Effects Of Exogenous Silicon On Seed Fertility And Heat-stress Physiology Of Hybrid Rice Under Heat Stress And Its Application

Recently, the occurrence of high temperature damage of rice in our country is an icreasing problem, especially for hybrid rice combination which is more sensitive to temperature and its production reduction is serious at high temperature’s year, and will make a serious threat to production safety of food in China. With inscrutability of rice heat damage occurrence, which bring fatal difficulties to predict disasters and instant defense. Application of exogenous substances to induce heat resistance of rice against the possible heat stresses directly may be an important technology pathway. If we can use a substance in the early growth stage of rice to induce heat resistance, that we will reduce or avoid effectively the damage caused by high temperature in the key growth period later. Exogenous silicon has better resistance against other abiotic stress adversity, but there only a little paper about seed fertility physiology, effect of induced resistance and its application of rice under heat stress. This study investigated the damage reduction effects of silicon applicated before jointing stage and the induced resistance at flowering stage. Focus on the effects on silicon and its preparation application on spikelet fertility and pollination performance and flag leaf general resistance index of rice, analysed the effects of sodium silicate and complex silicon preparation "Yumaguijia" on seed setting rate of hybrid rice. The results as below:1. Exogenous silicon increase pollination and seed fertility performance of hybrid rice under heat stress during anthesisThis experiment used mid-maturation indica hybrid rice Jinyou63and Shanyou63as experimental materials, sprayed sodium silicate3times continuously at jointing stage and treated by normal temperature, high temperature5d in a artificial plant growth chamber during anthesis. The results suggested that application of silicon at jointing stage can effectively enhance the anther soluble acid invertase activity, reduce pollen sterility, and increase pollen viability; increase the anther basal dehiscence width; increase the total number, germination number and pollen germination rate of pollens per stigma pollination under heat stress during anthesis; reduce two varieties seed setting rate reduction of13.4%,14.1%respectively. The application of exogenous silicon can enhance heat resistance of flower of rice, which suggested that exogenous silicon can induce heat resistance of rice flowering and can alleviate fertility losses.2. Exogenous silicon increase general resistance of hybrid rice under heat stress during anthesisTwo cultivars (Jinyou63and Shanyou63) were used in this study. By spraying sodium silicate3times continuously at jointing stage and treated by normal temperature, high temperature5d in an artificial plant growth chamber during anthesis. The results showed that exogenous silicon can significantly enhance chlorophyll content in rice flag leaf, increase net photosynthetic rate and stomatal conductance, reduce the accumulation of CO2concentration in the cells, enhance the photosyntheticrole, reduce the blade membranous accumulation of malondialdehyde (MDA) content, enhance the antioxidant protective enzymes SOD, POD, CAT activity to maintain the balance of the plants of reactive oxygen species generation and removal system to improve the plant body anti-oxidative capacity. So, exogenous silicon improved the flag leaf conventional resistance index of rice under heat stresses, increase the levels of conventional resistance of rice.3. Sodium silicate alleviate fertility losses of hybrid rice seed setting rate under field high temperatureJinyou63and Shanyou63as experimental materials, sodium silicate as silicon source, we seted4concentration (T-CK, Ommol/L; T-1.25,1.25mmol/L; T-2.50,2.50mmol/L; T-3.75,3.75mmol/L) and sprayed3times continuously at jointing stage, measured the changes of performance of anther dehiscence, pollination and seed setting rate during anthesis under field high temperature environment. The results shows that, compare to the control T-CK, the three treatments of simple sodium silicate (1.25mmol/L,2.50mmol/L,3.75mmol/L) can improve the number of pollen grains per stigma3.4%,30.5%, number of germination16.9%,39.6%, rate of germination11.3%,7.0%, percentage of florets with more than10germinated pollen grains9.3%,27.6%, decrease the percentage of florets with under20pollen grains18.8%,8.1%, of Jinyou63and Shanyou63respectively in mean; increase the anther basal dehiscence width19.0%,10.3%respectively; ensure the promotion of hybrid rice Jinyou63and Shanyou63seed setting rate10.6%and4.7%respectively. In conclusion, T-2.50treatement is the best, and improve the fertility of2cultivars2.6%,4.9%respectively under normal condition. Spraying3concentrations of sodium silicate at jointing stage can alleviate fertility losses hybrid rice seed setting rate under field high temperature, and plays an inportant role on improving the heat resistance of hybrid rice.4."Yumaguijia" alleviated fertility losses from field temperature extremity stresses in hybrid riceIn field condition, we used super hybrid rice Yliangyoul as experimental material, sprayed with various concentrations at its booting and flowering stages, to verify its effect and find the possible usage methods. Yliangyoul encountered typical hot stress in its meiosis stage and then chilly stress in its flowering stage. As a result, rice plants showed a profound down (<75%) in its seed setting rate comparing to that in the ordinary years (≥90%). In comparison with the check, nevertheless, plants with Youmaguijia with all the concentrations and in the all treatment times (or grouping) lessened the reduction with an average7.3%seed setting rates significantly. However, there were no significant differences among spraying times or concentrations in its alleviation effect, and neither any interaction between the two treatments. In conclusion, the preparation of Youmaguijia with all the concentrations and in the all treatment times alleviated fertility losses from field temperature extremity stresses in hybrid rice at key reproductive growth stages (meiosis stage and anthesis).In conclusion, application of exogenous silicon before or after jointing stage of rice may increase the heat resistance before or after anthesis. The induced resistance significantly increases the key enzyme activity of pollen content material and increase the vitality of pollen pollination and pollination effectiveness of rice under heat stress during anthesis. Meanwhile, increase the leaf photosynthetic performance and activities of protective enzymes significantly. In the field level, application of2.50mmol/L sodium silicate and some concentrations of silicon complex preparation "Yumaguijia" can alleviate seed fertility losses from high temperature. The application of silicon and its compound preparation may be an important pathway to alleviate rice heat injury in the future.