Association Between Some Physiological Characteristics and Yield in Spring Safflower under two Irrigation Regimes

In order to study the interrelations of photosynthetic rate and surfaces and leaf proline content with yield and yield components of safflower under different irrigation regimes, a field experiment in a split plot arrangement under a ranomized complete block design with four replication was performed at Lavark Reasrch Farm, Isfahan University of Technology, Isfahan, Iran in 2007. Two Irrigation levels, including irrigating after 80 mm (control) and 140 mm (water deficit) evaporation from a Standard Class A Pan were served as the main plots. Six safflower genotypes including Arak 2811, Kuseh, Nebraska-10, C111, S149 and K12 were considered as the subplots. Gas exchange rate at heading and flowering, leaf area index (LAI) and leaf proline content at %50 flowering, head/plant, seed/head, 1000 seed weight, grain and biological yield, oil content and oil yield were measured. Net photosynthetic rate differed among irrigation levels and genotypes. At both heading and flowering stages water deficit decreased mean net photosynthetic rate by more than 50% and the smallest mean was observed in genotype S149. Moisture deficit increased leaf proline content by %83, averaged over genotypes and the greatest mean was observed in genotype Kouseh. A 27% decrease in LAI and decreases in seed/head, head/plant and seed weight under water deficit irrigation led to over 27% decreases in grain yield, compared to the control irrigation level. Oil yield and biological yield per plant were decreased by irrigation level. The smallest means for LAI, grain yield, biological yield and oil content were observed in Nebraska-10, C111, Kouseh and S149, respectively. It could be concluded that with genotypes used in this experiment and the environmental conditions in 2007 in Isfahan, water deficit negatively affected both photosynthetic rate and LAI in safflower, resulting in significant decreases in grain and biological yield. An increased level of leaf proline content under water deficit did not prove to enhance the resistance of this oil seed crop to the later environmental constrain.