Format: ORAL

Marc Fradera-Soler1,2,3, Jozef Mravec2,4, Jesper Harholt5, Olwen M. Grace3,6, Bodil Jrgensen2

1 Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden 2 Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark 3 Royal Botanic Gardens, Kew, Richmond, Surrey, UK 4 Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Plant Science and Biodiversity Center, Nitra, Slovakia 5 Carlsberg Research Laboratory, Copenhagen, Denmark 6 Royal Botanic Garden Edinburgh, Edinburgh, UK

Succulent plants have specialized water-storage tissues with collapsible cell walls that reversibly fold as water is lost. However, the ecophysiological significance of cell wall traits has often been overlooked in succulents. We focused on southern African species of the leaf-succulent genus Crassula and used comprehensive microarray polymer profiling (CoMPP) and glycan-binding antibodies to analyse cell wall polysaccharide and glycoprotein content in leaves. We found significant differences in leaf glycomic profiles that can be linked to increased drought resistance in one of the two main growth forms in Crassula. Furthermore, some cell wall components correlate positively with increasing aridity, which suggests that they are likely advantageous in terms of arid adaptation. A deeper insight into the relationship between cell walls and the succulent function would be particularly useful given the potential of succulents as natural capital to mitigate the effects of climate change. Numerous hydathodes are another peculiarity of Crassula species, foliar structures that are usually associated with guttation. Foliar water uptake (FWU) through hydathodes has long been suspected in Crassula, particularly in species that occur in fog-influenced arid habitats in southern Africa. To provide empirical observations linking FWU to hydathodes in Crassula, we used the apoplastic fluorescent tracer Lucifer Yellow in combination with different imaging techniques. The resulting images confirm that hydathode-mediated FWU does indeed occur in Crassula and is likely widespread across the genus. Surprisingly, FWU is operational in Crassula species that occur in rather mesic environments, beyond fog-influenced arid habitats, and even in species with seemingly hydrophobic leaves, in which the hierarchically sculptured leaf surfaces may facilitate FWU thanks to hydrophilic leaf surface microdomains. These findings confirm the ecophysiological relevance of FWU in Crassula and reassert the importance of atmospheric humidity for some arid-adapted plant groups.