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The present study describes the floral morphology and evaluates pollen viability for the bromeliad Nidularium minutum Mez. during the flowering period 2018‒2019 through histochemistry and pollen germination tests. The inflorescences are nidular, capituliform with short branches bearing two to three odourless, bisexual and greenish-white flowers and with an androecium shorter than the gynoecium, consisting of six stamens with anthers featuring rimose dehiscence. The ovules are anatropous, displaying a small appendage in the chalazal region. The first flower opened in late November 2018 and flowering peak was in January 2019. Anthesis started at 6:55 a.m. and lasted until 8:49 a.m. Pollen/ovule ratio indicates facultative autogamy. The pollen grains are monads, medium to large, 2-(3)-porate, reticulate heterobrochate with abundant pollenkitt. A high frequency of unviable pollen grains with discrepant sizes was observed. The mature pollen grain is considered recalcitrant and therefore sensitive to desiccation. In vitro pollen germination after 48 hours was higher in BKM medium (64.77%) compared to SM (38.51%). Pollen viability was overestimated in all histochemistry tests, with Alexander (72.46%) being the closest to the in vitro germination rate. The results obtained for N. minutum bring new information about its floral biology as a subsidy to the cultivation of ornamental bromeliads that are at risk of extinction. [ABSTRACT FROM AUTHOR]

This is the first study on pollen from Xyris complanata using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Pollen in various conditions, including acetolysed, hydrated, and dehydrated states, were examined. The results show that X. complanata plants disperse their pollen in a linear polyad, comprising a cohesive elongate uniplanar tetragonal tetrad aggregate, consisting of 4 to 10 tetrads per unit. The cohesion within and between tetrads is accomplished by means of the fusion of the tectum. The individual grains are medium in size, pollen grains of intermediary tetrad are quadrangular in both polar and equatorial views, pollen grains of apical tetrad are obovoid in shape, both are triangular in frontal equatorial view, exine 3.0 ± 0.2 μm thick, ulcerate covered with a fossulate–perforate operculum, and heterobrochate microreticulate–perforate sculpturings. Pollen wall consists of the tectum, columellae, footlayer, and endexine, with pollenkitt. The dispersal unit and apertural type are distinctive characters, since, among Xyris, such features can only be found in pollen of X. complanata. The results of the present study contribute useful characters for the systematic study of plants in the genus Xyris. [ABSTRACT FROM AUTHOR]

Poaceae pollen grains are notoriously difficult to use as a tool for eco-palynological studies due to their relatively uniform morphology. This article uses light and scanning electron microscopy to describe the pollen morphology of 31 species of Malagasy grasses, including 11 endemic species and seven endemic genera that are described here for the first time. Our ultimate goal is to use these data to differentiate between primary and secondary grasslands in Madagascar, which is of important conservation significance. Our data show some species differences that are promising for future identification of fossil grains. Pollen morphological details are imaged and discussed. [ABSTRACT FROM PUBLISHER]

Bromeliaceae possess several features of pollen and anther wall development that are plesiomorphic for Poales, consistent with their putatively basal or near-basal placement in this order. For example, successive microsporogenesis and the monocotyledonous type of anther wall formation are both plesiomorphic features that occur commonly in other Poales, with a few notable exceptions, notably the simultaneous type of microsporogenesis in Rapateaceae. The intermediate type of tapetum development in Bromeliaceae was probably derived secondarily from a secretory type, which occurs in most other Poales except Typhaceae. [ABSTRACT FROM AUTHOR]