Optimizing Light Supplementary Strategy Of Lettuce By LED Light Source Under Different Temperatures And Light Intensities

[Objective] Temperature and illumination environment in solar greenhouse are changing with time and season.At present,the research on crop light supplement by LED light source is mostly focused on regulating the light quality,intensity and mode of light supplement,but it is particularly important to explore the interaction between other environmental factors and LED light supplement on crops.This experiment explored the effect of different power density LED light source on the net photosynthesis of lettuce population under the interaction of temperature and light environment,and explored the reasonable and economical power density of LED light supplement under different temperature and light environment,which laid a foundation for the optimization of light supplement mode in actual production.[Method]The artificial climate box was used to create the basic temperature and illumination conditions.The ambient temperature was set at 15,20,25,30 and 35?.The basic light intensity of 100,250,400,550 and 700 ?mol/m2·s was set at each temperature.Under the interaction of temperature and light,the pre-and post-illumination were measured by artificial supplementation with three kinds of LED power densities of 24,48 and 72 W/m2.The net photosynthetic rate of vegetable population,the energy utilization rate of LED light source and the economic analysis after light supplementation were calculated,and the following conclusions were drawn.[Conclusion] The net photosynthetic rate of lettuce population was basically the same at ambient temperature of 15-20? and basic light intensity of 100-400umol/m2·s.When the basic light intensity increased to 550 umol/m2·s,the net photosynthetic rate of lettuce population at 20?was significantly higher than that of lettuce population at15?.The net photosynthetic rate of lettuce population reached the highest at 25?,and reached the highest at 30?.The net photosynthetic rate began to decrease.The data showed that the net photosynthetic rate of lettuce population could be significantly increased by three kinds of power density light when the basic light intensity was below 550 umol/m2·s under different temperature treatments,and the higher the power density of light supplementation,the stronger the net photosynthetic rate of lettuce population.However,the net photosynthetic rate of lettuce population was not necessarily significantly different under different light supplementation treatments.Through further economic analysis,it is concluded that the maximum benefit can be obtained by using 72W/m2 high power density light supplement under 100 umol/m2·s basic light intensity at 15?,but the energy utilization rate of the light source is significantly lower than that of 24W/m2 supplement light treatment.The maximum benefit can be obtained by using 24W/m2 power density light supplement under250-550umol/m2·s basic light intensity,and the energy utilization rate is remarkably highest at20?.24W/m2 power density compensation has the highest energy utilization rate,but72W/m2 and 48W/m2 power density compensation have the greatest benefit under100-250umol/m2·s and 400-550umol/m2·s basic light intensity,respectively;24W/m2 power density compensation has the highest energy utilization rate under 100umol/m2·s basic light intensity at 25?,but 72W/m2 power density compensation has the greatest benefit under basic light intensity,and 72W/m2 power density compensation has the greatest benefit under basic light intensity.Under the condition of 250-400umol/m2·s the use of 48W/m2 power density to compensate the photovoltaic energy has the highest utilization rate and maximum benefit.Under the condition of 550umol/m2·s basic light intensity,the use of 24W/m2 power density to compensate the photovoltaic energy has the highest utilization rate and maximum benefit,while under the condition of 100-550umol/m2·s basic light intensity at 30?,the use of 72W/m2 power density to compensate the photovoltaic energy has the highest utilization rate and maximum benefit.When the monthly power consumption is more than 280 KW·h and the basic light intensity is as high as 700umol/m2·s,the power utilization rate is the highest and the maximum benefit is obtained by using 48W/m2 power density supplement.At35?,only when the basic light intensity is more than 400umol/m2·s and the monthly power consumption is less than 280 KW·h,the benefit is obtained by using 24W/m2 low power density supplement light.It is found that under the basic conditions,if only considering the economic supplementary light density,there exists a third of the cases where the energy utilization rate of light source is significantly lower than that of low power density light source,that is to say,it is a high-income situation which is obtained by wasting more energy.