Capparis odoratissima is a tree species native to
semi-arid environments of the northern coast of South America where low
soil water availability coexists with frequent nighttime fog. A previous
study showed that water applied to leaf surfaces enhanced leaf
hydration, photosynthesis, and growth, but the mechanisms of foliar
water uptake are unknown. Here we combine detailed anatomical
evaluations with water and dye uptake experiments in the laboratory, and
use immunolocalization of pectin and arabinogalactan protein epitopes to
characterize water uptake pathways in leaves. Abaxially, the leaves ofC. odoratissima are covered with peltate hairs, while the adaxial
surfaces are glabrous. Both surfaces are able to absorb condensed water,
but the lower surface has higher rates of water uptake. Numerous
idioblasts connect the adaxial leaf surface and the abaxial peltate
hairs, both of which contain hygroscopic substances such as
arabinogalactan proteins and pectins. The highly specialized anatomy of
the leaves of C odoratissima fulfills the dual function of
minimizing water loss when stomata are closed, while maintaining the
ability to absorb liquid water. Cell-wall related hygroscopic compounds
in the peltate hairs and idioblasts create a network of microchannels
that maintain leaf hydration and promote water uptake.
Keywork index : arabinogalactan proteins-AGPs, foliar water
uptake, idioblast, pectins, peltate hairs, sclerenchyma.