Leaf cell wall properties and stomatal density influence oxygen isotope enrichment of leaf water.

Authors: Ellsworth, Patrick; ELLSWORTH, PATRICIA - Washington State University; MERTZ, RACHEL - University Of Missouri; KOTEYEVA, NURIA - Russian Academy Of Sciences; COUSINS, ASAPH - Washington State University

Submitted to: Plant, Cell & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2023
Publication Date: 5/23/2023
Citation: Ellsworth, P.Z., Ellsworth, P.V., Mertz, R.A., Koteyeva, N.K., Cousins, A.B. 2023. Cell wall properties influence leaf water isotope enrichment depending on transpiration rates. Plant, Cell & Environment. pgs. 1-17. https://doi.org/10.1111/pce.14612.
DOI: https://doi.org/10.1111/pce.14612

Interpretive Summary: Stable isotopes in leaf water can improve our understanding of how physiology and anatomy affect how water moves through the leaf. By taking advantage of mutants that have altered cell walls, we were able to study the role of cell wall composition on the stable isotopic composition of oxygen in leaf water. We found that mutants with altered suberin content had higher tranpsiration than wildtype and that the mutation affected the isotopic composition of oxygen in leaf water. The response of stomatal density to growth light intensity was proportional to the response in the stable isotope composition of oxygen in leaf water of wildtype rice and mutants that do not produce mixed linkage glucan, a component of cell walls. These findings not only advance our understanding of stable isotopes in leaf water but advance our understanding of water transport in leaves. Integrating stable isotopes with physiology and anatomy facilitates the development of a complete leaf water transport model that incorporates leaf physiology, anatomy, and hydraulics.

Technical Abstract: The oxygen isotopic composition ('18OLW) of leaf water potentially can improve our understanding of the relationship between anatomy and physiology in leaf water relations. Leaf water isotope models such as the Péclet effect model have been developed to predict d18OLW, which incorporates influences of transpiration rate (E) and the mixing length (Lv) where source water in the xylem mixing with enriched mesophyll water from the sites of evaporation. Here we used two cell wall composition mutants to evaluate the effect of the cell wall on '18OLW. Suberin double mutant (Zmasft) in maize (Zea mays) were grown under two light intensities and RH, while mixed linkage glucan mutants (Cslf6) in rice (Oryza sativa) were grown under two light intensities. Zmasft double mutants had higher E and Lv, resulting in lower '18OLW, according to the Péclet effect. In Cslf6 mutants and wildtype, the change in '18OLW in plants grown under high and low growth light intensity co-varied with changes in stomatal density. These results show the influence of cell wall composition and stomatal density on '18OLW by altering the Péclet effect and that stable isotopes can facilitate our understanding of the role of plant anatomy and physiology in leaf water transport.