Morphological features of nectaries of some species of the genus Rosa (Rosaceae)

Abstract

Results are presented of our study of nectaries of 13 species of the genus Rosa from the collection of the M.M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine. Using light microscopy, we described and illustrated their morphological features in details. Nectaries of all studied species were floral, hypanthial, symmetrical, non-septally structural, mesenchymatous, and persistent. Based on location of the androecium, nectaries were intrastaminal, and only Rosa henryi was found to have amphistaminal nectary. Each species was morphologically differentiated from others by one or more characters. We analyzed morphological features (diameter of nectary and throat of hypanthia, thickness of nectary tissue around throat of hypanthia and on the edge, form of nectary on the longitudinal section), on that basis we allocated groups of nectaries based on their shape – convex (cone- and dome-shaped), curved, and flat ones. The latter is typical for Rosa roxburghii, which, according to a number of other morphological features, is separated by taxonomists in a monotypic (monospecific) subgenus. Based on surface characteristics of the nectary, Rosa xanthina with papillary growns and Rosa henryi with a uniformly humped relief stood out the most examined species. We emphasized reduction of thickness of nectary tissue in radial direction, except for Rosa spinosissima, in which thickness was almost even throughout the whole area of the nectary. The listed morphological differences can be used as additional diagnostic characters at the species level. Such features as the outline of the nectary throat and edges are quite variable within species and were not taxonomically significant. We present original figures and photographs of nectaries in an outline and on a longitudinal section.