This study aimed to investigate the differences in shoot and root traits, and water use and water use efficiency (WUE) in drought tolerant (DT) maize (Zea mays L.) hybrids under full and deficit irrigated conditions.  A two-year greenhouse study was conducted with four hybrids (one conventional hybrid, 33D53AM, two commercial DT hybrids, P1151AM, N75H, and an experimental hybrid, ExpHB) grown under two water regimes (I₁₀₀ and I₅₀, referring to 100 and 50% of evapotranspiration requirements).  Under water stress, the hybids P1151AM, N75, and ExpHB showed more drought tolerance and had either greater shoot dry weight or less dry weight reduction than the conventional hybrid (33D53AM).  However, these three hybrids responded to water stress using different mechanisms.  Compared with the conventional hybrid, the two commercial DT hybrids (P1151AM and N75H) had a smaller leaf area, shoot dry weight, and root system per plant.  As a result, these hybrids used less water but had a higher WUE compared with the conventional hybrid.  In contrast, the experimental hybrid (ExpHB) produced more shoot biomass by silking stage at both irrigation levels than all other hybrids, but it had relatively lower WUE.  The hybrids demonstrated different drought response mechanisms that may require different irrigation management strategies.  More investigation and validation are needed under field conditions and in different soil types.  

The photosynthetic characteristics of flag leaf and the accumulation and remobilization of pre-anthesis dry mass (DM) and nitrogen (N) in vegetable organs in nine wheat cultivars under different source-sink manipulation treatments including defoliation (DF), spike shading (SS) and half spikelets removal (SR) were investigated. Results showed that the SS treatment increased the photosynthetic rate (Pn) of flag leaf in source limited cultivar, but had no significant effect on sink limited cultivar. The SR treatment decreased the Pn of flag leaf. Grain DM accumulation was limited by source in some cultivars, in other cultivars, it was limited by sink. Grain N accumulation was mainly limited by source supply. The contribution of pre-anthesis dry mass to grain yield from high to low was stem, leaf and chaff, while the contribution of pre-anthesis N to grain N from high to low was leaf, stem and chaff. Cultivars S7221 and TA9818 can increase the contribution of remobilization of DM and N to grain at the maximum ratio under reducing source treatments, which may be the major reason for these cultivars having lower decrease in grain yield and N content under reducing source treatments.