5 CONCLUSIONS
Leaf water absorption has been widely studied in the major groups of
angiosperms, including magnoliids (eight genera), monocots (seven
genera), and eudicots (67 genera) (reviewed by Berry et al., 2019, and
by Dawson & Goldsmith, 2018), pointing to foliar water uptake as a key
factor affecting plant function in most ecosystems (Weathers et al.,
2019). However, the effect of foliar hydration in the overall plant
physiology is stronger in dry or semi-dry environments (Schreel et al.,
2019), such as the dryland tropical areas where C. odoratissimagrows, where the water in the soil is often a limiting resource, and
aerial water may become pivotal for plant growth and survival.
Our data strongly suggest that the pathway for water uptake inCapparis odoratissima is mediated by the interconnected
idioblasts and peltate hairs. We propose a model (Figure 8) that
involves apertures of the leaves toward the adaxial surface, which are
involved in water uptake, but may facilitate evapotranspiration.
Hygroscopic materials belonging to arabinogalactan proteins serve to
draw water into the lumen of the idioblasts, while pectins in the
mesophyll and the epidermis may further facilitate the incorporation of
water into leaf tissues. We believe that this cascade of biochemical and
physical events underlies the ability of Capparis odoratissimatrees to utilize atmospheric water resources.