Some ecophysiological responses to simulted drought of intergeneric hybrid rice Yuanyou No. l

derivedfrom a distant hybridization of Oryza×Sorghum .its paternal sorghum Taochanghong and maternal rice cultivar Gut 630

and a commercial hybrid rice Shanyou 63 were comparatively studied by means of adding PEG6000 into Yoshida's nutritional solution. The results obtained demonstrates that the germination of all materials were inibited to varying degrees and the germination coefficient sensitive to drought stress of YuanyouNo. 1(intergeneric hybrid)

Gui 630 (the maternal parent of Yuanyou No.1 ) and Taochanghong (the disantpaternal sorghum of Yuanyou No. 1

upland crop ) were 28. 97%

57. 66%

50. 92%

respectively

indicatingthat the tolerance to simulated drought of Yuanyou No. I was sign.ificantly better that its parents. Water content of leaves and roots

chlorophyll content and activities of nitrate reductase of leaves decreasod significantlyunder drought stress

but Yuanyou No. I showed the least decrease among all materials tested. Significant varietal differences exist in all characters related to photosynthesis among materials. &tier tolerance to droughtperformanced under simulated stress of intergeneric hybrid rico and 3--line hybrid rice proved their good fieldtolerance implying that physiological mechanism of drought tolerance exist both in intergeneric hybrid riceand 3-line hybrid rice.