Negative allometry of leaf xylem conduit diameter and double-wall thickness: implications for implosion safety

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 scales T versus D to trade off safety, flow efficiency, mechanical support, and cost.
We measured T and D in > 7,000 conduits of 122 species to investigate how T versus D scaling 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 between T and D. That is, narrower conduits, which are usually subjected to more negative pressures, are proportionally safer than wider ones. Higher implosion safety (i.e higher T/D ratios) was found in ast..., Study species
We sampled 122 species from the University of California Botanical Garden at Berkeley (‘UCBG’, 37.87, -122.23; Berkeley, CA, USA). Species selection maximized phylogenetic coverage, and included species with different growth forms, leaf sizes, and habitats. Because this garden collection often has a single or just a few individuals per species, our sampling approach was limited to a few branches (> 1 m long) collected from a single individual (woody species), or to a few leaves collected from 1-5 individuals (herbaceous species). Samples were collected in the morning, re-cut under water, re-hydrated overnight, and then used for the measurement of leaf anatomical and functional traits. As most of those traits are destructive, we used different leaves for each trait. 
  Anatomical measurements
Fresh and mature leaves (3-4 per species) were cut into 1 cm2 sections, fixed in FAA (formalin acetic acid), and embedded in paraffin blocks. Sections included different leaf portio..., , # Negative allometry of leaf xylem conduit diameter and double-wall thickness: implications for implosion safety

[https://doi.org/10.5061/dryad.b8gtht7mc](https://doi.org/10.5061/dryad.b8gtht7mc)

This dataset is part of the manuscript Matos et al., 2024 New Phytol. In this study, we measured leaf xylem conduit double-wall thickness (T) and lumen maximum diameter (D) in > 7,000 conduits of 122 plant species to investigate (1) how *T* versus *D* scaling varies across clades, habitats, growth forms, leaf and vein sizes; and (2) how the *T* versus *D* influences xylem safety against implosion.

## Description of the data and file structure

This dataset comprises the following files:

**(1) species_list.csv =** a comma separated file containing taxonomic information for the 122 plant species investigated in this study:

spp_code = species code comprising the three first letters of the genus and the three first letters of the species name;

Species_UCBG = species binomial nomenclature a...