Water-deficit and high temperature affected water use efficiency and arabinoxylan concentration in spring wheat

This study was conducted in a controlled environment to evaluate the combined effects of water-deficit (imposed at the stem elongation stage) and high temperature (imposed at the booting stage) on the water use efficiency (WUE) and arabinoxylan concentration of two spring wheat varieties (‘Superb’ and ‘AC Crystal’) commonly grown in Canada. The temperature treatments were 22/12 (day/night, T1) and 32/22 °C (T2). Overall, time to maturity under high temperature was 10 days shorter for ‘Superb’ than for ‘AC Crystal’, indicating that ‘Superb’ was more sensitive to high temperature stress. Leaf relative water content (RWC) and specific leaf area (SLA) were more sensitive to drought than to high temperature for both varieties. Drought and high temperature decreased (P < 0.05) biomass, water use and grain yield but increased WUE of ’Superb’ and ‘AC Crystal’. Without temperature stress, significant drought and variety effects were found on CID (carbon isotope discrimination) which was negatively correlated with WUE. All gas exchange parameters declined under drought and high temperature. High temperature increased the grain arabinoxylan concentration (especially the water-extractable arabinoxylans). The different arabinoxylan fractions were positively correlated with WUE suggesting that arabinoxylans can be increased by selecting for increased WUE.