Pollen morphology, viability, and stigma receptivity of Hohenbergia (Bromeliaceae) species occurring in the Atlantic forest biome with potential for landscaping and cut flowers

Abstract

Hohenbergia comprises 55 species, 53 of which are endemic to Brazil. Among these, 21 species are unique to Atlantic Forest fragments in the state of Bahia. Hohenbergia is a genus that has plants with landscaping and cut flower potential due to the attractive colors and durability of the inflorescences, easy adaptation, and management, among other features. Research on the floral and reproductive biology of these plants is crucial to understanding its taxonomy, conservation, and breeding. This study aimed to characterize the pollen and stigma morphology and assess pollen viability and stigma receptivity of seven Hohenbergia species with potential for landscaping and cut flowers. These evaluations were carried out using distinct methods at different stages of floral development, as they are innovative for these Hohenbergia species. For morphological analysis, pollen was examined using scanning electron microscopy and subjected to lactic acetolysis. Additionally, pollen viability was tested through in vitro germination and histochemical testing. We assessed stigma receptivity at various floral development stages. We also determined the amount of pollen grains for each species. All these species produced monad pollen, which were either heteropolar or isopolar, circular or elliptical, with various pore sizes, shapes, and number (bi- or triporate). These grains featured an ornamented aperture membrane and differences in the exine and its ornamentation. The stigmas of Hohenbergia species are conduplicate-spiral. Pollen demonstrated the highest viability at anthesis. Both methods for assessing stigma receptivity indicated increased enzyme activity at anthesis across all species. Our findings may contribute to taxonomy research of the genus and support further investigations on reproduction and conservation, as well as controlled crosses to obtain seeds for the ornamental plant market.