Analysis On The Effect Of LED Supplemental Lighting Position On Tomato In Winter Solar Greenhouse

Tomato,as the main crop variety in sunlight greenhouse,is fond of temperature and light.But light environment in greenhouse is often limited,and the shortening of sunshine duration in winter intensifies the weak light and light shortage.Especially for crops such as tomatoes,which have higher plants and cultivated in high density,in order to increase yield,producers often use artificial supplemental lighting to improve the light environment conditions in plants and enhance photosynthetic capacity,providing a good growth and development foundation for tomatoes.At present,the research of artificial supplemental lighting mainly focuses on the composition of the light source,light intensity,light period and so on,research on the placement position of supplemental lighting lamp tube is less.Therefore,according to the commonly used supplemental lighting lamp tube placement,this paper adopts the top(L1),side(L2)and bottom(L3)three supplemental lighting methods,taking the tomatoes without supplemental lighting as control,further researches on differences between the two supplemental lighting methods of the side and bottom,the different lighting directions of leaves and the different lighting leaf positions(leaf ages).In order to understand the supplemental lighting effects of the different placement positions,and determine a better supplemental lighting scheme for greenhouse,the main findings are as follows:1.The results of supplemental lighting experiments with different positions of lamp tubes showed that top supplemental lighting only increased the light of upper layer,bottom and side supplemental lighting could improve the light distribution of middle and low parts of the plant,especially the bottom supplemental lighting,making the overall light environment of the plant more uniform.The increasement of light at middle and lower layers made the net photosynthetic rate(Pn)of middle and lower layers increase greatly,while bottom supplemental lighting irradiated the back of leaves,the stomatal conductance(Gs)increased the most.The increasement of Pn with bottom and side supplemental lighting treatment promoted the accumulation of photosynthetic products in leaves,and more organic matter could be transported to the fruits.Due to the increasement of dry weight of leaves and fruits,the dry matter distribution ratio of fruits and leaves increased,and the bottom supplemental lighting increased the dry matter distribution ratio of fruits most significantly.Red and blue light can effectively promote fruit color conversion and quality improvement.Soluble sugar,soluble solids and Vitamin C(Vc)content of fruits treated with side and bottom supplemental lighting were significantly higher than those of the control,but there was no significant difference between the top supplemental lighting and control.All supplemental lighting treatments had no significant effect on organic acid content.In each treatment,the weight of single fruit was: bottom>side>top>control.All treatments consumed the same amount of electricity,and the electrical energy efficiency of single fruit per spike was: bottom>side >top supplemental lighting treatment.2.The back supplemental lighting was more effective than the top supplemental lighting treatment in promoting stomatal opening movement,and Gs increased accordingly,thus the net photosynthetic rate increased greatly compared to the control.The front and back supplemental lighting could both increase the maximum net photosynthetic rate of leaves.The thickness of the leaf lower epidermis with back supplemental lighting increased the most,the thickness of upper epidermis with front supplemental lighting increased the most significantly,the palisade tissue and sponge tissue were thickened,the leaf became thicker,the effect of back supplemental lighting was most obvious,and the palisade tissue with back and front supplemental lighting were arranged more closely and neatly.Overall,the supplemental lighting effect of the lower epidermis on the back of the leaf was better than that on the front.3.Chlorophyll content of leaves at 6~14 leave positions increased after supplemental lighting,chlorophyll a and chlorophyll(a+b)at 8 leave position increased the most,and chlorophyll b at 10 leave position increased the most.Supplemental lighting treatment increased Pn of 5~16 leaves to various degrees,and had the most obvious effect on photosynthesis of 7~11 leaves,with Pn of 7,8 and 9 leave positions increasing most.The maximum net photosynthetic rate(Pnmax)increased after supplemental lighting except for the leaves at 3 and 4 leave position.The back supplemental lighting had a significant effect on the specific leaf weight of 7~11 leaf positions,and 10 leaf position had the highest specific leaf weight increasement.The results showed that the supplemental lighting effect was best for the 7~11 leave positions,which promoted the growth and photosynthesis of the leaves.To sum up,LED supplemental lighting can obviously optimize the growth and development of tomato plants and fruits.The improvement of growth and physiological indexes of tomato leaves after the back supplemental lighting treatment was mostly better than that of the front.The supplemental lighting response of leaves at different leaf positions were the most sensitive at 7~11 leaf positions.Chlorophyll content,specific leaf weight and photosynthesis were all improved.The bottom supplemental lighting method has the best effect.