Can LED supplemental lighting increase tomato yield?
Low light and insufficient sunlight can cause light stress in crops, slowing their growth and development, delaying flower bud differentiation, reducing photosynthetic rate, and lowering yield and quality. Studies have shown that under low light and insufficient sunlight conditions, crop light saturation point and photosynthetic capacity decrease, and the accumulation of nutrients such as vitamin C and soluble sugars is reduced. Low light and insufficient sunlight increases the risk of lodging, reduces fruit yield, increases the rate of spoiled fruit, and decreases the increase in crop height and stem diameter. Light stress also causes slow crop growth, delayed flowering, low fruit set, reduced single fruit weight, and reduced nutrient accumulation, leading to decreased yield and quality. Artificial lighting is an effective means of addressing insufficient light in greenhouse agriculture. Therefore, exploring the impact of artificial lighting under low light and insufficient sunlight conditions on the yield and quality of greenhouse vegetables is of great significance for improving the yield and quality of greenhouse vegetables and promoting the development of greenhouse agriculture.
Tomatoes are a common greenhouse horticultural crop and a light-loving vegetable. Low light levels can easily lead to flower organ drop, increased inflorescence node position, excessive vegetative growth, and an increased rate of small fruits. When light intensity is below 80 µmol/(m²·s), tomato plants cannot normally enter the reproductive growth stage. In red-blue light combinations, more red light is beneficial for flowering, while more blue light has an inhibitory effect on flowering. Blue light can induce stomatal opening in leaves; supplementing with blue light helps enhance photosynthesis, promotes root growth and nutrient absorption, and improves fruit quality. Blue light also promotes anthocyanin accumulation in fruit by inducing the expression of anthocyanin-related genes in bell peppers. Green light can drive leaf photosynthesis and regulate nitrogen metabolism; excessive green light can trigger a shading effect in plants. Treating tomatoes with green light at night can improve leaf photosynthetic capacity and fruit quality. Far-red light can improve the seedling vigor index and induce hypocotyl growth in tomatoes. When tomatoes are treated with both red and far-red light, those treated with a higher proportion of far-red light exhibit stronger plant tolerance, and the content of lycopene, vitamin C, total phenols, and flavonoids in the fruit is significantly increased.
Photosynthetic pigments are both light-harvesting agents and light-conversion hubs in plants; their types and levels are crucial for photosynthesis. Supplementing tomatoes with green light during the mature and seedling stages revealed that supplementation during the seedling stage decreased chlorophyll content, while supplementation during the mature stage increased chlorophyll content. Studies by Ma Xiaojing et al. showed that appropriate supplementation significantly increased the photosynthetic pigment content of plants compared to those without supplementation. For light-loving crops such as tomatoes, artificial lighting in greenhouses can significantly increase yield. Yan Wenkai's research indicates that supplementing with different proportions of red and blue light can increase greenhouse tomato yield. Studies have shown that increasing supplemental lighting duration can improve crop yield; after supplemental lighting, the photosynthetic rate of plants increases, the photosynthetic time is prolonged, and crops accumulate more photosynthetic products, thereby increasing yield. This study found that all supplemental lighting treatments significantly increased tomato yield, with the treatment of adding red light to red-blue light showing the highest yield.
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