Effect of Planting Date on Growth And Assimilate Contribution of Assimilates on Seed Yield of Six Wheat Cultivars

In order to evaluation effects of sowing date on growth analysis, percent of contribution assimilates stored in stems to grains of different wheat cultivars, an experiment conducted during 2004/05 with three sowing date Oct. 12th (D1), Nov. 5th (D2), Nov. 30th 6 (D3) and six cultivars included MV17, Alamot, Toos, Alvand, Pishtaz and Marvdasht which arranged at split plot with three replication in Neyshabur. Results showed highest and lowest accumulation dry matter and mean of crop growth rate between heading and anthesis were in D2 and D1 respectively. The contribution of assimilates in grain weight was 45.3% and 30.6% in D3 and D2 respectively, heat stress and terminal drought stress and source limited in D3 may be involved this variability. Toos and Marvdasht have more and less assimilates remobilization among cultivars respectively. Optimum sowing date for winter and spring wheat was early October and early November respectively. In general, planting of spring wheat type cultivars recommended in Neyshabur for best performance, because they produce grain yield more than winter type (7334 vs. 7048 kg/ha). Therefore to achieve maximum production, spring types planting is recommended.