Cultivar difference in within-spike N remobilization in CWRS wheat
The objective of the present study was to compare four new CWRS wheat cultivars with two older cultivars, Neepawa and Marquis, in terms of spike dry matter and nitrogen accumulation and within-spike partitioning. Results showed that new cultivars had significantly higher kernel mass and N content per spike than old cultivars, which were mainly attributed to their higher accumulation rates, instead of accumulation duration. N remobilization from glumes occurred during the linear phase of grain filling and new cultivars started remobilizing N earlier and had a higher rates than old cultivars. N remobilization of rachis started later and the rate was smaller than glumes. New cultivars had higher total N remobilization and maximum remobilization rate from rachis than old ones. It seems that cultivars with large sink size had a high rate of accumulation and were able to remobilize more carbohydrates and N into the grains before maturity. Cultivars with small sink size had both relatively low accumulation rate and remobilization rate. Although visual observations showed that Marquis and Neepawa had 1-3 days longer maturity than new cultivars, grain accumulation of carbohydrates and N was minimal during these days because of the severe water stress and/or heat stress.
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