Effects Of Low Temperature And Low Light On The Growth And Development Of Greenhouse Cucumbers During The Seedling Stag

Cucumber is one of the most widely cultivated vegetables in China.In winter and spring,under the influence of low temperature and low sunlight stress,the growth and development of cucumber is prone to problems such as poor vegetative growth,slow flower bud differentiation,and decreased yield.In this study,the cucumber variety’Jinyou 101’was used as a test material to carry out a two-factor environmental control experiment with low temperature and low light.Day/night temperature settings are 13/3℃,16/6℃,19/9℃,22/12℃,light settings are 200 and 400μmol·m^-2·s^-1 levels,duration design 3,6,9,12d,with 28/18℃and 800μmol·m^-2·s^-1 as the control（CK）.After treatment at the seedling stage,the photosynthetic parameters,fluorescence parameters,antioxidant enzyme activities and osmotic adjustment substances of cucumber leaves,the endogenous hormones and sugar content of terminal buds were measured,and the growth stages,flower bud differentiation duration,growth indicators,biomass,The flowering and yield of each node of the main vine revealed the mechanism of the influence of low temperature and low light on the growth and development of cucumber in the seedling stage.The main research results are as follows:（1）The content of photosynthetic pigments（Chla,Chlb and Car）,light saturation point（LSP）,maximum photosynthetic rate（Pmax）and apparent quantum efficiency（AQE）decreased with the increase of stress and time,while the light compensation point（LCP）increased,that is,the photosynthesis of cucumber leaves decreased gradually.With the increase of stress and time,the J-I-P phase of the fast fluorescence induction kinetic curve（OJIP curve）of cucumber leaves decreased gradually,the parameters of energy distribution ratio（φPo,ψEo andφEo）decreased gradually,and the light energy absorbed（ABS/RC）and trapped（TRo/RC）per unit active reaction center gradually increased,but the light energy used for electron transport（ETo/RC）still decreased.The contents of malondialdehyde（MDA）and soluble sugar increased with the increase of stress and time,while the activities of antioxidant enzymes（SOD and CAT）and soluble protein content increased at first and then decreased.（2）With the strengthening of stress and the extension of time,the process of flower bud differentiation of cucumber was gradually delayed.The female flower node rate and fruit setting rate of cucumber treated at 13/3℃and 16/6℃decreased with the increase of stress and time,while the first female flower node position increased,and the female flower node rate,the first female flower node position and fruit setting rate were not significantly affected by the treatment of 19/9℃and 22/12℃,but the female flower node rate of 19/9℃treatment was always slightly higher than that of CK,indicating that the low temperature may promote the differentiation of cucumber female flower.The results of correlation analysis showed that the female flower node rate was significantly positively correlated with endogenous zeatin（ZT）and auxin（IAA）content in terminal bud,extremely significant positive correlation with glucose content,and significantly negative correlation with gibberellin（GA₃）.（3）With the increase of stress and the extension of time,the duration of seedling stage and vine stage of cucumber plants were gradually prolonged,the maturity stage was gradually shortened,and the change of fruit setting period was small,and the flowering period of 13/3℃and 16/6℃treatments increased with the extension of treatment time,while the flowering period of 19/9℃treatment was slightly shorter than that of CK,and22/12℃treatment was similar to CK.Compared with the radiation heat product model,the physiological development time model was more accurate in simulating the key growth stages of cucumber,and the RMSE for flowering stage,fruit setting stage and mature stage were 1.98,0.56 and 1.38 days,respectively.（4）The growth of cucumber plants was inhibited under the stress of low temperature and low light,and the growth of each growth index slowed down with the strengthening of stress and the prolongation of time;And a downward trend.The yield of 13/3℃and 16/6℃treatment decreased continuously with the prolongation of stress time,while the yield of19/9℃and 22/12℃treatment was not significantly affected.