Effect Of Ozone Stress On Growth And Yield Of Rice Liangyou084with Different Seedling Quality

In recent years, tropospheric ozone concentration has been sharp rising,,pessimistic estimate will rise to80nl L-1in2100. Because of the strong oxidation, ozone has toxic effects to crops. Hybrid rice, which very important for our country grain production, is sensitive to ozone. There have been many studies on the effects of ozone on rice, however, the effect of elevated ozone concentration on the growth and yield of different rice seedlings is not clear. In order to investigate the effects of elevated ozone concentration on phenology, plant height, SPAD value of flag leaf, photosynthesis parameters of flag leaf, dry matter production and distribution, nitrogen uptake and utilization, yield and yield components of hybrid rice different seedlings, using FACE system at Xiaoji town, Jiangdu County, Jiangsu Province, China (119°42’0" E,32°35’5" N). Two rice (II you084) seedlings:no tiller seedlings and with a tiller seedlings, were grown at ambient or elevated (target at50%above ambient) ozone concentration. Results showed as follows:1. On average, elevated ozone concentration advanced the heading date of the test seedlings for3.5days, the rice plant height significantly shorten for7%.2. Elevated ozone concentration very significantly reduced the SPAD value of flag leaf for5%,11%and14%on the date of after transplant63day,77day and86day, respectively. Corresponding period of no tiller seedlings were reduced by7%,11%and14%, a tiller seedlings decreased3%(P>0.1),11%and13%, in addition to the outer dimension were significant or very significant level.3. On average, elevated ozone concentration significantly reduced the net photosynthetic rates(Pn) of flag leaf for19%and26%on the date of after transplant76day and86day, respectively. For the stomatal conductance (Gs), corresponding period of the test seedlings were reduced by24%(P>0.1) and55%(P<0.05), respectively. While for the intercellular CO2concentration (Ci) and transpiration rate (Tr), there were no significant effect under elevated ozone concentration.4. The dry matter accumulation of the test seedlings under elevated ozone concentration was decreased by8%,9%,6%and22%on average at tillering, jointing, heading and maturity stages, respectively. The effect was significant at maturity stages. For the no tiller seedlings, elevated ozone concentration significantly or very significantly reduced the dry matter accumulation by13%and22%, respectively, while there were no significant effect on a tiller seedlings. The biomass accumulated from heading to maturity was significantly reduced by44%, no tiller seedlings and with a tiller seedlings was reduced by45%(P<0.01) and43%, respectively.5. there was no significant effect on the ratio of green leaf, yellow leaf, total leaf and panicle dry matter to total biomass of rice aboveground plant at different growth stages under elevated ozone concentration. Stem and sheath dry matter to total biomass of rice aboveground plant decreased slightly at tillering, jointing and heading stages, while maturity stages significantly reduced by13%.6. There was no significant effect of green leaf or leaf nitrogen content at different growth stages. Elevated ozone concentration significantly increased the nitrogen content of aboveground plant at maturity by11%. while there were no significant effect of nitrogen content of aboveground plant at tillering, jointing and heading stages. There was no significant effect of Stem and sheath nitrogen content at maturity stages, while the other stages all significant. Elevated ozone concentration significantly increased the nitrogen content of panicle at heading and maturity stages. There was no significant effect on the nitrogen accumulation of different organs at different growth stages. There was slightly effect on leaf or panicle nitrogen distribution under elevated ozone concentration. The effect of elevated ozone concentration on Stem and sheath nitrogen distribution varies due to the growth stages. On average, elevated ozone concentration very significantly reduced the nitrogen dry matter production efficiency at maturity by10%, while there was no significant effect at at tillering, jointing and heading stages. There was no significant effect of elevated ozone concentration on nitrogen use efficiency of grain and nitrogen harvest index.7. Elevated ozone concentration significantly reduced the number of spikelets per panicle by19%on average, the no tiller seedlings and a tiller seedlings was reduced by22%(P<0.05) and17%(P<0.01), respectively. Elevated ozone concentration significantly reduced filled grain weight by about5%, the average reduction is about1.5mg. There was no significant effect of Elevated ozone concentration on panicles per unit area and filled grain rate.8. On average, elevated ozone concentration significantly reduced grain yield by25%, the no tiller seedlings and a tiller seedlings was reduced by27%(P<0.05) and22%(P<0.05), respectively. Elevated ozone concentration significantly reduced theoretical yield by28%on average, the no tiller seedlings and a tiller seedlings was reduced by33%(P<0.05) and23%(P<0.01), respectively.In summary, elevated ozone concentration could shorten the phenology, reduced photosynthetic pigment content and net photosynthetic rate, thereby inhibiting the production of yield and dry matter accumulation, affecting grain number and grain plumpness, ultimately yield decreased significantly. From the perspective of cultivation practices, enhanced the seedling quality can alleviate the damage of ozone on rice in some degree.