Roderick Dewar, Teemu Hölttä and Yann Salmon have published a new paper on a simple analytically-solvable model of stomatal responses to above- and below-ground environmental factors, as well as internal sink activity. The model is based on an optimal trade-off between stomatal and non-stomatal limitations to photosynthesis, and its predictions are supported by experimental data from girdling and drought experiments. The paper is published in New Phytologist and is available here.