Barrios, Duniel

Seed heteromorphism is the formation of different seed morphs from the same individual. Two seed morphs have been preliminarily observed in Leptocereus scopulophilus. One morph shows an apparent natural scarification of its coat. Herein we describe the seeds, taking into account shape, coat integrity, surface, dimensions, mass and the position of germination cracks. We defined two seed morphs using the integrity of the spermoderma: fragmented seed coats (FSC) and complete seed coats (CSC). We also evaluated minimum germination time, germination rate and germinability. The seed morphs did not differ significantly in traits; however, regular striations along the cuticle of the periclinal walls were more visible in the FSC compared with the CSC. Both seed morphs displayed anticlinal cell boundaries in the border region that are channelled and straight in the dorsal-ventral region but difficult to define in the lateral region. We found four morphological variations in different positions where the radicle or cotyledons emerge and variations in cuticle thickness in different regions of the seed that could determine the formation of cracks during germination. All germination variants occurred in both seed morphs, albeit in different proportions. Germination was higher and faster for the FSC compared with the CSC. These germination differences could be related to a thinner cuticle in the FSC and the punctual release of its spermoderma, which facilitates a quick imbibition of the embryo and the breaking of the seed coat. Our results indicate that differences in germination parameters between the two seed morphs relate to differences in the percentage of dormant seeds, which favour the temporal expansion of germination and reduce competition between siblings. To propagate the species for conservation purposes, we recommend using FSC, while CSC may be used to establish a seed collection ex situ.

A brief summary of the progress made in the conservation programme for the threatened cacti of Cuba. Photography by the author. [ABSTRACT FROM THE AUTHOR]

Two extremely rare leptocerei from Cuba, in imminent danger of extinction in the wild, are the subject of a survey supported with finance from the BCSS Conservation Fund. Photographs supplied by the authors.

Some results of research on the ecology and natural history of Leptocereus scopulophilus(Cactaceae) in Cuba are presented. In so doing, it is hoped that this will stimulate additional new and innovative research into the entire genus Leptocereuswith a view to supporting further conservation efforts. Photography by the authors. [ABSTRACT FROM THE AUTHOR]

Vivipary is a relatively unusual trait in the angiosperms, documented in nearly 195 species of 78 vascular plant families, including 53 cactus species. In this paper we report the occurrence of vivipary in four Cuban cactus species (Leptocereus arboreus, L. scopulophilus, Harrisia eriophora and Selenicereus grandiflorus). For L. scopulophilus, we determined the frequency of vivipary and compared fruit traits in viviparous and non-viviparous fruits. We found that 18.9% of L. scopulophilus individuals had viviparous fruits. None of the fruit traits compared between viviparous and non-viviparous fruits differed significantly, although the pericarp is slightly thicker in viviparous fruits.

Studies of seed mucilage in a number of species suggest that it has multiple ecological roles dependent on species and their environmental context. We evaluate whether mucilage facilitates seed germination for Leptocereus scopulophilus Areces, as well as whether light conditions influence the effect of the mucilage. Three combined treatments of light conditions: (1) shade (10% of sunlight), (2) semi-shade (30% of sunlight), and (3) full light exposure (100% of sunlight), and two seed types (with mucilage and washed) were used. Germinability was affected by light conditions but no effect of mucilage was found; higher germination occurred in shade than in semi-shade conditions. There was no germination in full light conditions. Germination rate (T50) was not affected by light conditions or by the mucilage, or the interaction of both factors. Minimal time to germination (Tmin) was affected by mucilage; seeds with mucilage germinated 2 days later than washed seeds. Thus, facilitation for imbibition of water does not occur in L. scopulophilus seeds. Perhaps the presence of mucilage in seeds of this species serves other purposes such as seed adhesion to soil or to deter predators. [ABSTRACT FROM AUTHOR]