Günter Hoch published a new review in the annual book series Progress in Botany that summarizes the current state of knowledge about the consequences of low root temperatures for water uptake and hydraulic relations of temperate trees. Although the negative effects of low, non-freezing root temperatures on plant hydraulic functions are known since the beginnings of modern plant physiological research in the 19^th century, they have so far received surprisingly little attention in the context of a functional explanation for the cold distribution limits of plants. The cold soil induced hydraulic constraints derive mainly form the resistance to radial water transport in fine roots, which increases exponentially with decreasing temperature and severely limits root water uptake in temperature trees at around 5°C; a temperature threshold that is generally recognized as a global limit for growth in cold-adapted tree species.

In his review, Günter Hoch synthesizes the current understanding of the mechanisms behind the restricted root water uptake at low temperatures and the potential physiological reasons for the recently observed interspecific variations in cold sensitivity of root water uptake in temperate trees, with a particular focus on the role of aquaporins for the symplastic root water transport. The article further summarizes pervious experimental and observational studies on cold root induced hydraulic constraints in temperate trees, that demonstrated marked declines in tree water potential and growth at root temperatures between 10 and 0°C. The review finally proposes how incorporating these hydraulic restrictions at cold soil conditions can complement existing functional hypotheses for the cold range limits of temperate trees, and outlines future research directions aimed at improving predictions of soil temperature effects on tree productivity and distribution. 

Link to the article:

Hoch G (2026) Low root temperature-induced hydraulic constraints as a potential driver for the cold distribution limits of temperate trees. In: Progress in Botany. Springer, Berlin, Heidelberg. https://doi.org/10.1007/124_2026_97

Related current project:

COOLROOTS: Scrutinizing the effects of cool roots on water relations and growth of European temperate tree species. SNSF - project (2026 - 2030) PI: Günter Hoch, PhD: Daniël Rikkers