Effects of Zn and K foliar application on physiological traits and yield of spring safflower under drought stress

In order to study the effects of foliar application of Zn and K on yield and some physiological traits of spring safflower (Carthamus tinctorius L.), cv. Esfahan 14, under drought stress, a pot experiment was conducted in research greenhouse of Yasouj University. Experiment was a factorial based on completely randomized design with three replications. Factors consisted of drought stress (S1- without stress, S2- stress at vegetative stage, S3- stress at reproductive stage and S4- stress at seed filling stage) and foliar application of nutrients (F1- without foliar application, F2- foliar application of water, F3- foliar application of zinc sulfate and F4- foliar application of potassium sulfate). Results showed that in drought stress at vegetative phase, foliar application of potassium has maximum chlorophyll a (25.7%), proline (87.8%) and total soluble sugars (26.9%) compared to without foliar application. Foliar application, compared to without foliar application, increased chlorophyll a (26%), chlorophyll a+b (32%), proline (51%) and total soluble sugars (26.9%) at S3 stress. However, in stress at seed filling stage, total soluble sugars increased (41.4%) by foliar application only. Grain yield increased by foliar application of zinc and potassium at all stress treatments except the reproductive stage stress. Finally, foliar application of zinc and potassium increased the concentration of osmolytes, such as total soluble sugars and proline and led to improved osmotic adjustment and plant tolerant to drought stress.