Title: Evaluation of Morphological and Physiological Characteristics Associated with Early Vigor in Different Genotypes of Cotton (Gossypium hirsutum L.).

In order to evaluate the early vigor (early season dry matter accumulation) of cotton (Gossypium hirsutum L.) seedlings, two farm and laboratory studies were conducted in 2001. In this research, 12 cultivars with determinate, semi- indeterminate and indeterminate growth habits with normal and Okra leaf shapes were studied in a randomized complete block design with 4 replications and after dry matter evaluation of different cultivars seedling, cultivars were arranged to 3 groups: 1- with high early vigor 2- with medium early vigor 3- with low early vigor. Here after two cultivars from first group, once from second group and once from third group, were selected and some of their morphological and physiological characteristics were evaluated in both farm and lab phases. These selected cultivars were Oultan (from first group with normal leaf shape), red leaf Okra (from first group with Okra leaf shape), Deltapine 50 (from second group) and Shirpine 603 (from third group). The results of the farm study showed that red leaf Okra and Shirpine 603 had the highest and lowest dry matter and early vigor, respectively (P%5). Although there was no significant difference between Leaf Area Index (LAI) of Oultan and red leaf Okra. The Crop Growth Rate (CGR) of red leaf Okra was the most of all the 4 cultivars, because it had the highest Net Assimilation Rate (NAR). Deltapine 50 had the highest mean of Leaf Area Rate (LAR) and Leaf Weight Ratio (LWR) but it could not produce high dry matter, because its LAI and NAR were low. The results of the 29 laboratory phase showed that red leaf Okra could produce the highest seedling dry matter at twelve days after cultivation in incubator and had the most seed reserve utilization efficiency and germination capacity (P%5). It was shown that the highest correlation was between dry matter production and maximum Relative Growth Rate (rEarly vigorGerminationSeedling evaluation and Morphological and physiological characterestics.