Studies On Regulation Of ABA On Photosynthesis And Molecular Mechanism Of Tomato Under Sub-high Temperature And High Light Intensity Stress

Vegetable production in greenhouse has become an important part of modern agricultural country and tomato is one of the major vegetable crops in greenhouse cultivation. It is often affected by both sub-high temperature (35?) and high light intensity stress. As a result, plants often responses to various kinds of stresses and a variety of factors are integrated which can produce enhanced, overlap or antagonistic effects. ABA involved in many important processes of plant growth and development, and it also involved in regulating adversity. But the mechanism that ABA involved in regulating plant growth under sub-high temperature stress and high light intensity has remained unclear.In this study, tomato cultivar "Liaoyuanduoli", ABA-deletion mutant (sit) and wild type (RR) were chosen as test materials. We discovered the role of ABA in photosynthesis under sub-high temperature stress and high light intensity. From the point of photosynthetic, ABA synthesis, MYB transcription factor and antioxidant protection, we made a comprehensive and systematic analysis on the mechanisms of exogenous and endogenous ABA stress, which provided a theoretical basis for easing sub-high temperature stress injury. The main research results are as follows:1. In present, the decline of photosynthetic rate was co-determined by stomatal and non-stomatal factors under sub-high temperature stress and high light intensity. The study on gas exchange parameters of spraying distilled water treatment under daytime high temperature stress 3d and short-term stress llh showed that the decrease of net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci) and transpiration rate (E) was mainly induced by stomatal factors. After the daytime stress 3d and short-term stress 11h, gs and E continued to decline, while Ci increased, indicated that non-stomatal factors had restrictive effect. Time sequence of the harm to photosynthetic apparatus under sub-high temperature and high light intensity stress. When stress for 3h, electron transport of PS ? began to decrease, Rubsico carboxylase activity was significantly lower than CK after stress for 7h, PSI photoinhibition occurred 11h. It is used to predict that the sub-high temperature and high light intensity stress harm PSII firstly, followed by Rubsico carboxylase activity, finally PSI.2. In this text, exogenous ABA has delayed tomato leaves photosynthesis decline under sub-high temperature and high light intensity stress. Application of exogenous ABA could mitigate the harm to PS? of tomato leaves under sub-high temperature and high light intensity and had protective effect for PS? reaction center against stress. Compared with other treatments, application of exogenous ABA could slow the decline of photosynthetic rate (Pn) was caused by reduction of Rubisco carboxylase activity, ETR?, NPQ, Fv/Fo and Fv'/Fm'which protected PS? inactivate reactive center.Sub-high temperature and high light intensity stress could affect PSI. No obviously change in Y(I) of PS ? reaction centre during daytime high temperature stress 3 d and short-term stress 11 h. Y(I) and Y(NA)significantly decreased and Y(ND)significantly increased under daytime high temperature stress 5d and long-term stress 48 h. It showed that exogenous ABA had no effect on alleviate the harm of stress to PSI.3. The regulation of tomato leaf photosynthesis by endogenous ABA is mainly layed on its protection for PS ? and PSI. The values of Pn and E in RR also maintain a certain level after stress11h, and in sit almost came to zero. The ETR?, Y?, NPQ, qP, Fv/Fo and Fv'/Fm' of RR were significantly higher than sit. Endogenous ABA can protect PS ? better. Sub-high temperature and high light intensity stress no significant influence on PSI of RR, while significantly reduce the Y(I) for sit,but did not produce significant change to Y(NA),Y(ND) significantly increased at the same time,it shown that no photoinhibition in PSI.Therefore, endogenous ABA had some good effect to PSI.4. It was discovered the impact on ABA synthesis at the transcriptional level. Spraying exogenous ABA and stress significantly increased the expression level of ABA1 and AAO gene, the gene expression of NCED was affect only by exogenous ABA. ABA1 and NCED was not regulated by endogenous ABA, AAO was regulated by endogenous ABA under normal condition. After sub-high temperature and high light intensity stress, endogenous ABA could regulate transcription of ABA1 and AAO,unregulate the transcription of NCED. The expression level of ABA1 and AAO in RR was higher than that in sit, the same as the ABA content. The expression level of NCED and AAO in sit did not change and ABA content has not improved significantly under sub-high temperature and high light intensity stress.The response of MYB transcription factor in ABA-dependent pathway was also discovered under sub-high temperature and high light intensity stress. The gene expression of five MYB transcription factors, SIMYB308 (light-induced related) was regulated negatively, but SIMYB3061, SlMYB3062, SIMYB3063 (with pores and ABA-related) and SIMYB340 (temperature-dependent) were positive regulated under stress.5. In this study, the water-water cycle was also affected by sub-high temperature and high light intensity stress. Exogenous ABA could relieve the production of O2-, H2O2 and MDA, and at the same time, it improved the activity of antioxidant enzymes (CAT, POD, SOD, APX, GR, DHAR and MDHAR), which involved in the regulation of AsA-GSH cycle. In order to reduce the damage of plants, it enhanced the scavenging capacity of active oxygen.