Effect of foliar application of organic growth stimulators on physiological characteristics, yield and percentage of safflower oil (Carthamus tinctorius L.) under levels of drought stress

Drought is one of the most important factors in reducing plant yield, and understand the ways to deal with drought stress is very important. This experiment was performed to study the effect of foliar application of organic growth stimulants (Hamoon Green ®) on some physiological traits, yield, and oil content of Goldasht safflower cultivar under different levels of drought stress in the form of split plots in a randomized complete block design in the Research Farm No.1 of Zabol University located in Jazinak, Sistan Dam, in Zabol with three replications. The main factor of drought stress at 3 levels included full irrigation, irrigation up to the main stem flowering stage, and irrigation up to full flowering stage. The secondary factor was plant growth regulator at four levels including control, 8, 10, and 12 liters per hectare. Measured characteristics included plant height, number of leaves, number of heads per plant, 1000-seed weight, petal weight, stem diameter, seed protein percentage, grain yield, seed oil percentage, proline, catalase and peroxidase. The interaction of growth stimulant levels and drought stress was significant only on plant height, stem diameter, oil percentage, and proline concentration. The maximum plant height (64 cm) and percentage of oil (32.7%) were obtained from non-stress and foliar application of 12 liters of growth stimulant; the highest proline concentration was recorded under foliar application of 12 liters growth regulator the flowering stage of the main stem (0.38%); the maximum stem grain yield (1127.08 kg ha-1) was recorded with the plants sprayed with 12 liters of growth stimulant. In general, foliar application of growth stimulants moderated the negative effects of drought stress on some traits of safflower plant and improved grain yield by 36.6%. Also, irrigation up to the flowering stage of the main stem can lead to the yield similar to full irrigation.