Improvement of Physiological Quality of Deteriorated Tall Wheat Grass (Agropyron elongatum Host) Seeds by Hormonal Priming for Non-drought and Drought Stress Conditions

Seeds of most crops including those of range plants follow orthodox behavior. However, these seeds undergo aging even under favorable conditions, so that decreased viability and vigor related parameters are the main characteristics of deteriorated seeds. The effects of hormonal priming with auxin, cytokinin, gibberellin and abscisic acid at 0, 50, 100 and 150 ppm on physiological quality of tall wheat grass deteriorated seeds were evaluated (at Natural Resources Gene Bank of Iran in Research Institute of Forests and Rangelands). Germination percentage, seedling dry matter and number of seminal roots were not affected by drought stress (-0.5 MPa). However, stress condition decreased the rate of germination, vigor, seedling fresh weight, length of root, shoot and seedling, and increased Mean Germination Time (MGT) as well as root-shoot ratio. Priming improved germination percentage under drought stress. Germination percentage and rate of germination of primed seeds were higher than those in non-primed ones under drought conditions. Gibberellin and cytokinin induced more rapid germination in non-drought condition, while auxin decreased the rate of germination. Priming the seeds with gibberellin, abscisic acid and cytokinin at 50 and 100 ppm decreased and increased MGT in non-drought and drought conditions respectively. Seeds primed with gibberellin (100ppm) have the highest vigor index under non-drought condition, but in drought condition, cytokinin (50ppm) produced the highest vigor index. Auxin decreased root length; meanwhile, increased the number of seminal roots. All the priming treatments decreased root-shoot ratio. According to the results, it could be suggested that the enhancement of physiological quality of deteriorated seeds in tall wheat grass can be obtained through hormonal priming. Seed priming by either gibberellin (100ppm) and cytokinin (50ppm) or ABA (50ppm) would be helpful for improvement of seed performance under drought and drought conditions respectively.