Pollen morphology and viability ofTillandsia(Bromeliaceae) species by light microscopy and scanning electron microscopy

Tillandsiais the bromeliad genus containing the largest number of species, with wide geographic dispersion and an important ecological role in the ecosystems. Investigations of pollen morphology are important to support taxonomic and conservation studies as well as to choose promising species for cross-pollination to obtain hybrids. The objective of this study was to evaluate the morphology, production, and viability of pollen grains of 24Tillandsiaspecies that naturally occur in the state of Bahia, Brazil. Pollen grains were acetolized and analyzed by scanning electron microscopy. The pollen were germinated in vitro in two culture media (BM and BKM) and collected at three floral development stages (pre-anthesis, anthesis and post-anthesis). Pollen viability also was analyzed by staining with Alexander's solution and acetocarmine in three floral development stages. Variations in the ornamentation and size of the pollen were observed among the species studied, with the majority having medium size, whileT. polystachiaandT. junceahad large grains and the subgeneraDiaphoranthemaandPhytarrhizahad small grains. The pollen of the majority of species had bilateral symmetry, with a single irregularly shaped colpus, semitectate exine and reticulated-heterobrochate surface. The pollen presented high germination percentage, tube length and viability according to the histochemistry, except forT. recurvata,T. usneoidesandT. loliacea. The BKM medium and collection of pollen during anthesis produced the best results for theTillandsiaspecies. The results can support studies of the taxonomy and conservation of these species, which have great environmental importance and high value for ornamental purposes.