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

Abstract

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.

Allometric relationships between leaf and petiole traits across 31 floating-leaved plants reveal a different adaptation pattern from terrestrial plants

“…Species names were verified according to www.theplantlist.org , https://powo.science.kew.org/ and www.iwgs.org . In 2020, at least ten healthy similar-sized mature floating leaves with petioles of similar size were collected for 26 species to determine leaf stomatal and petiole vascular traits following Zhong et al (2020) . In 2021, an additional five floating-leaved plants were collected and measured.…”

“…construction of stem vs. leaf) during the process of water transport, which has shaped the evolution of plant function across vascular plants ( Enquist, 2002 , 2003 ; Coomes et al , 2008 ; Carins et al , 2014 ; Wen et al , 2020 ). For example, Zhong et al (2020) found that the balance of water exchange between liquid and gas phases depended on the consistent scaling between leaf total stomatal area and stem xylem area in seedlings of woody terrestrial species. Allometric relationships between photosynthetic, autotrophic tissues (e.g.…”

“…xylem) in plants are the result of natural selection on the optimization of carbon costs and nutrient allocation in plants ( West et al , 1999 ; Enquist, 2002 ). In addition, the hyperallometric scaling (slope significantly greater than 1; see Shingleton et al , 2009 ) between stomatal and xylem traits showed that stomata scale to xylem exponentially, and a proportionally larger increase in leaf stomata area is expected for the increase in xylem area per unit ( Zhong et al , 2019 , 2020 ).…”

Hydraulic‐stomatal coordination in tree seedlings: tight correlation across environments and ontogeny in Acer pseudoplatanus

“…However, understanding of hydraulic‐stomatal coordination in seedlings has been fragmentary, especially for only few months old plants. Seedlings of different species 3 wk after the opening of the first leaf show remarkable co‐variation in xylem and stomatal anatomical traits (Zhong et al ., 2020). Accordingly, also a strong coordination in physiological parameters might be expected.…”

Stomatal Arrangement Pattern: A New Direction to Explore Plant Adaptation and Evolution

“…Therefore, stomata are separated by various shapes, sizes, and numbers of intervening cells (including epidermal cells and subsidiary cells) in a particular arrangement on the leaf surface (Carpenter, 2005). Stomata are developmentally coordinated with mesophyll (Baillie and Fleming, 2020) and xylem (Brodribb et al, 2017;Zhong et al, 2020), and various plants break this "rule" and produce stomata arranged in clusters, which reduce water loss from plant leaves due to neighboring stomata interfere with each other (Franks and Casson, 2014;Lehmann and Or, 2015). In comparisons of high and low clustering genotypes that have similar stomatal density and size, operational stomatal conductance was consistently lower in lines with highly clustered stomata, and stomatal clustering was shown to significantly reduce carbon assimilation (Dow et al, 2014; Supplementary Figure 1).…”