تاثير اسيد آبسيزيك و سيتوكينين بر بهبود صفات جوانه زني و بنيه بذر زوال يافته دو رقم كلزا (Brassica napus L.) در تنش خشكي

Effects of Abscisic Acid and Cytokinin on Improvement of Seed Germination Characteristics of Two Canola (Brassica nap us L.) Cultivars with Different Vigor under Drought Conditions

This study was conducted to evaluate the effects of abscisic acid (ABA) and cytokinin (CYT) seed treatments on germination performance of two canola cultivars OF different vigor under drought stress. The experiments were carried out at Seed Laboratory of College of Agriculture, University of Tehran during 2004-2005. Canola cultivars Licord (winter variety) and Option 500 (spring variety) were the ones employed. To determine the seed viability in these cultivars a standard seed germination test under a randomized complete design was performed. Seeds were exposed to accelerated aging for 2,5, and 8 days using the accelerated-aging test and then treated with various concentrations of ABA and CYT. A factorial experiment of randomized complete design was employed to evaluate the improvement of the cultivarsʹ drought tolerance. Such measurements as germination percentage (%), germination index, as well as germination speed were carried out in all of the experiments. The results revealed that seed aging or deterioration and drought stress cause reduced seed vigor, reduced germination percentage and speed of germination. Germination percentage of Option 500 and Licord declined around 25% and 31%, respectively, following eight days of aging. Canola cultivars reflected significantly different when exposed to accelerated aging and drought stress conditions. In accelerated-aging and drought stress treatments, vigor, germination percentage, and speed of germination for Licord cultivar were significantly higher than those for Option cultivar. Treatment of these various aged seeds with ABA and CYT hormones improved their drought tolerance. Higher concentrations of these two hormones increased the level of tolerance. A hundred ^ml use of CYT or ABA improved germination rate by 22% and 29%, respectively. Aged seeds better germinated under ABA than CYT treatment.