Samara water absorption and floatation in sheoaks, Casuarina and Allocasuarina (Casuarinaceae)

Diaspores (samaras) of the sheoaks, Casuarina and Allocasuarina, have a mesocarp composed of hydrophilic fibres that, in Allocasuarina, rapidly expand on wetting, capturing significant quantities of water. The ecological function of this water capturing has been the subject of speculation but not quantification or experimentation. Therefore, the rate and quantity of water absorbed, and the floatation properties of samaras of accessions of Casuarina and Allocasuarina were assessed. Casuarina absorbed water slowly (~48 h) with median absorption of 90% (by weight) whereas Allocasuarina absorbed water rapidly (