Agriculture & Forestry, Vol. 64 Issue 1: 145-157, 2018, Podgorica 145 DOI: 10.17707/AgricultForest.64.1.17 Mehdi ABDOLAHI, Farid SHEKARI*, Jalal SABA and Esmaeil ZANGANI 1 SEED PRIMING WITH SALICYLIC ACID ENHANCED GAS EXCHANGES PARAMETERS AND BIOLOGICAL YIELD OF WHEAT UNDER LATE SOWING DATE SUMMARY This experiment was done to evaluate the effect of two planting dates and salicylic acid (SA) on wheat photosynthesis. Wheat seeds, cv. Alvand, primed with SA (0, 400, 800, 1200, 1600, 2000 and 2400 μM) at two planting dates (recommended planting date, 23 October, and late planting date, 22 November). Gas exchange parameters were measured in three growth stages (tillering, heading and grain filling). The highest and lowest rate of photosynthesis (P N ), stomatal conductance (g s ) and transpiration rate (E) of plants were observed in heading and grain filling stages, respectively. Seed pretreatment with SA enhanced photosynthetic parameters and carboxylation efficiency (CE), but, intercellular CO 2 concentration and water use efficiency (WUE) reduced by application of SA. It seems that application of SA had more effects on g s and E than P N . Among growth stages, the highest value of WUE was found in tillering and lowest in heading stage. Priming with SA compensated late sowing effects on plants P N . Chlorophyll content, chlorophyll a/b ratio and CCI values significantly increased in SA treated plants. Results show that priming with SA may reduce ameliorative effects of late sowing on wheat plant biomass production. Among SA concentrations, 1200 μM had highest value in both planting dates. Keywords: Carboxylation efficiency, Chlorophyll content, Photosynthesis rate, Water use efficiency. INTRODUCTION Photosynthesis and related gas exchange parameters influenced by many internal and external factors. For example, it is reported leaf ontogeny, heterophylly and position (Hejnak et al., 2014), age (Wang et al., 2014), seasonal changes and conditions (Ribeiro et al., 2009), sink effect (Nebauer et al., 2011) have considerable effects on photosynthesis rate and its regulation. Level of leaf development and/or morphological and anatomical stage of plant may influence photosynthesis rate (Hejnak et al., 2014). Also, environmental history of leaves affect their photosynthetic development (Fitter and Hey, 2012). 1 Mehdi Abdolahi, Farid Shekari*(corresponding author: shekari@znu.ac.ir), Jalal Saba and Esmaeil Zangani, Department of Agronomy, Faculty of Agriculture, University of Zanjan, IRAN Notes: The authors declare that they have no conflicts of interest. Authorship Form signed online.