Relationship between Carbon Isotope Discrimination, Mineral Content and Gas Exchange Parameters in Vegetative Organs of Wheat Grown under Three Different Water Regimes

Carbon isotope discrimination (Δ) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for Δ analysis, attempts have been made to identify alternative screening criteria. Ash content (ma) has been proposed as an alternative criterion for Δ in wheat and barley. A pot experiment was conducted to analyse the relationship between Δ, mineral content and gas exchange parameters in seedlings and leaves of bread wheat (Triticum aestivum L.). Plants of 10 genotypes were cultivated under three different water regimes corresponding to moderate (T3), intermediate (T2) and severe drought (T1) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. Δ and ma in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between Δ and ma in seedlings and leaves at elongation and anthesis stages in severe drought stress (T1). Δ was negatively associated with potassium (K) content in intermediate drought stress (T2) and positively with magnesium (Mg) content in T2 and T3 (moderate drought stress) in flag leaf at anthesis. There were negative correlations between Δ and single-leaf intrinsic water-use efficiency (WT) in T2 and T3 at anthesis stage. Stronger positive associations were noted between Δ and stomatal conductance (gs) in T1 and T2 than in T3 at anthesis. These results suggested that Δ is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while ma is a possible alternative criterion of Δ in wheat vegetative organs, especially in stressed environments. Significant association was found between Δ and K, Mg and Ca contents that would merit being better investigated.