Abstract: Lineor relations between biomass and radiation absorption were revealed in the well-irrigated treatments(control) in the glasshouse and all treatments in the field by trials using two cultivars, Brock and Renard. But the crop stressed by drought pre-anthesis (F₁ ) reduced the solar radiation conversion effe-ciency over the late growing period. The biomass accumulation was negatively affected mainly by the reduction of radiation absorbed, and to some less extent the conversion effeciency. Total and stem biomasses both were remarkably depressed by water stresses imposed preanthesisa and grain-filling periods, among which, more by the pre-anthesis drought. The patterns in biomass accumulation varied in two genotypes, for the accumulation in Renard post-anthesis turned slow. Water stresses intensified the removal of reserves from stems, more removal occurred in the late season stressed treatment. The course of grain filling could be well fitted by a three-phase segmented model. Pre-anthesis water stress quickened the grain growth to compensate partially the lowered grain number per ear; but late drought affected grain filling and thus the grain weight. Different patterns of grain filling were shown in the two cultivars, suggesting that the patterm of short-fast grain filling seem to enable the crop to escape the drought stress during late period.

Key words: Winter wheat, Water stress, Solar radiation absorption, piomass accumulation, Grain filling, Segmented fitting