Study On Differences In Ultrastructure And Gene Expression Of Leaves Between Wheat Varieties With Different Heat Tolerance

In the experiment, wheat seedlings with different heat tolerance were used as experiment materials. Under heat acclimation(34℃) and heat stress(49℃) , the relative conductivities of leaves were measured, the ultrastructural changes of mesophyllous cells were observed. Under heat shock(38℃), the differences in gene expression of leaves between thermotolerant and thermosusceptible varieties were analyzed by using cDNA amplified fragment length polymorphism(cDNA-AFLP). The causes that resulted in different heat tolerance between wheat varieties were discussed from several aspects of physiology, cytology and molecular biology. The results were as follows:1. Heat acclimation reduced relative conductivity of leaves, delayed the ultrastructural destruction of mesophyllous cells induced by heat stress, and the degree of delay was higher in thermotolerant varieties than that in thermosusceptible ones.2. In mesophyllous cell, vacuolar membrane was the most susceptible one to high temperature, and mitochondrion was more susceptible than chloroplast. In mitochondria, mitochondrial crista and inner membrane was more susceptible than outer membrane. In chloroplasts, though the arrangement of thylakoid membrane appeared disturbance priorly, the disintegration of thylakoid membrane was later than chloroplast envelope.The nuclear membrane of thermotolerant varieties was the most stable one to high temperature, and the thermal stability of nuclear membrane of thermosusceptible varieties was improved by heat acclimation. Thus, the thermal stability of cell nucleus(especially nuclear membrane) played an important role in maintaining the thermal stability of cell architecture, and was associated closely with heat tolerance of varieties.3. Under 60min' heat shock, the difference in quantity between heat shock gene expression and gene silencing of thermotolerant variety was more obvious than that of thermosusceptible variety. After 60min' heat shock, the quantity of heat shock gene expression of thermosusceptible variety was decreased rapidly. The important period of investigating the difference in gene expression was round about 60min' heat shock.Under heat shock, the comparative quantity of heat shock gene that expressed continuously of thermotolerant variety was larger and the continuous time of heat shock gene expression was longer than that of thermosusceptible variety.The relative conductivity of leaves, ultrastructural changes of mesophyllous cells under heat acclimation and heat stress, the differences in gene expression of leaves under hest shock can be used as physiologic, cytologic and molecular biologic indexes respectively for evaluating heat tolerance.