Anatomia caulinar e foliar de Pilea peperomioides Diels (Urticaceae) com ênfase nas suas estruturas secretoras
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2024-12-05
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Universidade Federal de Goiás
Resumo
Pilea peperomioides, commonly known as the "Chinese money plant," is native to China but is
commercially cultivated in Brazil due to its ornamental appeal. Given the scarcity of anatomical
studies on this species, the present research aimed to anatomically characterize the stem and leaf of
Pilea peperomioides, with an emphasis on its secretory structures, contributing to taxonomic and
ecological studies on the species. Botanical material was obtained from floriculture shops, and two
individuals were used. Samples of the leaf blade, petiole, and stem were fixed in FAA 50. After
embedding in Paraplast, the leaf blade and petiole samples were sectioned using a rotary
microtome. Hand sections were performed on the leaf blade for epidermis analysis and on the stem.
Paradermal sections of the leaf blade were stained with safranin, while transverse sections of the
blade, petiole, and stem were subjected to double staining with safranin and Astra blue or basic
fuchsin and Astra blue in tartaric acid. Semi-permanent slides were mounted in glycerin, and
permanent slides were mounted in glass varnish. The leaf is epistomatic, with anisocytic stomata.
In the leaf blade, the epidermis is uniseriate; stomata, lithocysts, and trichomes occur on the
adaxial surface and are positioned at the same level as the epidermal cells. The chlorophyllous
parenchyma is concentrated on the adaxial side, while the abaxial side has several layers of
water-storage hypodermis. The vascular system is composed of collateral vascular bundles. The
midrib has a plano-convex contour with a single collateral vascular bundle shaped like an open
arch; lithocysts occur sporadically on the most convex portion of the contour. The petiole has arounded contour with a uniseriate epidermis. Lithocysts are observed in transverse sections with
spherical cystoliths. Internally, there are two to three layers of collenchyma, followed by several
layers of filling parenchyma. The stem has a rounded contour and exhibits secondary growth. The
epidermis is uniseriate, with spherical cystoliths. Beneath the epidermis, periderm formation
occurs, followed by five to six layers of angular collenchyma. The cortex and medullary cells store
starch, which is abundant in the medulla. The secretory system consists of hydathodes, trichomes,
and secretory sacs. Hydathodes are distributed throughout the abaxial surface of the leaf blade,
forming depressions in the epidermis. Glandular trichomes, scattered on the adaxial surface of the
leaf, are peltate, consisting of a basal cell, a short stalk, and a multicellular head. Secretory sacs are
associated with larger vascular bundles in the interveinal regions, the central vein, the leaf margin,
and the petiole, where they occur adjacent to vascular bundles. In the stem, secretory sacs are
distributed in the cortex and medulla, the latter located near the primary xylem. Longitudinal
sections of the stem revealed that these cavities have an elongated lumen and can therefore be
classified as secretory ducts. P. peperomioides exhibits anatomical characteristics already described
for Urticaceae and the genus Pilea. This study provides a detailed characterization of the
hydathodes in P. peperomioides, an aspect that had not been previously investigated. Additionally,
the species has anatomical features associated with adaptation to the mountainous and humid
environments where it naturally occurs.
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Anatomia, Cistólitos, Bolsas secretoras, Hidatódios, Tricoma peltado, Anatomy, Cystoliths, Secretory sacs, Hydathodes, Peltate trichome
Citação
CANTUARIO, Nathalia Ferreira. Anatomia caulinar e foliar de
Pilea peperomioides Diels (Urticaceae) com ênfase nas suas
estruturas secretoras. 2024. 27 f. Trabalho de Conclusão de Curso
(Bacharelado em Ciências Biológicas) - Instituto de Ciências
Biológicas, Universidade Federal de Goiás, Goiânia, 2024.