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Parietaria debilis G. Forst. is gynomonoecious, which is a rare condition in the Urticaceae family and among angiosperms. Apetalous flowers of two different morph types (monoclinous, pistillate) occur in the same inflorescence and are reduced in size and in the number of whorls and of organs per whorl. The objective of this study was to compare the morphogenesis of monoclinous and pistillate flowers to determine whether the monoclinous flowers produce fertile gametophytes, and elucidate the pathways leading to the absence of stamens and to the changes in number of whorls and organs per whorl. Flower buds and flowers (non-fertilized, fertilized) were processed for surface and anatomical studies. Pollen ultrastructure and viability were determined. Inflorescences with fertilized flowers were checked for the presence and location of fruits/viable seeds. The monoclinous flower has four sepals, four stamens, and a uniovulate pseudomonomerous gynoecium. In the pistillate flower, the stamens are absent or, rarely, aborted. No petals are formed. The gynoecium is pseudomonomerous, originated as a central primordium that differentiates into two carpels, but only one develops and houses an ovule. Monoclinous and pistillate flowers produce viable seeds. Thus, our data confirmed that this species is indeed gynomonoecious. [ABSTRACT FROM AUTHOR]

The six distinct gland types described in Mimosoideae anthers vary from simple projections to robust and vascularized structures. The origin of these glands is attributed to an extension of connective. However, except for an illustrative recording of some developmental stages, nothing is known about the origin and gland development, which prevents their correct classification. This study aimed to elucidate the ontogeny of four of the six gland types detected in the anthers of Mimosoideae. The intention was to understand whether the morphological diversity results from different ontogenetic processes. For this, flower buds of various sizes of four Mimosoideae species with different types of glands were collected : Stryphnodendron adstringens (Piptadenia subtype Piptadenia), Tetrapleura tetraptera (Piptadenia subtype Adenanthera), Adenanthera pavonina (Piptadenia subtype Entada), and Pentaclethra macroloba (Pentaclethra type). The samples were processed for surface (scanning electron microscopy) and anatomical analyses (light microscopy). Despite their morphological differences, the glands share a common meristematic origin. They arise from simultaneous divisions in the first three layers of meristematic cells that cover the apical portion of the young anther. After the formation of the protuberance, the developing glands undergo different specialized processes that include (1) elongation of the epidermal cells in Piptadenia subtype Adenanthera and Piptadenia subtype Entada, (2) degradation of central gland cells in Piptadenia subtype Entada, (3) change from a rounded to a triangular shape in the Pentaclethra type, and (4) cell differentiation into a procambial meristem and subsequently into vascular tissue in the Pentaclethra type, resulting in the diversity encountered in the group. Their origin from protodermal and fundamental meristem cells characterizes the anther glands as emergences. Our data indicate a conserved meristematic origin of glands, favoring the hypothesis of homology of these structures and supporting the monophyly of the Mimosoideae clade. [ABSTRACT FROM AUTHOR]

Premise of research. This study compares the development of staminate and hermaphrodite flowers of Parkia multijuga and Stryphnodendron adstringens, two andromonoecious mimosoid trees, in order to determine whether diclinous flowers result from the same developmental processes. The issues involving the interesting structure of the perianth were also addressed. Methodology. Flowers and flower buds of various sizes were processed for surface and histological observations. Pivotal results. Five sepal primordia emerge in the floral meristem from the abaxial side in a sequential order in P. multijuga and from the adaxial side of the flower in a modified helical order in S. adstringens. Five petal primordia initiated simultaneously in P. multijuga and S. adstringens. The carpel primordium initiates concomitantly with five antesepalous stamen primordia in P. multijuga and after petal elongation in S. adstringens. All connections among floral organs in P. multijuga (gamosepaly, gamopetaly, epipetaly, and staminal tube) and S. adstringens (gamosepaly and gamopetaly) are postgenital. A sixth sepal primordium found in some S. adstringens flowers is formed late in the development. Early ontogenetic stages are similar between hermaphrodite and staminate flowers of both species, and only in middevelopmental stages does the carpel primordium stop elongating; no ovule, style, or stigma is formed, leaving only a small carpellodium in the center of the staminate flowers. Conclusions. Our ontogenetic studies show that carpel abortion, not carpel absence from inception, results in staminate flowers in two andromonoecious legumes. [ABSTRACT FROM AUTHOR]

The presence of mucilage cells in plants, studied mainly in vegetative organs, is a condition shared by several taxonomic groups and aspects related to their diversity have been discussed with systematic purposes. This study explores the flower distribution and classification of mucilage cells in Rosales species, with inferences about flower functions. Floral buds from fifty-seven species representing seven of nine families recognized in the Rosales were sampled and processed for light and transmission electron microscopy. Mucilage cells were found in about 40% of the studied species of Cannabaceae, Rhamnaceae, Ulmaceae, and Urticaceae families, whereas no floral mucilage cells were found in species of Elaeagnaceae, Moraceae, and Rosaceae. Mucilage cells were found in the epidermis and internal tissues of many organs of different floral morph types. There is a great diversity of forms of presentation of mucilage in cells, from smaller individualized single cells to very bulky cells and to completely filled mucilage reservoirs. In some cases, cells with mucilage apparently in the cell wall and others with mucilage in the vacuole seem to occur side by side. This diversity challenges the existing classifications of mucilage cells and reinforces the importance of ontogenetic and ultrastructural studies following the path of mucilage in cells in order to propose a more natural classification and to elucidate the evolution of mucilage cells in plants. [ABSTRACT FROM AUTHOR]