THE ROLE OF CALLISTEMON FRUITS AND INFRUCTESCENCES IN PROTECTING SEEDS FROM HEAT IN FIRES

A number of Australian plant species tolerate fires because seeds are protected in woody fruits and are released after fire, but there is li ttle information about the role of the fruit, or a collection of fruit s, in protecting seed from the heat of a fire. This study examined the effects of various temperatures applied to infructescences of Callist emon citrinus (Curtis) Skeels on seed germination. The protective role of the dense collection of fruits in maintaining seed viability was t ested by experimentally 'thinning' infructescences before heating. Hea ting of infructescences significantly increased the percentage of seed s germinating from less than 20% at room temperature to over 35% at 20 0 degrees C, but caused a decline, with further temperature increase t o 800 degrees C. There was a slight but statistically significant incr ease in the percentage germination of seeds from thinned infructescenc es. Increased germination following exposure to high temperature may b e a way for a plant to synchronise germination after high-intensity fi re, while spreading it out if seeds are released in the absence of fir e or after a low-intensity fire.