Seed morphology and anatomy of Rubus geoides Sm.

Abstract

Rubus geoides Sm. is a wild raspberry native in Patagonia. Its domestication can broaden the genetic base of the cultivated raspberry, prevent over exploitation of wild populations, and diversify fruit production in areas where few fruit species can be cultivated, like the Chilean Patagonia. One important step in the domestication of plant species is the unveiling of the reproductive biology of the species, particularly seed germination. The goal of this work was to study seed morphology and anatomy of R. geoides in order to identify possible factors that may affect germination and species identification based on seed morphology, since seed shape, surface sculpturing and raphe characteristics are discriminating factors for species identification within Rubus. Morphoanatomical studies were performed using both scanning electron microscopy (SEM) and light microscopy. Rubus geoides seeds turned out to be similar to those of R. idaeus. Seeds were pale brown, with a semi globular shape, sharpened at the apical region and oval toward the opposite end. Seed size was variable, showing an average 1.9 mm width, 2.6 mm length, and 1.3 mm thickness. Small rounded depressions and ridges sculptured seed surface. The endocarp was hard and rough, and consist of several layers of sclerenchymatous lignified cells with 139 mu m averaged thickness, which suggest that to enhanced germination seed may require its weakening or eventual elimination, as is done in other Rubus species. The embryo varied with seed size between 1.6 and 2.0 mm. Energy Dispersive X-Ray Spectroscopy allowed for the identification of the endosperm cells.