| The chloroplast light reaction characteristics were compared between super-high-yield hybrid rice Liangyoupeijiu and traditional hybrid rice Shanyou63in order to provide theoretical insights into physiological basis for high yield. Using fluorescence dynamics analysis and physiological and biochemical research techniques, in the field we systematically studied the primary response, electron transport chain and photophosphorylation during the reproductive period. The results showed that,(1) As compared to Shanyou63, chlorophyll content in functional leaves of Liangyoupeijiu was22.90%higher, it had a longer photosynthetic function duration and chla/chlb ratio was36.78%higher;(2) In the term of light absorption and distribution, there was no significant difference in light absorption per unit leaf area of functional leaves, but Liangyoupeijiu maintained a high and long stability period of light energy absorption capacity, the number of active reaction centers was more, the energy of heat dissipation was relatively fewer, the energy transferred into the electron transport chain was higher;(3) Fluorescence analysis showed that structures and status of the body side, the receptor side and the reaction center in PSIIperformed better than Shanyou63, indicated that Liangyoupeijiu had a higher efficient in the transforming light energy into electric energy;(4) In addition, oxygen evolution of the chloroplast, activities of electron transport chain and photophosphorylation were significantly higher, indicated that Liangyoupeijiu possessed some advantages in the energy converted into transforming electric energy into active chemical energy. For higher light energy absorption, transmission and conversion efficiency than Shanyou63, Liangyoupeijiu established a physicological basis of super-high-yield hybrid rice.One of the most important aspects of global change is that of stratospheric ozone depletion resulting from air pollution and the resulting increase in UV-B radiation reaching the surface of the Earth. Enhanced UV-B radiation can lead to a series of changes in plant growth, such as to affect plant morphological structure including plant height, the ratio of root and shoot, leaf size and biological yield, to hurt light system, to cause expression of genes and activities of photosynthetic protein enzymes dropping.In this paper, LYPJ was systematically studied the light reaction, carbon assimilation, chloroplast ultrastructure, the antioxidant system and thylakoid membrane proteins of the upper three functional leaves in detail during reproductive development based on the research light response characteristics of Liangyoupeijiu using the UV-B dose of5.4kJ m-2d-1to treat rice.The results were as follows:(1) Photosynthesis physiological indices showed that the upper three functional leaves of LYP J entered into senescence approximately15days after flag leaf emergence (DAE). Compared with the control, the chlorophyll (Ch1) content was greater in UV-B treated leaves, but the net photosynthetic rate (PN) and stomatal conductance (gs) remained relatively stable at lower values before35DAE, which were significant differences.(2) Increases in the absorption flux of photons per cross section (ABS/CSM), the phenomenological fluxes for trapping (TRo/CSM), the potential electron transport (ETo/CSm), the maximum quantum yield (Fv/Fm) and a decline in dissipation (DIo/CSM) might contribute to higher light energy absorption, transfer and the transformation of photosystem Ⅱ (PSII) in UV-B treated leaves.(3) Besides, the results showed a not significant increase of the electron transport rate (ETR). However, Ca2+-ATPase and photophosphorylation activities of UV-B treated leaves maintained a relatively stable lower value, suggesting that the carbon assimilatory power was less. The significant decreased activity of ribulose-1,5-bisphosphate carboxylase (RuBPcase) was greatly associated with the decline in photosynthetic efficiency.(4) Long term UV-B treatment delayed chloroplasts growth of flag leaves. Chloroplast membranes in UV-B treated flag leaves later swelled and disintegrated, and more stromal thylakoids were parallel to each other and were arranged in neat rows, which may be responsible for better manifest of the primary light reaction in UV-B treatment. It is likely that accumulation of starch and an increase in the number of lipid droplets and translucent plastoglobuli were results of inhibition of carbohydrate transport. Enhanced low intensity UV-B radiation tends to promote the absorption of light energy and the transport of electron, but result in the decrease of photophosphorylation and Rubisco activation. The extent of the damage to the chloroplast ultrastructure was consistent with the degree of inhibition of photosynthesis.(5) The changes of antioxidant systems in functional leaves under enhancing ultraviolet-B radiation were investigated. The results showed that antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activities increased signficiantly at first, then decreased, elevated at last. Peroxidase (POD) activities tended to increase; The contents of antioxidant substances ascorbic acid (ASA) and glutathione (GSH) increased under a long term UV-B stress, but amplitude was becoming smaller. The relative contents of hydrogen peroxide (O2-) and malon-dialhyde (MDA) increased at first, then slowly decreased. The reverse was true in soluble protein content. The results indicated that the change of the antioxidant systems was consistent with the performance of photosynthesis.(6) Proteomics study showed that photosynthetic response mechanism of thylakoids membrane in functional leaves of LYPJ response to low intensity UV-B included the following aspects:(a) Structure and important constituent proteins of PSII were not damaged, at the same time cofactor content increased, that showed light energy absorption and transformation of the ability of PSII were strengthened.(b)Increases in content of ATPase subunits indicated the stress had promoted the hydrolysis rate of ATP in order to slow down light energy accumulation.(c) Key enzymes participated in the regulation in carbon distribution between starch and sucrose, the Calvin cycle and glycolysis, whose activities decreased significantly, that showed the Carbon assimilation was obviously inhibited.(d) A great increase of stress response proteins opened different signal transduction pathways. |
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