A 50-year look-back on the efficacy of limited transpiration traits: does the evidence support the recent surge in interest?

Authors: Gleason, Sean; Polutchko, Stephanie; Allen, Brendan; OCHELTREE, TROY - Colorado State University; SPITZER, DANIEL - Colorado State University; LI, ZIQIANG - Colorado State University; STEWART, JARED - Collaborator

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2025
Publication Date: 4/23/2025
Citation: Gleason, S.M., Polutchko, S.K., Allen, B.S., Ocheltree, T.W., Spitzer, D., Li, Z., Stewart, J.J. 2025. A 50-year look-back on the efficacy of limited transpiration traits: does the evidence support the recent surge in interest?. New Phytologist. 246(4):1439-1450. https://doi.org/10.1111/nph.70071.
DOI: https://doi.org/10.1111/nph.70071

Interpretive Summary: We critically examine what is currently thought to be an important trait in crop species – limited transpiration (LT). The LT trait is thought to reduce water use early during the growth season, with this “saved” water being kept in soil without meaningful loss, until it is needed during flowering and grain production later in the season. While this seems like a good idea, we suggest that it has not yet been experimentally demonstrated in a convincing way. Our main concerns focus on two claims: first, the claim that early-season water use, which facilitates access to soil water by allowing additional root growth, is less important than saving water; and second, the claim that saved water will still be available in the soil for use weeks and months. We argue that using water and carbon early during a plant’s development is crucial for plant growth and that forgoing this water use will likely be detrimental to crops growing in most soils and climates. We suggest re-evaluating LT traits carefully, considering both water and carbon use throughout the plant's life. We advise against using LT traits unless they've been thoroughly tested in the specific soils and climates where they will be used. Instead, we propose focusing on improving how plants use water and invest carbon strategically for better overall growth.

Technical Abstract: We critically examine limited transpiration (LT) traits in crop species, which are claimed to conserve early season water for critical late season growth. Despite the theoretical appeal, we argue that empirical evidence supporting LT efficacy is insufficient to support the general acceptance of this theory. Our primary criticisms focus on two main claims: the undervaluation of early-season carbon assimilation and investment over the lifetime of the crop, and the overestimation of soil water savings efficiency. We argue that forgoing early season water use, and therefore also future investment of early season carbon in roots, leaves, and stems (improved resource acquisition), will negatively impact plant performance in most soil and climate contexts. Furthermore, we challenge the assumption that conserved soil water remains available for later use without loss, noting significant losses resulting from evaporation and other non-crop factors. We advocate for a rigorous re-evaluation of LT traits, incorporating a balance of water and carbon dynamics throughout the crop’s lifetime. We strongly caution against the adoption of LT traits where they have not been empirically evaluated in the soils and climates of interest to individual growers/breeders. We propose a more physiologically integrated approach to crop improvement, focusing on water extraction efficiency and strategic carbon investment.