Androecium anatomy of Isertia laevis , a polysporangiate species of Rubiaceae
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ORIGINAL ARTICLE
Androecium anatomy of Isertia laevis, a polysporangiate species of Rubiaceae Marina D. Judkevich 1 & Roberto M. Salas 1,2 & Ana M. Gonzalez 1,3 Received: 25 September 2020 / Accepted: 28 October 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract In this study, we performed an anatomical analysis of the polysporangiate anthers and the development of pollen in Isertia laevis (Rubiaceae) with the aim to elucidate the internal structure of these atypical anthers. For this purpose, flowers in successive stages of development were dissected and the anthers were processed for conventional anatomical analysis. The material was examined using light microscopy and scanning electron microscopy. The present study shows that the anthers of Isertia laevis have two thecae divided into multiple microsporangia. This division is due to the presence of transverse and longitudinal septa formed of parenchyma and idioblasts with crystals. The septa appear together with the microsporangia and remain in the mature anther, even developing fibrous thickening. As the anther matures, the idioblasts in the septa accumulate crystals until they break, facilitating the separation of the septa from the outer wall of the theca, and thus apparently assisting the process of dehiscence. The mature anther opens through the longitudinal dehiscence of each theca. In addition to the anatomy of the anther, the development and morphology of the pollen, and the presence of orbicules are described. The structure of the anthers of I. laevis is discussed with other polysporangiate species in the Rubiaceae and angiosperms. Keywords Isertieae . Multiple sporangia . Pollen development . Structure
Introduction The stamens are the male reproductive parts of angiosperm flowers and are formed of the anther where the pollen is produced, and the filament, which is responsible for nourishing and supporting the anther (Scott et al. 2004). In this group of plants, the anthers generally have a uniform organization represented by two thecae joined by vascularized connective
Handling Editor: Benedikt Kost * Marina D. Judkevich [email protected] 1
Instituto de Botánica del Nordeste, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional del Nordeste, Sargento Cabral 2131, CC 209, 3400 Corrientes, Argentina
2
Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Av. Libertad 5279, CC 209, 3400 Corrientes, Argentina
3
Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Sargento Cabral 2131, CC 209, 3400 Corrientes, Argentina
tissue, each theca containing two sporangia in which the pollen develops (D’Arcy and Keating 1996). However, some species deviate from this pattern of organization and their flowers have anthers with a larger number of sporangia. These anthers are mentioned in the literature as follows: polysporangiate, septate, or multilocellate anthers (Robbrecht 1984; Kirkbride 1985; Tobe and Raven 1986; Sudhakaran et al. 1995; Baumgra
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