Grain and Oil Yields of Safflower (Carthamus Tinctorius L.) Affected By Water Deficit and Growth Regulators

Abstract

Abstract In order to evaluate the effects of growth regulators on yield parameters and oil content of safflower (Carthamus tinctorius L.), a field experiment was conducted under different irrigation intervals in 2019. All plots were irrigated regularly until the seedling establishment and thereafter irrigation intervals were applied after 70, 100, 130, and 160 mm evaporation from class A pan, as normal irrigation and mild, moderate, and severe water deficits, respectively. Foliar sprays of water (control), putrescine (60 µg/L), and 24-epibrassinolide (25 µg/L) at a rate of 1,000 L/ha were applied slightly before flowering. The results revealed that means of plant biomass, grains per capitol, grains per plant, grain yield, harvest index, oil percentage, and yield were decreased under limited irrigations, but 1,000-seeds weight was only reduced under severe water deficit. However, fo-liar sprays of growth regulators, particularly putrescine, increased grains per plant, grain yield, and harvest index, leading to an improvement in oil yield per unit area under different levels of water supply. These results suggest that foliar application of putrescine is a superior treatment for improving the productivity of safflower plants under normal and stressful conditions.