The Research Of Deficit And Efficient Compensation Threshold In Tillering Stage In Two Double Season Super Hybrid Rice Varieties

Previous studies by our group showed that tillering stage of the double cropping superhybrid rice varieties was the nitrogen demanded critical period and sensitive stage. In orderto ascertain the tillering nitrogen sensitivity deficit threshold and efficient compensationthreshold, this test selected early super hybrid rice varieties Ganxin203and late super hybridrice varieties WufengyouT025, planted in the barrel test under normal supply water, thewhole tillering stage was divided by six time points: the begin, the6th day, the12th day,18th day, the24th day and the30th day, studied on that supplied the same amount anddouble amount after nitrogen deficiency at different time points, the influence on dry matteraccumulation, nitrogen accumulation, tillers, chlorophyll content, yield and its components,endogenous hormones, etc. Analysis of the compensation effect of nitrogen deficiency, theresults showed that:From0d to30d in the tillering stage of the early rice Ganxin203, yield per plant of Ndeficiency treatment showed first increased and then decreased trend. The N deficiencyconstant restoration treatment of the tillering24d, yield per plant showed the biggest declinecomparing with the tillering18d, therefore the tillering18d was N deficiency threshold.Similarly, the tillering N deficiency threshold of the late rice WufengyouT025was thetillering18d.The N deficiency double amount restoration treatment of the tillering24d, yield perplant, N recovery efficiency, N physiological efficiency and N agronomic efficiency showed thebiggest decline comparing with the constant restoration treatment of Ganxin203, thetillering24d was N efficient compensation threshold. The N deficiency double amountrestoration treatment of the tillering18d, yield per plant, N recovery efficiency, N physiologicalefficiency and N agronomic efficiency showed the biggest decline comparing with theconstant restoration treatment of WufengyouT025, the tillering18d was N efficientcompensation threshold.The effective panicles per plant, grain number per plant, and panicle seed setting ratewith N deficiency constant restoration treatment showed increased firstly and thendecreased trend. from0d to30d in the tillering stage of the early rice Ganxin203.The downrange of tillering24d compare with tillering18d with N deficiency constant restorationtreatment was the greatest. The thousand-seed weight with N deficiency constant restorationtreatment is no significant difference compare with N deficiency double restorationtreatment. It was consistent with efficient compensation threshold. The grain number perplant with N deficiency constant restoration treatment showed increased firstly and thendecreased trend from0d to30d in the tillering stage of the early rice WufengyouT025. The amplification the effective panicles per plant, grain number per panicle, grain number perplant, panicle seed setting rate and thousand-seed weight with N deficiency double amountrestoration treatment of the tillering18d compare with N deficiency constant amountrestoration treatment was the highest among the all treatments, that was consistent withefficient compensation threshold.In tillering18d of N application treatment, chlorophyll in tillering stage of early andlate rice were maintained higher content. From18d to24d of early rice tiller period, the dryweight of panicle showed the largest decline, with the same deficit threshold of per plantyield. However panicle and aboveground dry weight of WuFengYouT025mature periodshowed all first increased and then decreased, and inflection point of decline was thetillering18days, that was consistent with N deficiency threshold. The double amount of Napplication treatment than constant treatment of the later rice WufengyouT025, the highestincrease period of the dry weight of panicle and total aboveground was the tillering18days,this was same with N deficiency efficient compensation threshold.The tillering24d nitrogen deficiency constant restoration treatment of Ganxin203,endogenous IAA, GA3, ZR and ABA levels of the moderate tiller top second leaf were lowerthan18d treatment at5d and10d after of treatment, but were higher than18d treatment at15d after treatment. The tillering24d nitrogen deficiency double amount restorationtreatment of Ganxin203, endogenous IAA, GA3, ZR and ABA levels of the moderate andlittle tiller top second leaf were lower than18d treatment at10d after of treatment. Thetillering24d nitrogen deficiency constant restoration treatment of WufengyouT205,endogenous IAA and ZR levels of the strong and moderate tiller top second leaf were lowerthan18d treatment at15d after of treatment, but were higher than18d treatment at20d aftertreatment. The tillering24d nitrogen deficiency constant restoration treatment ofWufengyouT205, endogenous IAA, GA3and ZR levels of the strong, moderate and littletiller top second leaf were higher than18d treatment at20d after of treatment. Thecompensation type of12d,18d and30d constant N application treatments in the tilleringbelonged to overcompensation, the type of12d and18d double amount of N applicationtreatments belonged to equal compensation of Ganxin203. The compensation type ofconstant N application treatments in the tillering belonged to over compensation, the type of18d double amount of N application treatments belonged to over compensation ofWufengyou T025.