Safflower is well adapted plant for oil production or for medicinal purpose. This crop plant is originated from Iran and is tolerant against water deficit stress. However, in semi-arid Mediterranean climate terminal drought and heat stress adversely affect the safflower production. In order to investigate the influence of foliar application of proline (Pr: 10 and 20 mM) and glycinebetaine (GB: 2 and 4 mM) under well and deficit irrigation (37.23° N, 46.16° E). Foliar spray of compatible organic solutes started from middle vegetative growth and continued till seed filling stage. Comparison of well irrigated and stress conditions revealed that severity of water deficit stress (SI) was 0.25. Evaluation of growth-related morphological characteristics such as plant height, leaf area, canopy spread and percent ground cover showed that they considerably reduced by water deficit stress. However, foliar application of compatible solutes could somewhat increase growth related parameters. Results showed that water deficit stress noticeably reduced the chlorophyll content, while foliar spray could alleviate the water deficit stress effects when compared with intact plant (non-sprayed plants). The beneficial effect of GB was more prominent than Pr, especially under deficit irrigation condition. Principal component analysis (PCA) indicated that the best performance under well irrigated condition was obtained by application of 4 Mm GB while under deficit irrigation condition the best performance was recorded for plants treated with 2 and 4 Mm GB and 20 mM Pr. Overall, results of current experiments showed that foliar spray with high concentration of GB may can significantly alleviate the adverse effects of water deficit stress.
