Effects Of Different Air Humidity Treatments On Tomato Flower Bud Differentiation And Heat Shock Protein Expression Under High Temperature

In order to study the mechanism of the influence of high temperature and humidity on the differentiation process of tomato flower buds and the influence on the expression of heat shock protein.The tomato variety"Shouhe Fenguan"was used as the test material.The orthogonal test of air temperature,air relative humidity and treatment days was conducted in the agricultural meteorological experimental station of Nanjing University of information technology from March to June 2019 and April to July 2020.The air temperature(day temperature/night temperature)was set with four treatment levels:T1(32?/22?),T2(35?/25?),T3(38?/28?),T4(41?/31?);the air humidity was set at three levels:H1(50%)The treatment time was 2,4,6 and 8 days.The treatments of day/night temperature 28?/18?and air relative humidity 45%-55%were used as control(CK).The endogenous hormone,starch,soluble sugar content,plant height,stem diameter,dry weight per plant and seedling index of terminal bud were measured at each stage of flower bud differentiation of tomato.The expression of heat shock protein was measured at undifferentiated stage to study the mechanism of high temperature and high humidity on the process of flower bud differentiation of tomato.The main results are as follows:(1)The higher the temperature and humidity,the higher the plant height.The higher the ambient temperature and relative humidity,the lower the stem diameter.The temperature of35?and the relative humidity of 50%were beneficial to the photosynthesis during the flower bud differentiation stage,and could significantly promote the accumulation of dry weight per plant of tomato.The temperature over 35?and air relative humidity over 50%were not conducive to the accumulation of dry weight of tomato.In the whole stage of flower bud differentiation,the dry weight of tomato plant showed a"S"shaped trend.The logistic model was used to fit the dry weight of tomato plant in flower bud differentiation stage.The fitting equations of dry weight of tomato plant and flower bud differentiation days under different high temperature and high humidity treatments had high precision,R² were greater than 0.9.With the increase of temperature and air relative humidity,the strong seedling index decreased gradually.The strong seedling index was affected by plant height,stem diameter and dry weight of single plant.High temperature and high humidity could improve the height of tomato plant at flower bud differentiation stage,which was not conducive to plant growth and development.Tomato plants were overgrown,which reduced the number of plants with good growth.(2)Under the stress of high temperature and high humidity,the differentiation of tomato flower buds was delayed and the process was prolonged.The correlation between the duration of each differentiation stage and indicators such as soluble sugar,starch,free amino acids,soluble protein,endogenous hormones,etc.,was found to be"shouhefenguan"tomato flower bud differentiation Each stage had a greater correlation with soluble sugars,free amino acids,IAA,ABA,(IAA+GA₃)/ABA,among which,there was a significant negative correlation with soluble sugars,free amino acids,IAA,(IAA+GA₃),and There was a significant negative correlation with ABA,indicating that the higher the content of soluble sugar,free amino acids,IAA,(IAA+GA₃),the faster,and the higher the ABA content,the slower the flower bud differentiation rate.Using physiological development time and effective accumulated temperature as the scale,a simulation model of tomato flower bud differentiation period was established and tested by independent experiments.The results showed that the physiological development time model can better predict tomatoes under different high temperature and high humidity treatments than the effective accumulated temperature model.The flower bud differentiation lasted for days,the maximum value of the regression estimation labeling error(RMSE)between the simulated value and the observed value was 2.69,and the minimum value was 0.The accuracy of the model was high.(3)The relative expression levels of five heat shock genes in tomato leaves at the early stage of flower bud differentiation were analyzed by fluorescence quantitative PCR.The results showed that heat shock reaction occurred in tomato leaves under high temperature and high humidity,and the expression levels of HSP70,Hsp90,HSP110 and HO-1 were significantly higher than those of CK.The higher the temperature was,the more the expression levels of the above four heat shock proteins were The expression of HO-2 gene was significantly lower than that of CK under high temperature and high humidity treatment,which indicated that high temperature and high humidity were unfavorable conditions for HO-2 gene expression.It indicated that HO-2 gene had opposite expression effect with the above four genes in the face of high temperature stress.HSP110 had the highest physiological activity,and was more sensitive to high temperature and high humidity stress,with the highest expression.Although HO-2 gene could not directly improve tomato growth.However,it can improve the stress resistance of Tomato by cooperating with HSP family gene and HO-1 gene.