Xylem and phloem in petioles are coordinated with leaf gas exchange in oaks with contrasting anatomical strategies depending on leaf habit

As the single link between leaves and the rest of the plant, petioles must develop conductive tissues according to the water influx and sugar outflow of the leaf lamina. A scaling relationship between leaf area and anatomical traits of xylem and phloem is expected to improve the efficiency of these tissues. However, the different constraints compromising the functionality of both tissues (e.g., risk of cavitation) must not be disregarded. Additionally, plants present two main leaf habits (deciduous and evergreen) that may have different strategies to produce and package their petiole conduits to cope with environmental restrictions. In this study, we explore, in a diverse group of 33 oak species, the relationships between petiole anatomical traits, leaf area, stomatal conductance and photosynthesis rate. Results showed allometric scaling between anatomical structure of xylem and phloem with leaf area. We also found how photosynthesis and stomatal conductance at leaf-level are correlated with anatomical traits in the petiole. Nonetheless, the main novelty is how oaks present a different strategy depending on the leaf habit. Deciduous species tend to increase their diameters to achieve a greater leaf-specific conductivity. By contrast, evergreen oaks develop larger xylem conductive areas for a given leaf area than deciduous ones. This trade-off between safety-efficiency in petioles has never been attributed to the leaf habit of the species.

Esta investigación ha sido financiada por la subvención PID2022-631 136478OB-C32 financiada por MICIU/AEI/10.13039/501100011033 y por «ERDF A way of making Europe», por la subvención CNS2022-136156 financiada por MCIN/AEI/10.13039/501100011033 y European Union Next Generation EU/PRTR y por el grupo de investigación S74_23R del Gobierno de Aragón.

Quercus

Conductive Tissues

Leaf Habit

Petioles

Water Relations

Xylem Transport

Unpublished