Ginkgo biloba and Helianthus annuus show different strategies to adjust photosynthesis, leaf water relations, and cell wall composition under water deficit stress

[eng] Cell wall thickness (Tcw) determines photosynthesis and leaf elasticity. However, only a few studies in angiosperms addressed cell wall composition implication in regulating photosynthesis and leaf water relations through mesophyll conductance (gm) and bulk modulus of elasticity (ε) adjustments, respectively. Thus, we compared the phylogenetically distant Ginkgo biloba L. and Helianthus annuus L. under control and water deprivation to study the relationship between changes in cell wall composition (cellulose, hemicelluloses, and pectins) with gm and ε. Although no changes were found for Tcw, both species differently modified cell wall composition, resulting in different physiological consequences. H. annuus increased cellulose, hemicelluloses, and pectins in a similar proportion, maintaining ε. Additionally, it reduced photosynthesis due to stomatal closure. G. biloba did not decrease photosynthesis and largely increased hemicelluloses, leaf mass area, and leaf density, enhancing ε. Nonetheless, no association between cell wall composition and gm was found in either of the two species