Water content and GA3-induced embryonic cell expansion explain Euterpe edulis seed germination, rather than seed reserve mobilisation

Abstract

Euterpe edulis is a key ecological species in the Atlantic forest. However, illegal plant extraction has lowered its natural occurrence in many areas. A previous study showed that gibberellic acid (GA3) applied 12 days after sowing (DAS) increases the germination performance of this species, but the study did not find the reasons for this result. We reassessed the effects of the seed water content (51, 47, 43, and 39%) on the germination of this species. We hypothesised that after imbibition was initiated, the stage at which GA3 is applied to the seed would be irrelevant, and the anatomical changes in the embryo that are caused by GA3 would be observed more than 15 days after GA3 application. We also investigated whether GA3 induced seed reserve mobilisation. We observed the same percentage of germinated seeds regardless of the seed water content. However, the rate and time of germination were higher as the seed water content increased. GA3 improved the germination performance independently of the date on which GA3 was applied (0 or 12 DAS). This improvement was due to an embryonic cell expansion that was observed 60 DAS, rather than any seed reserve (carbohydrates and lipids) mobilisation that was caused by GA 3.