Further Considerations in Exploring the Relationship Between Water Potential and Stomata Behaviour

Stomata behaviour directly affects terrestrial water and carbon cycles by determining plant water loss and carbon drawdown from the atmosphere. Although there have been numerous studies on stomata behaviour controlled by environmental and internal physiological processes, researchers have not reached a consensus yet.

Here I focus on the effects of plant water potential on stomata behaviour not been explicitly represented in most current dynamic vegetation models (DVMs). Such omissions could lead to possible inaccuracies and uncertainties in predicting vegetation response to drought in DVMs.

Fig. 1 Soil-plant-atmosphere continuum.

The point at full stomatal closure plays a crucial role in stomatal behaviour and helps determine plant carbon gain and water loss. Leaf guard cells directly control stomatal conductance and the loss of guard cell turgor leads to stomatal closure. It is usually assumed that the pressure–volume relation of guard cell is the same as that of leaf cell and leaf turgor loss point (TLP) occurs at full stomatal closure. Experiments have shown that leaf turgor-mediated effects (hydraulic efficiency, osmotic potential, soil water potential) are the main driving factors of stomata closure, with individual contributions varying among species (Rodriguez-Dominguez et al., 2016). However, some studies also found that TLP is a bit higher than the water potential at full stomatal closure, indicating a difference between guard and other leaf cells (Bartlett et al., 2016). Another widely studied trait, xylem water potential at 50% loss of xylem conductivity (P50), occurs after stomatal closure, which is related to xylem dysfunction and mortality rather than stomatal closure (Brodribb et al., 2003).

Fig. 2 Stomatal behaviour

Soil-leaf water potential gradient plays an irreplaceable role in water transport, affecting stomatal conductance. Large water potential gradient may lead to excessive water loss and even xylem dysfunction, which can be avoided by the regulation of stomatal behaviour. Further studies need to be carried out to understand the control of stomatal behaviour in a more comprehensive and a unified framework.


Rodriguez-Dominguez, C. M., Buckley, T. N., Egea, G., de Cires, A., Hernandez-Santana, V., Martorell, S., and Diaz-Espejo, A.: Most stomatal closure in woody species under moderate drought can be explained by stomatal responses to leaf turgor, Plant, Cell & Environment, 39, 2014-2026, 2016.

Bartlett, M. K., Klein, T., Jansen, S., Choat, B., and Sack, L.: The correlations and sequence of plant stomatal, hydraulic, and wilting responses to drought, Proceedings of the National Academy of Sciences of the United States of America, 113, 13098-13103, 2016.

Brodribb, T. J., Holbrook, N. M., Edwards, E. J., and GutiÉRrez, M. V.: Relations between stomatal closure, leaf turgor and xylem vulnerability in eight tropical dry forest trees, Plant, Cell & Environment, 26, 443-450, 2003.


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