Plant water use theory should incorporate hypotheses about extreme environments, population ecology, and community ecology

Plant water use theory has largely been developed within a plant-performance paradigm that conceptualizes water use in terms of value for carbon gain and that sits within a neoclassical economic framework. This theory works very well in many contexts but does not consider other values of water to plants that could impact their fitness. Here, we survey a range of alternative hypotheses for drivers of water use and stomatal regulation. These hypotheses are organized around relevance to extreme environments, population ecology, and community ecology. Most of these hypotheses are not yet empirically tested and some are controversial (e.g. requiring more agency and behavior than is commonly believed possible for plants). Some hypotheses, especially those focused around using water to avoid thermal stress, using water to promote reproduction instead of growth, and using water to hoard it, may be useful to incorporate into theory or to implement in Earth System Models.

Automated summary

Plant water use theory has been developed within a plant-performance paradigm, which focuses on carbon gain and is based on neoclassical economic framework. However, this theory overlooks other values of water to plants, which could affect their fitness. In this survey, alternative hypotheses for drivers of water use and stomatal regulation are discussed, including their relevance to extreme environments, population ecology, and community ecology. While many of these hypotheses remain untested, some may have practical applications, such as incorporating them into theory or implementing them in Earth System Models.