Effect of heat shock on the germination of seeds of the species Acacia senegal L. and Acacia seyal Del. from sub-Saharan Africa (Ethiopia).

Abstract

Aim of the study: Understanding post-fire germination of tree species in arid and semi-arid zones of sub-Saharan Africa.Area of study: Ethiopian Acacia senegal L. and Acacia seyal Del. forests.Material and methods: Seeds were subjected to heat shocks at combinations of four temperatures (60º, 90º, 120º and 150ºC) and three exposure times (1, 5 and 10 minutes). A control was also included, resulting in a total of thirteen treatments. After the application of the heat shocks, the viability of no germinated seeds was assessed after immersion in a Tetrazolium solution. A mixed and a logistic model were used to analyse the influence of heat shock on germination.Main results: Results showed that germination depended on the species, the heat shock treatment and their interaction. Both species showed similar germination results at temperatures below 90ºC in all exposure times, however, germination in Acacia senegal was statistically higher in most of the heat shocks. On the other hand, germination probability decreased in both species, when the exposure time increased, although with a different behaviour. In 1 minute of time of exposure, the germination probability was higher than 60% in the two species throughout the temperature range. However, at 5 minutes of time and temperature smaller than 90°C, the probability of germination was higher than 70% in A. senegal and 50% in A. seyal. Although germination in both species was impacted by the different heat shocks, non-germinated seeds were viable.Research highlights: This paper showed, according to these results, that heat shock would negatively influence the regeneration of both species, and especially for A. seyal