“…In recent years, an increasing number of supplementary light technology using light emitting diodes (LEDs) has been used in agricultural production [17][18][19][20]. The improvement in the growth, yield, and quality of crops has been confirmed by many studies [6,[21][22][23].…”
Insufficient exposure to light in the winter may result in a longer production periods and lower quality of seedlings in greenhouses for plug growers. Supplementary artificial lighting to plug seedlings may be one solution to this problem. The objective of this study was to assess the effects of the duration of the supplementary light on the growth and development of two watermelon cultivars, ‘Speed’ and ‘Sambok Honey’ grafted onto ‘RS-Dongjanggun’ bottle gourd rootstocks (Lagenaria siceraria Stanld). Seedlings were grown for 10 days in a glasshouse with an average daily natural light intensity of 340 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) and daily supplementary lighting of 8, 12 or 16 h from mixed LEDs (W1R2B1, chip ratio of white:red:blue = 1:2:1) at a light intensity of 100 μmol·m−2·s−1 PPFD, a group without supplementary light was set as the control (CK). The culture environment in a glasshouse had 25/15 °C day/night temperatures, an 85 ± 5% relative humidity, and a natural photoperiod of 8 h. The results showed that all the growth and development parameters of seedlings grown with supplementary light were significantly greater than those without supplementary light (CK). The 12 and 16 h supplementary light resulted in greater growth and development parameters than the 8 h supplementary light did. The same trend was also found with the indexes that reflect the quality of the seedlings, such as the dry weight ratio of the shoot and root, total biomass, dry weight to height ratio of scions, and specific leaf weight. The 12 h and 16 h light supplements resulted in greater Dickson’s quality indexes compared to the 8 h supplementary light, and the 12 h supplementary light showed the greatest use efficiency of the supplementary light. 16 h of daily supplementary light significantly increased the H2O2 content and the antioxidant enzyme activities in seedlings compared to the other treatments. This indicated that 16 h of supplementary light led to certain stresses in watermelon seedlings. In conclusion, considering the energy consumption, 12 h of supplementary light was the most efficient in improving the quality of the two cultivars of grafted watermelon plug seedlings.
“…In recent years, an increasing number of supplementary light technology using light emitting diodes (LEDs) has been used in agricultural production [17][18][19][20]. The improvement in the growth, yield, and quality of crops has been confirmed by many studies [6,[21][22][23].…”
Insufficient exposure to light in the winter may result in a longer production periods and lower quality of seedlings in greenhouses for plug growers. Supplementary artificial lighting to plug seedlings may be one solution to this problem. The objective of this study was to assess the effects of the duration of the supplementary light on the growth and development of two watermelon cultivars, ‘Speed’ and ‘Sambok Honey’ grafted onto ‘RS-Dongjanggun’ bottle gourd rootstocks (Lagenaria siceraria Stanld). Seedlings were grown for 10 days in a glasshouse with an average daily natural light intensity of 340 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) and daily supplementary lighting of 8, 12 or 16 h from mixed LEDs (W1R2B1, chip ratio of white:red:blue = 1:2:1) at a light intensity of 100 μmol·m−2·s−1 PPFD, a group without supplementary light was set as the control (CK). The culture environment in a glasshouse had 25/15 °C day/night temperatures, an 85 ± 5% relative humidity, and a natural photoperiod of 8 h. The results showed that all the growth and development parameters of seedlings grown with supplementary light were significantly greater than those without supplementary light (CK). The 12 and 16 h supplementary light resulted in greater growth and development parameters than the 8 h supplementary light did. The same trend was also found with the indexes that reflect the quality of the seedlings, such as the dry weight ratio of the shoot and root, total biomass, dry weight to height ratio of scions, and specific leaf weight. The 12 h and 16 h light supplements resulted in greater Dickson’s quality indexes compared to the 8 h supplementary light, and the 12 h supplementary light showed the greatest use efficiency of the supplementary light. 16 h of daily supplementary light significantly increased the H2O2 content and the antioxidant enzyme activities in seedlings compared to the other treatments. This indicated that 16 h of supplementary light led to certain stresses in watermelon seedlings. In conclusion, considering the energy consumption, 12 h of supplementary light was the most efficient in improving the quality of the two cultivars of grafted watermelon plug seedlings.
“…In vertical farming systems, plants are exposed to a restricted number of constant environmental parameters, including lighting, during the day [10]. The combinations of red (R) and blue (B) light-emitting diodes (LEDs) are used as the most efficient and sufficient light for normal plant growth and productivity [11,12].…”
Controlled environment agricultural (CEA) systems create technological opportunities for the higher nutritional value of vegetables and herbs. It was hypothesized that UV-A light, supplementing basal light emitting diode (LED) illumination in CEA, would enhance growth and nutritional value (nutraceutical compounds and mineral element contents) in purple and green basil in a UV-A wavelength-specific manner. Therefore, blue (452 nm) and red (662 nm) 1:10 basal LED lighting (250 μmol m−2 s−1, 16 h) was supplemented with 1 mW cm−2 of 343, 366, 386, or 402 nm UV-A LED light for green ‘Italiano classico’ and purple ‘Red rubin’ basil cultivation. Different wavelengths have specific impacts for two basil genotypes, and certain light wavelengths should be selected to boost growth or to alter the contents of specific nutraceutical compounds. UV-A/violet 402 nm light enhanced growth, chicoric acid, β carotene, lutein, and zeaxanthin contents in green basil, while 343 nm UV-A light increased fresh weight, ascorbic acid, and carotenoid content in purple basil. UV-A light of 386 nm has the most negligible impact on reducing mineral element (P, Ca, Fe, K, Mg, Mn, and Zn) contents in basil. Understanding the wavelength dependence of plant responses to UV-A is essential for optimizing quality preservation and improving basil cultivation in controlled environment systems.
Terrestrial organisms and ecosystems are being exposed to new and rapidly changing combinations of solar UV radiation and other environmental factors because of ongoing changes in stratospheric ozone and climate. In this Quadrennial Assessment, we examine the interactive effects of changes in stratospheric ozone, UV radiation and climate on terrestrial ecosystems and biogeochemical cycles in the context of the Montreal Protocol. We specifically assess effects on terrestrial organisms, agriculture and food supply, biodiversity, ecosystem services and feedbacks to the climate system. Emphasis is placed on the role of extreme climate events in altering the exposure to UV radiation of organisms and ecosystems and the potential effects on biodiversity. We also address the responses of plants to increased temporal variability in solar UV radiation, the interactive effects of UV radiation and other climate change factors (e.g. drought, temperature) on crops, and the role of UV radiation in driving the breakdown of organic matter from dead plant material (i.e. litter) and biocides (pesticides and herbicides). Our assessment indicates that UV radiation and climate interact in various ways to affect the structure and function of terrestrial ecosystems, and that by protecting the ozone layer, the Montreal Protocol continues to play a vital role in maintaining healthy, diverse ecosystems on land that sustain life on Earth. Furthermore, the Montreal Protocol and its Kigali Amendment are mitigating some of the negative environmental consequences of climate change by limiting the emissions of greenhouse gases and protecting the carbon sequestration potential of vegetation and the terrestrial carbon pool.
Graphical abstract
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