Physiological responses of wheat (Triticum aestivum L.) to deficit irrigation and sowing density

To evaluate the effect of sowing density (۳۰۰, ۴۰۰, ۵۰۰, ۶۰۰ and ۷۰۰ plants/m۲) on the growth of wheat under deficit irrigation (۱۰۰, ۷۵ and ۵۰% crop water requirement, I۱۰۰, I۷۵ and I۵۰, respectively), an experiment was carried out during ۲۰۰۹ and ۲۰۱۰. In both years, deficit irrigation resulted in a considerable reduction in yield, yield components, leaf area index (LAI) and leaf water potential (Ψw). In contrast, the canopy temperature (CT) significantly increased under deficit irrigation. Furthermore, increasing of sowing density from ۳۰۰ to ۶۰۰ plants/m۲ resulted in a significant increase in grain yield under I۱۰۰ and I۷۵. Maximum grain yield as ۵۲۵.۹ and ۵۶۴.۲ g/m۲ was obtained in the first and the second years, respectively in sowing density of ۶۰۰ plants/m۲ and I۱۰۰. This sowing density was also the proper density in I۷۵ and I۵۰ irrigation regimes. Increasing of sowing density reduced ۱۰۰۰-grain weight and grain number per spike and increased spike number per square meter. In the first year, increasing of sowing density from ۳۰۰ to ۶۰۰ plants/m۲ caused a significant increase in LAI in all irrigation regimes, while in the second year, maximum LAI was observed in ۷۰۰ plants/m۲ sowing density. It was found that increasing of sowing density significantly reduced the Ψw and the CT in both well-watered and deficit irrigation. In conclusion, the results suggest that ۶۰۰ plants/m۲ would be the optimal sowing density under different water conditions. Alleviation of water stress by the increasing sowing density was found to be associated partly with enhanced LAI and reduced CT.

Keywords:

Canopy temperature , Leaf area index , Leaf water potential , Yield