Availability of water and inorganic nutrients in the persistent leaf bases of the grasstree Kingia australis, and uptake and translocation of labelled phosphate by the embedded aerial roots

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Abstract
Numerous lateral branches of the concealed aerial roots of the grasstree Kingia australis ramify through the persistent leaf bases, suggesting a role in uptake of water and nutrients localed up to 8 m above ground. These leaf bases were shown to hold up to more than three times their weight in water. Water and nutrients (N, P and K) available in the leaf bases may greatly exceed that in an equal volume of surface soil, especially during the dry summer months. At this time, 32P injected# among the leaf bases is strongly absorbed by the aerial roots and translocated to the meristematic regions of other laterals beneath the point of application, but mostly to the stern and leaves above it. Scattered vascular bundles in the pith are the major routes for the rapid distribution of “P up and down the trunk following its departure from the aerial roots. Water and nutrients stored in the leaf bases and their subsequent uptake by the associated aerial roots may therefore contribute significantly to this species’ tolerance of long summer droughts and extremely impoverished soils.