Abstract
Connarus suberosus is a typical species of the Brazilian Cerrado biome, and its inflorescences and young vegetative branches are densely covered by dendritic trichomes. The objective of this study was to report the occurrence of a previously undescribed glandular trichome of this species. The localization, origin and structure of these trichomes were investigated under light, transmission and scanning electron microscopy. Collections were made throughout the year, from five adult specimens of Connarus suberosus near Botucatu, São Paulo, Brazil, including vegetative and reproductive apices, leaves and fruits in different developmental stages, as well as floral buds and flowers at anthesis. Glandular trichomes (GTs) occurred on vegetative and reproductive organs during their juvenile stages. The GTs consisted of a uniseriate, multicellular peduncle, whose cells contain phenolic compounds, as well as a multicellular glandular portion that accumulates lipids. The glandular cell has thin wall, dense cytoplasm (with many mitochondria, plastids and dictyosomes), and a large nucleus with a visible nucleolus. The starch present in the plastids was hydrolyzed during the synthesis phase, reducing the density of the plastid stroma. Some plastids were fused to vacuoles, and some evidence suggested the conversion of plastids into vacuoles. During the final activity stages of the GTs, a darkening of the protoplasm was observed in some of the glandular cells, as a programmed cell death; afterwards, became caducous. The GTs in C. suberosus had a temporal restriction, being limited to the juvenile phase of the organs. Their presence on the exposed surfaces of developing organs and the chemical nature of the reserve products, suggest that these structures are food bodies. Field observations and detailed studies of plant-environment interactions, as well as chemical analysis of the reserve compounds, are still necessary to confirm the role of these GTs as feeding rewards.
Highlights
The family Connaraceae comprises 12 genera and from 110 to 200 arboreal, shrub, or vine species that are widely distributed in tropical regions
Glandular trichomes, consisting of an uniseriate multicellular peduncle and a multicellular secretory portion that is generally very colorful, are found in Cnestis, Connarus, Jollydora, Manotes, and Rourea; a second type of unicellular glandular trichome is characteristic of Manotes
Glandular trichomes (GTs) are encountered in the midst of dendritic trichomes (Fig. 1A-C) that lend a rusty-tomentose aspect to the indument
Summary
The family Connaraceae comprises 12 genera and from 110 to 200 arboreal, shrub, or vine species that are widely distributed in tropical regions. Jongkind (1989) identified six types of trichomes in paleotropical members of the Connaraceae, of which two were glandular According to this author, glandular trichomes, consisting of an uniseriate multicellular peduncle and a multicellular secretory portion that is generally very colorful, are found in Cnestis, Connarus, Jollydora, Manotes, and Rourea; a second type of unicellular glandular trichome is characteristic of Manotes. Glandular trichomes, consisting of an uniseriate multicellular peduncle and a multicellular secretory portion that is generally very colorful, are found in Cnestis, Connarus, Jollydora, Manotes, and Rourea; a second type of unicellular glandular trichome is characteristic of Manotes In these genera, the distribution of GTs is essentially limited to the stem axes and floral organs. Glandular trichomes have been observed on the endocarp of paleo and neotropical species of Connarus (Dickison 1971, Corner 1976, Forero 1983, Jongkind 1989)
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