Mechanisms for the relationships between water-use efficiency and carbon isotope composition and specific leaf area of maize (Zea mays L.) under water stress

The quick assessment approaches for accurately measuring water-use efficiency (WUE) in maize under water stress are important to water-saving agriculture. We investigated how and whether carbon isotope composition (delta C-13) and specific leaf area (SLA) could be used to assess WUE for maize as influenced by water stress. A pot experiment was conducted twice during six typical maize (Zea mays) growth stages of seedling, jointing, booting, tasseling, filling and maturity, respectively. The ratio between the activities of ribulose 1,5-bisphosphate carboxylase (Rubisco) and phosphoenolpyruvate carboxylase decreased bundle sheath leakiness (phi) under water deficiency, caused more C-13 to be assimilated, and resulted in increased delta C-13 in leaves. Water stress increased the fractionation of C-13 when assimilates were transported from leaf to stem, indicating that water stress affected leaf expansion and translocation of assimilates from leaf to stem, and resulted in thicker leaves and lower SLA. WUE showed significant positive correlations with leaf delta C-13 and SLA, implying that leaf delta C-13 and SLA could effectively reflect the drought adaptation and high WUE under different water conditions.