Effects Of Chitosan Treatment On Photosynthetic Character And Chloroplast Thylakoid Membrane Fatty Acid Composition Of Leaves In Hybrid Rice(Oryza Sativa L.) Under Low Temperature

In the first part of the experiment, a newly-developed super-high-yield hybrid rice (Oryza sativa L.) cultivar Liangyoupeijiu seedlings were used to study the effects of low night chitosan treatment on thylakoid membrane fatty acid composition; the other papers studied the photosynthetic function, antioxidation character and chloroplast ultrastructure of flag leaves at full-exhibition period, discussing effects of chitosan treadment on more resistance to low temperature. The results showed as follows:1. The seedlings of rice Liangyoupeijiu (Oryza sativa L.) were treated with 0.1%, 0.3%, 0.5% and 0.7% of chitosan at cold resistance in order to study the effects of chitosan on chilling-tolerane activity. The chilling-tolerance of seedling of rice could be increased with chitosan treatment. The concentration of chitosan at 0.5% showed the most effective result. Compared with chlorophyll content, absorption spectra, fluorescence spectra, composition of membrane lipid acids and electron transport activites of photosystems (PS I and PS II) and the index of unsaturated fatty acid (IUFA) and Fo increased, while Fv/Fm fell lower. The results indicated that chitosan treatment improved cold resistance of rice seedlings, which protected the membrance system, alleviated the damage to photosynthetic organization under low temperature.2. After flag leaves full exhibition, chitosan treatment alleviated the low temperature injury of Langyoupeijiu thylakoid membranes. The chitosan treatment reduced minimal fluorescence (Fo) content of rice leaves and alleviated the decreases in PS I and PS II activies, optimal/maximal photochemical photochemical efficiency of PS II in the dark (Fv/Fm),the non- photochemical quenching (qN) the photochemical quenching (qP) and Yeild. The cultivar sprayed with chitosan maintained the higher photosynthesis efficiency and increased the qN to dissipate superfluous solar energy absorbed. The chitosan treatment improved cold resistance of Langyoupeijiu, which protected the membrane system and alleviated the damage to photosynthetic organization under low temperature.3. The IUFA of thylakoid membranes were increased firstly and then decreased all of the three cultivars during growing period; The IUFA of low temperature treatment were normally higher than that of normal temperature comparison, the increased extent of treated with chitosan was bigger. The main fatty acids in the thylakoid membranes of the three cultivars were 16:0, 18:0, 18:1, 18:2, 18:3, and the contents of 16:0 and 18:3 were higher than other four. After flag leaves' full exhibition, percent of 16:0, 18:0, and 18:1 were all increased, but 18:2 and 18:3 decreased. Compared with the normal temperature, percents of saturated fatty acids of thylakoid membranes were reduced, the ones of unsaturated fatty acids added; The change extents of the saturated fatty acids and the unsaturated fatty acids treated with chitosan under low temperature were greater than only under the low temperature. MDA content of the two cultivars under low temperature was higher than that of filed-grown plants. Effects of chitosan treatment were significantly. The results showed that: there were distinctly positive relationships between IUFA and chilling-resistance. Chitosan treatment induced that Langyoupeijiu had strongger chilling-resistance and more decisive advantage of photo-energy conversion to maintain the natural function of photosynthesis system under low temperature.4. In the prophase of functional leaves, the chloroplast in the cell was oval or narrow shape and more number. The volume of cell nucleus was small, karyotheca and nuclear pore was clear, the karyoplasms in nucleus was dense and uniformity. With time runned, the volume chloroplast was enlarged, the thlylakoid membrane was illegibility and starch grain was larger in volume. The nucleolus and mitochondria did not change at this point. Lamella of chloroplast was turbulent in the anaphase of leaves senescence. The nucleolus was large in volume. Number of mitochondria were reduced. Karyoplasm was given out of nucleus. Low temperature stress has little effect on leaf ultrastructure at early period, but in the middle-evening, chillness stress added the disorganization of chloroplast,and this case showed later in rice with chitosan treatment.