Allometric co‐variation of xylem and stomata across diverse woody seedlings

• Published in: Plant, cell and environment cell and environment, 2020-09, Vol.43 (9), p.2301-2310
• Main Authors: Zhong, Mengying, Cerabolini, Bruno E. L., Castro‐Díez, Pilar, Puyravaud, Jean‐Philippe, Cornelissen, Johannes H. C.
• Format: Article
• Language: English
• Subjects: Blood vessels; Growth rate; individual stomatal area; individual vessel area; Leaves; Liquid phases; minor vessel number; Original; Planting density; Plants; Scaling; Seedlings; Stomata; stomatal number; total stomatal area; Vapor phases; Variation; Water exchange; Water transport; Xylem; xylem cross‐sectional area
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13826

Leaf stomatal density is known to co‐vary with leaf vein density. However, the functional underpinning of this relation, and how it scales to whole‐plant water transport anatomy, is still unresolved. We hypothesized that the balance of water exchange between the vapour phase (in stomata) and liquid phase (in vessels) depends on the consistent scaling between the summed stomatal areas and xylem cross‐sectional areas, both at the whole‐plant and single‐leaf level. This predicted size co‐variation should be driven by the co‐variation of numbers of stomata and terminal vessels. We examined the relationships of stomatal traits and xylem anatomical traits from the entire plant to individual leaves across seedlings of 53 European woody angiosperm species. There was strong and convergent scaling between total stomatal area and stem xylem area per plant and between leaf total stomatal area and midvein xylem area per leaf across all the species, irrespective of variation in leaf habit, growth‐form or relative growth rate. Moreover, strong scaling was found between stomatal number and terminal vessel number, whereas not in their respective average areas. Our findings have broad implications for integrating xylem architecture and stomatal distribution and deepen our understanding of the design rules of plants' water transport network. We addressed the hypothesis that the balance of water exchange between the liquid and vapour phase should depend on the convergent scaling between the summed stomatal areas and summed xylem cross‐sectional areas, both at the whole‐plant and single‐leaf level, across diverse woody seedlings of different ecological groups. The attempt has broad implications for integrating xylem architecture and stomatal distribution and for our understanding of whole‐plant water management, also in relation to the West–Brown–Enquist model and the pipe model of vascular hydraulic architecture.