Seed ecology in a population of Acaciaholosericea

Abstract

One population of seed from 18 trees of Acaciaholosericea A. Cunn. ex G. Don from Western Australia was studied. Seeds were weighed individually and germinated in replicates of 25 to try to describe population behaviour under constant temperatures between 17 and 40 °C. Total germination peaked at between 95 and 99% at temperatures between 17 and 35 °C and then dropped sharply to 45% at 40 °C. Temperatures between 17 and 35 °C, therefore, did not influence total germination, and all respective slope coefficients were the same over the entire temperature range. This reflects a very wide optimal temperature range for germination. In all cases, seeds slightly heavier than the mean (11.6 mg) reached the highest rate of total germination. Peak germination occurred in progressively heavier seeds as temperatures were raised from 17 to 40 °C. The germinative rate was also found to decrease as seed weight increased at temperatures between 25 and 35 °C. This was true for seeds from single trees and for pooled seed. At 20 and 40 °C, however, lighter seeds tended to lose the ability to germinate quickly. Lighter seeds also tended to germinate well without a boiling pretreatment, whereas heavier seeds needed to be boiled for 90 s before germination could proceed. Boiling tended to kill the lightest seeds. Seeds weighing between 8 and 10 mg were able to germinate more quickly initially than either lighter or heavier seeds, regardless of which trees the seeds came from.