Physiological dormancy in seeds of Thespesia cubensis (Malvaceae), endemic and endangered tree of Cuba

Abstract

Thespesia cubensis is an endemic tree of Cuba, which is Critically Endangered, has little natural regeneration and nothing is known about its regeneration mechanisms. Therefore, the objective of the present investigation was to characterize functional traits of its seeds, particularly related to dormancy, germination and seedlings to favor its propagation. Fresh fruits were collected from adult trees that grow in Conuco key (best preserved population, in the northwest of Central Cuba) to obtain seeds. The seeds had an average initial moisture content of 13.21%, were permeable to water and had a developed embryo of the folded type. In addition, the seeds allocated 54.7% of their mass to the formation of cover structures and showed an initial viability of 100%. Germination evaluated under nursery conditions began at an average of 4.3 days, but only reached 59% of final germination at 16 days after sowing; the rest of the seeds that did not germinate at the end of the experiment (30 days) remained alive and hydrated. Consequently, a part of the lot (more than 40%) presented physiological dormancy (PD), possibly due to the mechanical barriers imposed by the seminal covers to embryo growth. The present work is the first report of PD in Thespesia seeds. The ecological role of the identified life history traits is discussed and practical recommendations for increasing germination under nursery and direct field sowing conditions are provided.