Effects of Priming by Salicylic Acid on Yield and Growth Indices of Safflower (Carthamus tinctorus L.) Plants Under end Season Drought Stress

Salicylic acid is a plant hormone which had enhancing effects on growth and yield of plants under different environmental conditions. It is proposed, salicylic acid could be used as growth regulator for improving plant growth under water stress conditions. The effects of salicylic acid on yield and growth indices on safflower plants was investigated in a split, split plot in complete randomized block design. Water stress in two levels, normal irrigation and cut off irrigation after flowering, as main plot, safflower genotypes in four levels, including Isfehan Local, Gilla, Lesaf and Dincer, as sub plots and priming in five levels, including 0, 700, 1400, 2100 and 2800 µM salicylic acid as sub, sub plot were studied. Results showed that plants in normal conditions had highest leaf area index (LAI), leaf area duration (LAD), net assimilation rate (NAR), seed yield and seed and oil harvest index compared to plants in stress conditions. Water stress leads to rapid decrease in leaf area and decrease of greenness period. Among the genotypes, Dincer and follow it, Lesaf in both irrigated and stress conditions had highest LAI, specific leaf weight, LAD, NAR, seed yield and seed and oil harvest index. Also, Dicer had lowest leaf area ratio (LAR). By contrast, Gilla had highest LAR and lowest seed yield. In irrigated plots, plants which primed with 2800 µM salicylic acid had highest seed yield and growth indices. On the other hand, under stress condition treated plants with 1400 µM salicylic acid had better performance. It is possible in higher priming levels, plants had more leaf area and because of higher transpiration and rapid loss of storage soil water, they had not enough moisture in grain filling period. Therefore, treatments with lower leaf area had better performance.