The Role of Callistemon Fruits and Infructescences in Protecting Seeds from Heat in Fires

Abstract

A number of Australian plant species tolerate fires because seeds are protected in woody fruits and are released after fire, but there is little information about the role of the fruit, or a collection of fruits, in protecting seed from the heat of a fire. This study examined the effects of various temperatures applied to infructescences of Callistemon citrinus (Curtis) Skeels on seed germination. The protective role of the dense collection of fruits in maintaining seed viability was tested by experimentally ‘thinning’ infructescences before heating. Heating of infructescences significantly increased the percentage of seeds germinating from less than 20% at room temperature to over 35% at 200˚C, but caused a decline, with further temperature increase to 800˚C. There was a slight but statistically significant increase in the percentage germination of seeds from thinned infructescences. Increased germination following exposure to high temperature may be a way for a plant to synchronise germination after high-intensity fire, while spreading it out if seeds are released in the absence of fire or after a low-intensity fire.