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 (Delta) has been proposed as an indirect selection criterion for transpiration efficiency and grain yield in wheat. However, because of high cost for Delta analysis, attempts have been made to identify alternative screening criteria. Ash content (m(a)) has been proposed as an alternative criterion for Delta in wheat and barley. A pot experiment was conducted to analyse the relationship between Delta, 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 (T-3), intermediate (T-2) and severe drought (T-1) stress obtained by maintaining soil humidity at 75 %, 55 % and 45 % of the humidity at field capacity respectively. Delta and m(a) in seedlings and leaves showed significant differences among the three water treatments. Significant positive correlations were found between Delta and m(a) in seedlings and leaves at elongation and anthesis stages in severe drought stress (T-1). Delta was negatively associated with potassium (K) content in intermediate drought stress (T-2) and positively with magnesium (Mg) content in T-2 and T-3 (moderate drought stress) in flag leaf at anthesis. There were negative correlations between Delta and single-leaf intrinsic water-use efficiency (W-T) in T-2 and T-3 at anthesis stage. Stronger positive associations were noted between Delta and stomatal conductance (g(s)) in T-1 and T-2 than in T-3 at anthesis. These results suggested that Delta is a good trait as an indirect selection criterion for genotypic improvement in transpiration efficiency, while m(a) is a possible alternative criterion of Delta in wheat vegetative organs, especially in stressed environments. Significant association was found between Delta and K, Mg and Ca contents that would merit being better investigated.