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Response of growth, yield and quality of edible-podded snow peas to supplemental light-emitting diode lighting during winter greenhouse production
Canadian Journal of Plant Science
Abstract
The occurrence of low natural light levels during winter months is a major limiting factor for greenhouse plant production in northern regions. To determine the effects of supplemental lighting (SL) on winter greenhouse production of pea pods, plant growth, pod yield, and quality were investigated under SL at a photosynthetic photon flux density (PPFD) of 50, 80, 110, and 140 μmol m ⁻² s ⁻¹ , plus a no-SL control treatment, inside a Canadian greenhouse from January to March. Light-emitting diodes with a red-to-blue PPFD ratio of 4:1 and a 16 h photoperiod were used for the lighting treatments. During the trial period, the average natural daily light integral (DLI) inside the greenhouse was 6.6 mol m ⁻² d ⁻¹ and the average daily temperature was around 13 °C. Compared with the control, SL treatments increased pod yield and promoted plant growth, as demonstrated by faster main stem extension and greater aerial biomass. Also, total pod yield (g plant ⁻¹ or no. plant ⁻¹ ) and some growth traits (e.g., stem diameter, branch number, leaf thickness, and leaf chlorophyll content) were proportional to supplemental PPFD within the range of 0–140 μmol m ⁻² s ⁻¹ . However, SL levels of 50–80 μmol m ⁻² s ⁻¹ , corresponding to a total (natural + supplemental) DLI of 9.4–11.1 mol m ⁻² d ⁻¹ , resulted in the best pod quality based on evaluations of individual fresh mass, length, soluble solids content, succulence, and firmness. Therefore, a total DLI ranging between 9.4 and 11.1 mol m ⁻² d ⁻¹ can be recommended as a target light level for greenhouse production of pea pods using SL under winter environment conditions.
... Although a bunch of studies has investigated the effect of monochromatic environments on the physiological and nutraceutical traits of plants, little information is present about the application of supplemental narrowband lights in a greenhouse environment. In literature is reported that different light recipe supplementation increased plant productivity and yields in tomato, pak choi, snow pea, and strawberry plants (Gomez et al., 2013;Zheng et al., 2018;Kong and Zheng, 2019;Lauria et al., 2023), as also altered the biosynthesis of some secondary metabolites in fruit and vegetables, (e. g., leafy greens, snow pea, tomato, and strawberry; Matysiak and Kowalski, 2019;Zheng et al., 2018;Nguyen et al., 2022;He et al., 2022;Lauria et al., 2023) and in medicinal species (e.g., Taxus baccata; Chiocchio et al., 2022). Indeed, plants have evolved accessory defense lines that are activated concurrently with excessive light (e.g., light supplementation) and consist of secondary metabolites acting in support of the action of primary antioxidant defense lines (Brunetti et al., 2015). ...
... For example, LED supplemented tomato plants reported an increased node number, fruit number and total fruit fresh weight when compared with non-supplemented plants (Gomez et al., 2013); supplemental blue light induced an increase in health promoting compounds (phenolics, flavonoids, anthocyanins, and glucosinolates) in pak choi and, simultaneously, a blue light intensity-related yield was observed. At the same time, increased red light induced a higher yield and quality in snow pea than in non-supplemented plants (Kong and Zheng, 2019) and a higher yield and anthocyanin accumulation were observed in strawberry fruit supplemented with red light (Lauria et al., 2023). The supplementation with this monochromatic light also promoted pathogen tolerance in strawberry fruit by the upregulation of genes involved in cell wall development (Lauria et al., 2023). ...
... Accordingly, the present work shows that supplemental R light reduced stem length likely due to the unbalance of R:FR ratio as also evidenced through the inhibition of gibberellin 20-oxidase in Arabidopsis thaliana (Hisamatsu et al., 2005). Moreover, exclusively B light was reported to increase petiole length in arugula (Kong et al., 2019), but in our case, the perception of full-spectrum light background in the greenhouse could have attenuated B light responses on strawberry plants. Leaf biomass and total leaf area were not affected by R light supplementation as also claimed by Demotes-Mainard et al. (2016). ...
This work offers new insights into the physiological and biochemical responses of strawberry plants to red (R), green (G), blue (B) and white (W- R:G:B; 1:1:1) LED light supplementation (250 µmol m − 2 s − 1; 5 h d − 1). Gas exchange and chlorophyll a fluorescence parameters, pigment content, antioxidant enzyme activities and oxidative stress markers (i.e., H2O2 and malondialdehyde by-products - MDA) were measured in plants grown for 60 days with light supplementation. Supplementation with R light induced a reduction of net CO2 assimilation rates (–13% on average with respect to the other treatments) which is not dependent to R-triggered stomatal closure, but rather to the biochemical activity of the photosynthetic apparatus. Despite that, biometric parameters (leaf biomass/area) were not significantly affected by these physiological changes, suggesting that those alterations were not the result of a distress, but rather an efficient eustress to stimulate plant antioxidant defenses. Indeed, R light promoted the activity of antioxidant enzymes and R-enriched plants showed the highest level of H2O2 and MDA, which could explain the higher tolerance to Botrytis cinerea observed in a previous experiment. The above is supporting for the role of R light enrichment as a priming eustress which could be useful in strawberry indoor cultivation as a way to promote fruit enhancement in terms of antioxidant compounds and fruit tolerance to pathogens thus reducing agrochemical inputs.
... Tender shoots of peas (Pisum sativum L.), including 2-4 pairs of leaves and immature tendrils and may also include small flower buds or blossoms, are referred to as pea shoots [1]. Pea shoots have become popular as a specialty vegetable in certain regions of Asia and Africa due to their mild "pea-pod" flavor, characterized by a delicate, crisp, light, and refreshing taste [2,3]. Notably, the levels of chlorophyll, carotenoids, vitamin C, total phenols, flavonoids, and other bioactive compounds, along with their antioxidant capacity in the leaves, exceed those found in lettuce, spinach, and celery [4,5]. ...
... Kong et al. [7] suggested that the optimal supplementing light scheme for the greenhouse production of pea shoots in winter was a PPFD of 50-80 µmol m −2 ·s −1 with a photoperiod of 16 h·d −1 . It was also proposed that DLI between 9.4 and 11.1 mol m −2 ·d −1 could be used as the target level for the greenhouse production of pea pods in winter [3]. Our correlation analysis ( Figure 6) revealed a significant relationship between light intensity and the fresh weight and dry weight of pea shoots, suggesting a significant improvement in pea shoot yield. ...
Pea shoots is a popular vegetable in certain regions of the world due to their unique taste and abundance of health-promoting phytochemicals. The perishable nature and susceptibility to root rot of pea shoots necessitate a new soilless production system located close to the market. This study compared the growth of pea shoots using various cultivation methods in an LED plant factory. The results showed that early topping (4 days after transplanting, ET) promoted early harvest compared to later topping (20 days after transplanting, LT) and increased the number of harvested shoots by extending the harvest time to 2.8 times, ultimately resulting in a substantial yield improvement. Moreover, the yield of ET with a lower planting density (72 plants m−2, ET-LD) was 8.7% higher than ET with a higher planting density (126 plants m−2, ET-HD). Particularly, the average shoot fresh weight (AFW) under ET-LD exceeded that of ET-HD by 48.9%. It is advisable to consider adopting ET-LD for the cultivation of pea shoots in LED plant factories. Based on ET-LD, the yield, nutritional quality, and light use efficiency of pea shoots were further explored at different stages under three levels of light intensity (50, 100, and 150 μmol m−2·s−1). Contrasted against a light intensity of 50 μmol m−2·s−1, AFW, number of harvested shoots, and total fresh yield under a light intensity of 150 μmol m−2·s−1, increased by 60.2%, 62.8%, and 165.1%, respectively. Meanwhile, AFW, photosynthetic capacity, soluble sugar and vitamin C levels in leaves, as well as light use efficiency and photon yield, initially increased and then decreased with the extension of the planting period. Among these, soluble sugar, light use efficiency, and photon yield started to decrease after reaching the maximum value at 60–70 days after transplanting. In conclusion, a light intensity of 150 μmol m−2·s−1 with a photoperiod of 16 h d−1 using LEDs, combined with early topping within a planting period of 60–70 days, proves to be suitable for the hydroponic production of pea shoots in LED plant factories.
... Differing from red light, BL relative to no SL reduced fruit number, which was increased by red light [87]. In our study on podded peas grown in a greenhouse under SL at a PPFD of 50−140 µmol m −2 s −1 , RB-LED (20% B) did not affect flower initiation regardless of lighting intensities, compared with no SL, despite increased pod yield, promoted plant growth, and improved pod quality [96]. Possibly, the effect of low-to modest-intensity BL from SL on the flowering of these plants was covered by background lighting or natural light. ...
Blue light is an important light wavelength in regulating plant flowering. In a controlled environment (CE) plant production systems, blue light can be manipulated easily and even precisely through electric lighting, especially with the advancement of light-emitted diode (LED) technologies. However, the results of previous studies in the literature about blue-light-mediated flowering are inconsistent, which would limit its practical application in CE plant production while implying that an in-depth study of the relevant physiological mechanism is necessary in the future. This review consolidates and analyzes the diverse findings from previous studies on blue light-mediated plant flowering in varying high-value crops from ornamental plants to fruits, vegetables, and specialty crops. By synthesizing the contrasting results, we proposed the possible explanations and even the underlying mechanisms related to blue light intensity and exposure duration, its co-action with other light wavelengths, background environment conditions, and the involved photoreceptors. We have also identified the knowledge gaps based on these studies and outlined future directions for research and potential application in this promising field. This review provides valuable insights into the important and diverse role of blue light in plant flowering and offers a foundation for further investigations to optimize plant flowering through lighting technologies.
... Some studies have found that exposing plants to different wavelengths of light-emitting diode (LED) can effectively promote fruit ripening [16], increase the nutrient content of fruit [17][18][19], and improve fruit quality [20]. Red-blue light promoted the accumulation of total carbohydrates, starch, and sucrose in tomatoes [21]; supplementation of greenhouse-grown peas with red-blue light promoted their growth and increased the content of soluble sugars [22]; and in experiments on sweet oranges, ultraviolet light and red-blue light accelerated fruit ripening and affected the content of organic acids, hexoses, and carotenoids in fruit [23]. However, these studies have been scattered across different horticultural crops, and few trials have been conducted to systematically study table grapes [24,25]. ...
Protected cultivation is currently one of the main cultivation modes for grape production, but the long-term use of plastic film will have a certain negative impact on the light environment in vineyards, which in turn causes poor colouring, low sugar content and a lack of aroma in some red grape varieties. Supplementing light can be an effective way to mitigate these problems. In this study, vines of three red table grape varieties (‘Summer Black’, ‘Xinyu’ and ‘Queen Nina’) cultivated in a plastic greenhouse were supplemented with red, blue, white and red-blue light from veraison to harvest. All four supplemental light treatments increased the content of anthocyanins, sugars and volatile compounds in three grape varieties compared to CK (no supplemental lighting). Red-blue light treatment was the most favourable for the accumulation of anthocyanins and sugars, and the grapes treated with blue light had the highest content of volatile compounds. The grapes treated with red-blue light all obtained the highest composite scores via principal component analysis. For most of the sensory properties, the highest scores were obtained by the red-blue light-treated grapes. The results of this study will be useful in improving the colouring, sugar, and aroma content of grapes under protected cultivation.
... It is estimated that by 2050, approximately 175 million people will develop zinc deficiencies, and 122 million may be protein-deficient. Additionally, light levels during the winter months are a limiting factor for crop production in northern regions [30,31], and a good strategy to improve yield would be switching to an earlier sowing date, which requires varieties with a phenology well adapted to such a cropping cycle. Over the last few decades, the effects of single abiotic stress on legume crops have been widely studied, but several stresses tend to co-occur under field conditions. ...
Legumes have an important role in European agriculture. They assimilate N2 to sustainably support maximum crop growth, in turn providing high-protein food for human consumption and livestock feed. However, the extent of the area for legume cultivation in Europe has declined due to the lower economic competitiveness of legumes in relation to other crops, particularly of cereals and oilseed. To increase yields, there is a need to increase the genetic diversity of legumes in terms of adaptation to environmental stresses. We attempted to address this by conducting field and controlled experiments under drought vs. nondrought and different photoperiod conditions. The current study identified the physiological and agronomic traits correlated with productivity and quality performance in five economically important grain legume species (Pisum sativum, Phaseolus vulgaris, Cicer arietinum, Lupinus spp., and Vicia faba). In all species, the days to flowering and seed yield were affected by temperature and photoperiod. For cool-season legume species, long-day photoperiods were favorable and days to flowering was negatively correlated with the average air temperature. For the warm-season legumes, short-day photoperiods and warm temperatures were favorable. Under drought stress, the C/N balance, leaf nutrient (Ca, Fe, and K) concentrations, and yield were significantly reduced, contrary to Zn accumulation, and this information may contribute to improving our understanding and ability to develop sustainable growth. Based on our results, we conclude that the drought-tolerant and photoperiod-insensitive legume genotypes identified in this study constitute valuable starting materials for future programs aimed at improvement of legume productivity at a global/regional scale, which helps to strengthen the competitiveness and economic growth of legumes for European farmers.
... For end-of-day (EOD) and night-break treatments, the boxes colored yellow represent light, white boxes represent night, and colored boxes represent a light treatment without any other light source.crops supplementary lighting showed an increased length and yield of pea shoots (Pisum sativum;Kong et al. 2019) and improved flavor, nutrient content, and yield of pak choi (Brassica campestris ssp. chinensis var. ...
For many growers, established and newcomers, the determination of the optimal light spectrum for growing crops can be challenging and highly dependent on crop species and variety. With the increased popularity of LED lighting, the capability to fine-tune a light spectrum has never been greater. Here, we break down the fundamental roles of the major spectral regions (ultraviolet, blue, green, red, and far-red) and explain the effect on plant growth, yield, and crop quality (i.e., greenness, coloration, flavor) when applied in isolation or combination. The first part of this review examines plant responses to light stimuli and the potential benefits for growers. We also discuss how LED lighting can be used to manipulate plant growth and development to improve crop productivity and/or value. We suggest some basic LED light "recipes" that could be used by growers to deliver specific growth effects and provide an easy-to-use visual reference guide. The second part of this review explores the impact of light treatments on crop productivity. Increased productivity is weighed against the ongoing costs associated with various light treatments, modeled in the context of UK electricity pricing. Light is an essential resource for all plants, providing the energy necessary for photosyn-thesis, the process that enables plants to grow. However, light also plays a major role in influencing plant morphology and physiology, which is dependent not just on light intensity but also the spectral quality (color) of light. The effects of intensity and quality on plant performance and morphology are discussed in this review, with emphasis on how light can be used to improve the quality and quantity of crop yield.
... Light energy is one of the main parameters in photosynthesis, artificial light can be utilized when there is insufficient sunlight or to modify the plant's natural cycle. A reduction of 1 % in light will decrease the crop yield by 1 % (Kong and Zheng, 2019). High-performance greenhouses carefully control the daily light integral by activating supplemental lighting when there is insufficient daylight and using screens when excess insolation exists (Bambara, 2018). ...
It is expected that European biogas production will double by 2030 and quadruple by 2050. There are currently more than 18,943 biogas plants operating in Europe. With the emergence of biogas upgrading technologies, biogas is upgraded into biomethane with carbon dioxide as a byproduct. A common practice in biomethane plants is to release carbon dioxide (CO2) into the atmosphere instead of utilizing it as an input for greenhouses or algal farming. In this study, the unutilized 1,900,000 m3/y carbon dioxide from the biogas plant in Bruck an der Leitha (Austria) will be used for greenhouse crop farming. This study aims to determine the number of hectares of greenhouses that can be enriched with this CO2. An optimal greenhouse enriched with CO2 will be designed for the production of local crops to reduce the biogas plant carbon dioxide emissions. The daily daylight, solar radiation, crops carbon dioxide uptake rate and the 5,200 m3 of carbon dioxide daily available were utilized to calculate the optimal greenhouse areas with and without onsite CO2 storage for completely closed greenhouses and partially opened greenhouses with double polyethylene walls and standard glass walls.
... Nighttime SL had similar effects as daytime SL on plant growth, as demonstrated by similar plant biomass and total leaf area. The reason for this may lie in the fact that plant growth depends on the total daily light amount they received [34,35], since daytime SL had the same daily light integral as nighttime SL. This also supports the important role played by daily light integral in winter-spring greenhouse production [36]. ...
Winter–spring greenhouse vegetable production is limited by low-level natural light, resulting in decreased growth and quality. To investigate whether short-term pre-harvest supplemental lighting (SL) with light emitting diodes (LEDs) can address this issue, a study was conducted in a greenhouse in Dallas, Texas. Red leaf lettuce (Lactuca sativa L. ‘Red Mist’) plants grown in a hydroponic system were treated with daytime or nighttime SL with red (R) and blue (B) LEDs (RB-LED), blue and UVA LEDs (B/UVA-LED), or white LEDs (W-LED) for three days before harvest and compared to those without SL (control). All SL treatments provided a photon flux density of 167 μmol·m−2·s−1 for 12 h daily. Compared with the control, SL treatments increased leaf thickness and greenness, antioxidant capacity, and concentrations of phytonutrients such as anthocyanins, carotenoids, and total phenolics; however, shoot fresh biomass and total leaf area were generally not affected by SL. There were no differences in all of the above traits among W-LED, RB-LED and B/UVA-LED. Compared with daytime SL, nighttime SL increased leaf greenness and carotenoid concentration. In summary, all three LEDs with different spectra were effective in improving lettuce quality as short-term pre-harvest SL sources and nighttime SL was more effective than daytime SL; however, plant fresh weight and total leaf area were not affected.
... To obtain healthy and normally developed plants, as well as an economically profitable harvest in the autumn-winter period, especially for the countries located in latitudes with short daylight hours, the plants must be grown under the conditions of the supplemental lighting of greenhouses [4,7,8]. ...
The purpose of this study was to determine the role of various LED (light-emitting diode) light units in ensuring high-quality growth and development of plants, as well as to obtain high-quality seedlings of strawberries and ground cover rose. We studied the physiological reactions of garden strawberry (“Melga” variety) and ground cover rose (“Fairy” variety) plants under controlled conditions and obtained the data on the effect of light quality on plant biological productivity, dynamics of growth processes, photosynthesis rate and transpiration. Regardless of the type of studied crops, the tallest plants were obtained under conditions of supplementary lighting by the lamp with blue/green/red ratio in the spectrum 17/29/54 % (option 1) and the lamp with ratio 18/45/37 % (option 2). At the same time, the dry weight of leaves and roots, as well as the biological productivity of strawberry plants in experimental options 1 and 2 exceeded by 41% than in the control plants (under high pressure sodium lamp). For garden strawberry we recommend the LED in the option 2, for the ground cover rose optimal is the option 1.
... In addition to light spectra (e.g., R and B), light intensity can also affect plant morphology (Johnson et al., 2020;Jones-Baumgardt et al., 2019). For most species, increasing light intensity leads to a shorter and thicker stem, more side branches, and darker leaf color (Craver et al., 2018;Gerovac et al., 2016;Kong and Zheng, 2019). It appears that a combination of light spectra and intensity is necessary to regulate campanula stock plant morphology. ...
Short campanula ( Campanula portenschlagiana ‘PGM Get MEE’ ® ) stock plants present a difficulty in machine-harvesting of cuttings. Light adjustment may be an effective approach to mediate plant elongation. Two experiments were performed to 1) investigate whether short-term (five weeks) daily 24-h dynamic lighting (DL) with red and blue light-emitting diodes (LEDs) can promote elongation without inducing flowering, and 2) explore whether DL can be used to modify stock plant morphology to improve the cutting quality and rooting success in a controlled environment. Two lighting treatments were used: concurrent lighting (CL) with red (85%) and blue (15%) LEDs (RB) at 100 µmol·m ⁻² ·s ⁻¹ and DL with red (170 µmol·m ⁻² ·s ⁻¹ ), blue (30 µmol·m ⁻² ·s ⁻¹ ), and RB (100 µmol·m ⁻² ·s ⁻¹ ) LEDs sequentially at three different lighting stages, respectively, in both experiments. In Expt. 1, at final harvest of stock plants, the side branches were longer under DL compared with CL, but the five (= 2 + 2 + 1) weeks of 24-h daily lighting resulted in visible flower buds under both treatments. Based on the results of Expt. 1, a second experiment (Expt. 2) was conducted with the same cultivar and experimental conditions, but with a shorter photoperiod (10 h·d ⁻¹ ) for 11 (= 8 + 2 + 1) weeks. In Expt. 2, at final harvest, DL compared with CL caused more upright side branches, and reduced the dry biomass of side branches with one branching order and leaf chlorophyll content. However, the harvested cutting quality and rooting success were similar between both treatments. In both experiments, side branch number under DL was greater compared with CL at the end of the first lighting stage. Stock plants under DL were taller from the second lighting stage on to final harvest compared with CL, and the final heights of stock plants under DL met the target for machine-harvest in both experiments. Therefore, if the lighting strategy is further optimized, DL can potentially benefit controlled-environment production of campanula cuttings.
... One hypothesis as to why no CL-injury was observed is that the total DLI was below the critical point for cucumbers. During the winter months in southern Ontario, solar DLI is typically below 10 mol m −2 d −1 [33,34]. During the production stage of a cucumber crop, plants have been observed to grow adequately in up to 25 mol m −2 d −1 [35] above which photo-oxidative stress is observed. ...
Continuous lighting (CL, 24h) can reduce the light intensity/light capital costs used to achieve the desired amount of light for year-round greenhouse vegetable production in comparison to short photoperiods of lighting. However, growth under CL has led to leaf injury characterized by chlorosis unless a thermoperiod or alternating light spectrum during CL is used. To date, there is no literature relating to how cucumbers (Cucumis sativus) respond to CL with LEDs in a full production cycle. Here, we evaluated a mini-cucumber cv. “Bonwell” grown under 4 supplemental lighting strategies: Treatment 1 (T1, the control) was 16 h of combined red light and blue light followed by 8 h of darkness. Treatment 2 (T2) had continuous (24 h) red light and blue light. Treatment 3 (T3) was 16 h of red light followed by 8 h of blue light. Treatment 4 (T4) was 12 h of red light followed by 12 h of blue light. All treatments had a supplemental daily light integral (DLI) of ~10 mol m−2 d−1. Plants from all treatments showed similar growth characteristics throughout the production cycle. However, plants grown under all three CL treatments had higher chlorophyll concentrations from leaves at the top of the canopy when compared to T1. The overall photosynthetic capacity, light use efficiency, and photosynthetic parameters related to light response curves (i.e., dark respiration, light compensation point, quantum yield, and photosynthetic maximum), as well as the quantum yield of photosystem II (PSII; Fv/Fm) were similar among the treatments. Plants grown under all CL treatments produced a similar yield compared to the control treatment (T1). These results indicate that mini-cucumber cv. “Bonwell” is tolerant to CL, and CL is a viable and economical lighting strategy for mini-cucumber production.
... Snow pea is a specialty vegetable that can be consumed either as tender shoots (i.e., pea shoots) or as immature pods (i.e., pea pods) (Kong et al., 2018;Kong and Zheng, 2019;Miles and Sonde, 2003). Also, the snow pea crop has a much smaller canopy size, shorter growth period, and lower water and fertilizer requirements than tomato (Jett et al., 2004;Miles and Sonde, 2003). ...
Intercropping can increase land use efficiency in high tunnel crop production, but it may also lead to decreases in yield and quality of main crops due to the potential competition for resources. This study evaluated the agronomic viability of intercropping snow pea ( Pisum sativum L., ‘Ho Lan Dou’) with cherry tomato ( Solanum lycopersicum L. var. cerasiforme ‘Sarina hybrid’) without additional inputs of water and fertilizers on peas in an organic high tunnel production system under Southern Ontario climate conditions in Guelph, Ontario, Canada (lat. 43.5 °N, long. 80.2 °W) during 2015 and 2016. In each 80-cm-wide bed, the tomato crops were planted alternately in double rows spaced 30 cm apart, with in-row spacing of 110 cm, which resulted in a planting density of ≈24,000 plants/ha. The snow pea seeds were sown between the tomato plants (i.e., within the same beds as tomatoes) in holes (two seeds per hole), with four rows in each bed and in-row holes spaced 10 cm and at least 25 cm away from the tomato plants, which resulted in a seeding rate of ≈650, 000 seeds/ha. The same amount of water or fertilizer was applied to the intercropping and nonintercropping plots based on the needs of the cherry tomato plants. Plant growth, fruit yield, and quality were compared between tomato plants with and without intercropping. Intercropping with snow peas did not affect total marketable fruit yield, unmarketable fruit percentage, fruit quality traits (e.g., individual fruit weight, soluble solids content, dry matter content, and postharvest water loss), or early-stage plant growth of the cherry tomato. Therefore, it is at least an agronomical possibility to intercrop snow peas with cherry tomatoes on the same beds without additional inputs of water and fertilizer on snow peas in an organic high tunnel system. The additional yield of pea shoots or pods in the intercropping treatment also increased economic gross returns in the high tunnels, although the economic net return might vary with the costs of seeds and labor involved in snow pea growing.
... For microgreens, the recommended minimum DLI has been elusive in the literature. However, for greenhouse vegetable (including microgreens) production in southern Canada, the yield and most quality metrics increased with the increasing DLI within the range of 6.9 to 24 mol · m -2 · d -1 (Jones-Baumgardt et al., 2020;Kong et al., 2018a;Kong and Zheng, 2019). Consequently, winter greenhouse production under low natural light conditions is a great challenge for growers due to the decreased yield and quality of horticultural crops, including microgreens. ...
To determine whether supplemental blue light (B) or far-red light (FR) overnight can promote microgreen elongation to facilitate machine harvesting and improve microgreen quality and yield, two common microgreen species, mustard ( Brassica juncea ) and arugula ( Eruca sativa ), were grown in a greenhouse in Guelph, Ontario, Canada, during January 2019. Low-intensity (14 μmol·m ⁻² ·s ⁻¹ ) B or FR was applied to microgreens overnight from 1730 hr to 0630 hr , and no supplemental lighting (D) was used as a control. After 2 weeks of light treatments, B compared to D promoted stem elongation by 16% and 10%, respectively, and increased crop yield by 32% and 29%, respectively, in mustard and arugula. B compared to D also increased the cotyledon area in mustard and leaf mass per area in arugula and enhanced cotyledon color in both species despite having no effects on total chlorophyll, carotenoid, and phenolic contents. However, FR did not increase stem length or fresh weight compared with D, reduced plant height compared with B in both species, and reduced the cotyledon area in arugula. FR, compared with D and B, reduced the stem diameter and phytochemical contents of both species. Therefore, low-intensity B can be applied overnight for winter greenhouse microgreen production because of its beneficial effects on appearance quality and crop yield without negatively affecting nutritional quality.
Background and objectives: Light is one of the environmental factors influencing plant growth and development. Nowadays, LED lamps are light sources that researchers focus on and are recommended for plant production. In recent years, agricultural experts have focused on plant growth regulators to improve the quality and stability of the cultivation system. Biological elicitors induce secondary metabolites and hypersensitive responses by activating defense mechanisms. The phytohormone abscisic acid transmits messages under living and non-living stress conditions. Methodology: The current research was carried out in 2021 in the greenhouse of Shahid Fozveh Biological Research Center as factorial in a completely randomized design in 5 replications. For this purpose, the effect of experimental factors, including four concentrations of abscisic acid (0, 5, 10, and 20 mg/liter) and five different day lengths (16, 14, 12, 10, and 8 hours of light) on the growth characteristics and content of photosynthetic pigments of the cannabis plant (Cannabis sativa L.) was evaluated. For each light level, five rows were considered, and each row contained four pots (a total of 20 pots for each level). Based on the results of the preliminary experiment, above each set of 20 pots, 4 LED lamps with 9 watts power and 90 lumens radiation intensity were placed and connected to a timer (with time intervals of 16, 12, 14, 10, and 8 hours). Before the flowering phase, the whole plants were sprayed with zero, 5, 10, and 20 milligrams per liter of abscisic acid solutions. The spraying was repeated three times at 24-hour intervals. Following spraying, plant leaves were collected to evaluate morphological traits and pigment levels.
Microgreens growing under electric (artificial) lighting in controlled environments often have short hypocotyls, which can be difficult for machine harvest. To investigate whether early-stage dark treatment can promote hypocotyl elongation without compromising microgreen yield and quality, two different seed-size species, sunflower (Helianthus annuus ‘Black oil’) and arugula (Eruca sativa ‘Rocket’), were tested. Seeds of sunflower and arugula were sown in pots, and the pots were placed inside support trays. During the first 5 days after seeding, half of the pots per species within each tray were covered with an upside-down black tray as dark treatment, and another half were kept under light. The light treatment was provided by continuous (24-h) lighting with a combination of red (85%) and blue (15%) light-emitting diodes at a photosynthetic photo flux density of around 100 μmol·m ⁻² ·s ⁻¹ . After 5 days of dark treatment, the black covers were removed and the plants were grown under the above lighting treatment till harvesting. The microgreens were harvested at 7 d and 12 d after seeding for sunflower and arugula, respectively. Early-stage dark treatment promoted hypocotyl elongation by 26% and 28% for sunflower and arugula, respectively. Microgreen yield was increased by 13% for sunflower and reduced by 24% for arugula under dark treatment. Dark treatment increased cotyledon succulence by 14% for sunflower, but reduced cotyledon size by about 25% for arugula despite increases in red color and succulence of arugula hypocotyls. For both species, cotyledon color and soluble solids content were not affected by dark treatment.
Supplemental lighting can enhance yield when sunlight is limited, as in winter. As the effect of frequent cloudy or rainy days in other seasons on plant growth and yield remains unclear, we investigated the effect on tomato (Solanum lycopersicum) and compensation by supplemental LED inter-lighting. Plants were grown under 30% shade cloth on 0%, 40%, or 60% of days. Lower leaves were illuminated with red and blue LED inter-lighting modules from right after first anthesis, or not illuminated. Shading during 40% and 60% of days diminished daily light integral (DLI) by 26% and 40%, respectively, and reduced shoot dry weight by 22.0% and 23.3%, yield by 18.5% and 23.3%, and fruit soluble solids content by 12.3% and 9.3%. In contrast, supplemental inter-lighting improved the light distribution within plants and compensated DLI, and maintained similar yield and soluble solids content in both shade treatments as in the control. These results clearly show that supplemental LED inter-lighting could efficiently compensate for a shortage of light for plant growth, photosynthesis and thus yield under the lack of sunshine.
Low natural light levels during the winter months are a major limiting factor for greenhouse production in northern regions. To determine the effects of supplemental lighting (SL) on winter greenhouse production of pea shoots, crop growth, yield, and quality were investigated under the treatments of supplemental photosynthetic photon flux density (PPFD) of 50, 80, 110, and 140 μmol m⁻² s⁻¹, all with a 16 h photoperiod, plus a no-SL control treatment, inside a Canadian greenhouse from December to March. Light-emitting diodes with a red to blue PPFD ratio of 4:1 and peak wavelengths at 665 and 440 nm were used for the lighting treatment. During the trial period, the average natural daily light integral (DLI) inside the greenhouse was 5.3 mol m⁻² d⁻¹ and the average daily temperature was around 13 °C. Compared with the no-SL control, SL of 50–140 μmol m⁻² s⁻¹ increased stem length and leaf number before the first harvest and promoted the cumulative yield (kg m⁻²) of pea shoots throughout the five harvest times. The total yield (kg m⁻²) of five harvests and weekly average stem extension rate were proportional to supplemental PPFD within the range of 0–140 μmol m⁻² s⁻¹; however, SL of 50–80 μmol m⁻² s⁻¹, corresponding to total (natural + supplemental) DLI of 8.1–9.8 mol m⁻² d⁻¹, resulted in the best integrated quality based on the evaluation of individual fresh mass, soluble solids content, succulence, and firmness. Therefore, a total DLI ranging between 8.1 and 9.8 mol m⁻² d⁻¹ can be suggested as a target for winter greenhouse production of pea shoots under conditions similar to this trial.
Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m⁻² s⁻¹ measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter.
Inter-lighting, applying supplemental light within crop canopy, has been shown to improve plant vertical light distribution and light use efficiency, with HPS (high pressure sodium) lamps in Scandinavia. However, it is not feasible on vegetables cultivated with the popular twin-row system (narrow row) used in major greenhouse vegetable production area in northern regions because of its high bulb temperature. Light emitting diodes (LEDs) have low operating temperature and thus are potentially a good fit for inter-lighting. Therefore, the effects of LED inter-lighting on plant growth, fruit yield, and light and energy use efficiency were investigated in this study. To optimize the production system with lighting, different levels of top HPS lighting, LED inter-lighting, and plant densities were also evaluated. Two experiments were conducted. Experiment one evaluated single row of LED inter-lighting module per twin-row (36.7 µmol m-2 s-1) without or with top HPS (165 µmol m-2 s-1) at 2.8 and 3.6 plants m-2, respectively. Experiment two evaluated double rows of LED inter-lighting modules per twin-row (73.4µmol m-2 s-1) without or with top HPS lamps (120 µmol m-2 s-1) at 2.8 plants m-2. LED inter-lighting improved fruit yield and quality. However, it had similar light use efficiency as the top HPS lighting based on the light reaching the crop canopy. Higher plant density at strong top HPS lighting (165 µmol m-2 s-1), improved the response to LED inter-lighting, and the response to LED inter-lighting was better at the lower top HPS lighting (120 µmol m-2 s-1). Therefore, the response of mini-cucumbers to LED inter-lighting can be optimized by using proper crop management and top/inter-light ratio. Because LED inter-lighting allowed more light to reach crop canopy and higher efficiency of electricity to light conversion, the plants grown with LED inter-lighting achieved higher energy use efficiency than that with the top HPS in both experiments.
The influence of growing season on some physiological and biochemical variâtes related to fruit yield and quality was investigated in melon (Cucumis mélo L.) plants cultivated in nutrient film technique in a greenhouse located at Pisa, Central Italy, from mid-March to mid-June, or from mid-July to mid-September. Compared with spring, the plants grown in summer exhibited faster growth and development, but produced fewer fruits of larger size and poorer quality due to reduced sucrose content. Growing season did not affect total leaf area, but dry-matter production and partitioning to the fruits was significantly lower in summer than in spring. Summer fruit ripened within 30-35 d after anthesis, about 14 d fewer than in spring. Higher average temperature was presumably responsible for earlier fruit maturation in summer, as in both seasons all melons were harvested after 450-500 degree-days (base temperature of 12°C) from anthesis. Fruit swelling did not account for the reduction of sucrose content in summer-grown fruits, which instead was due to shortage of photoassimilate supply and inadequate sucrose synthesis, as suggested by the rate of leaf gas exchange and the activity of sucrose phosphate synthase in the fruit flesh, as determined during the final stages of fruit development. Lower solar radiation was presumably responsible for the reduced leaf carbon assimilation in summer, as growing season did not affect leaf turgor, stomatal conductance, mineral status and chlorophyll content.
We report the results of research carried out in Campania between 2000 and 2002 with the aim of determining the fruit quality of everbearing alpine strawberry (local cv "Regina delle Valli") grown under plastic (IR-PE) double-tunnels using the nutrient film technique (NFT). Comparisons were made of four electrical conductivity (EC) levels (1.3, 1.6, 1.9 and 2.2 mS *cm-1) of the nutrient solutions, in factorial combination with crops arranged in pairs on two vertical overlapped layers in a randomised split-plot design. A control crop was grown with the current technique in the same tunnels and the same density as with NFT, i.e. with plants spaced 25 cm along the row and in double-rows 40 cm apart on black PE mulched ridges (80 cm wide). Fruit obtained in spring, in comparison with the autumn, showed higher values of dry matter and refractive index, reducing sugars (glucose and fructose) and sucrose, acids (citric, malic, succinic and ascorbic), calcium, potassium, iron and chloride; in autumn, instead, magnesium, copper, nitrates, phosphates and sulphates were more concentrated in the fruit. The higher crop layer caused a greater accumulation of all the analytes, except for the nitrates which did not vary. The 2.2 mS-cm-1 treatment resulted in the highest levels of all the organic constituents; Fe, Cu, Zn and Cl showed a different trend, as the maximum concentrations corresponded to 1.9 mS-cm -1 EC. The control fruit attained, in autumn, the lowest values for most of the organic components and of the mineral anions, in comparison with those in hydroponics; only the inorganic cations were generally more concentrated with the traditional technique. In spring, the organic constituents and the mineral anions were again found in higher quantities in the fruits obtained by saline solutions, but only with regard to the higher crop level; by contrast, an intermediate accumulation of the minerals was recorded in the control, the four EC treatments within the lower layer which also often showed lower values of the inorganic cations.
In the present study, we investigated the effects of supplemental lighting (SL) with white, red, and blue light-emitting diodes (LEDs) on the yield and quality of tomato grown under the single-truss tomato production system (STTPS). SL was applied for 28 days during the rapid fruit development stage. Based on the same power consumption, the light treatments with the white and red LEDs increased the fresh yield of tomato by 12 and 14%, and the dry yield by 16 and 14%, compared with the control (without SL), respectively. Based on the unit photons emitted, the white LEDs showed high efficiency as the red LEDs in increasing tomato yield, followed by the blue ones. The results were probably due to the white LEDs that contained more than 50% of green light characterized by high penetration into the canopy. The sugar and ascorbic acid contents were not affected by SL from the LEDs. These results indicated that the white and red LEDs were effective in enhancing tomato yield and, in particular, the white LEDs with a combination of red, blue, and abundent green light would be more suitable to the use of STTPS at a high plant density.
Karlo' and `Rosana', two Boston-type lettuce ( Lactuca sativa L.) cultivars, were subjected to various light treatments in greenhouses equipped with one of two propane heating systems. Photoperiods of 16, 20, 24, or 24 hours for 2 weeks after transplanting and then 16 hours (24–16) and photosynthetic photon flux of 50 or 100 μmol·m –2 ·s –1 provided by supplementary lighting (high-pressure sodium vapor lamps) were compared to natural light during four experiments performed in greenhouses between Sept. 1989 and May 1990. Using supplementary lighting resulted in significant increases in biomass (≤270%), head firmness, and tipburn incidence and decreases in production cycle length (≈30%). Treatment effects were most pronounced during the months when natural-light levels were low. Fresh weights were higher for `Karlo' than `Rosana'; however, `Rosana' was less susceptible to tipburn than `Karlo'. In general, the radiant heating system resulted in earlier crop maturity and a higher incidence of tipburn than the hot-air system.
The extent and time course of changes in photosynthetic activities of leaves and isolated chloroplasts was followed in pea plants which were adapted to low light (60 µmol photons m-2 s-1, 400-700 nm, 16 h light/ 8 h dark cycles), and subsequently transferred to higher light (390 µmol photons m-2 s-1). The photosynthetic rates of leaves in CO2-saturating conditions, measured at light saturation or subsaturation, increased with no noticeable lag, doubling within 1 week after transfer to high light. In contrast, the increase of in vitro ribulose-1,5-bisphosphate carboxylase activity (~ 130%) and photosystem II electron transport capacity (~ 60%) occurred with an apparent lag of - 1 day after transfer to high light. The capacity for uncoupled whole-chain electron transport also increased slowly (~ 70%). Whilst the total chlorophyll (Chl) per unit leaf area remained steady, the Chl a/Chl b ratio increased with no apparent lag phase from 2.7 in low irradiance to 3.2 in high irradiance within 1 week. The results demonstrate that, following an increase of growth irradiance, pea leaves readily increase the capacity for utilising high light effectively, even when the total chlorophyll per unit leaf area remained constant. However, a better understanding of the time course of response requires measurements of other chloroplast parameters.
Field pea yields in three sowing-time experiments in 1985, and two experiments in 1986, were split into the following components: pods m-2, seeds pod-1 and average seed size. In both years pods m-2 was the component most strongly correlated with yield, but the others were also positively correlated with yield. Multivariate analysis of variance showed that pods m-2 contributed more than the other components to the site and sowing-time main effects in both years. Seeds pod-1 made no contribution in either year, but average seed size contributed to the site main effect in 1985 and to the sowing time and cultivar main effects in 1986. These results identify pods m-2 as the most responsive component to environmental effects on field pea yield. Pods m-2 was split into stems m-2 and pods stem-1, or into the rate of pod formation and the duration of pod formation. Variation in both stems m-2 and pods stem-1 contributed to differences in pods m-2 in the 1986 experiments. In a comparison of two Derrimut pea crops grown at Merredin in 1984 and 1985, the duration of pod formation and the rate of pod formation both varied. Variation in the rate of pod formation was due to differences in stems m-2 rather than in rates of pod formation stem-1. Pods formed early in the reproductive phase contributed much more to total seed yield than those formed later. This was due to later-formed pods containing fewer seeds and being more likely than early-formed pods to abscise before reaching maturity. The proportion of total seed yield carried on the first three reproductive nodes varied from 64.3% to 94.2%. This proportion was higher in harsher environments. It is suggested that in short growing-season environments increased pod formation rates are desirable to allow compression of the pod formation period, so that fewer pods will be formed late in the reproductive phase when the environment is most limiting.
Plant functional traits are the features (morphological, physiological, phenological) that represent ecological strategies and determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem properties. Variation in plant functional traits, and trait syndromes, has proven useful for tackling many important ecological questions at a range of scales, giving rise to a demand for standardised ways to measure ecologically meaningful plant traits. This line of research has been among the most fruitful avenues for understanding ecological and evolutionary patterns and processes. It also has the potential both to build a predictive set of local, regional and global relationships between plants and environment and to quantify a wide range of natural and human-driven processes, including changes in biodiversity, the impacts of species invasions, alterations in biogeochemical processes and vegetation–atmosphere interactions. The importance of these topics dictates the urgent need for more and better data, and increases the value of standardised protocols for quantifying trait variation of different species, in particular for traits with power to predict plant- and ecosystem-level processes, and for traits that can be measured relatively easily. Updated and expanded from the widely used previous version, this handbook retains the focus on clearly presented, widely applicable, step-by-step recipes, with a minimum of text on theory, and not only includes updated methods for the traits previously covered, but also introduces many new protocols for further traits. This new handbook has a better balance between whole-plant traits, leaf traits, root and stem traits and regenerative traits, and puts particular emphasis on traits important for predicting species’ effects on key ecosystem properties. We hope this new handbook becomes a standard companion in local and global efforts to learn about the responses and impacts of different plant species with respect to environmental changes in the present, past and future.
Consumer interest worldwide in the quality of vegetable products has increased in recent years. Product quality is a complex issue. As well as visual characteristics, properties such as texture, the content of minerals and vitamins, flavor and other organoleptic characteristics must be considered. In addition, new knowledge shows that vegetables are appreciated for their beneficial health effects in humans and underlines the importance of nutraceutic properties. Many research studies have documented methods for achieving a high-quality vegetable product. Indoor production for fresh vegetables offers advantages compared to outdoor production with regard to quality assurance principally, because the products are not exposed directly to the rapid changes of climate conditions. On the other hand, vegetable cultivation in a greenhouse under artificially created conditions also affects the internal quality of the product. This is reflected in a different taste and flavor compared with field vegetables. Changes in external as well internal quality attributes of greenhouse vegetables subjected to light intensity, temperature, vapor pressure deficit (VPD), and CO2 enrichment of the atmosphere concentration are discussed in this paper.Referee: Dr. J. M. White, Vegetable Production Specialist, Mid-Florida Research and Education Center, UF/IFAS, 2725 Binion Road, Apopka, FL 32703, USA
Thomson, Betty F., and Pauline Monz Miller. (Connecticut Coll., New London.) The role of light in histogenesis and differentiation in the shoot of Pisum sativum. III. The internode. Amer. Jour. Bot. 50(3): 219–227. Illus. 1963.—Seedlings of Pisum sativum were grown under constant conditions and exposed daily to red or white fluorescent light or kept in total darkness. Counts and measurements of internodal cells in both transverse and longitudinal directions show that light does not alter the sequence or pattern of tissue differentiation, including the sequence of xylem maturation within the vascular bundle. Light does accelerate the rate of a constant course of differentiation. Light advances the time of division and enlargement of cortex, xylem, phloem, and pith cells in the longitudinal direction but reduces both the final number and the final length attained in all cases. It is concluded that light accelerates all phases of shoot growth and differentiation and that cell division and elongation in the later phases of internodal growth are reduced by light because of accelerated cell maturation.
Carbon assimilation accumulation and partitioning was studied in one-year-old fruiting limbs of greenhouse-grown 'Ruiguang 5' nectarine (Prunus persica L. var. nectarina Ait), affected by about 10%~12% shading treatment (simulating the light intensity decrease due to dust accumulation on greenhouse covering by adding old plastic film to it) during the second rapid swell of peach fruit growth. The results showed that net photosynthesis rate and starch content decreased markedly and total soluble sugar content changed little in leaves of terminal shoot under shading conditions. After labeling terminal shoot by 14CO2, more carbon was found to export from fed shoot to the nearby fruit and less carbon to the distant fruits. Moreover, a reduction of carbon assimilation partitioning in mesocarp was also observed within fruit. Fruits harvested in fruiting limbs by shading treatment were observed to have less fresh weight and transverse diameter and poor red coloration. Therefore, to improve the fruit quality it is necessary to increase the sunlight intensity inside greenhouse as far as possible during the second rapid swell of peach fruit growth.
Experiments in glasshouse and controlled environment facilities investigated the effect of different fruit removal and lighting/shading treatments on the pattern of tomato yields. While the removal of flowering trusses resulted in a yield loss about eight weeks later, there was little loss in cumulative yield as assimilates were distributed to neighbouring trusses. In the growth room experiment, increased photosynthetic photon flux density (PPFD) for one week resulted in a period of increased yield from 4-6 weeks after the start of the treatment, followed by suppressed yields due to smaller fruits on subsequent trusses. However, neither fruit load nor assimilate availability appeared to be responsible for the fluctuations in yield recorded within the glasshouse crop. In this experiment fruit size remained fairly consistent (except when fruit removal treatments were applied), whereas the number of fruits picked per week exhibited much greater variability. This was the case even when all trusses were pruned to leave five fruits, and so was not due to a cycle in the number of fruits set per truss. The flushes in yield were found to be a consequence of a hastening of fruit maturation.
Sweet pepper (Capsicum annuum L.) plants were grown under natural or supplemental lighting that extended the photoperiods to 16, 20, or 24 hours. Increasing the photoperiod to 16 and 20 hours increased pepper plant yields, but continuous light (24 hours) decreased yields compared to the 20-hour photoperiod. In a second experiment, plants were exposed to a photoperiod of 14 or 24 hours and either pruned to one fruit every four nodes or not pruned. During the first weeks of treatments, plants grown under continuous light had higher shoot mass (fresh and dry) and yields. After 7 to 8 weeks of treatments, plants under continuous light grew more slowly than plants exposed to a 14-hour photoperiod. At the end of the experiment, shoot mass and yields of plants grown under a 14-hour photoperiod were equal to or higher than plants under continuous light. So, it seems possible to provide continuous lighting for a few weeks to improve growth and yields. Limiting the number of fruit per plant increased shoot mass and decreased yields, but had no effect on the general response of pepper plants to photoperiod treatment. Leaf mineral composition was not affected by photoperiod treatment, indicating that reduced growth and yields under continuous light were not due to unbalanced mineral nutrition. Leaf starch and sugar contents were increased under continuous light. However, fruit pruning treatments did not modify the pattern of starch and sugar accumulation under the different photoperiod treatments. Reduced growth and yields measured under a 24-hour photoperiod are probably explained by starch and sugar accumulation in leaves as a result of leaf limitations rather than a sink limitation.
This paper reviews the available information on the photoperiod aspects of the use of supplemental lighting for greenhouse tomato and sweet pepper production. Optimal growth and yields of tomato and sweet pepper were obtained under photoperiods of 14 and 20 hours, respectively. Longer photoperiods did not further improve growth and yields and even decreased growth and yields in some cases. Although long term use of continuous light is detrimental to tomato and pepper plants, vegetative growth and fruit production of both species can be improved by short term use (5 to 7 weeks) of continuous lighting. Compared to shorter photoperiods, continuous light (24-h photoperiod) increased the leaf levels of hexoses in tomato, of sucrose in pepper and of starch in both species. The accumulation of starch and sugar in leaves under continuous light indicate a limitation of tomato and pepper plants to export the photosynthate out of their leaves. Such a limitation would explain the fact that extra light energy provided by continuous lighting did not result into growth and yield gains. The increased leaf hexose levels in tomato and increased leaf sucrose in pepper suggest that the limiting steps of the export of photosynthate are respectively the synthesis of sucrose and the loading of sucrose in the phloem. Under greenhouse conditions, continuous light caused leaf chlorosis in tomato but not in sweet pepper. Development of leaf chlorosis in tomato under continuous light was related to a decrease of the chlorophyll concentration in the leaves. Compared to tomato, higher levels of carotene and xanthophylls (photoprotective pigments) in pepper leaves probably provided a better protection of the photosynthetic apparatus against excessive light, thus preventing the destruction of chlorophylls and the development of leaf chlorosis in pepper. The severity of leaf chlorosis varied with the type of lamps (high pressure sodium, HPS versus metal halide, MH) used to provide the supplemental light, indicating that the spectral composition of the light received by plants may also play a role in the development of leaf chlorosis. Under continuous light, the response of tomato and pepper plants to HPS lamps versus MH in the greenhouse differed from the response in growth chambers. These differences between greenhouse and growth chamber could be related to the light spectral quality (presence or absence of natural light) and/or the daily variation in the climatic conditions (larger day/night differential in greenhouse).
Hanging basket (HB) production alters the light environment in the lower canopy of ornamental greenhouses by intercepting and altering the spectral quality of incoming light. If shading is sufficiently high, the quality of the lower crops can be reduced. This work investigated changes in light quantity and quality at the lower crop level caused by HB production in Ontario, Canada. Light sampling occurred at three commercial greenhouse facilities throughout the Spring 2012 HB season. The greenhouses represented a range of HB densities (1.8, 2.4, and 3.0 baskets/m2) and different HB canopy architectures (one, two, and three tiers of HBs). Light samples were taken at three fixed locations within each greenhouse facility: outside, HB level, and lower crop level. Photosynthetically active radiation (PAR) was logged continuously at each location within each greenhouse environment. Spectral scans were made at each sampling location, within each greenhouse facility, at various times throughout the season to assess how HB production altered the red to far red ratio (R:FR) at lower crop level. As the season progressed, outdoor daily light integrals (DLIs) more than doubled from <20 to >40 mol•m-2•d-1. Light reduction caused by polyethylene films and structural components varied among locations, but remained steady throughout the season, averaging 48.3% for the three locations. As the HB crops matured, the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively. Mean lower crop level DLIs were all very similar, between 9.4 and 9.9 mol•m-2•d-1. Accordingly, there may be insufficient light below HB canopies to produce high-quality crops of many varieties of bedding plants that are commonly grown in Ontario. The one- and two-tiered systems reduced the R:FR at lower crop level by 14% and 10%, respectively, whereas the three-tiered system caused no reduction. More work is required to determine if the observed far red shift is sufficient to alter crop quality. These case studies provide a backdrop against which to help determine and interpret horticultural management strategies for a variety of greenhouse crops.
Additional Index words. glazing, plastic film, structured plastic panels, glass, PE, PVC, PC, PMMA, FRP Summary The diversity of coverings for the greenhouse and other plant production structures has increased dramatically during the past four decades. This has resulted from the availability of new types of covering materials, and enhancements of previously existing materials, as well as the demand for technological improvements within the expanding controlled environment agricultural industry. The types of coverings currently available are dominated by plastics. These range from traditional glass to the recent advent of polymer plastics, such as thin films or multi-layer rigid thermoset plastic panels. Available enhancements such as ultra-violet radiation (UV) degradation inhibitors, infrared radiation (IR) absorbency, and anti-condensation drip surfaces, as well as their physical and spectral properties are discussed. The selection of specific covering alternatives has implications for the greenhouse superstructure and its enclosed crop production system.
Improvements in lighting technology (more efficient lamp types, luminaires etc.) and lighting strategy for plant growth have resulted in a considerable increase in the use of supplementary lighting for many greenhouse crops. Year-round production is now a reality in many pot plants, cut flowers and vegetable crops even grown at locations far north. Supplementary lighting (SL) has a significant influence on several important processes in plants such as photosynthesis and growth, photomorphogenesis, floral evocation, flower development, yield and quality. This paper mainly deals with the impact of (SL) on these processes. Some important aspects of SL will be discussed of such as 1) Light integral per day (daily light sum), 2) Light level versus light integral, 3) Duration of lighting per day (photoperiod), 4) Light spectrum (light quality) 5) Interaction between natural light and SL and 6) Interaction between SL and CO2 enrichment.
Chinese Pea, Chinese Pea Pod, Chinese Snow Pea, Dry Pea, Edible-Podded Pea, Edible Pod Pea, Field Pea, Garden Pea, Green Pea, Honey Pea, Pea, Peas, Podded Pea, Round-Podded Snow Pea, Round-Podded Sugar Pea, Shelling Pea, Snap Pea, Snow Pea, Sugar Pea, Sugar Snap Pea, Stringless Snowpea, Sweet Pea
Sweet Granadilla is native to the Andes Mountains between Bolivia and Venezuela, with Peru as the main producer. It grows as far south as northern Argentina and as far north as Mexico. Outside of its native range it grows in Florida, New Zealand, China and in tropical highlands of East Africa, South Africa Sri Lanka, Jamaica, Indonesia, Hawaii, Papua New Guinea and Australia. The major producing countries are Peru, Venezuela, Colombia, Ecuador, Brazil, South Africa, and Kenya. The main importing countries are the United States, Canada and Europe (Belgium, Holland, Switzerland, and Spain).
Solid-state lighting based on the use of light-emitting diodes (LEDs) is potentially one of the biggest advancements in horticultural lighting in decades. LEDs can play a variety of roles in horticultural lighting, including use in controlled environment research, lighting for tissue culture, and supplemental and photoperiod lighting for greenhouses. LED lighting systems have several unique advantages over existing horticultural lighting, including the ability to control spectral composition, the ability to produce very high light levels with low radiant heat output when cooled properly, and the ability to maintain useful light output for years without replacement. LEDs are the first light source to have the capability of true spectral composition control, allowing wavelengths to be matched to plant photoreceptors to provide more optimal production and to influence plant morphology and composition. Because they are solid-state devices, LEDs are easily integrated into digital control systems, facilitating special lighting programs such as "daily light integral" lighting and sunrise and sunset simulations. LEDs are safer to operate than current lamps because they do not have glass envelopes or high touch temperatures, and they do not contain mercury. The first sustained work with LEDs as a source of plant lighting occurred in the mid-1980s to support the development of new lighting systems to be used in plant growth systems designed for research on the space shuttle and space station. These systems progressed from simple red-only LED arrays using the limited components available at the time to high-density, multicolor LED chip-on-board devices. As light output increases while device costs decrease, LEDs continue to move toward becoming economically feasible for even large-scale horticultural lighting applications.
Pea is an important grain legume and vegetable in the South of Europe where it is grown on small farms and gardens using traditional varieties and methods during the winter. Variability in old, unimproved varieties needs to be determined in order to create useful genetic variation for broadening the narrow genetic base of commercial cultivars and for making efficient use of available resources. One hundred and four unimproved pea varieties and ten elite cultivars were evaluated in 1991 and 1992 at two locations for seed and vegetable quality, canopy and agronomic traits. Significant genotype by environment (G x E) interactions were found for protein concentration, fresh seed size and weight, canopy traits, pod length and weight, days to flowering, and days to fresh seed and pod maturity. There were significant differences between unimproved pea varieties for all traits studied except for seed soluble sugars and seed tanderness. Most of the significant differences for seed and vegetable quality traits were observed in the unimproved germplasm from the South of Europe when compared with differences within the elite germplasm. Data from the evaluation of available pea germplasm provide information needed by breeders to develop varieties efficiently for the different needs of growers, processors and feed manufacturers. The relevance of these results in devising breeding strategies is discussed.
The daily light integral (DLI) is a measurement of the total amount of photosynthetically active radiation delivered over a 24-hour period and is an important factor influencing plant growth over weeks and months. Contour maps were developed to demonstrate the mean DLI for each month of the year across the contiguous United States. The maps are based on 30 years of solar radiation data for 216 sites compiled and reported by the National Renewable Energy Lab in radiometric units (watt-hours per m-2·d-1, from 300 to 3,000 nm) that we converted to quantum units (mol·m-2·d-1, 400 to 700 nm). The mean DLI ranges from 5 to 10 mol·m-2·d-1 across the northern U.S. in December to 55 to 60 mol·m-2·d-1 in the southwestern U.S. in May through July. From October through February, the differences in DLI primarily occur between the northern and southern U.S., while from May through August the differences in DLI primarily occur between the eastern and western U.S. The DLI changes rapidly during the months before and after the vernal and autumnal equinoxes, e.g., increasing by more than 60% from February to April in many locations. The contour maps provide a means of estimating the typical DLI received across the U.S. throughout the year.
Lignin is a polymer formed from monolignols derived from the phenylpropanoid pathway in vascular plants. It is deposited in the cell walls of plants as part of the process of cell maturation. Lignin is considered an anti-quality component in forages because of its negative impact on the nutritional availability of plant fiber. Lignin interferes with the digestion of cell-wall polysaccharides by acting as a physical barrier to microbial enzymes. Lignification therefore has a direct and often important impact on the digestible energy (DE) value of the forage. There are a number of plant-related factors that affect lignification in individual plants and plant communities. Lignification is under genetic control and there are considerable differences in lignin concentration and composition among species and even genotypes within species. Genetic differences in lignification are first expressed at the cellular level and are affected by biochemical and physiological activities of the cell. As cells differentiate, differences in lignification occur depending on the tissues and organs being developed. Lignification tends to be most intense in structural tissues such as xylem and sclerenchyma. Plant organs containing high concentrations of these tissues, such as stems, are less digestible than those containing lower concentrations. The relative proportion of lignified tissues and organs typically increases as plants mature so there is often a negative relationship between digestibility and maturity. All of these plant processes respond to environmental factors that can affect the extent and impact of lignification. Temperature, soil moisture, light, and soil fertility can have either direct or indirect effects on lignification. The most useful management practices for minimizing the negative effects of lignification are manipulation of the plant community such that it contains more desirable species and harvest management to maintain plants in a vegetative stage of development. /// La lignina es un polímero formado de monolignoles derivados de la vía fenilpropanoide de las plantas vasculares. Se deposita en las paredes celulares de las plantas como parte del proceso de maduración de la célula. En los forrajes, la lignina se considera como un componente anti-calidad por su impacto negativo en la disponibilidad nutricional de la fibra de la planta. La lignina interfiere con la digestión de los polisacáridos de la pared celular al actuar como barrera física para las enzimas microbianas. Por lo tanto, la lignificación tiene un impacto directo, y a menudo importante, en el valor de la energía digestible (ED) del forraje. Hay un número de factores relacionados con la planta que afectan la lignificación de las plantas individuales y de las comunidades vegetales. La lignificación esta bajo control genético y hay considerables diferencias entre especies, y aun entre genotipos de la misma especie, respecto a la concentración y composición de la lignina. Las diferencias genéticas de lignificación se expresan primeramente a nivel celular y son afectadas por las actividades bioquímicas y fisiológicas de la célula. Conforme la célula se diferencia ocurren diferencias en la lignificación, dependiendo de los tejidos y orgános que se estén desarrollando. La lignificación tiende a ser mas intensa en tejidos estructurales como el xilema y esclerénquima. Los órganos de la planta que contienen altas proporciones de estos tejidos, tales como los tallos, son menos digestibles que aquellos que contienen bajas concentraciones. La proporción de tejidos y órganos lignificados típicamente aumenta conforme la planta madura, por lo que a menudo hay una relación negativa entre la digestibilidad y madurez. Todos estos procesos de la planta responden a factores ambientales que pueden afectar la cantidad e impacto de la lignificación. La temperatura, humedad del suelo, luz y fertilidad del suelo pueden tener también efectos directos o indirectos en la lignificación. Las practicas de manejo mas útiles para minimizar los efectos negativos de la lignificación son la manipulación de las comunidades vegetales para que contengan mas especies deseables y el manejo de la cosecha para mantener las plantas en estado vegetativo.
The global increase in energy prices, the urgent need to reduce CO2 emissions to the atmosphere and the high energy usage are currently the major threats to the greenhouse industry. Optimised control of the lighting quality, quantity and periodicity can contribute to improvements in the productivity and energy efficiency of greenhouses. In this paper, the effects of dynamic control of supplemental lighting intensity on electricity consumption and fresh weight accumulation of lettuce plants are investigated. The use of the dynamic lighting control resulted in a 20% reduction in the electricity consumption in comparison to a similar lighting system operated under a discontinuous on–off regime. However, there was no statistically significant difference between both regimes in terms of plants’ average fresh weight accumulated per electrical energy unit consumed.
Perception of fruit and vegetable flavor is a composite of sensory responses in the nose and mouth to aroma and taste. A diverse array of fruit and vegetable constituents including acids, sugars, volatiles and many other compounds individually elicit sensory responses that are recognized in total as flavor. Accumulation of these compounds during development as well as dynamic changes during ripening and/or senescence are determined in large part by the genetics of each species as well as developmental stage at harvest. However, other factors that influence development prior to harvest subsequently impact flavor. For horticultural crops, environment, cultural practices, agrichemicals and nutrition are some of the factors impacting flavor through effects on plant development.
In intensive horticultural cultivation natural light levels often limit crop production during several periods. For an optimum plant production and product quality light intensity, spectrum and photoperiod have to be adapted to the needs of the crops at every moment. Light has to be optimised together with all other growth factors like temperature, humidity and CO2. For a sustainable greenhouse production the use of freely available sunlight has to be preferred. New transparent greenhouse covering materials, like ETFE, glass with new anti-reflection coatings or materials with micro-surface structures, transmit a very high amount of light into the greenhouse. Other new materials are able to scatter the incoming light and make it diffuse. Diffuse light penetrates deeper into the canopy, increases light interception by the crop, influences micro-climate and increases crop production by 6.5-9.2% in The Netherlands, the potential in lower latitudes is even higher. Other materials manipulate light spectrum. Photoselective nettings have been developed in different colours influencing morphogenesis and crop production. Fluorescent plastic films combine effects on morphogenesis with high light transmission, especially important for higher latitudes. When sunlight is optimized it can still be necessary to add artificial light to ensure a year-round supply of horticultural products. There is still room for improving the crop energy efficiency under artificial lighting by changing duration and intensity of lighting, different growing systems and plant densities. Since artificial lighting requires a high amount of energy, new artificial lighting systems have been developed, such as interlighting and light emitting diodes (LED). LED give the possibility for true light spectrum control in the future. The (partial) replacement of HPS lamps by LED systems is currently under investigation in Dutch greenhouses. Integration in current growing systems has full attention. In order to reach a high sustainable and economic beneficial production the factor light has to be integrated and optimized within the total horticultural system
Pea ( Pisum sativum L.) yields are generally highly dependent on seed number. The objective of the present study was to investigate seed and plant development of 10 contrasting genotypes of pea with differences in seed size (0.1–0.3 g seed ⁻¹ ), foliage type (semi‐leafless and leafed), and number of branches. The periods of seed set and seed filling were studied in the field for 2 yr at two sowing dates. Seed water content (WC) was closely related to seed development. Seed water content at beginning of seed filling and at physiological maturity corresponded to 0.85 and 0.55 g g ⁻¹ fresh weight, respectively. The progression of flowering, beginning of seed filling, and physiological maturity along the stem were linearly related to cumulative degree days from the beginning of flowering. The rates of progression of flowering and of beginning of seed filling were not dependent on environmental conditions, but they were significantly different among genotypes. Conversely, the duration of the lag phase, time between flowering and beginning of seed filling at the first node, remained stable in spite of differences in seed size. The onset of physiological maturity was more variable. Duration of seed filling varied among environments, but genotypes had similar durations in spite of differences in seed size. Seed number on the main stem was fixed when the seeds of the last reproductive node began to fill. The delimitation of the seed set period showed genetic variability for the beginning of the period, depending on the first reproductive node number, and its duration.
Experiments were conducted to determine the effect on soybean seed yields and yield components of increasing the amount of light available in the soybean leaf canopy and to evaluate the photosynthetic contribution of leaves at different levels in the canopy.
Wide spectrum fluorescent lamps were placed at three levels in the canopies of ‘Amsoy’ and ‘Wayne’ varieties planted in rows 50‐cm and 100‐cm apart. White reflective polyethylene strips were placed between the rows. At harvest each plant was divided into top, middle, and bottom thirds corresponding to the levels of artificial lamps in the canopy.
Measurements of apparent photosynthesis (AP) and respiration of individual soybean leaves were made with a plexiglass single leaf photosynthesis chamber. AP and respiration rates (rag CO 2 /dm ² /hr) were determined by recording the change in CO 2 concentration with time in a closed system.
Adding light increased the yields of bottom, middle, and top canopy positions of plants 30, 20, and 2%, respectively. Light‐rich plants had more seeds, nodes, pods, branches, pods per node, seeds per pod, and a higher oil content than normal plants. Protein content and seed size were decreased by adding light.
The rates of AP of bottom and middle soybean leaves were 13 and 60% of the 20.2 mg CO 2 /dm ² /hr rate of top leaves under natural canopy conditions. When exposed to full sunlight, bottom and middle leaves fixed 258 and 50% more CO 2 , respectively, than when naturally shaded.
Respiration rates decreased with depth in the canopy. Top, middle, and bottom leaves had respiration rates of 6.8, 4.3, and 2.8, mg CORespiration rates decreased with depth in the canopy. Top, middle, and bottom leaves had respiration rates of 6.8, 4.3, and 2.8, mg CO 2 /dm ² /hr, respectively.
Abstract This review concerns both the botanical and the practical aspects of commonly recognized texture qualities of fruits and vegetables. Interrelationships between tissue structure and composition provide a wide variety of textural qualities in fresh and processed fruits and vegetables. Structural sources of textural appearance are described for several fruits and vegetables. Various examples of specialized supporting and fibrous tissues are also described with reference to problems of texture quality in frozen and dehydrated products. The roles of plant cell wall composition and of cellular contents, such as starch, are discussed with specific examples of manipulative control of texture in several processed products.
The measurements were made to provide a basis for discussion of the definition of “photosynthetically active radiation”. The action spectrum, absorptance and spectral quantum yield of CO2 uptake were measured, for leaves of 22 species of crop plant, over the wavelength range 350 to 750 nm. The following factors were varied: species, variety, age of leaf, growth conditions (field or growth chamber), test conditions such as temperature, CO2 concentration, flux of monochromatic radiation, flux of supplementary white radiation, orientation of leaf (adaxial or abaxial surface exposed). For all species and conditions the quantum yield curve had 2 broad maxima, centered at 620 and 440 nm, with a shoulder at 670 nm. The average height of the blue peak was 70% of that of the red peak. The shortwave cutoff wavelength and the height of the blue peak varied slightly with the growth conditions and with the direction of illumination, but for the practical purpose of defining “photosynthetically active radiation” the differences are probably insignificant. The action spectrum for photosynthesis in wheat, obtained by Hoover in 1937, could be duplicated only with abnormally pale leaves.
The effects of precooling, modified atmosphere packaging (MAP) and controlled atmosphere (CA) storage on the storability of snow pea pods (Pisum sativum L. var. saccharatum) at 5°C were determined. Bagging pods with polymethyl pentene polymeric films (PMP) of 25 and 35 μm thickness, in conjunction with precooling, modified the in-bag atmosphere concentration to approximately 5 kPa O2 and 5 kPa CO2, leading to better maintenance of the pod external quality (appearance and color), as well as internal quality (chlorophyll, ascorbic acid, and sugar contents). Sensory scores were also maintained. Under CA storage at 5°C, gas compositions ranging from 5 to 10 kPa O2 with 5 kPa CO2 were the best storage conditions of those tested, since changes in organic acid, free amino acid and sugar contents, and pod sensory attributes were slight, corroborating the MAP results. The appearance of pods stored under CA conditions was much better than that of air-stored pods (control). Low O2 (2.5 kPa with 5 kPa CO2) and high CO2 (10 kPa with 5 kPa O2) concentrations have a detrimental effect on quality of stored pods since they developed slight off-flavors, but this effect is reversible since it was partially alleviated after ventilation.
Seedless cucumber (Cucumis sativus L.) cv. Flamingo was grown in winter time in glass, double-inflated polyethylene (D-poly) and twin-wall acrylic (acrylic) greenhouses with or without 16 h (3:00–19:00 hours) of supplemental lighting to investigate the effects of the cover materials and supplemental lighting on plant growth, photosynthesis, biomass partitioning, early fruit yield and quality. Supplemental lighting promoted plant development and increased leaf chlorophyll, leaf photosynthesis, plant biomass and early marketable yield production. Supplemental lighting also increased biomass allocation to fruit, fruit dry matter content and skin chlorophyll content. There was little difference in leaf photosynthesis rates of plants under the three cover materials although solar irradiance on sunny days was much higher in glass than in D-poly houses. Dry matter production of plants grown in glass houses was higher than in D-poly and acrylic houses, but dry matter partitioning was not different under the three greenhouse covers. The high dry matter production in glass houses was translated into high fruit dry matter content, but not high early marketable yield. Cucumber early marketable yield in glass houses was similar to that in D-poly but lower than in acrylic houses. The supplemental lighting sufficiently compensated for the loss of solar radiation in D-poly and acrylic houses.
Photosynthetic efficiency, primary productivity, and N(2) reduction were determined in peas (Pisum sativum L. var. Alaska) grown at light intensities ranging from severely limiting to saturating. Plants grown under higher light intensities showed greater carboxylation and light capture potential and higher rates of net C exchange. Uptake of N(2), computed from measured C(2)H(2) reduction and H(2) evolution rates, also increased with growth light intensity, while the previously proposed relative efficiency of N(2) fixation, based on these same parameters, declined. The plot of N/C ratios (total nitrogen content/plant dry weight) increased hyperbolically with light intensity, and the plot of N(2)/CO(2) uptake ratios (N(2) uptake rate/net CO(2) uptake rate) increased linearly. Both plots extrapolated to the light compensation point. The data indicate that the relative efficiency of N(2) fixation is not necessarily correlated with maximum plant productivity and that evaluation of a plant's capacity to reduce N(2) is related directly to concurrent CO(2) reduction. A measure of whole plant N(2) fixation efficiency based on the N(2)/CO(2) uptake ratio is proposed.
Peas: food sense guide to eating fresh fruits and vegetables
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Effects of shading and ethephon on carbon assimilates distribution partitioning in fruit limb of greenhouse-grown 'Dajiubao' peach
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