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Northwest University of Science and Technology (2005)

Study on the Phase Responses and Mechanisms of Different Winter Wheat Varieties to Drought

Zhao Li Ying

Titre : Study on the Phase Responses and Mechanisms of Different Winter Wheat Varieties to Drought

Auteur : Zhao Li Ying

Grade : Doctoral Dissertation 2005

Université : Northwest University of Science and Technology

Résumé partiel
The dryness is one of world difficult problem. The response of crops to drought stress involves not only the research of highly effective water resources use, but also the grain production. Plants respond to drought stress by altering their cellular metabolism and invoking various defense mechanisms. Much study had showed that there existed a phase response to water deficit, and also classified different stages, such as acclimation, damage, repair and compensation. Now there are few studies about this, so it is very necessary to probe the changes of different physiological indicators under drought, which will helpful to provide theoretical basis for different phase response.In the paper, two winter wheat varieties, shaan 253 and changwu134, were used in the experiments. Water culture in artificial growth shelter and potted were designed to investigate response of physiological characteristics and growth, and also the effect of altered water condition on photosynthetic characteristic and water utilization efficiency. Some physiological indicators of osmotic adjustment and antioxidant defense systems and chlorophyll fluorescence parameters were analyzed, at the same time, the relationship of active oxygen species production and chlorophyll fluorescence quenching was discussed. The major results are as follows:1. In the course of osmotic stress, the relative water content, water potential, leaf area, osmotic potential at full tugor showed the trend of drop, however osmotic adjustment capacity showed the trend of increase. They have not displayed the stage response. However, root length, root area, R/S, proline, soluble sugar, K+, free amino acid, SOD, CAT, Vc showed first increase then drop, which indicated that these indicators exists the process of adaptation - injury. The initial increase is one kind of positive response for drought resistance, following reduction was thought the performance of injury.2. The content of O2- and H2O2 showed the trend of derease-increase-derease. Water stress induced generation of reactive oxygen species accumulation and then up-regulated the activities of antioxidant enzymes in wheat leaves. Therefore, the content of O2- and H2O2 reduced. When the production of reactive oxygen species excess the capability of scavenging system, ROS content then increased. The content of MDA showed the same trend with O2- and H2O2, indicated that the production of ROS was related to the membrane lipid peroxidation during the osmotic stress course.3. During the osmotic stress, there was difference in the accumulation of osmotic adjustment matters, SOD, CAT, POD activities and anti-oxide matters such as Vc, Car, GSH for two wheat varieties. The accumulation of the soluble sugar, free amino acid, Vc and Car in Shaan 253 after forces 18h is obviously higher than that of Changwu 134 after stress 18h, but on the contrary of osmotic adjustment, K+ content, SOD, POD, CAT activity, GSH. The production of O2- and H2O2, also MDA content in Changwu 134 is lower than Shaan253, moreover, ROS was eliminated by anti-oxide matters in Shaan 253 and by protected enzyme system in Changwu 134. Above all indicated that the different varieties suffered same stress had the different drought resistance mechanisms, which provided the theory basis for breeding resistant varities.4. The activity of SOD isoenzymes such as MnSC^ CuZnSOD and FeSOD changed with increase of drought among the different isoenzymes, the region of FeSOD has the most changement, followed the CuZnSOD, MnSOD only showed little changement.5. The chlorophyll fluorescence parameters were significantly affected with the increase of osmotic stress. Fv/Fm showed first increased and then decreased, and Fv/Fo showed the trend of derease-increase-derease, which indicated that photoinhibition had not happened at the first stage of osmotic stress, however, with the increase of osmotic stress, decreased Fv/Fm showed that photoinhibition happened in wheat seedlings and resulted in the decrease of OPS II and ETR.

Mots clés : winter wheat PEG-6000 modulated drought osmotic adjustment antioxidant defense system chlorophyll fluorescence water use efficiency

Présentation (Dissertationtopic)

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