Physiological parameters and grain yield as influenced by time of transplanting and rice (Oryza sativa) hybrids

A field experiment comprising 4 dates of transplanting (15, 25 June and 5, 25 July) in conjunction with 4 genotypes (3 hybrids :'ORI 161' 'PMS2A/IR318 02, 'PMS10A/PR106' and 1 inbred variety 'HKR 126') was conducted during rai ny season of 1993 and 1994. Crop-growth rate (CGR) prior to panicle-initiat ion (PI) stage was higher in July transplanting, whereas it increased signi ficantly in 25 June planting during post-PI stage through flowering period. Leaf-area duration (LAD) during pre-PI stage was the longest in the most d elayed planting, but 25 June planting excelled over other dates during flow ering period of crop growth. Leaf-area ratio (LAR) was the highest in June- planted crop at all the time intervals. Panicles/m(2), grain and straw yiel ds were higher in 25 June-planted crop, followed by 5 July. Spikelet steril ity was maximum in 25 July and minimum in 25 June-transplanted crop. Hybrid 'ORI 161' ('PHB 71') exhibited superiority to other genotypes in CGR, LAD, grain yield and straw yield. Spikelet sterility (%) was lowest in 'ORI 161 ', followed by 'HKR 126'.