| Chinese cabbage is native to China and has always played an important role in agricultural production and people in China.Chinese cabbage is planted in cool environment,high temperature in summer has always restricted the production of summer Chinese cabbage,Therefore,it is very urgent to cultivate heat-resistant Chinese cabbage varieties.In the selection process of heat-resistant varieties,the method of heat resistance selection of parents has become an important factor restricting the screening of heat resistance.It is necessary to find a quick and simple method for identifying heat resistance.In the study,Through the research on the indexes of 45 Chinese cabbage varieties in adult stage,seedling stage and germination stage.Accurate and efficient identification of heat tolerance of Chinese cabbage was selected for each period,and a set of methods and techniques suitable for heat tolerance identification of Chinese cabbage were established.Established a set of methods and techniques suitable for the identification of heat tolerance of Chinese cabbageOn the basis of this,physiological studies on Chinese cabbage varieties with different heat tolerance were carried out.1 In the adult stage,the Chinese cabbage varieties sown on June 10,July 10,and August 10 were investigated in the field,and the leaf ball hardness,ball number,and yield per plant were investigated.The results show,On June 10,the hardness of the top of the ball and the relative yield per plant can be used as indicators for the heat tolerance of Chinese cabbage,and 13 heat-resistant Chinese cabbage varieties were selected for production reference.2 In the seedling stage,the cabbage seedlings were treated at 39 °C/32 °C,32 °C/25 °C,25 °C/18 °C,and the results showed that 39 °C/32 °C was the best temperature for identifying heat resistance.Under this temperature treatment,the change of heat injury index of Chinese cabbage seedlings increased from 0.85% at 1 d of high temperature stress to 38.71% at 7 d.Although the coefficient of variation decreased from the initial 234.57% to 65.77%,the range was increased from the initial 7.50% to 75.00%,reflecting the large difference in heat damage index of different Chinese cabbage seedlings.3.The germination rate,germination potential and relative germination index of each sample at 25 °C,32 °C,39 °C were counted during germination,and clustering analysis was carried out by germination related germination.The results showed that the relative germination rate and relative vigor index at 39 °C were only classified into heat-sensitive type by the intermediate type.According to the change of the comprehensive evaluation in the field,the comprehensive evaluation value of No.11 was 1.38,which was comprehensively evaluated in the field.The minimum value is in the middle type,and the other clustering results are consistent.4 The differences in the growth and physiological characteristics of different heat-tolerant Chinese cabbages were studied on the physiology of different heat-tolerant Chinese cabbage varieties on June 10 and August 10.The results show that the absolute growth in high temperature environment does not reflect the heat tolerance of the plant,and the relative growth can better reflect the tolerance of the plant.On June 10,the activities of SOD,CAT and POD in roots and leaves were significantly higher than those on August 10,and the growth rate of heat-resistant varieties was higher than that of heat-sensitive varieties.The change of MDA content of heat-resistant varieties was smaller than that of heat-sensitive varieties.40.57%,44.35%.The yield and quality of Chinese cabbage under the sowing date on June 10 was significantly lower than that on August 10,and the quality of heat-resistant Chinese cabbage was better than that of heat-sensitive varieties under high temperature,but the growth quality was poor under normal environment.5 The net photosynthetic rate(Pn),transpiration rate(Tr),instantaneous water use efficiency(WUE)and stomatal conductance(Gs)of different heat-tolerant Chinese cabbage varieties were different at different sowing times.There were differences in photosynthetic parameters of different heat-tolerant Chinese cabbage varieties under the same sowing date.The net photosynthetic rate(Pn),transpiration rate(Tr)and instantaneous water use efficiency(WUE)were all asymmetric double-peak curves,and at 8 The highest of the heat-sensitive variety Xiaqi 56 was planted on the 10 th of the month.Comparing the leaf microstructures of different heat-tolerant Chinese cabbages,it was found that the leaf structure and sponge tissue of the two Chinese cabbages had differences in the sowing date on June 10,while the depleted density two cabbages had significant differences.There are no differences in the remaining pore measurements. |
