SEM studies on the leaf indumentum of six Melastomataceae species from Brazilian Cerrado

Camilla Rozindo Dias Milanez,Silvia Rodrigues Machado

doi:10.1590/2175-7860201162113

Camilla Rozindo Dias Milanez, Silvia Rodrigues Machado

Open Access

https://doi.org/10.1590/2175-7860201162113

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Abstract

Abstract The wide diversity of their trichomes, which vary from simple unicellular to very complex structures, is a remarkable characteristic in Melastomataceae. This paper characterizes the leaf indumentum of Miconia albicans (Sw.) Triana, M. chamissois Naudin, M. fallax DC., M. ligustroides (DC.) Naudin, Microlepis oleaefolia (DC.) Triana and Rhynchanthera dichotoma DC., typical species from Brazilian cerrado. Samples collected from the median third of young and mature leaf blades were processed following the usual scanning electron microscopy techniques (SEM). We observed ten morphological types of trichomes and four of emergences. With five different types, four of which are reported for the first time, Rhynchanthera dichotoma is the species that presents the most diverse indumenta. A mixed type of trichome formed by a glandular and a branched non-glandular portion called "lateral-gland" was observed in M. ligustroides. Such non-glandular portion presents different degrees of development. A correlation is suggested between the stage of development of the non-glandular portion and the exposition to light of these "lateral gland" on young leaves.

Highlights

Melastomataceae is the largest family of Myrtales, with 166 genera and approximately 4,570 species, predominantly distributed in tropical and subtropical regions (Clausing & Renner 2001)
The analysis of the leaf surfaces of the species under study revealed the occurrence of 14 different morphological types of indumenta: Miconia albicans (Sw.) Triana
Trichomes were usually denser on the young leaves of all the species studied here

Summary

Introduction

Melastomataceae is the largest family of Myrtales, with 166 genera and approximately 4,570 species, predominantly distributed in tropical and subtropical regions (Clausing & Renner 2001). According to Wurdack (1986), Melastomataceae present the most diverse indumentum types among the angiosperms, even though only about 11% of the neotropical species have been studied. The type of indumentum and the morphology of trichomes are important to classify Melastomataceae and circumscribe their genera and species The distinction between the types of trichomes and the structure of the indumentum is not often clearly drawn in the literature. Such distinction is important in an ecological context because it is likely that environment has a greater influence on indumentum modifications than on changes in the type of trichome (Johnson 1975). Leaves developing in environments with high radiation tend to show high trichome density (Crawley 1997; Sandquist & Ehleringer 1997)

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