Investigating the effect of shading on dry matter remobilization, yield, and yield components of different rice cultivars

In an attempt to investigate the effect of shading (source limitation) on dry matter remobilization, yield, and yield components of different rice cultivars, a field experiment was carried out in the research farm of the Agricultural Services Centers of Rezvanshahr during 2007-2008. The study followed a factorial, randomize-complex-block design. The variety and treatment factors, which were respectively at two (Hashemi and Hybrid I) and four (control, light shading, moderate shading, and heavy shading) levels, were carried out in three replications. The treatments in the present study began 10 days before anthesis and ended 10 days after it. The analysis of the results indicated that the shading treatments had a significant effect (at P<0.01) on the seed yield, biological yield, harvest index, the panicle length, the number of grains in each panicle, the number of spikelet on the panicle, and 1000-grain weight. The highest and lowest grain yields belonged to the Hybrid I in the control condition with an average of 8962/3 kg/ha and Hashemi in the heavy shading condition with an average of 1503/3 kg/ha, respectively. The heavy shading treatment had the lowest yield in both types of cultivars. The shading treatments had a significant effect (at P<0.01) on the remobilization of stem and leaves’ dry matter. From among the aerial parts of the plant, the stem had the highest share in the remobilization process. Hashemi cultivar had the least amount of dry matter remobilization probably due to its limited sink space and production capacity. Generally speaking, the results revealed that Hashemi cultivar had a more limited sink space in comparison to the Hybrid I.