| Plant hormones were induced by specific environmental information in plant cells, and they play important roles in signal transduction, regulation of plant stress resistance, especially, there is a close connection between abscisic acid, gibberellin and plant stress resistance. In order to investigate the effect of exogenous ABA and GA on utilization of ginger light energy under water stress. In this study, ?Laiwu big ginger‘ as the test material, adopt sand culture, and use PEG-6000 as simulation of drought treatment, The effects of exogenous ABA and GA on endogenous hormone content, reactive oxygen species metabolism, photosynthetic parameters, chlorophyll fluorescence parameters, leaf pigment content and relative water content in Ginger Leaves under drought stress were studied. The main results are as follows.1. Exogenous ABA significantly increased the content of endogenous ABA in ginger leaves. In spite of drought stress, the content of ABA in ginger leaves showed a slow increasing trend, but the rate and extent of the increase was significantly lower than that of ABA. With the increase of ABA content the promotion of stomatal closure, thereby reducing the water loss, exogenous ABA treatment significantly increased the ginger leaf relative water content, at the end of the experiment, drought stress in ginger leaves subjected to RWC is on camera than to reduce 22.73%, but PEG + ABA treatment only reduce the 13.14%.2. The superoxide anion(O2-) production rate and hydrogen peroxide(H2O2) content in ginger leaves increased continuously under drought stress, and the content of malondialdehyde(MDA) in ginger leaves also increased continuously, O2- production rate H2O2 and MDA content increased by 212.7%, 296.8% and 152%, respectively, as compared with the control under the stress of ninth days. Superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) increased rapidly in the early stage of stress, after reaching a peak in the late stress continued to reduce. The ascorbic acid and glutathione cycle of ginger leaves were damaged by drought stress at the same time. However, exogenous ABA significantly increased in ginger leaves of SOD, POD, CAT activity of antioxidant enzymes and increased glutathione and reductive ascorbic acid content, reduce the accumulation of reactive oxygen species in ginger leaves, thus improving the ginger drought resistance.3. The drought stress accelerated the decomposition of chlorophyll, the photosynthetic apparatus of the plant, and caused the leaf water deficit, so the photosynthetic capacity of the leaves was seriously affected by the stress. The main factors causing the decrease of Pn were changed to non stomatal limitation by stomatal limitation. after ABA application, the Pn of ginger leaves significantly reduced in the early stress stage, while in the late stage of treatment, the Pn of ginger leaves gradually picked up. During the processing, the Pn were reduced by stomatal restriction. water stress makes the energy absorbed by the ginger leaves more heat in the form of heat dissipation, reducing its photochemical efficiency, exogenous ABA treatment, ginger leaves of Fv/Fm, PSII and q P decreased were significantly reduced, maintain leaf PSII light and energy absorption and transfer of normal.4. Drought stress increased the electrolyte permeability and MDA content of ginger leaves, For after treatment for 9 days, the electrolyte permeability and MDA content of PEG treatment increased by 140.4% and 154.1%, respectively compared with that before treatment, The electrolyte permeability and MDA content in the treatment with GA were increased by 23.03% and 17.05%, respectively compared with PEG treatment at ninth days. In addition, the addition of GA significantly increased the activity of SOD, POD and CAT in ginger leaves, the activity of SOD, POD and CAT still showed a trend of decline, but exogenous GA slowed down the time. For example, a simple PEG treatment of CAT, SOD in the treatment of third days and first days later on the gradual reduction, and the processing of the GA is to add sixth days after the treatment, therefore, the accumulation of reactive oxygen species is reduced, especially in the early stage of stress.5. Exogenous GA3 significantly increased stomatal conductance of ginger leaves under drought stress, and improved the assimilation ability of CO2, thus effectively improved photosynthesis under drought stress, and reduced the Pn of ginger leaves. For example, the sixth day of treatment, PEG treatment compared to the control ratio has been reduced by 61.07%, while the external application of GA3, only reduced by 34.03%. The external application of GA3 delayed the dominant time of non stomatal limitation, and protected the light and mechanism of ginger leaves. Exogenous GA3 had an obvious improvement in the pigment content of leaves under stress, allows the blade to maintain higher chlorophyll levels, improve the Fv/Fm, diameter of PSII and q P, reduce the NPQ, and effectively improve the leaf photochemical efficiency, although the role of post-processing GA3 weakened, but when applied with GA3, to a certain extent, ease the drought stress on plant growth inhibition. |
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