The Association of Biomass Allocation With Growth and Water Use Efficiency of Two Triticum aestivum Cultivars

We investigated traits that might improve performance of wheat (Triticum aestivum L.) in a dry environment, and examined if the response to drought is different for cultivars with a contrasting biomass allocation pattern, using two cultivars with either a high (Katya) or small (Mexipak) proportion of biomass allocated to the leaves. Plants were grown in pots placed in the field, under well-watered conditions and under intermittent drought. Katya allocated a greater proportion of its biomass to both leaves and roots, and a smaller proportion to stems than Mexipak did. The growth rate of Katya was not higher despite a higher investment in leaf area and a slightly higher rate of photosynthesis, possibly due to concomitantly higher respiratory losses. Under well-watered conditions, the efficiency of water use for growth was higher for Katya than for Mexipak, due to a lower water use at a similar growth rate. Differences in water use per plant were determined by the rate of water loss or uptake, rather than by the amount of roots or leaves. A high water use efficiency was independent of growth rate. We conclude that a lower rate of water use due to a lower transpiration per unit leaf area linked with a high leaf area can contribute to improve the performance of wheat cultivars in a water-limited environment.