Changes induced by multi-stage water stress on maize growth, water and nitrogen utilization and hormone signaling under different nitrogen supplies

Water availability and nitrogen (N) supply are two major issues that affect plant productivity, however, the processes of water and N utilization and their hormone regulation are not conclusive in response to varying water-N interaction. The objective of this study was to evaluate the effects of water stress (WS) at different growth stages on maize plant development, root morphology, water utilization, hormone signaling and N accumulation under various N conditions. A set of controlled drought stress at 60% field capacity was conducted from bell (V12) to tassel (VT) stage (V12-VT, denoted as W1W2), from silk (R1) to milk (R3) stage (R1-R3, denoted as W2W1) and their compound stages (V12-R3, denoted as W1W1) under high- and low-N supply, respectively. The results indicated that compared to the well-watered control (W2W2), W2W1 reduced root length, root area, and shoot dry matter by 4.68–19.15%, 5.92–11.97% and 4.38–29.61%, respectively, while W1W2 promoted the root system and improved the shoot growth, grain formation and plant water use efficiency (WUEp). High N supply tended to aggravate WS with a poorer root system and lower leaf water potential (ψleaf) but higher leaf abscisic acid (ABA) accumulation at different growth stages. Leaf ABA significantly increased while stomatal conductance (Gs) decreased under WS and N-rich environment, hence increasing leaf intrinsic water use efficiency (WUEi). Root zeatin-riboside (ZR) was higher for well-watered and N-rich conditions. Moreover, leaf ABA significantly increased with the decrease of ψleaf (R2 =0.51 for R3, R2 =0.35 for dough stage (R4)) and the variation of ψleaf was relatively constant (≤0.3 MPa) with different water treatments, indicating that maize performed isohydric behavior to response water stress and N-rich environment. This study suggests that to promote the potential of water- and N-saving and improve crop productivity in maize cultivation, mild water stress at vegetative growth stages and appropriate N supply are of great importance.