Effects Of Different Water Stress On Active Oxygen,stoma And Photosynthesis Characteristics Of Wheat And The Transportation Passway Of H₂O₂ Between Guard Cell And Cubsidiary Cell Of Maize

H2O2 is an important signaling molecule, which plays an important role in the process of controlling the stomatal movement of plants. Studies have found that H2O2 can induce cytoplasmic alkalinization, the increase in cytoplasmic Ca2+ concentration can activate intracellular protein kinase/protein phosphatase system and make cell membrane depolarization, leading to activation of the plasma membrane anion channel and the efflux of K+ channel, the passivation of the K+ channel, and finally to promote the increase of the guard cell water potential, cause the dehydration shrinkage and induce stomatal closure. But at present, the related studies are only limited to the role of guard cells in the stomatal movement, and the relevant reports on the role accessory guard cells play in the process of are few. And in previous experiments we found that cells in the process of H2O2 distribution is changed in stomatal subsidiary, indicating that H2O2 in accessary guard cells may has a supporting role in the guard cells leading stomatal movement. In order to further verify the assumption, we chose wheat as research material, the stomatals of which are composed of guard cells and accessary guard cells, focused on the changes in the distribution of H2O2 in guard cells and accessary guard cells, the leaf photosynthetic characteristics and ROS metabolism, when water stress induced different stomatal conductance. In addition, the transport routes of H2O2 between guard cells and accessory guard cells were also analyzed in this paper. H2 O and H2O2 are similar, and it can be freely through the cell membrane in theory. But in view of previous experimentally observed phenomenon, namely H2O2 concentration in maize guard cells, accessory guard cells and adjacent epidermal cells have significant differences, and showed a periodic change following the movements of the stomatal, which cannot be explained by free diffusion. It is now found that during the process of stomatal closure of Arabidopsis response to stress, the sharp rise of H2O2 is activated by the surrounding cells, and enlarged by the intercellular space,then transferred into the guard cells. Another study showed that some aquaporins can promote the transmembrane transporter of H2O2. Accordingly, we envisage the possibility of aquaporins in control of H2O2 flowing among guard cells and accessory guard cells. In order to explore the research, the second part did fluorescence quantitative PCR analysis of ZmPIP2;4, ZmPIP2;5 and ZmPIP2;6 aquaporin., on the base of the determined theory which is shown by AQUAPORIN inhibitors, that aquaporins works in transferring H2O2 bettwen guard cells and accessory guard cells. The results are as follows:In the first part of the experiment,we used the pot to control water, and chose leaves in winter wheat(Xiaoyan 22) as the experimental objects, use the determination of physiological index, photosynthesis and H2 DCFA fluorescence labeling and other experimental means,to research the winter wheat leaves under four water treatments(normal water supply CK; mild water deficit LS; moderate water deficit MS; severe deficit in water SS) in ROS content, malondialdehyde(MDA) content, the activity of ROS- scavengingsystems- related protective enzymes, the stomatal density and photosynthetic performance index. At the same time, the effect of light or dark treatment and PEG-simulated drought treatment on the distribution of H2O2 in wheat epidermis was observed. The results showed that with the increase of water stress, H2O2 and MDA in wheat leaves increased gradually; the stomatal density of leaves increased, and photosynthetic performance index(transpiration rate, photosynthetic rate and intercellular CO2 concentration) showed a downward trend. In the wheat epidermis which were under PEG simulated drought treatment, the H2O2 distributed in the guard cells in the control group, while it distributed in the accessory guard cells in the stress treatment group, and its content increased with the PEG concentration.In the second part of the experiment, the source and removal mechanism of H2O2 in the epidermal accessory guard cells of maize were studied by pharmacological experiments, fluorescence staining and fluorescence quantitative PCR technology. Ttreated by H2O2 and aquaporin inhibitor at the same time, we discovered that the transfer of H2O2 in guard and accessory guard cells is related to the aquaporin. In the process of dark- to- light conversion, adding an appropriate concentrations of AgNO3 and processing an appropriate long time, it can block the H2O2 in the accessory guard cells to the outward transportation. In turn, in the process of light-to-dark conversion, adding an appropriate amount of AgNO3 and processing an appropriate long time, could block the H2O2 in the accessory guard cells to the inward transportation. Experiments showed two theories, one of them is that H2O2 in accessary guard cells is exogenous, and removed by the outward transport; the other one is that aquaporins is the channel of H2O2 in accessory guard cells. Through further fluorescence quantitative PCR on potential transport H2O2 aquaporin study, we found that, ZmPIP2;5 is very likely to participate in the transport process of H2O2 in guard cells. This experiment combined numbers of multiple experimental methods, explored the transportation of H2O2 in maize epidermal guard and accessory guard cells, and provide some experimental evidence to illustrate the function of accessory guard cells in plants of accessory guard cells in the stomatal opening and closing.