Pollen morphology and viability of Lymania (Bromeliaceae) species with ornamental potential

The genus Lymania belongs to the Bromeliaceae family and currently has ten endemic species in Northeast Brazil, restricted to the Atlantic Forest domain, the vast majority threatened with extinction and with ornamental potential. Studies of pollen morphology and viability provide important information for taxonomic, reproductive, and species conservation. The aim of this study was to evaluate the morphology and viability of pollen grains of nine threatened Lymania species endemic to the Northeast region of Brazil and with ornamental potential. Pollen morphological characters were observed using Scanning Electron Microscopy (SEM) and Light Microscopy (LM). For the histochemical tests, two dyes were used: Alexander's solution and fluorescein diacetate, at three stages of floral development (pre-anthesis, anthesis, and post-anthesis). The pollen grains collected in these stages were germinated in vitro in two culture media (BM and SM). We observed that all species have monad pollen grains except for L. languida, with medium-sized grains arranged in tetrads, with oblate to suboblate shape, bilateral symmetry, triporate or biporate, semitectate or eutectate exine and reticulate-heterobrochate, psilate or perforate ornamentation. Most Lymania species showed higher germination percentage, pollen tube growth and viability when pollen was collected at anthesis. The SM culture medium and the pollen grain sampling at the floral anthesis stage were the most suitable for the Lymania species. Our investigation of the structure of pollen grains and pollen viability of these species provides important data for taxonomy, as well as for controlled crosses, obtaining seeds, or conservation trials, especially regarding threatened species.