Effects of Priming with Salicylic Acid on Safflower Seedlings Photosynthesis and Related Physiological Parameters

Generally, primed seeds produce larger and heavier plants than non-primed seeds. This may be simply due to rapid emergence and extension of leaf growth, or the influence of other physiological processes. The effect of seed pretreatment with salicylic acid (SA) on some physiological and photosynthetic characteristics of the safflower seedlings, cv. Goldasht, was examined under field condition. The treatments were different levels of SA (including zero or hydropriming, 400, 800, 1200, 1600, 2000 and 2400 µM and a treatment of the non-primed seeds as the control). Priming enhanced photosynthesis rate (PN) chlorophyll content index (CCI), relative water content (RWC) and seedling dry weight. Also, primed seeds had higher stomatal conductance (gs) and transpiration rate (E) than the control and the hydroprimed treatments. The lowest intercellular CO2 (Ci) and highest cell membrane stability was obtained in 2400 µM SA. But values of the control treatment were opposite. In addition, highest carboxylation efficiency (CE) and photosynthetic water use efficiency (WUEb) were found in 2000 and 2400 µM of SA. It seems seed priming with SA, increased gs and hence PN by improving RWC status. This was associated with enhanced WUE and CE at higher levels of SA. A positive relationship was found between WUEb and PN, CE and RWC but negative relationship with Ci. It seems that increase in plants dry weight by priming not only was the result of rapid growth rate, but also the enhancement of PN, RWC and chlorophyll content.