García-Beltrán, José A.

Heteromorphism in seeds of Leptocereus scopulophilus (Cactaceae) from Pan de Matanzas, Cuba

Digital Document

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.

Digital Document

Vivipary is the germination of a seed inside of a fruit before it is separated from the mother plant. In the present study, the populations of several Cuban cactus species are explored in search of vivipary and Leptocereus scopulophilus is used as a model species to evaluate the effectiveness of vivipary in the establishment of offspring. Vivipary is a relatively common phenomenon in Cuban cacti from different ecosystems with variable temperature, rainfall and salinity, whose frequencies of population vivipary and average of viviparous seedlings per fruit are usually low. In L. scopulophilus, vivipary does not constitute a more efficient reproductive strategy that favors establishment, which is typically the limiting factor for the perpetuation of viviparous species. On the other hand, viviparous seedlings will be favored in environments with high levels of humidity and availability of safe sites, which are sporadic in semiarid environments.

Vivipary in Cuban cacti: A pioneer study in Leptocereus scopulophilus

Digital Document

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.

Efecto del fuego sobre la estructura poblacional de Hypericum styphelioides en la Reserva Ecológica Los Pretiles, Cuba

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Fires are ecological disturbances that change the structure of populations, and accordingly demographic response is determined by the particular attributes of each species. The present study evaluates the effect of fire on a population of Hypericum styphelioides subsp. styphelioides through its population structure. The structure of the population in unburned and burned areas was characterized. In the burned area, medium reproductive adult occurs in larger numbers and its density is higher in comparison to the unburned area, this pattern could have been determined by a post-fire population explosion. On the other hand, the classes below the medium reproductive adult were less represented in the burned area, probably as a consequence of the continue decline on the recruitment of younger individuals of each generation due to the reduction of nutrient levels after the fire. This pattern matches the similarity of the densities of these performance classes and the overall density between both areas. Furthermore, the smaller dimensions found in medium and small breeding adults in the burned area of the pine forest also indicates the nutrient deficiency that affected the growth of the individuals after the fire. However, similar dimensions found among vegetative adults of both areas may indicate the recovery of the levels of nutrients in the burned area of the pine forest to the pre-fire levels, by the accumulation of organic matter.

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