The Modeling of Development Stages of Sunflower on the Basis of Temperature and Photoperiod
This experiment was conducted at the Station of Agricultural Research and Natural Resources, Khoy, Iran in 2007 and 2008 to evaluate the effect of temperature and photoperiod on the duration of development stages of sunflower. A randomized complete block design using a 8 x 3 factorial arrangement with four replications involving eight plantings (29th April, 4th May, 14th May, 24th May, 1st June, 10th June, 19th June and 28th June) and three sunflower cultivars ('Sor', 'Eroflor', 'Azargol'). From the results obtained, all development stages, especially the generative phase were influenced by planting date. The duration of each development stage decreased with the delay in planting. The designed models indicated that the minimum temperature and photoperiod were directly proportional to the development rate (DR) of the whole life cycle of different sunflower cultivars. DR decreased from emergence (E) to physiological maturity (PM) as day length increased. The relationship between DR and photoperiod could be used as a practical model for estimating E to PM duration of these sunflower cultivars.
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