DOI: 10.5061/dryad.8pk0p2nxc
title: Within-leaf variation in embolism resistance is not a rule in compound-leaved angiosperms

description: Premise Hydraulic segmentation, caused by the difference in embolism
 resistance across plant organs, provides a sacrificial layer of cheaper
 plant organs, like leaves, to protect more costly organs, such as stems,
 during drought. Within-leaf hydraulic segmentation has been observed in
 two compound-leaved tree species, with leaflets being more vulnerable than
 the rachis or petiole. Many herbaceous species have compound leaves, and
 some species have leaflets that are associated with pulvini at the base of
 the lamina, which could provide an anatomical means of preventing embolism
 from spreading within a leaf due to the high concentration of
 vessel-endings in the pulvinus. Methods We assessed embolism resistance
 across the leaf in three diverse palmately and pinnately compound-leaved
 herbaceous species, one of each with a pulvinus. We used the optical
 vulnerability method to simultaneously investigate whether hydraulic
 segmentation occurred across the leaves of six compound-leaved herbaceous
 species and one compound-leaved deciduous tree species. Results We found
 considerable variation in embolism resistance across the six diverse
 herbaceous species measured but no evidence of hydraulic segmentation
 across both the palmately- and pinnately-compound leaves of the six
 herbaceous species and the one deciduous tree species. In two species with
 pulvini, we observed major embolism events crossing the pulvinus,
 spreading from the rachis or petiole into the lamina, and embolizing both
 tissues at the same water potential. Conclusion   We conclude
 that there is little evidence for within-leaf hydraulic segmentation in
 compound-leaved herbaceous species and that the presence of a pulvinus
 does not provide a barrier to embolism spread in herbaceous plants.
 Further, that hydraulic segmentation is not a rule in compound-leaved
 angiosperms.
description: Plants were cultivated in the Lilly Greenhouses at Purdue
 University (West Lafayette, Indiana, USA) in 5-L pots containing
 commercial potting mix and were maintained under greenhouse conditions for
 4 to 7 months, except <em>Eranthis hyemalis</em><em>,
 </em>which was gathered from Horticulture Park on the Purdue campus
 in February 2023. Plants in the greenhouse were watered daily and received
 weekly applications of liquid fertilizer (Miracle-Gro, Scotts Company LLC,
 OH, USA). Conditions in the glasshouse were maintained under a natural
 photoperiod and controlled day:night temperatures of 28:22°C.  Samples of
 <em>Ailianthus altissima</em> (“Tree of Heaven”), were
 collected in June of 2024 from Horticulture Park on the Purdue campus
 (n=3) and immediately bagged and brought back to the lab to rehydrate.
 Vulnerability curves of the rachis and lamina were conducted using the
 optical vulnerability method and subsequent image analysis outlined by
 (Brodribb et al., 2016). Three plants from each species were brought to
 the laboratory, and the roots were carefully washed, or in <em>A.
 altissima </em>3-5 year old trees were cut at the base and
 transported back to the lab. The maximum vessel length of <em>A.
 altissima</em> was determined using the air-injection method (Ewers
 and Fisher, 1989) from three branches from three individuals. During
 dehydration, neighboring leaves were used to measure water potential using
 a Scholander pressure (PMS International, OR, USA) chamber every two
 hours. Embolism resistance was determined from leaf image stacks, which
 were then analyzed for embolism events exclusively in the rachis or lamina
 for the six herbaceous species, while A. altissma consisted of three image
 stacks for each replicate, corresponding to stem, petiole, and leaflet.
 Images were analyzed using ImageJ software following the instructions at
 GitHub (https://www.opensourceov.org/), and the OSOV toolbox was utilized to facilitate image analysis (https://github.com/OpenSourceOV/imagej-scripts). One-way and two-way ANOVAs were conducted with R version 3.6.1 (R Development Core Team, 2018) to test for significant differences between the leaflet lamina and the rachis or petiole between the same species (α=0.05) and between P12, P50, and P88 water potentials. Pairwise comparisons were made with the Tukey honest significant difference test for the difference at P<sub>12</sub>, P<sub>50,</sub> and P<sub>88 </sub>between the same species (α=0.05). The “multcompView” function was used to denote letters that indicate significant differences between the leaflet lamina and the rachis or petiole.
description: # Within-leaf variation in embolism resistance is not a rule in
 compound-leaved angiosperms
 [https://doi.org/10.5061/dryad.8pk0p2nxc](https://doi.org/10.5061/dryad.8pk0p2nxc) Hydraulic segmentation, caused by the difference in embolism resistance across plant organs, provides a sacrificial layer of cheaper plant organs, like leaves, to protect more costly organs, such as stems, during drought. Within-leaf hydraulic segmentation has been observed in two compound-leaved tree species, with leaflets more vulnerable than the rachis or petiole. Many herbaceous species have compound leaves, and some species have leaflets associated with pulvini at the base of the lamina, which could provide an anatomical means of preventing embolism from spreading within a leaf. To determine if hydraulic segmentation is also a rule in herbaceous angiosperms, we assessed embolism resistance across the leaf in three diverse palmately and pinnately compound-leaved herbaceous species (n=3), one of each with a pulvinus. We used the optical vulnerability method to simultaneously investigate whether hydraulic segmentation occurred across the leaves of six compound-leaved herbaceous species and one compound-leaved deciduous tree species. We found considerable variation in embolism resistance across the six diverse herbaceous species measured but no evidence of hydraulic segmentation across both the palmately- and pinnately-compound leaves of the six herbaceous species and the one deciduous tree species. In two species with pulvini, we observed major embolism events crossing the pulvinus, spreading from the rachis or petiole into the lamina, and embolizing both tissues at the same water potential. Given this dataset, we conclude that there is little evidence for within-leaf hydraulic segmentation in compound-leaved herbaceous species and that the presence of a pulvinus does not provide a barrier to the spread of embolism in herbaceous plants. Further, that hydraulic segmentation is not a rule in compound-leaved angiosperms. ## Description of the data and file structure The data for this manuscript is organized in the CSV file in two sheets titled "README" and "RAWDATA". The "README" file contains a list of each of the variables in the "RAW DATA" sheet, with a corresponding description. The "RAW DATA" sheet is organized by Species, Number, Organ, P.12, P.50, and P.88.