Pollen grain morphology and the characterization of additional structures related to pollen dispersion can help to understand the strategies presented by species as well as their taxonomic ...circumscription. This work investigates the morphology of pollen grains and orbicules of Cedrela fissilis Vell. and Cedrela odorata L., two threatened species of the genus Cedrela P. Browne (Meliaceae A. Juss.) in Brazil. Observations of pollen grains and orbicules of the species were carried out pre- and post-chemical treatment of the samples, under light and scanning electron microscopy, aiming at recognizing structures, detailing morphological characterizations and taking measurements, the last of which were submitted to statistical treatment. The results demonstrate that the pollen grains of the two species are medium in size (measuring between 25 and 50µm), radially symmetrical, isopolar, prolate-spheroidal and 4,5-colporate with subcircular to subquadrangular amb and psilate ornamentation; the orbicules also have a smooth surface and measure about 7 to 10µm. Variation was observed in the size of pollen grains, which presented high coefficient of variation and in the orbicules, as well as in the number of apertures.
Oncophoraceae are acrocarpous mosses that predominantly grow as tufts or cushions and especially occur on rocks and soil. The recognition of Oncophoraceae as a distinct family, as well as its generic ...circumscription, is not consensus among authors, and the pursuit for new information to improve its characterization is incessant. The present work aims to characterize the spore morphology and ultrastructure of 19 species (eight genera) occurring in the Americas and to evaluate the relevance of palynological data to circumscribe species, contributing to support other palynological studies. Observations were performed under Light and Electron (Scanning and Transmission) Microscopes. A Cluster Analysis was performed in order to evaluate the meaning of the palynological data, especially concerning the establishment of the species circumscription. Spores are monads, small to medium sized (10.40 to 44.20 μm), radially symmetric, subcircular in amb, heteropolar or apolar; the surface is ornamented by granules, gemmae and bacula. Anisomorphic spores were observed in eight studied species and are reported herein for the first time. The Cluster Analysis shows two groups with low similarity, which primarily differ by the polarity of the spores. The circumscription of Kiaeria and Cynodontium is corroborated by palynological characterization and endorsed by Cluster Analysis.
Water scarcity, a common stress factor, negatively impacts plant performance. Strategies to cope with it, such as desiccation tolerance, are becoming increasingly important to investigate. However, ...phenomena, such as intraspecific variation in stress responses have not received much attention. Knowledge of this variability and the environmental drivers can be leveraged to further investigate the mechanisms of desiccation tolerance. Here we tested for variation in desiccation tolerance in
among colonies and sexes within the same riparian zone. Field-collected dehardened plants were subjected to a desiccation event, under controlled conditions and then rehydrated. Plant water status, photosynthetic rates, net carbon gain, and efficiency of photosystem II (PSII) were assayed to evaluate tissue desiccation, basic metabolic processes and plant recovery. To establish a linkage between plant response and environmental factors, field light conditions were measured. We detected intraspecific variation, where a more exposed colony (high percentage of open sky, large temporal range of light quantity, and high red/far-red ratio) showed sex differences in desiccation tolerance and recovery. Overall, PSII recovery occurred by 72 h after rehydration, with a positive carbon gain occurring by day 30. This within species variation suggests plastic or genetic effects, and likely association with light conditions.
Pollen grain morphology of Bromeliaceae species collected in areas of the Atlantic Rainforest of southeastern Brazil was studied. The following species were analyzed: Aechmea bambusoides L.B.Sm. & ...Reitz, A. nudicaulis (L.) Griseb., A. ramosa Mart. ex Schult.f., Ananas bracteatus (Lindl.) Schult.f., Billbergia distachia (Vell.) Mez, B. euphemiae E. Morren, B. horrida Regel, B. zebrina (Herb.) Lindl., Portea petropolitana (Wawra) Mez, Pitcairnia flammea Lindl., Quesnelia indecora Mez, Tillandsia polystachia (L.) L., T. stricta Sol., T. gardneri Lindl., T. geminiflora Brongn. and Vriesea grandiflora Leme. Light and scanning electron microscopy were used and the species were grouped into three pollen types, organized according to aperture characteristics: Type I - pantoporate pollen grains observed in P. petropolitana, Type II - 2-porate pollen grains, observed in the genera Ananas, Aechmea and Quesnelia, and Type III - 1-colpate pollen grains, observed in the genera Billbergia, Pitcairnia, Tillandsia and Vriesea. Pollen data led to the construction of an identification key. The results showed that the species analyzed can be distinguished using mainly aperture features and exine ornamentation, and that these characteristics may assist in taxonomic studies of the family.
Spores from 19 species of the subgenus Aloma Kindb. of the moss genus Fissidens were analyzed by light and scanning electron microscopy. Aloma is the largest subgenus of Fissidentaceae and is ...characterized by the presence of a peristome of scariosus type. The spores of the subgenus Aloma are present in monads, size small to very small, heteropolar, plano-convex, with a proximal aperture region, and the sporoderm is formed by a perine, exine, and intine. The intine is not stratified, the exine is psilate, and the perine granulated. The ornamentation elements may occur singly or grouped on the surface of the spore. The aperture region shows irregular contours, ranging from circular to elongated, due to the weakness of the sporoderm proximal pole. The observed variations among species are related to different patterns of distribution of the sporoderm granules and nanogranules. Quantitative analysis combined with qualitative results did not allow all species of the subgenus Aloma to be distinguished. The results of this study demonstrate that the spore is a useful tool for taxonomic studies, and suggest that its characters be included in phylogenetic analyses, to assist in the reconstruction of the evolutionary history of mosses.
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