| Pulsed light is not only a kind of high frequency intermittent light source,but also a kind of high quality light source which can improve the utilization rate of plant light energy and realize efficient conversion of light energy.The predecessors'study show that based on the same illumination time,pulsed light under high frequency and high duty ratio can obtain the same biomass compared with continuous light,but pulsed light power consumption by the static power consumption?affected by the duty ratio?and dynamic power consumption?affected by frequency?,low frequency and duty ratio are not conducive to plant growth,but too much can cause light increases power consumption.So it is important for actual production to investigated the relative energy saving frequency and duty ratio and does not affect production of the combination.With lettuce as test materials,this study first explores the net photosynthetic rate,under different frequency and duty ratio.Based on the study,we established a model of pulsed light photosynthetic response,and studied rate of different pulsed light influence on th lettuce growth and photosynthetic based on conduction of same light photosynthetic characteristics as continuous light,attempts to provide theoretical basis and technical parameters for the optimization of pulsed light parameters..The main findings are as follows:?1?By measuring the photosynthetic parameters of lettuce leaves at different frequencies and duty ratios of pulsed light,the results showed that the photosynthetic rate of lettuce leaves increased gradually with the increase of frequency and duty ratios,and tended to be stable at the same photosynthetic rate as continuous light.In most cases,the instantaneous energy utilization rate of lettuce leaves decreased gradually with the increase of duty ratios and frequency,and the increase shows a gradual upward trend and tends to be stable.?2?The mathematical model of photosynthetic response to pulsed light was established based on the net photosynthetic rate of lettuce leaves at different frequencies and duty ratios.Through the marginal effect analysis and interaction analysis,we found that Pn affected by the interaction of frequency and duty ratio,frequency and duty ratio increase of the lettuce leaves Pn,but with the increase of duty ratio or frequency,the lower promoting effect and gradually tend to be zero,this is the same change rule compared with the measured values.The model has a high degree of goodness of fit?0.9887?.Through experimental verification and analysis,the average error between the measured value and the predicted value is 3.1%,and the maximum error is 9.1%,indicating that the model established is relatively accurate and of high accuracy.?3?Based on the same net photosynthetic rate and continuous light,by setting up 20%,2048 Hz?T1?,40%,512 Hz?T2?,80%,128 Hz?T3?three combination of frequency and duty ratio of pulsed light processing,and the continuous light?100%duty cycle?for comparison,found that under different pulse light treatment of lettuce,the ground dry and fresh weight,plant height,leaf width,and Pn,qP,?PS?and ETR had no significant difference compared with continuous light,and the contents of total soluble sugar,reducing sugar and nitrate nitrogen were better than continuous light,the quality of the lettuce under T1 treatment is best,compared with a continuous light,the difference of VC and soluble protein content was not significant,but compared with CK,the soluble total sugar,reducing sugar content increased 64.32%and 72.98%,nitrate content was reduced 41.94%.?4?Considering the yield,the combination of frequency and duty ratio with minimum power consumption without affecting the yield can be obtained according to the model.However,in actual production,the appropriate light source with pulsed light should be selected according to different production requirements and in combination with the yield,quality and energy consumption of plants under different pulsed light frequencies and duty ratios. |
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