Oxygen isotope discrimination of wheat and its relationship with yield and stomatal conductance under irrigated conditions

Abstract

This study was carried out to determine the different irrigation regime effects on oxygen isotope discrimination of stemwater $(Delta^{18}O^s;)$ and its relationship with grain yield (GY), aboveground biomass (BM), and stomatal conductivity (gs) of winter wheat.For this purpose a field experiment was conducted between 2009 and 2011 in a semiarid region of Turkey under rainfed (RF), deficit(DI), moderate (MI), and full irrigation (FI) conditions. The highest GY and BM (4.5 t $ha^{-1}$ and 14.5 t $ha^{-1}$) were measured from theFItreatment. However, the difference between the yield of DI and FI treatments was insignificant. It might be recommended that theDI treatment be used for wheat irrigation to increase water-use efficiency for semiarid climate conditions. Average $(Delta^{18}O^s;)$ values wereobtained as 35.36‰, 34.56‰, 34.35‰, and 33.18‰ for RF, DI, MI, and FI treatments, respectively. Applied irrigation water and GYwere found to be strongly negatively related to $(Delta^{18}O^s;)$, so it may be a useful predictor of yield in irrigation programs. Effects of waterregime on yield probably reflected the correlation with the isotopic composition of transpiration. A negative relationship was obtainedbetween average $(Delta^{18}O^s;)$ and gs at a significant level for which the correlation coefficient was 0.68. However, the relationship was positivebetween GY and $g_s$..