Study On The Disaster Mechanism Of Low Temperature Oligoillumination At Flowering Stage Of Greenhouse Tomato

In order to study the stress degree of different treatment duration on plants under different low temperature and low light,this paper took tomato variety"Shouhe Fenguan F1"as the test material,carried out artificial environment control experiment,and designed the orthogonal test of temperature,light and treatment duration.Daily minimum and maximum temperature:3/13,6/16,9/19,12/22℃4 levels,daytime maximum light intensity set 400 and 200μmol·m^-2·s^-12levels,duration 3,6,9,12 days,The growth and development,damage degree of photosynthetic system,physiological and biochemical indexes of stress resistance,fruit quality and yield of tomato under different treatments were measured.The main results are as follows:（1）Low temperature and lack of radiation reduced the growth and development rate of tomato plants,and affected the plant morphogenesis.With decrease of temperature and light intensity,the flower bud differentiation process continuously extend,6℃when delay time longest flower bud differentiation,stress can increase the differentiation of prolonged period of time,at the same time,plant height,stem diameter,hypocotyl growth,leaf quantity,leaf area per plant growth inhibition degree aggravating,continue to affect the bud differentiation stage to the end of the flower bud differentiation,3℃has the most significant effect.The treatment time was prolonged and crop morphological indexes were severely inhibited.（2）With the deepening of temperature and light stress treatment,crop photosynthetic pigments were seriously damaged,and the energy transfer process of the photosynthetic system was also greatly affected,and the utilization capacity of photosynthesis decreased.By comparing the right-angle hyperbola model,right-angle hyperbola modified model,non-right-angle hyperbola model and exponential equation,it was determined that the right-angle hyperbola modified model had the best overall fitting effect on tomato light response,and the non-right-angle hyperbola model had higher fitting accuracy under low light conditions.The characteristic parameters of the fitting curve showed that the changes of LSP and P_max showed a decreasing trend with the decrease of treatment temperature,light level and treatment time,and the minimum value appeared at 3℃.The changes of LCP and R_d were opposite.The maximum value occurs at 12d,and AQE increases significantly under strong weak light treatment.（3）Sl MYB41 was overexpressed under low light stress of 200μmol·m^-2·s^-1 and lower than6℃.It was concluded that low light could make tomato more sensitive under the environment of lower than 6℃,and light had weak effect on gene expression at 3℃.Sl COR413IM1 was upregulated with decreasing temperature and reached the maximum expression at 6℃and400μmol·m^-2·s^-1 light intensity.The expression content of Sl DHN increased gradually with the decrease of temperature,which was seriously affected by temperature.With the temperature decreasing,the antioxidant enzyme activity in tomato leaves increased to the peak at 6-9℃and then decreased and deactivated.The Sp content increased gradually with the decrease of temperature,and reached the maximum value at 3℃,while the Pro content increased firstly and then decreased with the decrease of temperature,and reached the maximum value at 9℃.（4）With the decrease of temperature,the fruit setting rate of tomato plants decreased,resulting in the reduction of single fruit quality,the number of normal fruit,and serious yield reduction.Lower light intensity resulted in higher fruit setting rate,lower single fruit weight,lower malformed fruit rate and lower fruit shape index,but higher normal fruit number and yield.The increase of treatment time led to the first increase and then decrease of fruit setting,and the appearance quality of fruit decreased,and the yield decreased seriously.（5）Principal component analysis was conducted on the indexes of stress treatment,and the comprehensive score showed that 3℃had the greatest damage to tomato seedlings,while 12℃had the least damage to tomato seedlings.Growth index（plant height）,senescence index（CAT）,photosynthetic index(P_max),photosynthetic pigment（Chla）and fruit index（weight per fruit）were selected as the judging basis for grade classification of low temperature oligocarpic stress.The low temperature oligoillumination stress index（LTO）was constructed,and at seedling stage was classified as normal（0<LTO≤1）,mild（1<LTO≤2）,moderate（2<LTO≤4）,severe（4<LTO≤6）,extra weight（6<LTO）5 levels.