| The character of drought resistance of Brazilian upland rice-IAPAR9 was studied deeply and systematicly with comparison of some rice varieties-Moroberekan,Azucena Maratelli,Sariceltik,Biliang you 96 and Xiang zao xian 24,by the methods of pot and field culture. This research exposed firstly and totally the mechanism of drought resistance in Brazilian upland rice-IAPAR9 and provided a good theoretical basis for utilizing resource of drought resistant germplasm in upland rice and developing product of upland rice. The main results were as follows:1,The results of morphology and anatomy showed that:(1) The correlation between drought resistant ability of rice and its length,volume weight were significant (r was 0.8607,0.7381,0.7149 respectively);IAPAR9 had a middle level of roots;Both number and area of conduct in roots of rice were decreased greatly under drought stress,but IAPAR9 could maintain larger growth than others while drought was serious (40% soil saturated water content )and treated time reached 100 days,this should be one of matter bases on which it had a good drought resistant ability. Meanwhile,we found that numbers of roots conduct of rice varieties were different,for example,number of roots conduct in Xiang zhaoxian24,BaLiang you96,IAPAR9 and IRAT104 were 3,4,7,8 respectively while they were in seedling stage.(2) The correlation between drought resistant ability of rice and it's weight of stems and leaves,plant height,leaf area were also significant (r was 0.7393,0.809r,0.6550 respectively),but it was correlative negatively(r=-0.6732) between number of stems and tillers and its drought resistant ability. The result appeared that 1APAR9 had a stronger maintaining water ability because its water content of stems and leaves was more than that of general varieties.(3) Leaf stomatal density of rice varieties was not correlative to its drought resistant ability (r=0.1015),but it would be decreased greatly with the cut of soil water content (-26 --44%) and stomatal area was also cut down. Both number of vascular bundles,air cavities andconduct area of vascular bundles,area of air cavities in leaves were greatly cut down,but thickness of waxen film would not be affected;IAPAR9 could maintain stronger conduct and aired tissue while it encountered drought stress,This was its another matter base of good drought resistance. 2 The results from physiologic studies showed that:(1) The correlation between photosynthetic rate of rice varieties and its drought resistant ability in the serious drought stress was significant (r=0.6216). IAPAR9 had higher photosynthetic rate under drought stress;Meanwhile,total chlorophyll content of rice leaves would be cut down smoothly in drought stress,and conditions of stomatal resistance was very complicated,but it would be increased in totally;IAPAR9 had a low level of stomatal resistance.(2) Soluble sugar of rice varieties would be in creased,and protein content varied little in drought stress but free proline would increase greatly,and the correlation were not significant between them and drought resistant ability of rice varieties (r was -0.4463,-0.5007,-0.4000 respectively). IAPAR9 had middle level of soluble sugar protein and proline.(3)Transpiration rate would cut down with decreasing of soil water content when soil water content was 60%-80% soil saturated water content,once under 60% soil saturated water content,each variety would have different appearance;Meanwhile,Water use efficiency was varied complexly under drought stress,and IAPAR9 had higher WUE.(4)The correlation between leaf water potential and drought resistant ability of rice varieties was significant (r=0.7328).It varied apparently to levels of drought,and varied not apparently to time of drought;IAPAR9 had a higher tissue water potential;Moreover,water content of stems and leaves could indicate drought resistant ability of varieties too(r=0.6867);IAPAR9 had higher water content of stems and leaves;but the correlation between roots vigor and drought resistant ability was negative (r=-...
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