Abstract: The results show that there is closely relatlonship between the effects of sterile cytoplasms on dry mat ter pdriuctlon and partioning and on the yield performance o[ hybrid rice at late growth stage. Nonsignificantly-positive sterile-cytoplasmic effects on dry matter production, ranging from 1.37～1.47g·m^-2·day^-1 on an average, are found at early growth stage of hybrid rice across 4 supply N treatments, but the situation is quite different at late growth stage, especially in exposure of hybrid rice to nitrate stress. The nonsignificantly-positive effects of sterile cytoplasms on dry matter production and on the grain yield of hybrid rice are detected, in turn leading to increased grain yield of hybrid rice under favorable nitrogen conditions(150～240 kg N·hm^-2 ), the reverse is true under unfavorable nitrogen supply(≤60 kg N·hm^-2 or≥330 kg N·hm^-2 ). Further analysis suggests that this process is closely related to the activities of RUBPcase, ATPase and defense enzymes at late growth stage of hybrid rice, indicating the same reaction of cytoplasmic effects on them, particularly under the nitrate stress. Finally the physiological relationship between polyamine metabolism and changes in the activities of defense enzymes and the amount of free radicals is also discussed in this paper.

Key words: Hybrid rice, Dry matter production, Defense enzymes, Free radicals, Cytoplasmic effects, N₂O, soil organic carbon, intercropping, legume., CO₂