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Water shortage in the arid-semiarid regions of China seriously hampers ecosystem construction. Therefore, elucidation of the mechanisms by which vegetation in that area responds to drought stress may enable us to improve utilization of limited water resources and thus contend with the problem of drought and water shortage. We studied Bothriochloa ischaemum, a native grass species, conducted potting control tests to compare several indicators of B. ischaemum grown under three different moisture conditions (80%, 60%, 40% Field capacity represent sufficient water supply, mild water stress, and serious water stress, respectively). Plant response parameters measured included biomass accumulation, root morphology, transient water use efficiency (WUE), stable carbon isotope ratio (δ13C), and stable carbon isotope discrimination (Δ13C) of various plant organs and their interrelationships. B. ischaemum had the greatest WUE under mild drought stress. However, serious drought stress resulted in considerable decline in overall biomass but substantial increase in root-to-shoot ratio and fine-root biomass. Coarse-root biomass dropped appreciably, indicating that serious drought stress leads to allocation non-uniformity of the carbon “sink.” δ13C and Δ13C of stem correlated considerably with root morphology, suggesting the feasibility of characterizing WUE, biomass, and root morphology of B. ischaemum via the stable carbon isotope approach. Our evaluation of 21 drought resistance indicators of B. ischaemum showed that under a given moisture treatment gradient one can isolate an optimal indicator to express growth, morphology, and physiology, to improve the accuracy of depicting plant drought resistance and simplify the drought resistance indicator system. This study elucidates the response mechanism of B. ischaemum to drought stress and provides theoretical support to screening of drought-resistant plants across the arid-semiarid regions of China.

As an important pathway for movement of rainfall or sprinkler irrigation water through a crop canopy to the ground, stemflow is of great significance for utilization efficiency of sprinkler irrigation water and for crop growth. In this study, under simulated indoor artificial rainfall, the stemflow rates (SF) of corn plants (Zea mays) in different corn growth stages (V4 stage $ VT stage) under different rainfall intensities (I) were observed, and the relationships among stemflow, leaf area (LA), and I were analyzed. Based on these results, stemflow models were developed. The results showed that for all corn growth stages, the average SF of a single corn plant was about 55.69 mL/ min, accounting for 45% of total rainfall. SF increased as a power function of corn LA and I, and the percentage of stemflow in total rainfall increased as a power function of corn LA. Theoretical, semi-empirical, and empirical models of corn SF and stemflow proportion (SR) of total rainfall were established by analyzing the relationships among LA, I, and stemflow. All three models were used to estimate SF and SR in different corn growth stages and achieved desired accuracy. The semi-empirical and empirical models were more accurate in predicting and simulating corn SF, but the calculation and application of the semi-empirical model was relatively simpler. The empirical model of SR enabled a more accurate calculation of the percentage of stemflow in total rainfall.