Abstract
Leaf-level water use efficiency (WUEi) is often used to predict whole plant water use efficiency (WUEwp), however these measures rarely correlate. A better understanding of the underlying physiological relationship between WUEi and WUEwp would enable efficient phenotyping of this important plant trait to inform future crop breeding efforts. Although WUEi varies across leaf age and position, less is understood about the regulatory mechanisms. WUEi and WUEwp were determined in Australian (cv. Krichauff) and UK (cv. Gatsby) wheat cultivars. Leaf gas exchange was measured as leaves aged and evaluated in relation to foliar abscisic acid (ABA) and 1-aminocyclopropane-1-carboxylic acid (ACC) concentration, chlorophyll content and Rubisco activity. Carbon dioxide (CO2) assimilation (A) declined more rapidly as leaves aged in the lower WUEwp genotype Gatsby. Both ACC concentration and Rubisco activity declined as leaves aged, but neither explained the variation in A. Further, stomatal conductance (gs) and stomatal sensitivity to ABA were unchanged as leaves aged, therefore WUEi was lowest in Gatsby. Maintenance of A as the leaves aged in the Australian cultivar Krichauff enabled greater biomass production even as water loss continued similarly in both genotypes, resulting in higher WUEwp.
Highlights
Wheat contributed 20% of the world’s calories in 2003 and continues to be one of the most globally significant cereals next to corn and rice [1]
This study focused on the impact that leaf age has on A, gs, and water use efficiency (WUEi), and their relationship to
Both wheat cultivars Krichauff (KR) and Gatsby (GA) used more water in the longer GH experiment than in the controlled environment (CE) experiment, but there were no genotypic differences in water use (Figure 1a)
Summary
Wheat contributed 20% of the world’s calories in 2003 and continues to be one of the most globally significant cereals next to corn and rice [1]. Wheat yield and whole plant water use efficiency (WUEwp ) are negatively impacted by water deficit conditions [3,4,5], which are becoming more prevalent in many wheat growing regions (e.g., The North China Plain) [6,7,8]. Intensive agriculture in these regions extracts more groundwater than is replaced through drainage, causing a decline in aquifer water tables, which in turn decreases agricultural sustainability [8]. Many studies measure leaf-level water use efficiency (WUEi —carbon dioxide (CO2 ) assimilation per stomatal conductance) via infrared gas analyzers
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