CARACTERIZAÇÃO MORFOANATÔMICA E HISTOQUÍMICA DAS GLÂNDULAS FOLIARES DE ROSA lucieae Franch. & Rochebr. ex Crép (Rosaceae)

Abstract

Secretions are commonly present in vascular plants and may consist of a variety of secondary and/or primary metabolites. Sticky secretions in plants, consisting of resins or mucilages, can be produced by glandular trichomes or colleters. In Rosaceae, secretory structures such as glandular trichomes, colleters and hydathodes have been recorded in different species. Our study offers a morphoanatomical description of the leaf glands of Rosa lucieae, revealing the identity and secretory function of these glands. For this, leaves of R. lucieae were collected at different stages of development and submitted to usual light microscopy techniques, including histochemical tests and scanning electron microscopy. Two types of leaf glands were identified: type I, called colleters; and type II, glandular trichomes. The colleters have a parenchymal axis surrounded by a palisade secretory epidermis and a thick cuticle. A stalk may or may not be present. This type of gland is associated with leaf teeth or occurs on teeth and on the margins of stipules and may be deciduous on expanded leaves. On the other hand, glandular trichomes are persistent, have a stalk of variable size and a secretory epidermis covered by a thin cuticle. They are found at the base of the leaflet, petiolule, rachis, petiole and on the margins of the stipules. Colleters predominantly secrete mucilage and glandular trichomes secrete lipids and terpenes. The secretory activity of the colleters is predominant in the leaf primordia, keeping the leaflets together and protecting meristems and leaves from desiccation. The glandular trichomes, in turn, maintain secretory activity at different stages of leaf development, protecting different regions of the leaf against pathogens and herbivores.