Abstract
In this research the response of nine cultivars of Subclover to drought stress induced by polyethylene glycol 8000 during the stage of germination and seedling growth on the levels of drought 0, -2, -4, -6 and –8 (bar) in 20 0C were studied. With increasing of drought stress the percentage and rate of germination decreased and germination in all cultivar approached 0 in the-8 bar of drought. But the sensitivity of germination rate to changes of drought stress was more than the percentage of germination. The cultivar of Denmark and York had the highest rate of germination on all levels of drought and Larisina cultivar had the least rate of germination. The length of root and shoot was also significantly decreased with increasing drought stress and the percent of decrease of the shoot length in comparison with the drought stress was more than the length of root, or the sensitivity to drought stress of shoot length was more than root length. With increasing of drought stress in all cultivar, the dry weight of seedlings decreased significantly .The percent of decreasing was different among cultivars. In most cultivars in the – 4 bar level of drought, the dry weight of seedling, decreased more than 50 percent compared to control. The results of this research showed that drought stress affects on all germination parameter and seedling growth of subclover and the subclover is a sensitive plant to drought, however, the response of the studied cultivars was different. The cultivars Goss and York stand without any decrease in seedling dry weight up to –2 bar, but the dry weight of the dry seedling in Stenwart and Banch cultivars decreased from 0 drought.

Keywords: Subclover (Trifolium subterraneum L.), Drought stress, Germination, Seedling growth