Effect Of Brassinosteroid On The Resistance Of Tomato And Cucumber Under Chilling Temperature At Night

Tomato（Solanum lycopersicum L.）and cucumber（Cucumis sativus L.）are all the major vegetable crops cultivated in greenhouse.Their growth and development are easily affected by adverse environmental factors.Temperature is one of the important environmental factors which affect the growth and development,yield and quality of tomato and cucumber.Brassinosteroids（BRs）is a steroid hormone necessary for plant growth and development,which can regulate a series of stress responses in plants and improve plant stress resistance.There are many reports on BRs against temperature stress,but few reports on the BRs’ability to withstand nighttime hypothermia.Tomato and cucumber were used as materials to study the effect of exogenous BRs against night-time low temperature environment.The main results are as follows:1.To study the effect of different night temperature on tomato and the role of exogenous BRs in it.Tomatoes with 4 leaves and 1 heart were divided into two groups,and pre-exogenous 0.2μM EBR and equal amount of H₂O respectively.Then they were divided into three groups.The treatments temperature were day/night temperature:25/18℃,25/12℃,25/6℃.The results showed that the photosynthesis of tomato decreased at low night temperature,the growth of plant slowed and the biomass of plant decreased.At low night temperature,exogenous BRs increased the photosynthesis and antioxidant enzyme activities of tomato and increased the biomass of tomato,indicating that BRs could mitigate the adverse effects of low night temperature on plants.2.To study the effect of different night temperature treatments on the growth of cucumber and the role of exogenous BRs in it.Cucumber with three leaves and one heart was selected and divided into two groups.0.2μM EBR and the same amount of H₂O were pre-applied separately.Then they were divided into three groups which were placed in the day/night temperature of 25/20℃,25/15℃,25/10℃.The results showed that at low night temperature,the expression of key genes of cucumber Calvin cycle decreased,photosynthesis decreased,the growth of plant slowed and the biomass of plant decreased.At low night temperature,pre-exogenous EBR increased the photosynthesis of cucumber,the biomass of plant,the antioxidant enzyme activity and the expression of related antioxidant genes.These results indicate that exogenous BRs can mitigate the adverse effects of night hypothermia on plants.