Effect of Water Deficit, Ultraviolet Radiation and Carbon Dioxide Enrichment on Quantitative Traits of Durum Wheat (Triticum turgidum L. var. Durum Desf.)

Physiological study of wheat varieties under abiotic stress conditions is a very important factor for improving their future productions. This research work was conducted in the Research Greenhouse of Faculty of Agriculture, Tarbiat Modarres University in 2006, to study leaf quantitative traits of durum wheat under different levels of carbon dioxide (400 and 900 ppm), ultraviolet radiation (UV A, B and C) and water deficit (up to 60% of field capacity). The experiment was factorially performed in a complete block design arrangement of three replications. In total, decreases were observed in: grain yield (157.27-38.05 g/m2), plant height (60.69-50.69 cm), leaf relative water content (68.00-54.90%), chlorophyll content (50.53-17.62%) and maximum quantum efficiency in photosystem II (from 0.565 to zero), in durum wheat under water deficit and when ultraviolet radiation intensity increased from A to C level. In this situation, proline increased from 3.28 to 24.46 (µg g-1 FW). Proline and grain yield variations were different as affected by carbon dioxide. At UVA, B and C radiations and no water deficit condition, durum wheat grain yield decreased (from 157.27 to 89.48 g/m2) with CO2 enrichment, while proline being increased from 3.28 to 12.45 (µg g-1 FW). Under water deficit accompanied by CO2 enrichment, durum grain yield increased, while proline being decreased. Carbon dioxide enrichment in the absence of water deficit increased vegetative growth while decreasing reproductive growth. This was while at stress conditions, grain yield increased due to an improvement in leaf relative water content along with reduction in stomatal conductance. The above results indicate that the three main environmental stresses which reduce leaf chlorophyll content, specific leaf area and plant protection (due to negative effects of these stresses) decrease yield and yield components in this variety of wheat.