| As a new type of energy saving plant light source,LED pulsed light has gradually attracted people’s attention.It affects plant growth and development by changing the frequency and duty ratio.Previous studies have found that under certain frequency and duty ratio pulsed light treatment,the net photosynthetic rate of lettuce is not significantly different from that of continuous light.In other words,light plays basically the same role as continuous light in the process of stroboscopic irradiation,which is of great significance for the research and development of energy-saving supplementary light lamps in plant factory.In this study,glass lettuce was used as the experimental material.Firstly,the effects of different duty ratios of 128 Hz LED on growth and photosynthetic fluorescence characteristics of lettuce were explored.Based on this and previous studies,the effects of pulsed light treatment with multiple frequency and duty ratio combinations on chlorophyll fluorescence characteristics of lettuce were thoroughly explored.In addition,the effects of pulsed light on the growth of lettuce were studied in detail through long-term experiments,and the preliminary analysis of omics was made.Finally,based on the preliminary test results,the appropriate pulsed light parameters were selected to design the LED energy-saving plant light supplement lamp,and the energy saving and light supplement effect was verified in the field with Chinese cabbage as the test material.The main findings are as follows:(1)The chlorophyll content,photosynthetic parameters,biomass,light energy utilization,chlorophyll fluorescence parameters and power consumption of LED lamp panel of lettuce treated with different duty ratios of pulsed light were measured.The results showed that: LED pulsed light with different duty ratios could save energy in different degrees.The chlorophyll content,biomass,ФPSII and ETR of lettuce treated with high duty ratio were not significantly different from those of continuous light.Although the light energy utilization rate of 20% duty ratio treatment was significantly higher than that of continuous light treatment,it was not conducive to the normal growth of lettuce.In conclusion,the high duty ratio not only achieves the same light supplement effect of continuous light under the premise of saving electricity,but also is more conducive to promoting PSII photosynthetic electron transfer and improving the photosynthetic potential of crops.(2)The chlorophyll fluorescence parameters of lettuce leaves under the combination of14 frequencies and 5 duty ratios were measured.The results showed that:Pulsed light with low frequency and low duty ratio would reduce the photosynthetic activity of lettuce leaves.Low duty ratio below 2 Hz would cause damage to PSII.Compared with continuous light,pulsed light with high frequency and low frequency and high duty ratio would not affect the PSII activity,photosynthetic electron transport and energy distribution of lettuce leaves.(3)The effects of pulsed light frequency and duty ratio on growth of lettuce were studied,and the preliminary analysis of transcriptome and metabolome was conducted.The results showed that: The effects of D20 on lettuce were significantly lower than those of D60 treatment and continuous light in morphological index,biomass,photosynthetic index and fluorescence index,while the differences of F64-D60 and F128-D60 pulsed light in biomass,photosynthetic pigment,photosynthetic parameters and fluorescence parameters were not significant.According to the previous results,transcriptome and metabolomic analysis were performed on F64-D20 and F64-D60,and a total of 1766 differentially expressed genes were annotated into KEGG pathway,among which 35 differentially expressed genes related to photosynthesis were similar in expression trend to the previous physiological indicators.In terms of metabolome,porphyrin and chlorophyll metabolism and carbon metabolism pathways were mainly analyzed,which contained 19 and 12 different metabolites,respectively.(4)According to previous research results,the design of 256 Hz,60% duty ratio of LED plant,as the fill light and LED light continuously comparing and natural conditions,to Chinese cabbage as test object,the extension of the fill light field experiment,the indexes of Chinese cabbage were tested,photosynthetic parameters,chlorophyll fluorescence parameters and biomass as well as the daily power consumption as the fill light.The results showed that the effect of LED pulsed light and continuous light were basically the same.Both of them significantly improved the plant height,plant width,shoot weight and chlorophyll fluorescence(ΦPSII,ETR and q L)indexes of Chinese cabbage,and the daily power consumption of LED pulsed light was 38.75% less than that of continuous light,which is beneficial to the promotion and application of LED energy-saving light supplement technology. |
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