effect of transplanting time on grain yield and physiological traits in grain filling period in rice cultivars

dry matter remobilization, grain filling rate and duration has principle role on rice grain yield, and environment condition directly affect on them. for study the influence of climate factors a factorial field experiment in randomized complete blocks design with three replications conducted at haraz extention and technology development centre in spring 2013. treatments included rice cultivars namely; samadi, tarom hashemi, local tarom, shiroudi, keshvari, gohar and transplanting times (5th may, 20th may and 10th june). results showed that dry matter remobilization rate, stem dry matter remobilization efficiency, grain filling rate and duration, and grain yield varied significantly among different transplanting times. transplanting time on 5th may was higher than other two transplanting dates in all traits except for grain filling rate. tarom hashemi had highest and improved variety, shiroodi had lowest grain filling rate. dry matter remobilization rate, stem dry matter remobilization efficiency, effective grain filling duration, and grain yield was higher in shiroudi among rice cultivars. grain yield negatively correlated with grain filling rate. increasing in grain filling duration with increased dry matter remobilization had more effective role in rice cultivars grain yield. increasing temperature in vegetative growth phase with increasing in accumulated growing degree day accompanied with decreasing in tiller number, less tiller number caused higher grain filling rate and lower grain filling duration and dry matter remobilization restriction that decreased grain yield.