Abstract
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.
Highlights
Water resources are scarce in arid-semiarid regions of China, which is the main limiting factor of ecological system in this area, and the key factor to control ecosystem structure (Zou et al, 2016)
A plant adapts to prolonged drought stress via changes in the root system morphological conformation, photosynthetic product allocation to aboveground, and underground portions, and more efficient utilization of the limited soil water
Such “source-sink” relationships vary with species, with CO2 concentration, as well as with drought stress intensity and duration (Fernández et al, 2002; Xu et al, 2005); for example, when the root system grows to reach a water source, the root and shoot compete for carbohydrates and most assimilation products are allocated to the root system, resulting in a higher root-to-shoot ratio (Xu et al, 2003; Wei et al, 2005)
Summary
Water resources are scarce in arid-semiarid regions of China, which is the main limiting factor of ecological system in this area, and the key factor to control ecosystem structure (Zou et al, 2016). Plant Responses to Drought Stress factors of local plant growth and vegetation restoration (Xu et al, 1997; Wei et al, 2004). Several studies indicate that plant root systems play an important role in plant adaptation to a drought stress habitat (Toorchi et al, 2002; Pu et al, 2010; Zhang et al, 2012).
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