Synflorescence morphology of species of Typha L. (Typhaceae): anatomical and ontogenetic bases for taxonomic applications

Jordano Dorval Tavares De Carvalho,Jorge Ernesto De Araujo Mariath

doi:10.1590/0102-33062019abb0140

Jordano Dorval Tavares De Carvalho, Jorge Ernesto De Araujo Mariath

Open Access

https://doi.org/10.1590/0102-33062019abb0140

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Abstract

The inflorescence of plants of the genus Typha L. consists of a polytelic system with the fertile region containing staminate flowers in the terminal portion and pistillate flowers in the basal portion. Although some useful morphological information has been provided to characterize species of the genus, various divergent typologies have arisen due to mistaken interpretations that ignore the different degrees of branching in this indeterminate system. The present study aimed to identify structural homologies by comparing the morphology and ontogeny of the synflorescences of Typha domingensis, T. latifolia and their putative hybrid, T. x provincialis, using standard micro-techniques for light and electron microscopy. Analysis revealed that the synflorescence of species of Typha should be considered a homothetic triple raceme. New diagnostic characters are proposed for both the pistillate and staminate portions. Differences among the apices of the pistillate portions are compared for the first time, and mainly involve the rate of lengthening of the second order branch, which is species specific. The data and interpretations proposed in this study should serve as a basis for proposing homologies for different structures of the synflorescences of species of Typha.

Highlights

The genus Typha contains 10 to 15 species of aquatic plants that are characterized mainly by their cylindrical synflorescences with thousands of diclinous flowers packed in a terminal fertile zone subtended by a long peduncle
The analyzed species of Typha have polytelic synflorescences with a cylindrical, narrow peduncle, which subtends the fertile region of the synflorescence up to 2m, with its height sometimes reaching over the nomophiles (Fig. 1A-D)
Anthesis of staminate flowers is perceptible in T. latifolia (Fig. 1B) due to the sudden lengthening of the filaments (Fig. 1H)

Summary

Introduction

The genus Typha contains 10 to 15 species of aquatic plants that are characterized mainly by their cylindrical synflorescences with thousands of diclinous flowers packed in a terminal fertile zone subtended by a long peduncle. Some species of Typha possess an apparent gap without flowers or branches between the staminate portion and the pistillate portion of the synflorescences, such as with Typha domingensis, T. angustifolia and T. minima This gap is a common diagnostic characteristic for species, it is recurrently variable in populations, mainly due to the presence of hybrids or intraspecific variation (Kim & Choi 2011). Besides this morphology, other characteristics of synflorescences are used for taxonomic purposes, such as the color of the surface of the pistillate portion, the presence of bracteoles and the proportion of the pistillate portion in relation to the staminate portion in the fertile region. These characteristics are considered stable in some infrageneric clades, but extremely variable if hybrids and phenotypic variation among populations is considered, which makes it difficult to identify most of the species and established hybrids (notospecies) (Kim & Choi 2011)

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