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Dryad

Within-leaf variation in embolism resistance is not a rule in compound-leaved angiosperms

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Dec 12, 2024 version files 16.94 KB

Abstract

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.