بررسي ارتباط برخي از شاخص هاي رشد با عملكرد كشت دوم آفتابگردان در منطقه ورامين

Studying Relations of Some Growth Idices of Sunflower as a Second Crop in Varamin Region

An experiment based on a randomized complete block design with three replications was conducted in 2001, to determine a suitable sunflower cultivar as a second crop, in Varamin region. The cultivars under study were belonged to three early (Zariya, Hybrid 25 and Chernianka), middle ( Armavirski, Hybrid 33 and Golshid) and late ( Progress, Record and Gabor) maturity groups and in two types, hybrid (Hybrid 25, Hybrid 33 and Golshid) and commercial (other cultivars). The stem dry matter in all cultivars increased until the stage of 50 percent flowering, but decreased afterwards. Total dry weight of shoots increased in all cultivars, but a slight decrease in some cultivars, due to falling of leaves and other plant parts, which was observed in later stages. CGR, due to the presence of proper environmental conditions, increased from beginning of growth period, and reached to its maximum value in the flowering stage and then decreased. RGR of different maturity groups, was decreased from the beginning of growth period. The rate of decrease was faster at the beginning but stower in the later stages when interplant competition, due to canopy expansion, decreased. LAI increased until the stage of 50 percent flowering and decreased afterwards. The rate of increase was slow at first and then, due to relative leaf area expansion and higher rate of photosynthesis, increased rapidly and reached to its maximum value in the stage of 50 persent flowering. It was finally decreased because of shading and senescence of lower leaves, decreased. The Hybrid 25 was the highest yielding cultivar but was not significantly different from Progress, Record, Gabor, Hybrid33 and Chernianka. Among maturity groups, late maturing cultivars, because of their longer period from planting to 50 percent of flowering and seed filling duration, yielded more than the others.