Extranuptial nectaries in bromeliads: a new record for Pitcairnia burchellii and perspectives for Bromeliaceae.

Nectar plays important roles in the relationship between plants and other organisms, both within pollination systems and as a defense mechanism. In the latter case, extranuptial nectaries (ENNs) usually attract patrolling arthropods that reduce herbivory. ENNs have been frequently reported within the "xeric clade" of Bromeliaceae, but their occurrence in other groups of bromeliads is largely unexplored, especially considering their position, secretory activity and structure. After observing the presence of ants constantly patrolling the inflorescences of Pitcairnia burchellii Mez, we searched for the presence, secretory activity, and structure of ENNs in this species. We also provide a brief review of the occurrence ENNs in Bromeliaceae. The distribution of nectaries was assessed using ant-exclusion experiments, while structural analysis was performed using standard methods for light and scanning electron microscopy. The presence of sugars in the secretion was assessed by thin-layer chromatography and glucose strip tests. Nectaries in P. burchelli are non-structured glands on the adaxial surface of floral bracts and sepals. Bracts and sepals are distinct spatial units that act over time in the same strategy of floral bud protection. Literature data reveals that ENNs might be more common within Bromeliaceae than previously considered, comprising a homoplastic feature in the family. Future perspectives and evolutionary and taxonomic implications are discussed.

Pollen morphology and viability in Bromeliaceae.

Pollen morphology characterization is important in taxonomy, conservation and plant breeding, and pollen viability studies can support breeding programs. This study investigated pollen morphology and male fertility in 18 species of Bromeliaceae with ornamental potential. For morphological characterization, pollen grains were acetolyzed and characterization of exine was done using scanning and transmission electron microscopy. Pollen viability was investigated by in vitro germination and histochemical tests. Species belonging to Aechmea and Ananas genera presented medium size pollen, except for Ae. fasciata, with large pollen. Al. nahoumii, P. sagenarius and the Vriesea species analyzed showed large pollen, except for V. carinata, with very large pollen. Pollen of Aechmea, Ananas and P. sagenarius presented bilateral symmetry, diporate, exine varying from tectate to semitectate. Al. nahoumii and Vriesea species presented pollen with bilateral symmetry, monocolpate; exine was semitectate, reticulate and heterobrochate. Germination percentage and tube growth were greater in SM and BKM media. Histochemical tests showed pollen viability above 70% for all species, except for Ananas sp. (40%). Pollen morphology is important for the identification of species, especially in this family, which contains a large number of species. High rates of viability favor fertilization and seed production, essential for efficient hybrid production and conservation.

Pollen morphology and viability in Bromeliaceae

ABSTRACT Pollen morphology characterization is important in taxonomy, conservation and plant breeding, and pollen viability studies can support breeding programs. This study investigated pollen morphology and male fertility in 18 species of Bromeliaceae with ornamental potential. For morphological characterization, pollen grains were acetolyzed and characterization of exine was done using scanning and transmission electron microscopy. Pollen viability was investigated by in vitro germination and histochemical tests. Species belonging to Aechmea and Ananas genera presented medium size pollen, except for Ae. fasciata, with large pollen. Al. nahoumii, P. sagenarius and the Vriesea species analyzed showed large pollen, except for V. carinata, with very large pollen. Pollen of Aechmea, Ananas and P. sagenarius presented bilateral symmetry, diporate, exine varying from tectate to semitectate. Al. nahoumii and Vriesea species presented pollen with bilateral symmetry, monocolpate; exine was semitectate, reticulate and heterobrochate. Germination percentage and tube growth were greater in SM and BKM media. Histochemical tests showed pollen viability above 70% for all species, except for Ananas sp. (40%). Pollen morphology is important for the identification of species, especially in this family, which contains a large number of species. High rates of viability favor fertilization and seed production, essential for efficient hybrid production and conservation.

Morpho-histodifferentiation of Billbergia Thunb. (Bromeliaceae) nodular cultures.

Nodule cultures are formed through an intermediate morphogenetic route that lies between organogenesis and somatic embryogenesis. Although well described in many species, different aspects of the morphological and histological development of nodules remain to be clarified. Based on their threatened status and high ornamental value, Billbergia alfonsi-joannis and Billbergia zebrina, two epiphytic bromeliad species endemic to the South American Atlantic Forest, were studied. Nodular cultures were induced to grow from nodal segments taken from etiolated seedlings grown in vitro for 12 weeks in the dark on MS medium supplemented with 1 µM TDZ. Samples were taken for analysis weekly over 8 weeks of growth and analyzed under light, transmission electron, and scanning electron microscopes. Morphological and histological analysis showed that nodular clusters originated from stem pericycles and consisted of a polycenter, cambial tissue, cortical parenchyma, and a covering tissue. The polycenter consisted of an organizational center dispersed in parenchymal tissue. Each organizational center was formed by a vascular system surrounded by a bundle sheath. A cambial tissue surrounded these polycenters, promoting the regeneration of new nodules and leading to the formation of buds and roots. Primary nodules could generate secondary nodules in a repetitive process. Thus, histological analysis revealed the origin and formation of nodular cultures. These new data will support the establishment of micropropagation protocols and regeneration on a large scale for these species.

Leaf epidermis of the rheophyte Dyckia brevifolia Baker (Bromeliaceae).

Some species of Dyckia Schult. f., including Dyckia brevifolia Baker, are rheophytes that live in the fast-moving water currents of streams and rivers which are subject to frequent flooding, but also period of low water. This study aimed to analyze the leaf epidermis of D. brevifolia in the context of epidermal adaptation to this aquatic plant's rheophytic habitat. The epidermis is uniseriate, and the cuticle is thickened. The inner periclinal and anticlinal walls of the epidermal cells are thickened and lignified. Stomata are tetracytic, located in the depressions in relation to the surrounding epidermal cells, and covered by peltate trichomes. While the epidermal characteristics of D. brevifolia are similar to those of Bromeliaceae species, this species has made particular adaptations of leaf epidermis in response to its rheophytic environment.

Candida bromeliacearum sp. nov. and Candida ubatubensis sp. nov., two yeast species isolated from the water tanks of Canistropsis seidelii (Bromeliaceae).

Strains belonging to two novel yeast species, Candida bromeliacearum and Candida ubatubensis, were isolated from the bromeliad tank of Canistropsis seidelii (Bromeliaceae) in a sandy coastal plain (restinga) ecosystem site in an Atlantic rainforest of south-eastern Brazil. These species were genetically distinct from all other currently accepted ascomycetous yeasts, based on sequence divergence in the D1/D2 domains of the large-subunit rDNA and in the small-subunit rDNA. The species occupy basal positions in the Metschnikowiaceae clade. The type strains are Candida bromeliacearum UNESP 00-103(T) (=CBS 10002(T)=NRRL Y-27811(T)) and Candida ubatubensis UNESP 01-247R(T) (=CBS 10003(T)=NRRL Y-27812(T)).