Effects Of Artificial Lighting On Photosynthesis And Growth Of Tomato In Chinese Solar Greenhouse

Light is one of the most important environmental factors for affecting plant growth.In Chinese solar greenhouse,light is often a limiting factor for vegetable production in Winter due to low solar angle and the influence of weather conditions such as cloudy and haze days.Moreover,For high wire fruit vegetables,light is not evenly distributed inside plant canopy,particularly in the middle and lower canopies,which substantially limits photosynthesis and consequently production,this occurs even in Summer season.Therefore,Artificial light is widely used as an effective way to deal with the lack of illumination in Chinese solar greenhouse.However,in real production,the selection of the supplementary light source,the position of the light and the lighting strategy is not clear,and the study of electric use efficiency for greenhouse lighting has not been investigated.In this context,this study uses LED as the light source to conduct the experiment with different red/blue light ratios.At the same time,the effects of different ways and combinations of light(LED plus HPS)on the growth,photosynthesis and yield of tomato in Chinese solar greenhouse were investigated.Finally,the effects of LED interlighting and fruit load on the growth,yield and fruit quality of melon were explored.1.Experiment was conducted in the Chinese solar greenhouse with tomato.Different red and blue light proportion LED(R/B=4:1,R/B=7:1,R/B=9:1)were used for the treatments of the plant,and control(CK)treatment without artificial light,the effects of different red and blue light proportion on the growth and yield of tomato were studied.Results showed that,compared with the control treatment,the three interlighting treatments significantly increased tomato yield,with enhancement of 25.9%,28.5% and 22.7% for R/B=4:1,R/B=7:1 and R/B=9:1,respectively.The total aboveground dry matter production was increased by 26.2%,30.4%,28.4% for R/B=4:1,R/B=7:1 and R/B=9:1,respectively.Interlighting treatments also increased the maximum photosynthetic rate and light absorption at the wavelength of 500-650 nm for the upper canopy leaves,decreased the specific leaf area as well.Conclusion: the growth and yield of plants were enhanced by the interlighting,but there was no significant differences in plant growth among different lighting treatments because of the relatively low artificial light intensities compared with solar radiation.2.Experiment was conducted in the Chinese solar greenhouse with tomato.A CSG was divided into three sections,and three treatments were arranged,respectively.They were top lighting with HPS lamps(TL),TL plus interlighting with LEDs(TL+IL),and control treatment without artificial light.The experiment was conducted to study the effects of lighting on greenhouse environment,tomato growth,yield,dry matter accumulation,fruit quality and power utilization efficiency.The results showed that supplementary artificial light improved the uniformity of light distribution from south to north side of CSG.Tomato yield was increased by 21.8% and 32.9% in TL and TL+IL,respectively,compared with yield of control treatment.Higher yield under supplementary artificial light resulted from a larger number of ripe fruits rather than bigger fruit size.Moreover,fruit quality was improved by supplementary artificial light as indicated by a higher total soluble sugar content.It is not economicallyfeasible as 28.8 kWh electricity was required for increasing 1 kg tomato yield in CSG.Conclusion: the growth and yield of plants were enhanced by interlighting.Top lighting increased yield as improvement of total dry matter production,while interlighting increased yield as the fruit maturation were promoted.However,the efficiency of the supplementary lighting is low,and it needs to be improved in the production application.