Temperature effects on Acrocomia aculeata seeds provide insights into overcoming dormancy in neotropical savanna palms

Seed tolerance to the elevated temperatures of soils during the spring/summer seasons or due to the passage of fire is an important adaptation for Cerrado (neotropical savanna) seeds. The present work evaluated the influence of elevated temperatures on the seed viability and germination of the palm tree Acrocomia aculeata. The seeds were immersed in water at 70 °C (thermal shock) for 1, 3, 5, 10, 30, 60, 120, 300, 420 and 600 s. In another experiment, seeds were maintained in dry (heat treatment) or moist (stratification) conditions, at temperatures of 35, 40, 20/30, 18/35 °C, or at room temperature (mean 22 °C) for 15, 30 or 60 days. The effects of these treatments on embryo viability as well as on seed germination were evaluated. Embryo survival was high until 300 s of exposure to thermal shock; high mortality was observed with longer exposures. Thermal shocks did not stimulate seed germination, and high rates of seed deterioration were observed with exposure to high temperature for 300 s or more. Heat treatments, at any temperature, did not stimulate germination, while stratification at 35 °C for 30 and 60 days resulted in increased germination (13 and 25% respectively). The temperature of 40 °C, in both dry and moist conditions, resulted in the loss of embryo viability. Acrocomia aculeata seeds have a considerable tolerance to high temperatures; furthermore, stratification at 35 °C is probably important in overcoming seed dormancy in soil seed banks and constitutes a successful propagation method for the species.