Response Of Growth Physiology,Yield And Quality Of Cucumber Under Substrate Culture To Different Irrigation Lower Limit

In order to find out the suitable lower limit of irrigation and realize agricultural water-saving.In this experiment,the cucumber variety "Bote 209" was used as the test material,and the substrate potting was used.Four irrigation lower limit treatments were set,which were 50%,60%,70% and 80% of the field water capacity respectively A.According to B,C and D,the upper limit of irrigation was set as 90% of the field water capacity.TDR350 was used to control the water content of the substrate.The effects of different lower limits of irrigation on the growth of cucumber plants,water status of leaves,antioxidant system and diurnal variation of photosynthesis,fluorescence parameters,yield and quality were studied.The growth,yield and quality phases of four treatments were selected and the principal component analysis was used to evaluate the 22 indexes.The main results are as follows:1.The plant height and leaf area of 80% field water capacity irrigation lower limit were significantly higher than other treatments,but the stem diameter was 70% field water capacity irrigation lower limit was the highest and significantly higher than other treatments,which indicated that properly reducing the irrigation lower limit was conducive to the increase of stem diameter;under different irrigation lower limits,there was a certain difference in the distribution proportion of dry matter of yellow melon,in which the root dry matter accounted for the total plant dry matter and the ratio of fruit dry weight to plant dry weight was the highest at the lower limit of 70% field water capacity.2.The free water and relative water content of the lower irrigation limit of 70%-80% field water capacity were higher,and the cell sap concentration was more suitable than the other two treatments,which was conducive to maintaining the normal shape of leaf cells;the MDA and pro content of the lower irrigation limit of 70% and 80% field water capacity were lower than the other two treatments,and the activity of antioxidant enzymes was 60% > 50% > 70% > 80%.3.Fv/Fm,?PSII,qP of 50% field water capacity irrigation lower limit were significantly lower than the other three treatments,while NPQ was significantly higher than the other three treatments,which indicated that the treatment significantly inhibited the transformation of cucumber light energy.70%-80% field water capacity irrigation lower limit had higher Fv/Fm,?PSII,qP and lower NPQ,which was conducive to the effective transformation of light energy and high light energy conversion rate.4.The content of chlorophyll a and chlorophyll b in the lower limit of 70% field water capacity was the highest;the research on the diurnal change of photosynthesis showed that the Ci change trend of 70% and 80% field water capacity was basically the same,and the Ci change trend of 50% and 60% field water capacity was the same;the Tr peak value of 50% field water capacity appeared earlier than the other three treatments,and the lower limit of irrigation was 50% field water capacity The results showed that the peak value of water yield appeared at 12:00,while the other three peaks appeared at 14:00.The reasons for the phenomenon of “photosynthetic noon break” in each treatment were also different.The reason for the phenomenon of "photosynthetic noon break" in the lower limit of 70% and 80% field water holding capacity was stomatal limiting factor,while the lower limit of 50% and 60% field water holding capacity was non stomatal limiting factor.In the whole process,70% and 80% of Pn were higher than the other two treatments.5.The weight of single fruit,the number of fruit per plant and the yield per mu all showed a gradual upward trend.The lowest irrigation limit of 80% of the field water capacity was the highest,but there was no significant difference between the weight of single fruit and the yield per mu and 70% of the treatment.However,the water use efficiency first increased and then decreased.The lowest irrigation water use efficiency of 70% of the field water capacity was the highest,with an increase of 33.14%,13.23% and 10.30% compared with 50%,60% and 80%.6.The length,thickness,water content and commercial melon rate of cucumber fruit increased gradually,with the highest of 80% field water capacity irrigation lower limit;the content of soluble protein,soluble sugar,K and Ca in cucumber fruit increased first and then decreased with the increase of irrigation lower limit,with the highest of 70% field water capacity irrigation lower limit.7.The principal component analysis showed that the evaluation indexes of the effect of different irrigation lower limit on the growth,yield and quality of cucumber were reduced from the initial 22 aspects to three principal components,which achieved the goal of dimension reduction.The three principal components replaced the information of the original index by 100%.The comprehensive evaluation results showed that the scoring order of each treatment was 70% field water holding capacity,80% field water holding capacity,60% field water holding capacity and 50% field water holding capacity in turn Lower limit of irrigation quantity.In conclusion,the lower limit of irrigation is 70-80% of the field water capacity,which is more suitable for the growth and development of cucumber.However,from the perspective of water conservation,the lower limit of irrigation of 70% of the field water capacity does not reduce the yield,but can improve the quality and water use efficiency of cucumber.Therefore,70% of the field water capacity can be used as the lower limit of water conservation irrigation of cucumber cultivated in substrate.