Quantitative expression of developmental processes as a function of water temperature in rice (Oryza sativa L.) under a cool climate
2001
Shimono, H. (Hokkaido Univ., Sapporo (Japan)) | Hasegawa, T. | Iwama, K.
Development of rice plants (Oryza sativa L.) under flooding conditions is strongly affected by water temperature (Tw). Although a number of models for the developmental progress have been developed based on air temperature, quantitative expression of the effect of Tw is still limited. We therefore conducted a three-year field trial in Sapporo (43deg04'N), Japan to determine the effect of Tw during the vegetative and reproductive periods in the development of rice plants. Cool water of ca. 15degC was irrigated for 20-34 days during each period and three to four plots with different Tw were provided. The average daily Tw in each plot ranged from 17.0 to 26.0degC. The process of rice development was expressed by the developmental index (DVI, Horie and Nakagawa sup7). The average developmental rate (DVR, the reciprocal of growth duration) was closely and linearly correlated with Tw during the vegetative (r=0.914*) and reproductive periods -(r=0.979***) and the relations was conserved over the years. This simple correlation between DVR and Tw agreed well with the data that were not used for parameterization (The mean square error = 2.4 d). Tw-dependent variation in the developmental stage such as leaf number, panicle length and culmlength were well expressed as a function of DVI. The developmental response to Tw in the present study will improve the accuracy of estimation of developmental progresses and can be incorporated in the crop growth model.
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