analysis of the changes in land use in this region, we found that ca. 50% of the forested area had been converted to either oil palm or rubber plantations from 1971 to 1996. Almost all of the lowland dipterocarp forest that had developed in the flat and alluvial topography had vanished from this region, except in the Pasoh FR. Thus, very little area was left to be managed by the MUS approach, which was originally designed for extracting timber with a longer logging cycle (>70 years) in this type of forest. By examining the canopy and stand structure and the species composition of these forests, we found a greater density of semi-medium (6-10 cm in diameter) and medium trees (10–30 cm), a higher density of canopy-forming trees with relatively smaller crowns, and a higher density of non-commercial canopy-forming trees in the regenerating forest. These findings suggest that the MUS was incompletely implemented, since this system originally aimed to encourage the development of a uniform forest structure with a large number of sound commercial timber trees by removing noncommercial trees. Owing to the high density of canopy-forming trees, which probably resulted from incomplete post-logging thinning and vegetation-control operations, structural development was delayed in the regenerating forest. In addition, the species composition and the distribution of wildlife in the regenerating forest differed from those in the primary forest. We also found that the total aboveground biomass in the regenerating forest had not fully recovered to the level in the primary forest even 40 years after logging. We suggest that “follow-up operations” should be undertaken, with a special concern for encouraging the structural development of the stand, which we consider to be crucial for ecologically sustainable management.
O uso de telas coloridas representa um novo conceito agrotecnológico, que pretende combinar a proteção física das plantas com a filtragem seletiva da radiação solar para promover respostas fisiológicas desejáveis, reguladas pela luz. O objetivo deste trabalho foi verificar o efeito do sombreamento com telas coloridas sobre características biométricas, anatômicas e fisiológicas de Artemisia vulgaris. As plantas foram cultivadas em vasos distribuídos inteiramente ao acaso sob os tratamentos de tela colorida tipo Cromatinet (50%) vermelha, azul e pleno sol (sem tela). Os resultados indicam que as variáveis analisadas de A. vulgaris foram mais afetadas pela intensidade luminosa do que pela qualidade espectral da luz. O diâmetro do caule e o número de grãos de amido foram indiferentes aos tratamentos, enquanto as variáveis altura, relação raiz:parte aérea, espessura foliar, teor de clorofila e carotenóides foram influenciadas pela intensidade luminosa. A área foliar, a biomassa seca da planta e o número de cloroplastídeos foram afetados tanto pela intensidade quanto pela qualidade do espectro luminoso incidente.
Field experiment was undertaken at research farm of IARI, New Delhi to study the effect of change in the microenvironment under different colour shade nets during summer and rainy season, of 2012 on yield of spinach. Spinach crop was sown under different colour shade nets such as red, green, black, white along with control (without shade net) during summer and rainy season. Crop duration from sowing to harvesting was 62 days in summer and 58 days in rainy season. Different weather parameters were measured at regular interval in each treatment. Results showed that the light intensity, incoming radiation, canopy temperature, air temperature, soil temperature were found to be lower under different colour shade nets compared to the control. However the relative humidity, soil moisture were found to be higher under colour shade nets compared to control.
Maize-soybean intercropping is a common system in several countries. However, different spatial patterns of maize and soybean can directly affect the light environment of soybean growth under this system through the combined effects of the altered light quality and the reduced light quanta. This work aimed to investigate the differences in the light environment of the soybean canopy in terms of the red:far-red (R/FR) ratio and the photosynthetically active radiation (PAR) as well as the different rates of soybean seedling growth under maize-soybean relay strip intercropping and soybean sole planting, to analyze the relationship between the morphological characteristics and the light environment, and to assess the relative contributions of the R/FR ratio and PAR transmittance to soybean seedling growth in intercropping conditions.
The liana Artabotrys hexapetalus (L.f.) Bhand., which is widely planted in the Tropics and native to African rain forests, produced new reiterations (new leader shoots) normally and after damage induced by Hurricane Andrew (August 24, 1992). In each new orthotropic shoot, there is a gradient in lateral branch structures from basal thorns, to vegetative leafy branches, to distal leafy flowering branches. We noted that reiterations developing in shade had more thorns than similar reiterations developing in full sun. Tents with clear (66% photosynthetically active radiation [PAR]) and shaded plastic film (12%–14% PAR) were placed over nodes when the axillary buds began to expand to produce reiteration shoots. After 2 mo of growth inside the tents and in the open, the types of lateral outgrowths (thorn vs. branch) were recorded. Shoots in spectrally neutral shade (red to far red of full sun) and spectrally altered shade (red to far red of canopy shade) produced significantly more thorns at the lower nodes of the shoots as compared to those in full sun. Shoots in control clear plastic tents were the same as those in full sun. We conclude that the fate of lateral bud development is controlled by irradiance (light level) but not by light quality. Increased thorn production in shade could be advantageous to plants growing in the deep shade of rain forests. Thorns in the self-shaded regions of the plant, and well below the forest canopy, could aid in protection from herbivory and in climbing by acting as hooks.
To elucidate whether dipterocarp species, dominant late-successional species of tropical forests in Southeast Asia, actually have a disadvantage when planted on open site in terms of their photosynthetic characteristics, we investigated photosynthesis in dipterocarp seedlings planted in the open on degraded sandy soils in southern Thailand. These species were compared with seedlings of Acacia mangium Willd., a fast-growing tropical leguminous tree, which is often planted on degraded open site in Southeast Asia. The dipterocarp seedlings had an irradiance-saturated net photosynthetic rate (P
N), stomatal conductance (g
s), carboxylation efficiency, and photosynthetic capacity comparable to or superior to those of A. mangium. In particular, seedlings of Dipterocarpus obtusifolius Teijsm. ex Miq. showed an irradian-ce-saturated P
N of 21 µmol m−2 s−1, a value higher than any previously reported for a dipterocarp species, accompanied by high g
s (0.7 mol m−2 s−1) and high photosynthetic capacity. Thus dipterocarp species do not necessarily have a disadvantage in terms of their photosynthetic characteristics on open sites with degraded sandy soils.
Seedlings of the red mangrove, Rhizophora mangle L., were grown under light conditions differing in both photosynthetic photon flux density (PPFD) and spectral quality (red:far-red ratio, R:FR). During the first 8 mo of development, parameters of stem, leaf, and root growth were affected by PPFD. Significant responses to lowered R:FR, however, were limited to internode extension. The results are moderately indicative of a strategy to persist in shade, but illustrate the complexity of light responses and suggest that precise categorization as shade-tolerant or -intolerant may be unbefitting for this species at this particular stage of development.
Distributions of many humid tropical tree species are associated with specific soil types. This specificity most likely results
from processes at the seedling stage, but light rather than nutrient levels is generally considered the dominant limitation
for seedling growth in the tropical forest understory. If nutrients are limiting and allocation to belowground resources differs,
seedling growth responses to shade should also differ. Here we tested the effects of soil type and light environment on the
seedling growth of two canopy tree species in the genus Inga with different soil-type and light-environment affinities as adults. Inga alba is a shade-tolerant soil generalist and I. oestediana is a light-demanding soil specialist. We used four native soils and three light levels (1 and 5% of full sun in shade houses
and the forest understory). All growth variables were greatest in 5% full sun, with highest growth rates for the light-demanding
soil-type specialist. Soil type significantly affected growth parameters, even at the lower light levels. The specialist grew
best on the soils with the most soil phosphorus where adult trees typically occur. Leaf tissue nitrogen:phosphorus ratios
suggest increased phosphorus limitation in the low phosphorus soils and with increased light level. Light and soil interacted
to significantly affect seedling biomass allocation, growth, and net assimilation rates, indicating that the seedling shade
responses were affected by soil type. Seedlings growing on high nutrient soil allocated less to roots and more to photosynthetic
tissue. Adult distributions of these two Inga species may be a result of the different growth rates of seedlings in response to the interactive effects of light and soil.
An experiment was conducted with Heliocarpus appendiculatus, a pioneer or large gap species of tropical moist forest in Costa Rica, and Dipteryx panamensis, a small gap species. Seedlings were grown in full sun, partial (80%) shade, and full (98%) shade. After one month of growth they were switched between environments and grown for two more months.
Growth in height of Heliocarpus was greatly affected by irradiance, being increased in response to full shade and decreased in full sun. Height of Dipteryx was unaffected by irradiance level. Survival of Heliocarpus seedlings was only 49% in full shade, whereas Dipteryx had 100% survival. Biomass of Heliocarpus was not significantly greater in full sun than in partial shade whereas it was for Dipteryx. The response of root: shoot ratio was similar for both species. They were lowest in full shade and highest in full sun. Heliocarpus exhibited greater changes in leaf thickness, specific leaf weight, and stomatal density than did Dipteryx. Stomatal conductance of both species was lower in full shade and full sun than in partial shade.
The results of the experiment indicate that growth of Heliocarpus is more plastic than that of Dipteryx in response to changes in irradiance. Previous environment did not affect the response to the present environment in either species. Both species responded positively to increases in irradiance.
Seedlings of six subtropical rainforest tree species representing early (Omalanthus populifolius, Solanum aviculare), middle (Duboisia myoporoides, Euodia micrococca) and late (Acmena ingens, Argyrodendron actinophyllum) successional stages in forest development were grown in a glasshouse, under four levels of neutral shade (60%, 15%, 5%, 1% of photosynthetically active radiation (PAR) in incident sunlight) and three levels of selectively filtered shade (producing 15%, 5%, 1% of PAR). This design served to analyse the interactions between reduced photon flux density (PFD) and reduced red/far-red (R/FR) ratio in their effects on selected photosynthetic characteristics of each species. The light-saturated rate of photosynthesis was significantly influenced by growth irradiance in five of the six species, with all of these showing a non-linear decrease in maximum assimilation rate from 60% down to 1% PAR. The degree of acclimation to this range was not clearly related to the successional status of the species. Dark respiration was more sensitive to growth irradiance in the early- and mid-stage species than in the late-stage species. Although levels of dark respiration were clearly greater in leaves of early- and mid-stage species from the highest light levels, differences between successional groups were negligible at 1% PAR. Growth in filtered shade, typical of that beneath a closed canopy, resulted in lower photosynthetic capacities and quantum yields in those species which did respond. Although dark respiration rates were more sensitive to filtered shade in the early-stage than in the late-stage species, there was no evidence from other gas exchange characteristics to suggest that overall sensitivity to light quality (as characterised by the R/FR ratio) is greater in early successional-stage species.
A comparison is made of the light acclimation potential of seedlings of three canopy species of the tropical rain forest of Los Tuxtlas, Mexico: Cordia megalantha, Lonchocarpus guatemalensis, and Omphalea oleifera. These species showed similar growth rates in a range of microhabitats. Gap dynamics were simulated by transferring plants between three environments: beneath a closed canopy, a small gap, and a large gap. Plants of all three species were able to adjust their morphology and growth rates in response to changes in light availability. Growth rates increased when plants were moved to a (larger) gap, and decreased when plants were moved to a more shaded environment. Shade-grown plants were able to acclimate faster to increasing light availability than sun-grown plants to decreasing light availability. Also, plants moved from shady to sunny conditions showed higher relative growth rates than sun control plants, whereas sun-grown plants when moved to the shade showed lower relative growth rates than shade control plants. Species differed in their response to gap dynamics. Omphalea could not acclimate morphologically to shading, but reacted faster than the other species in response to the occurrence of a large gap. Acclimation potential seemed to be related to plasticity in physiological rather than in morphological traits. Suppressed seedlings of all three species performed well in the shade, and were able to acclimate rapidly to gap-conditions.
1. The role of light quality and quantity on steady-state photosynthetic characteristics, efficiency of lightfleck utilization (LFUE) and growth was evaluated in seedlings of tropical rain-forest trees. 2. The pioneer species, Cecropia obtusifolia and Heliocarpus appendiculatus, and the shade tolerant species, Rheedia edulis, were grown in a greenhouse under contrasting red/far-red (R/FR) ratios characteristic of the open and the shaded forest understorey but with the same low photosynthetically active radiation (PAR). Additionally plants were grown in a high PAR environment with a R/FR characteristic of the open. 3. The pioneer species responded strongly to R/FR in terms of greater height growth and a shift in allocation to stem growth over leaf growth in low R/FR (simulated shade) as compared to high R/FR (open). Light quality, however, had no significant effect on steady-state photosynthetic characteristics or LFUE for any species. 4. Increased light quantity, by contrast, caused photosynthetic acclimation leading to higher photosynthetic capacities. The pioneer species showed a larger capacity for photosynthetic acclimation to light environment than the shade species. LFUE was also affected by light quantity, with the low-light grown plants showing higher LFUE than the high-light grown plants. 5. Results provide evidence that light quality does not play an important role in modulating steady-state and dynamic photosynthetic characteristics during acclimation to shade, even in species that exhibit morphogenetic responses to light quality.
The photosynthetic responses of three tropical tree species were investigated in the contrasting micro-environments of the canopy, a gap and the understory of a tropical forest in north-eastern Australia. Measurements were made with a small transportable field gas exchange apparatus on the evergreen species Argyrodendron peralatum (F.M. Bailey) Edlin ex I.H. Boas and Castanospermum australe (Cunn.) Frazer and Cook, which regenerate in the understory and the deciduous gap species Toona australis (F. Muell.) Harms. Acclimation to the prevailing light environment was evident in all species, with the canopy leaves having higher light saturated photosynthetic rates, dark respiration rates and stomatal conductances than the understory leaves. For A. peralatum, leaves in the gap were generally intermediate between those in the canopy and understory. There was no evidence for acclimation to the differences in temperature or leaf-air vapour pressure deficits between the canopy and understory leaves. Determinations of the daily courses of CO<sub>2</sub> uptake showed that although the daily photon flux density (PFD) in the understory was only 3% of that at the canopy top, leaf carbon gain was nearly 10% of that measured for the canopy leaf. In the understory, photosynthesis during sunflecks accounted for about one third of the daily carbon gain. There was no evidence that temperatures or leaf-air vapour pressure deficits significantly limited CO<sub>2</sub> uptake in the canopy.
A survey of the responsiveness of plant species, typical of open and shade habitats, to simulated natural shade-light quality (i.e. white light plus supplementary far-red) has demonstrated a systematic relationship between habitat and certain developmental responses. Supplementary far-red light has a much greater effect on stem extension rate, petiole length, and leaf dry weight: stem dry weight ratio of the open habitat, shade-intolerant species. Far-red effects on leaf chlorophyll content show no such systematic grading. These results are discussed in relation to habitat adaptation. In most cases, the relationship between developmental response and the estimated phytochrome photoequilibrium, which is established by the radiation treatment, is linear. This is taken as an indication of phytochrome involvement in shade perception.
The theory of gap regeneration dynamics proposes that different species of tree partition canopy gaps because they are preferentially adapted to a particular gap size class. A variety of gap sizes would therefore favour the regeneration of a range of species. The theory has been used to explain the extraordinarily high tree species diversity of tropical rain forests. A test was mounted in lowland evergreen dipterocarp rain forest in the Danum Valley, Sabah, East Malaysia by the creation of ten, artificial canopy gaps ranging in size from 10 m2 to 1500 m2 (6 to 30% canopy openness). The responses of established populations of seedlings of three dipterocarp species (Hopea nervosa, Parashorea malaanonan and Shorea johorensis) with contrasting silvicultural reputations were monitored for 40 months in these gaps and under closed forest. There were significant differences in survival and growth under closed forest between these three species. However, in gaps, the most important determinant of seedling survival and growth was seedling size at the time of gap creation, regardless of species. An ability to persist for long periods under closed forest and slowly accumulate growth may bestow an enormous size advantage on seedlings when gaps occur. Generalizations on the regeneration dynamics of dipterocarp rain forests need to be modified in the light of this result. Further observations for several years are important to see whether forest recovery eventually converges on predictions from the original paradigm.
Iridescent blue leaf coloration in four Malaysian rain forest understory plants, Diplazium tomentosum Bl. (Athyriaceae), Lindsaea lucida Bi. (Lindsaeaceae), Begonia pavonina Ridl. (Begoniaceae), and Phyllagathis rotundifolia Bl. (Melastoma- taceae) is caused by a physical effect, constructive interference of reflected blue light. The ultrastructural basis for this in D. tomentosum and L. lucida is multiple layers of cellulose microfibrils in the uppermost cell walls of the adaxial epidermis. The helicoidal arrangement of these fibrils is analogous to that which produces a similar color in arthropods. In B. pavonina and P. rotundifolia the blue-green coloration is caused by parallel lamellae in specialized plastids adjacent to the abaxial wall of the adaxial epidermis. The selective advantage of this color production, if any, is unknown.
Among 13 tropical tree species on Barro Colorado Island, species with high seedling mortality rates during the first year in shade had higher reltive growth rates (RGR) from germination to 2 months in both sun (23% full sun) and shade [2%, with and without lowered red: far red (R:FR) ratio] than shade tolerant species. Species with higher RGR in sun also had higher RGR in shade. These interspecific trends could be explained by differences in morphological traits and allocation paterns among species. Within each light regime, seedlings of shade-intolerant species had lower root: shoot ratios, higher leaf mass per unit area, and higher leaf area ratios (LAR) than shade tolerant species. In contrast, leaf gas exchange characteristics, or acclimation potential in these traits, had no relationship with seedling mortality rates in shade. In both shade tolerant and intolerant species, light saturated photosynthesis rates, dark respiration, and light compensation points were higher for sungrown seedlings than for shade-grown seedlings. Differences in R:FR ratio in shade did not affect gas exchange, allocation patterns, or growth rates of any species. Survival of young tree seedlings in shade did not depend on higher net photosynthesis or biomass accumulation rates in shade. Rather, species with higher RGR died faster in shade than species with lower RGR. This trend could be explained if survival depends on morphological characteristics likely to enhance defense against herbivores and pathogens, such as dense and tough leaves, a well-established root system, and high wood density. High construction costs for these traits, and low LAR as a consequence of these traits, should result in lower rates of whole-plant carbon gain and RGR for shade tolerant species than shade-intolerant species in shade as well as in sun.
Four tree species of Shorea section Doona (Shorea megistophylla, Shorea trapezifolia, Shorea disticha, Shorea worthingtonii) were investigated for differences in seedling growth among related species. These species occur together as canopy emergents in rain forest of southwest Sri Lanka. Seedlings of each species were grown in light treatments that simulated a range of light environments found in the groundstorey of the rain forest. Seedlings of S. megistophylla grew most in the full-sun treatment. The other species grew tallest in treatments that provided partial shade or lower amounts of direct sunlight. For two of these species, S. disticha and S. worthingtonii, greatest proportions of seedling dry mass allocated to roots were in either dark-understorey shade or long durations of direct sunlight. Seedlings of S. megistophylla allocated the greatest proportion of dry mass to roots in the full-sun treatment. In the dark-understorey shade seedlings of S. trapezifolia had the least proportion of dry mass allocated to roots compared with the other species. This might predispose S. trapezifolia to more stress during drought periods. Under treatments providing high amounts of light S. megistophylla increased leaf area by increasing the size of its leaves. For S. worthingtonii and S. trapezifolia, leaf area increased by the production of more leaves rather than by an increase in area of individual leaves. Leaf area increase by number was less marked for S. disticha. Findings suggest an explanation for the co-existence of these Shorea species in this rain forest. High light environments like that in the centre of a large canopy disturbance promotes growth of S. megistophylla seedlings. Smaller canopy openings that expose seedlings to some direct sunlight favour growth of S. trapezifolia and S. disticha. Light regimes of the forest understorey and gap edge favour seedling growth of the more shade-tolerant S. worthingtonii.
The light environment experienced by plants in natural vegetation is strongly dependent upon interactions with neighbors. For plants in dense stands, reduced irradiance can lead to reductions in growth and fitness. Spectral light quality is also altered beneath a leaf canopy, and can serve as an important signal of competition for light. Recent physiological studies indicate that plants can perceive the quality of light reflected from neighbors as an accurate predictor of future competition, and respond morphologically even before they are directly shaded. These findings have important implications for plant population biology, and provide a valuable opportunity for the study of adaptive plasticity.
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