How Wheat Outsmarts Drought

Scientists Harrison Day and Brodribb have been examining the behaviour of wheat plants (Triticum aestivum L. ‘Krichauff’) under extreme drought conditions, investigating how the plant’s “hydraulic system” responds to lack of water. Their research, published in Annals of Botany, is important because it deepens our understanding of how such plants survive in adverse conditions. This could have major implications for global food security, especially in regions where water scarcity is a pressing issue.

The researchers discovered that under extreme water stress, wheat plants prioritize delivering water from the roots to the reproductive tissues over other parts of the plant, such as leaves. This drought-resistance strategy enables the plants to continue reproducing even when water is scarce. This ability means that wheat, and possibly other annual grasses, have evolved systems to maintain their life cycles even in extreme drought conditions.

The problem the wheat is trying to overcome is ‘xylem cavitation,’ a process where the water-conducting tubes, called xylem, within a plant become blocked with air bubbles during periods of drought. These blockages can cause the plant to wilt and even die. However, in the case of wheat, even under extreme water stress, specific parts of the plant’s xylem system, particularly those supplying the reproductive tissues, continue to function, ensuring the plant’s reproductive success.

Harrison Day and Brodribb used a series of rehydration experiments following severe dehydration to confirm this theory. In their article, they write:

The xylem in the roots and peduncles of wheat plants showed greater resistance to water stress-induced cavitation than the leaves, supporting our hypothesis that water supply to reproductive tissues would be maintained during extreme drought thus maximizing the chance of reproductive success. The functional implications of building greater cavitation resistance in tissues supplying the seeds compared with leaves were demonstrated during rehydration. Xylem supplying the wheat spike maintained sufficient capacity to rehydrate the reproductive tissue after a drought stress strong enough to completely cavitate and kill the flag leaf.

Harrison Day & Brodribb 2023.

READ THE ARTICLE
Harrison Day, B.L. and Brodribb, T.J. (2023) “Resistant xylem from roots to peduncles sustains reproductive water supply after drought-induced cavitation of wheat leaves,” Annals of Botany, 131(5), pp. 839–850. Available at: https://doi.org/10.1093/aob/mcad048.