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Summary There is a long‐standing idea that the timing of leaf production in seasonally cold climates is linked to xylem anatomy, specifically vessel diameter because of the hydraulic requirements of expanding leaves.We tested for a relationship between the timing of leaf out and vessel diameter in 220 plants in three common gardens accounting for species’ phylogenetic relationships. We investigated how vessel diameter related to wood porosity, plant height and leaf length. We also used dye perfusion tests to determine whether plants relied on xylem produced during the previous growing season at the time of leaf out.In all three gardens, there was later leaf out in species with wider vessels. Ring‐porous species had the widest vessels, exhibited latest leaf out and relied less on xylem made during the previous growing season than diffuse‐porous species. Wood anatomy and leaf phenology did not exhibit a phylogenetic signal.The timing of leaf out is correlated with wood anatomy across species regardless of species’ geographic origin and phylogenetic relationships. This correlation could be a result of developmental and physiological links between leaves and wood or tied to a larger safety efficiency trade‐off.
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Negative allometry of leaf xylem conduit diameter and double‐wall thickness: implications for implosion safety
Summary Xylem conduits have lignified walls to resist crushing pressures. The thicker the double‐wall (T) relative to its diameter (D), the greater the implosion safety. Having safer conduits may incur higher costs and reduced flow, while having less resistant xylem may lead to catastrophic collapse under drought. Although recent studies have shown that conduit implosion commonly occurs in leaves, little is known about how leaf xylem scalesTvsDto trade off safety, flow efficiency, mechanical support, and cost.We measuredTandDin > 7000 conduits of 122 species to investigate howTvsDscaling varies across clades, habitats, growth forms, leaf, and vein sizes.As conduits become wider, their double‐cell walls become proportionally thinner, resulting in a negative allometry betweenTandD. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e. higherT/Dratios) was found in asterids, arid habitats, shrubs, small leaves, and minor veins.Despite the strong allometry, implosion safety does not clearly trade off with other measured leaf functions, suggesting that implosion safety at whole‐leaf level cannot be easily predicted solely by individual conduits' anatomy.
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- Award ID(s):
- 2025282
- PAR ID:
- 10610833
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 242
- Issue:
- 6
- ISSN:
- 0028-646X
- Format(s):
- Medium: X Size: p. 2464-2478
- Size(s):
- p. 2464-2478
- Sponsoring Org:
- National Science Foundation
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