Study of some effective phenologic and physiologic characteristicson sunflower hybrids yield

In order to Study of some effective phenologic and physiologic characteristics on 18 sunflower hybrids yield under optimum conditions, an experiment was conducted as randomized complete block design with three replications at the research field of Seed and Plant Improvement Institute-Karaj in 2006-2007. The result indicated that the hybrids showed significant difference in phonologic characteristics, number of photosynthesis active leaves and leaf area index in seed filling stage, photosynthesis active radiation and red to far red ratio in bottom canopy, radiation interception, 1000 seed weight, seed yield and seed oil content, whereas in seed number per plant and harvest index not significant difference. In this experiment, intermediate and late maturity hybrids had the great leaf area index and with the better photosynthesis active radiation absorption. Also it had the maximum radiation interception and produced the highest seed yield in comparison with early maturity hybrids. Correlation coefficients analysis demonstrated that seed yield had positive and significant correlation with filling stage duration, reproductive stage duration, growth stage duration, leaf area index, 1000 seed weight, seed oil content and harvest index, whereas red to far red ratio in bottom canopy has the negative and significant correlation with seed yield. Mehr hybrid with long flowering duration (6 days) and moderate growth period (98 days), could be used for optimum conditions. Therefore it had the high leaf area index (3.3) and radiation interception (0.98) and produced the highest seed number per plant (980), seed yield (3861 kg.ha^-1) and seed oil content (48.3).