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

Authors: SEMA KALE ÇELİK, SEVİNÇ MADENOĞLU, BÜLENT SÖNMEZ, KADRİ AVAĞ, UFUK TÜRKER, GÖKHAN ÇAYCI, ALİ CİHAT KÜTÜK, LEE KHENG HENG

Abstract: This study was carried out to determine the different irrigation regime effects on oxygen isotope discrimination of stem water (Δ¹⁸O_s) and its relationship with grain yield (GY), aboveground biomass (BM), and stomatal conductivity (g_s) 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 the FI treatment. However, the difference between the yield of DI and FI treatments was insignificant. It might be recommended that the DI treatment be used for wheat irrigation to increase water-use efficiency for semiarid climate conditions. Average Δ¹⁸O_s values were obtained as 35.36%₀, 34.56%₀, 34.35%₀, and 33.18%₀ for RF, DI, MI, and FI treatments, respectively. Applied irrigation water and GY were found to be strongly negatively related to Δ¹⁸O_s, so it may be a useful predictor of yield in irrigation programs. Effects of water regime on yield probably reflected the correlation with the isotopic composition of transpiration. A negative relationship was obtained between average Δ¹⁸O_s and gs at a significant level for which the correlation coefficient was 0.68. However, the relationship was positive between GY and gs.

Keywords: Stable isotopes, transpiration, semiarid conditions

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