Combined role of burying and fruit structures in maintenance of viability and vigor of macaúba palm seeds after fire

Abstract

Acrocomia aculeata (macaúba palm) is a promising oilseed species for bioenergy, found in fire-prone areas. However, the effects of fire on the viability of macaúba palm embryos in fruits and during seed bank formation in the soil are unknown. This study aimed to evaluate the viability of A. aculeata embryos in response to fire and high temperatures. In the first assay, macaúba palm fruits and pyrenes were arranged on the soil surface and buried at 2 cm following fire exposition. Control treatment, buried fruits, and pyrenes showed no differences and presented embryos with high viability, contrasting with fruits and pyrenes in the soil surface. In a second assay, pyrenes and seeds were exposed to 80° C in a water bath for 30, 60, 180, and 300 seconds. The exposition of seeds to 80°C for 30 seconds, resulted in low viability (10%) and absence of vigorous embryos. Pyrenes presented greater viability (74%) and vigor (46%) after 60 seconds of exposure to thermal stress. Viable embryos were found in pyrenes exposed up to 180 seconds in high temperature. The soil and the structure of the macaúba’s palm endocarp play an important role in the tolerance of its embryos to fire and heat.