3.5 Hydathode-mediated foliar water uptake
The results of the experiment showed that FWU could be induced in
drought-stressed plants of all but one (i.e. C. perforata )Crassula species examined (Fig. 8 ). In all species in
which FWU could be induced, well-watered plants showed no or very little
uptake of the tracer compared with drought-stressed plants. In all
species that absorbed the tracer, LYCH fluorescence could be detected in
the hydathodes of the leaf surface exposed to the tracer, in most
vascular bundles within the leaf, and even in the hydathodes of surfaces
that were not exposed to the tracer, which indicates efficient
redistribution of absorbed water. Varying degrees of tracer fluorescence
were also observed in the indumentum of several species. The
redistribution of absorbed water within the leaves was most noticeable
in the two species with planar leaves, given that they were easier to
image (Fig. 9 ).