Morphology and seed anatomy in representtive Viola species (Violaceae).

SANSO, A. M. & XIFREDA, C. C

Tandil

Congreso; V Congreso Argentino de Ciencias Morfológicas; 2006

Sociedad Argentina de Ciencias Morfológicas

The dispersal of seeds by ants is a widespread phenomenon involving many groups of plants. Majority of Viola species (Violaceae) are diplochores. Their seeds, small, with undeveloped elaiosomes are first ejected ballistically from the capsule, in order then to be located and removed by ants. Other seeds,  large and with well developed elaiosomes depend on the presence of some medium-sized ground-foraging ant species for dispersal and they are confined to species of a single group, Viola sect. Viola subsect. Rostellatae. The aim of this study is to describe and to compare the morphology and seed anatomy of representative Viola species belonging to each one of these groups - V. roigii Rossow/ V. maculata Cav.  and V. odorata L.-, with particular enphasis in the elaiosome. Seed samples for anatomical studies were fixed in glutaraldehyde in phosphate buffer, dehydrated and embedded in Spurr ´s resin. Stained cross sections were observed by light microscopy. Micromorphological studies were carried out with scanning electronic microscopy.  The elaiosome is composed by small basal cells, and the outer ones, very elongated. Both types of cells present lipids but the outer ones, in greater quantity. Seed coat surfaces exhibit characteristical cellular patterns and the mechanical layer presents differences in relation with the number of elongated sclereid rows.