Pseudobulbs are bulb-like enlargement stems present in many genera of Orchidaceae (Asparagales), described in the literature as reserve organs, especially for water, which help these plants to survive in epiphytic environments. Pseudobulbs have a predominance in the subfamily Epidendroideae, mainly in epiphytic orchid and with sympodial growth. Recent studies in Orchidaceae focus on systematic features, and the few studies on anatomical organization are only descriptive. There is a scarcity of studies focused on developmental anatomy, and questions such as mechanisms related to pseudobulb ontogenesis in the family remain unanswered. In Orchidaceae two morphological patterns of pseudobulbs are recognized: one with a well-marked node and internode (compound pseudobulb), and the other as a large internode (simple pseudobulb). For this study we selected the three species of Isabelia Barb.Rodr. that present simple pseudobulb (Isabelia virginalis Barb.Rodr, Isabelia pulchella (Kraenzl.) Van den Berg & M.W.Chase and Isabelia violacea (Lindl.) Van den Berg & M.W.Chase) and aiming to compare with a compound pseudobulb of Pseudolaelia vellozicola (Hoehne) Porto & Brade, which is a phylogenetically close representative of Isabelia. The objectives of the work are: 1) to understand the development of the two morphological patterns of pseudobulbs in Orchidaceae and 2) to analyze the nature of the pseudobulb considering the possibility of being a swelling of the stem axis, as described in the literature, or a structure formed from the development of the leaf constitutive base. For this, the collected material will be submitted to plant anatomy techniques. In light microscopy, serial sections will be made at different stages of pseudobulb development. Shoot apices will be submitted to scanning electron microscopy to observe the stages of leaf primordia. Results are expected to clarify the ontogeny of pseudobulbs, elucidating questions about their origin.
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