Comparative anatomy of Clethra scabra Pers. (Clethraceae) in different altitudes in Serra da Mantiqueira, Minas Gerais state, Brazil

Abstract

To verify the influence of altitude on the anatomical structure of leaves and the secondary xylem of branches of individuals of the species Clethra scabra Pers. (Clethraceae) occurring in the Serra da Mantiqueira, state of Minas Gerais, samples were collected at altitudes of 1500, 1700, 1900 and 2100 m (meters). The collected leaves and branches were fixed and prepared following usual plant microtechnical procedures. Quantitative anatomical analyzes were performed using image analysis software. The leaves of C. scabra are hypoestomatic with triseriate epidermis and stellate trichomes, dorsiventral mesophyll, palisade parenchyma with one to two cell layers and the spongeous parenchyma with four. The central rib with developed xylem and the vascular bundle involved by the sclerenchyma sheath. Analysis of variance (ANOVA) and Scott-Knott test demonstrated that the thickness of the leaf blade, mesophyll and palisade parenchyma did not present statistically significant differences between the evaluated altitudes. The secondary xylem showed a decrease in the length of the vessel elements with increasing altitude at the 2100 m elevation and the tangential diameter of the vessel elements increased at the two lowest altitudes and then reduced. The Carlquist and the mesomorphic vulnerability indices decreased along the altitudinal gradient. Fiber length and diameter decreased with increasing altitude. Thus, altitude influences the anatomical changes presented by leaves and branches of C. scabra, which can be related to its phenotypic plasticity in response to different environmental conditions.

Keywords: Carne-de-vaca; Nebular forest; Mesophyll; Secondary xylem