Axial Tracheids Widening Across Vein Orders in Ginkgo biloba Leaves and Their Relationship with Hydraulic Path Length
Key Laboratory of Biodiversity and Environment on the Qinghai-Tibetan Plateau, Ministry of Education, School of Ecology and Environment, Xizang University, Lhasa 850000, China
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Biology 2026, 15(8), 598; https://doi.org/10.3390/biology15080598
Submission received: 2 March 2026
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Revised: 27 March 2026
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Accepted: 3 April 2026
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Published: 10 April 2026
(This article belongs to the Section Ecology)
Simple Summary
Many plants possess a specialized structure-the xylem conduit-in their leaves that facilitates efficient water transport from the leaf base to the tip. However, our understanding of how this structure functions in plants with unusual leaf vein patterns remains limited. To fill this knowledge gap, we focused on Ginkgo (Ginkgo biloba), an ancient relict plant species, to investigate how water-conducting structures vary from the leaf base to the tip. We collected and measured 108 ginkgo leaves from three distinct sites. Our observations revealed that the water-conducting tracheids are wider near the leaf base and narrower in higher-order veins, and tracheid diameter scales positively with hydraulic path length. Specifically, as the vein order increases, tracheids become progressively narrower from the main vein at the leaf base to the tiny veins at the leaf edge. Our findings improve our understanding of the structural adaptations that ensure efficient water transport in leaves, providing new insights into this fundamental physiological process in plants.
Abstract
Leaves of vascular plants exhibit a tip-to-base xylem conduit widening pattern, which minimizes hydraulic resistance as leaves expand. The extent to which different leaf vein orders conform to this pattern remains largely unexplored, particularly in species with dichotomously branching veins. In this study, we focused on Ginkgo biloba, a model species with dichotomous venation, to explore tracheid variation across leaf vein orders and its linkage with hydraulic path length. Across 108 leaves from three sites, tracheid hydraulic diameter (D) scaled significantly with hydraulic path length (L) at an overall scaling slope of 0.33 (95% CI: 0.31–0.34, r2 = 0.53, p < 0.001). Scaling exponents differed significantly among sites and vein orders, and D decreased progressively with increasing vein order. This study provides a potentially valuable approach for investigating the effects of hydraulic path length on xylem conduit diameter and offers a framework for subsequent research on plant venation and hydraulic transport networks.
