Wheat acclimate to water deficit by modifying carbohydrates metabolism, water use efficiency, and growth

Abstract

Water deficit is an important yield-decreasing factor in winter wheat (Triticum aestivum L.). Normally, it has been hypothesized that plants under water deficit suffer from carbon (C) shortage and their growth is thus limited. In this study, the changes in plant growth and carbohydrate metabolism during wheat adaptation to water deficit were investigated. The results showed that water deficit induced a decrease in stomatal conductance and transpiration as early avoidance responses to water deficit. Mild deficit stimulated lateral root development, thus facilitating water uptake. While leaf relative expansion rate was decreased more than photosynthesis, water deficit leads to a more positive C balance. Carbohydrate metabolites measured (starch and sugars) showed a diurnal turnover that often increased under mild water deficit suggesting that these metabolites were readily available for being metabolized in source organ or exported to roots. The relative growth rate in mild deficit plants was higher than that in well-watered treatment, although leaf growth was decreased. Water deficit induced a shift of metabolism enzymes activities that was indicative of increased, rather than decreased, C availability. These results showed that wheat seedlings exhibited fast acclimation to changes in environmental conditions which results in an increased availability of C for the roots, and increased turnover of C metabolites. Mild water deficit increased water use efficiency through increasing dry matter production and saving water use.