Soils drive convergence in the regulation of vascular tension in land plants

Terrestrial vascular plants operate under negative water potential, which results in hydraulic tension in the vascular system. Vascular tension varies with transpiration and soil drying, and it is regulated by stomata, pressure-activated valves on the leaf surface. We hypothesize that soil physical constraints drive convergence in the operational range of leaf vascular tension. Based on a meta-analysis of 19 diverse species, we find that stomatal regulation of transpiration is activated when leaf vascular tension reaches a narrow target of 1.3±0.6 MPa. This value matches the range (1.4±0.6 MPa) predicted from an optimal soil water extraction model. Optimality in plant vascular tension appears to have evolved by selection for a narrow range of osmotic pressure in the leaves of diverse AASAQAQSAspecies growing across enormously variable environments.
, , No new materials were generated in this study, but data were taken from the literature. The main data is a subset of the dataset collected by Anderegg et al. (2018), complemented with two crop species from Tardieu & Simonneau (1998). These data contain time-point measurements of transpiration rate and leaf water potentials of 19 species in total (for many species, there are additional variables measured). Additionally, we compare observations of initial transpiration reduction (leaf water tension when stomatal regulation is activated) with (i) predictions of soil water extraction by plants using the soil-plant hydraulic model developed by Carminati & Javaux (2020); (ii) measurements of leaf osmotic pressures collected by Bartlett et al. (2012); (iii) observations of minimum leaf water potentials, as well as leaf water water potentials at 50% loss in xylem conductivity compiled by Choat et al. (2012).
, # Soils drive convergence in the regulation of vascular tension in land plants

Dataset DOI: [10.5061/dryad.kkwh70shp](https://doi.org/10.5061/dryad.kkwh70shp)

## Description of the data and file structure

### Files and variables

#### File: anderegg_Tr_psi_md_psi_pd_available.csv

**Description:** This dataset is a subset of the dataset collected by Anderegg et al. (2018), filtered for species that contain at least transpiration and leaf water potential measurements (predawn & midday).

##### Variables

* Species: Species name; Trmmol: transpiration rate in (mmol m-2 s-1); LWP: (midday) leaf water potential in MPa; LWPpredawn: (predawn) leaf water potential in MPa, among others.

*Missing Values:* Note that missing data values are indicated by multiple identifiers, such as \"-9999\", \"NA\" and empty cells, as the original data structure was kept unchanged.

#### File: bartlett2012.xlsx

**Description:** The original dataset compiled by Bartlett et al. (2012), containing observations of ...