Temperature-induced self-sealing capability of Banksia follicles

Many plants in fire-prone regions retain their seeds in woody fruits in the
plant canopy until the passage of a fire causes the fruit to open and release
the seeds. To enable this function, suitable tissues are required that effectively
store and protect seeds until they are released. Here,we showthat three different
species of the Australian genus Banksia incorporate waxes at the interface
of the two valves of the follicle enclosing the seeds, which melt between 458C
and 558C. Since the melting temperature of the waxes is lower than the opening
temperatures of the follicles in all investigated species (B. candolleana,
B. serrata, B. attenuata), we propose that melting of these waxes allows the
sealing of micro-fissures at the interface of the two valves while they are
still closed. Such a self-sealing mechanism likely contributes to the structural
integrity of the seed pods, and benefits seed viability and persistence during
storage on the plants. Furthermore, we show in a simplified, bioinspired
model system that temperature treatments seal artificially applied surface
cuts and restore the barrier properties.