Relationship Between Root And Leaf Photosynthetic Physiological Characteristics Of Rice

In order to promulgate between the root system and the leaf photosynthesis characteristic contacts. In the present study, we use the rice varieties of Liangyoupeijiu, the japonica Rice Variety of Yujingliuhao and upland rice variety of 738 as test materials which be planted in large scale. Response of photosynthesis characteristics, gas exchange, chlorophyll fluorescence parameter, key enzymes activities of photosynthetic apparatus, chloroplast thylakoid membrane proteins expression, content of osmoregulation substance in roots and leaves, key enzymes activities of root respiratory metabolism, changes of hormone content(ABA,CTK,IAA,GA3), changes of H2O2 content, changes of anti-oxygen protective enzyme were detected as the main indexes when rice varieties were subjected to short water stress(30min and 150min). Study on response mechanism of photosynthesis characteristics, regulating effect of osmoregulation substance, the efforts of root respiratory metabolism on photosynthesis characteristics, regulating and interaction effect of changes of hormone content on photosynthesis characteristics, ABA chemical signals transfer and transduction between roots and leaves under short water stress. The main results of this study were as followings.1. The change range of changes of photosynthesis characteristics is smaller in 30min short water stress, and the net photosynthetic rate, transpiration Rate and carboxylation efficiency begin to reduce after 15min stress treatment, while the stomatal conductance begin to reduce more early at about 5-10min stress treatment, and water use efficiency have less change or kept steady, and stomatal limitation value keep steady rising. The results of photosynthetic fluorescence characteristics after 150min water stress showed that index of which reduced more significantly and larger. The net photosynthetic rate and transpiration rate showed changing in three steps: changes larger in the first 30min and maintained stable during 30-90min and with larger reduced amplitude after 90min, while the changes larger amplitude of stomata conductance was from 30 to 60min. At the same time, intercellular CO₂ concentration reduced during 0-90min and begins to increase after 90min treatment, and water use efficiency showed raised during 30-60min, and the stomata limitation value exhibits a decreased trend at the late stress treatment.2. The Responses of Leaf Water Potential changed obviously after the short water stress, especially in serious stress. Cell membrane permeability in roots and leaves has been affected seriously, and membrane permeability will change. The result that changes of osmoregulation substance in roots and leaves during the short water stress showed the content of proline and soluble sugar change faster in short time, especially since 20min. Compared with the changes of osmoregulation substance in roots and leaves, the absolute value and change range of proline in roots are all greater than those in leaves, while the absolute value and change range of soluble sugar in leaves are all greater than those in roots.3.The result that the efforts of different roots treatment method (whole root, half-root, wipe out half-root) on photosynthetic characteristics after water stress showed that net photosynthetic rate, transpiration Rate, intercellular CO2 concentration, carboxylation efficiency and water use efficiency all showed a trend of decrease, while the stomatal limitation value also showed an ascending trend, and more significantly especially after 20min. Half-root treatment can reduced the range of leaf photosynthetic characteristics changes. Photosynthetic characteristics of leaf changes obviously especially the change of stomatal conductance if the half-root of stress treatment be wiped after 20min treated and other indexes all showed unchanged or some degree of improvement.The experiment of different roots treatment method on leaf water potential also showed that the treatment of wipe out half-root can reduced the range of leaf water potential changes, and even some degree of improvement.4. The content of CTR, IAA and GA3 in roots and leaves decreased in short times, and the content of ABA increased obviously. The half-root treatment can reduced the range of changes, and the content of hormone in leaves decreased obviously by wiping the half-root after 20min treatment. Designing the treatment of whole root, half-root and wipe out half-root, we can calculate the changes of content of ABA and Zr in leaves after 30min different roots treatment, and then calculate out the average rate of ABA and Zr which respectively reach 7.5 ng/g.W.min-1 and 0.034 ng/g.W.min-1 that transport from roots to leaves within the 30 min. Ratios of ZR/ ABA, IAA/ABA, GA3 / ABA and (ZR+GA3) / ABA in roots and leaves exhibit a downward trend during the drought process. The change of the ratio of whole root is the largest, and the wipe out half-root treatment reduced the range of this change. The change of the ratio of (ZR+GA3) / ABA is also bigger, and maybe it is a sign that growth of rice becomes very slow, and it also a protective physiological mechanism.5. The result that the effects of Inhibitor of root respiratory metabolism treatment on leaves photosynthetic characteristics showed that the photosynthetic characteristics of leaves will change by different Inhibitors in normal conditions, especially the treatment of HgCl2, of which the change of net photosynthetic rate reached 35.8%. The change of stomatal conductance is largest in the indexes of photosynthetic characteristics, which reduced by 75.1% within 30min under HgCl2 treatment. DNP treatment also has different degree of variation, however, the photosynthetic characteristics indexes of Na3PO4 treatment basically has no change except intercellular CO2 concentration。The results indicate that the short water stress have significant influence on key enzyme of root respiratory metabolism. Different water gradient can reduce the ATP synthase, cytochrome oxida and sesuccinate dehydrogenises of root, and existing obvious difference between those treatments, and the enzyme activity decrease occurred since 10min drought stress generally.6. The enzyme activity has different degree while in all different rice varieties, especially since 90min later. There are difference existing different rice varieties, for example, Liangyoupeijiu has high enzyme activity of RuBP carboxylase, however, it decreased with large range in the later treatment. Using the method of SDS polyacrylamide vertical slab electrophoresis, the results of difference of chloroplast thylakoid membrane proteins expression under water stress indicate that Liangyoupeijiu and 738 all have a new difference protein band, and different rice varieties also have various protein band, and Yujingliuhao have no protein variation during the drought process.7. Synthesis inhibitor of ABA can change the photosynthetic characteristics of half-root water stress, especially for the change of stomatal conductance. After the synthesis inhibitor of ABA treatment, the content of ABA have somewhat decrease, especially for the change in leaves. The content of H2O2 in root and leaves can also be affected by the synthesis inhibitor of ABA, particularly for the change of content of H2O2 in leaves. Using the method of wiping out half-root, we can also calculate out the average rate of H2O2 which reach 0.051μmol.g-1.FW.min-1 that transport from roots to leaves. It is reveals that it is little content of H2O2 which transport from roots to leaves, and the chief result of the change of H2O2 content in leaves should be the self produced H2O2.