| Chill of grain fills at tillering stage of early season rice and wind of cold dew oflate rice at heading stage are important meteorological disasters for the rice product in thearea of double cropping such as Jiangxi province and so on. Nitrogen is an importantregulatory factor for rice "fitness cultivated". However, serious yield losses are oftencaused by improper use of nitrogen fertilizer in production, especially cause of excessiveamount of nitrogen suffering low temperature. Up to now, little is known about theinfluence of low temperatures to rice in high nitrogen condition. According to this,double cropping super rice varieties early rice GanXin203and WufengyouT025werechosen fertilized with two different nitrogen levels (high nitrogen and normal nitrogen) inearly rice tillering and late rice heading periods respectively with normal temperature andlow temperature treatment. In this study, Physiological indicators such as chlorophyll,photosynthetic indexes, osmotic adjustment substance, MDA content and systemprotection enzymes, hormones, nitrate reductase and so on were measured and the yieldand its components were investigated. The main results are as follows:1Coupling effects of the low temperature and high nitrogen on yield formation andits physiological mechanism of early super hybrid rice at tillering stage.The yield per plant of GanXin203with high nitrogen-low temperature(15℃)treatment was the lowest among the four groups of different nitrogen and temperaturetreatment and the difference reached significant level compared with that of highnitrogen-CK(28℃) and normal nitrogen-CK while no significant difference with normalnitrogen-low temperature. Compared to the latter three groups, the yield per plant withhigh nitrogen-low temperature treatment decreased32.45%、28.99%、15.11%respectively.This showed that high nitrogen and low temperature formed with a certain couplingeffects on the yield of GanXi203. The grain weight, maximum number of tillers,effective panicles, each grain number and harvest index except seed setting rate underhigh nitrogen-low temperature were lower than those with normal nitrogen-lowtemperature treatment. This Further show high nitrogen compare with normal nitrogenunder the low temperature are not conducive to the formation of production of GanXin203. Effective panicles, each grain number and harvest index under high nitrogen-lowtemperature decreased than those with high nitrogen-CK, the same to normalnitrogen-low temperature compared to normal nitrogen-CK and the decrease of theformer was greater than the latter. Grain per panicle, effective panicles and harvest indexwas the main reason of the decline of the yield per plant.The difference of physiological indices among four groups with different nitrogenfertilization and temperature treatment: on the first day after cold treatment, the MDA content, POD activity, ABA and IAA levels of leaves of the high nitrogen-lowtemperature treated samples were higher than the rest of the3treatment, while CATcontent and soluble protein content reversed; Free proline content with high nitrogen-lowtemperature was lower than that with normal nitrogen-low temperature, however, therecovery rate of proline content was slower; The SOD activity of samples treated withhigh nitrogen-low temperature was equal to that with normal nitrogen-low temperature,but the falling range of the SOD activity from the former VS high nitrogen-CK wasgreater than that from the latter VS normal nitrogen-CK; chlorophyll content with highnitrogen-low temperature was higher than with normal nitrogen-low temperature frombeginning to end, except on the third day after cold treatment, the change of nitratereductase is as same as chlorophyll content; GA3, and ZR content had no consistentpattern among each treatment. On the third day after cold treatment, the GA3levels ofleaves of the high nitrogen-low temperature treated samples were highest; After coldtreatment, the ZR levels of leaves of the two nitrogen treatment have no big difference.2Coupling effects of the low temperature and high nitrogen on yield formation andits physiological mechanism of late super hybrid rice at heading stage.The yield per plant of WufengyouT025with high nitrogen-low temperature (18℃)treatment was the lowest among the four groups of different nitrogen and temperaturetreatment and the difference reached significant level compared with that of highnitrogen-CK (28℃) and normal nitrogen-CK, while no significant difference with normalnitrogen-low temperature. Compared to the latter three groups, the yield per plant withhigh nitrogen-low temperature treatment decreased34.44%,27.3%,0.99%respectively.This showed that high nitrogen and low temperature formed with a certain couplingeffects on the yield of super rice WufengyouT025. Except grain weight, the seed settingrate and harvest index under high nitrogen-low temperature declined largely and be thelowest at last and the seed setting rate reached a significant difference level compared tothe other3treatment groups accompanying the significant difference level of the harvestindex compared to that with high nitrogen-CK and normal nitrogen-CK, while onsignificant difference against to the treatment of normal nitrogen-low temperature. Thefurther decline of seed setting rate of the rice treated with high nitrogen-low temperaturewas the main reason that causing the sharp fall of the yield per plant.The difference of physiological indexes among four groups with different nitrogenfertilization and temperature treatment: The MDA content of the high nitrogen-lowtemperature treated samples was the highest among the four groups and that continued5days after treatment. Soluble protein and free proline content with high nitrogen-lowtemperature were higher than that with normal nitrogen-low temperature. At the first dayafter treatment, the SOD activity with high nitrogen-low temperature was equal to that with normal nitrogen-low temperature and POD activity was higher than that with normalnitrogen-low temperature. But the increasing rate of the former was slower. The CATactivity with high nitrogen-low temperature treatment was lower than that with normalnitrogen-low temperature treatment. The ABA content was lower than that with normalnitrogen-low temperature treatment except at the second day after treatment. Littledifference of the GA3content existed among the four groups in the first three days. and inthe fifth day after treatment, the GA3content with high nitrogen-low temperaturetreatment was lower than that with normal nitrogen-low temperature treatment. The firstday after treatment, IAA content with high nitrogen-low temperature treatment washighest while ZR reversed. The net photosynthetic rate, stomatal conductance andtranspiration rate of the samples treated with high nitrogen-low temperature were higherthan that with normal nitrogen-low temperature, except the sixth day after cold treatmentand chlorophyll content and nitrate reductase activity was always higher in highnitrogen-low temperature treated than that of normal nitrogen-low temperature treated. |
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