Variations in Seed Germination, Competency for Dormancy Induction and Seedling Death under High Temperature Stress in Domesticated and Wild Safflowers
摘要
Safflower is a drought-tolerant plant cultivated commonly in low-water areas where the plant usually experiences high temperature stress with the resultant decline in seedling establishment. Therefore, in this study physiology of seed germination and seedling establishment under high temperatures was investigated in the domesticated Carthamus tinctorius (cv. Sofeh and Sina) and the wild C. oxycanthus and C. glaucus safflower seeds. Seed germination and seedling establishment were recorded at temperatures ranged from 5 to 45°C under light and dark conditions and with or without GA3 supplementation. Seeds from C. tinctorius were able to germinate in a higher temperature range (5–40°C) than the wild species (5–35°C). Primary dormancy was observed only in C. glaucus species which could be alleviated partly by either light or GA3. High temperatures (35°C and above) declined seed germination through the induction of thermo-inhibition and/or thermo-dormancy in all three species and especially in C. glaucus. However, this condition mainly led to seedling death in C. tinctorius. Thus, the increased seedling death under high temperatures in C. tinctorius may limit their cultivation under current and future warming scenarios and causes a decrease in the percentage of establishment and ultimately yield. Breeding efforts therefore, should focus on developing high temperature-tolerant cultivars specifically those lacking thermo-inhibition, thermo-dormancy, and heat-induced seedling death through recruitment of desired traits from the wild safflower species.