This experiment was conduced to clarify the effects of growth temperature and radiation on grain weight increase and grain nitrogen accumulation in rice. Final grain weight became heavy and grain-filling duration shortened with radiation increase during grain-filling period (GFP). In addition, grain nitrogen accumulated duration during GFP was influenced strongly, but final grain nitrogen content was influenced slightly by accumulated radiation (AR). Accumulated effective temperature (AET) described well variation of grain weight (GW) and grain nitrogen content (GN), but GW and GN showed large variation under different radiation during GFP, when related with AET or AR, indicating that there was a limiting in describing variation of GW and GN by any single factor between AET and AR. However, AET multiplied by AR could describe relatively well the variations of GW and GN regardless of radiation during GFP.
This experiment was conducted to clarify the effects of source and sink related characteristics on grain weight increase and grain nitrogen accumulation in rice. Source was modified by leaf removing treatment with no sink modification in 2002 and sink and source were modified at the same time by different sowing dates, N fertilization rates, row spacings, and thinning treatments at heading in 2007. Grain weight (GW) and grain assimilates produced by photosynthesis during grain-filling (GW P ) increased with the increase of source, while the grain assimilates retranslocated from leaf and stem (GW T ) decreased. Among the source-related characters, shoot dry weight were most closely related with GW. GW was dependant on GW P rather than on GWT. Grain nitrogen content (GN) and grain nitrogen absorbed from soil during grain-filling (GN S ) increased with the increase of source, while the grain nitrogen retranslocated from leaf and stem (GN T ) decreased. Shoot nitrogen content among the source-related characters was related most closely with GN. The contribution of GN T to GN was relatively large although GN depended more largely on GN S than GN T . In addition, GN was supplied firstly from GN S or from GN S and GN T at the same time.
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