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VERVAEKE, * E. PARTON, R. DEROOSE, AND M.P. DE PROFT Department of Applied Plant Sciences, Laboratory of Plant Culture, Catholic University of Leuven, W. De Croylaan 42, B-3001 Heverlee, Belgium. E-mail: [email protected] ABSTRACT. The authors determined morphometric data of different floral features and in vitro pollen germination of six cultivars representing four genera and two subfamilies of Bromeliaceae. Important floral characteristics for plant breeding are pollen germination and style length. Pollen viability was for all cultivars more than 40% and high enough for successful pollination. Stylar length varied much for the different cultivars. Scanning electron microscopy (SEM) was used to examine important flower character­ istics. The pollen of Aechmea Jasciata were biporate, and those of Tillandsia cyanea, Vriesea X vimimalis­ rex X carinata and V. splendens were monosulcate. Pollen grains of A. chantinii and Guzmania lingulata were inaperturate. The exine layers of all taxa were reticulate in structure with the exception of A. chantinii, which was smooth. Four stigma types were detected: convolute-blade, conduplicate-spiral, simple-erect, and coralliform. Petal appendages of Vriesea were tongue-like and absent in G. lingulata and T. cyanea. Aechmea Jasciata and A. chantinii had complex petal appendages. Ovules of all cultivars possessed char­ acteristic chalazal appendages. Key words: Bromeliaceae, ovary, ovules, petal appendages, pollen, stigma INTRODUCTION dium amount of specialized glandular cells, the papillae (Heslop-Harrison & Shivanna 1977, Bromeliaceae are predominantly neotropical Knox et al. 1986). epiphytic herbs or terrestrial xerophytes com­ Brown and Gilmartin (1989) studied more prising about 62 genera and 2800 species (Smith than 400 Bromeliaceae for stigma morphology. & Downs 1974, Benzing 1980, W. Till unpubl. Five types account for all known variation. data). Bromeliads tend to be ornamental and are Small paired or single outgrowths from the base easy to cultivate. In spite of the size of the fam­ of each petal, known as petal appendages are ily and its horticultural importance, little is common in Bromeliaceae and are most probably known about the floral architecture and repro­ involved in intrafloral nectar management (e.g., ductive biology (Gilmartin & Brown 1986, nectar retention, presentation, and delivery) Benzing 2000). The family is traditionally divid­ (Brown & Terry 1992). An important taxonomic ed into three subfamilies: Pitcaimioideae, Til­ aspect is pollen grain appearance (Halbritter landsioideae, and Bromelioideae (Smith & 1992). The most significant diagnostic features Downs 1974, 1977, 1979). Pitcaimioideae and of pollen grains are their size, shape, apertures Tillandsioideae have mostly hypogenous flow­ (germination pores), and exine surface structure ers, and the fruits are capsules. Bromelioideae (Shivanna & Rangaswamy 1992). Pollen viabil­ have epigenous flowers and baccate fruits ity indicates the ability of the pollen grain to (Benzing 1980, Dahlgren et al. 1985). The flow­ deliver sperm cells to the embryo sac following er structure of bromeliads is neither primitive compatible pollination (Shivanna et al. 1991, nor highly evolved. The flowers are mostly bi­ 1997). Tests for germination capacity and nor­ sexual and basically three-parted; there is a mal pollen tube growth on in vitro media pro­ three-chambered ovary topped by a style with a vide a direct and reliable assessment of viability three-lobed stigma. Three petals alternate with (Heslop-Harrison et al. 1984). Pollen of many an equal number of smaller sepals. The six sta­ plant species, typically binucleate pollen, ger­ men (usually) are positioned in two whorls of minates and grows well in culture. Bromeliaceae three each (Benzing 1980, 2000). Bromeliads, have binucleate pollen (Brewbaker 1967, Johri like most monocots have a hollow (open) style. et al. 1992). The ovules are anatropous, bitegmic, and cras­ The goal of this study was to present a survey sinucellate with the micropyle formed by the in­ on flower characteristics: morphometric data, ner integument (Davis 1966, Johrl et al. 1992). stigma type, papillae, petal appendages, pollen Bromeliads have wet stigmas with a low to me- grain, and ovule morphology of six economical­ ly and horticulturally important cultivars. Most * Corresponding author. studies on bromeliad flower morphology deal 78 VERVAEKE ET AL.: BROMELIAD FLOWER BIOLOGY I 79 TABLE 1. Flower characteristics at anthesis of Aechmea jasciata (AP), Aechmea chantinii (AC), Vriesea X vimimalis-rex X carinata (VMC), Vriesea splendens (VS), Guzmania lingulata (GL), and Tillandsia cyanea (TC). Plant AF AC VMC VS GL TC Length (cm) Bract 6.1 ± 0.6 0.9 ± 0.1 4.0 ± 0.3 6.3 ± 0.2 5.1 ± 0.3 Sepal 2.5 ± 0.1 1.7 ± 0.1 3.0 ± 0.2 2.4 ±