Developmental morphology of Apinagia multibranchiata (Podostemaceae) from the Venezuelan Guyanas

Abstract

Apinagia (c. 50 spp.) is the largest genus of American Podostemaceae. Apinagia multibranchiata (Matth.) Royen is a haptophyte endemic to the Venezuelan Guyanas. It fits well with the Podostemoideae bauplan known from other New World genera, such as Marathrum and Mourera. Shoots arise in pairs from filamentous creeping adhesive roots. During the rainy season submerged vegetative shoots grow up to more than a metre long. They are normally unbranched and provided wihdistichously arranged leaves which are laterally flattened into one plane. The lanceolate leaves may show a fimbriate tip. Tufts of threads are found on the upper leaf surface which faces the sky. When the water recedes in December‐January, ascending reproductive shoots (up to 15 cm long) are formed which branch syrnpodially. The first module produces a variable number of leaves. Distal leaves are often double‐sheathed (dithecous). Their inner sheaths are fused into a tube that covers the first flower bud. Daughter modules arise from the outer sheaths of the distal leaves. These modules consisting of two double‐sheathed leaves and a flower are repeated giving rise to 2–15 stalked flowers. The flowers are entomophilous and provided with 6–29 pink stamens. Architecture and developmental morphology of A. multibranchiata are compared with other members of the genus.

Development of the floral shoot and pre-anthesis cleistogamy inHydrobryopsis sessilis(Podostemaceae)

“…erect, radial and actinomorphic) and polyandrous, i.e. they possess as many as 40 stamens in either one or two complete whorls or with meristic variation (Rutishauser & Grubert, 2000). In contrast, flowers of the Old World Podostemoideae are monosymmetric (i.e.…”

“…Although several investigations on floral morphology and diversity in Podostemaceae have been carried out (Willis, 1902a, b; Rutishauser & Huber, 1991; Jäger‐Zürn, 1997; Mathew & Satheesh, 1997; Rutishauser, 1997; Rutishauser et al. , 1999; Rutishauser & Grubert, 1999, 2000; Uniyal, 2001; Uniyal & Mohan Ram, 2001; Ameka, Pfeifer & Rutishauser, 2002; Jäger‐Zürn & Mathew, 2002; Rutishauser & Pfeifer, 2002; Ameka et al. , 2003), a coherent account on floral ontogeny, the development of essential organs, mode of pollination and breeding system is lacking.…”

“…, 2003), a coherent account on floral ontogeny, the development of essential organs, mode of pollination and breeding system is lacking. Some scientists have stated that the flowers of this family are entomophilous (Willis, 1902b; Sculthorpe, 1967; Grubert, 1974; Rutishauser, 1997; Rutishauser & Grubert, 2000; Okada & Kato, 2002), anemophilous (Willis, 1902b; Cook, 1988; Philbrick & Novelo, 1997; Rutishauser, 1997; Ameka et al. , 2002) or hydrophilous (Hall, 1972; Philbrick, 1984a).…”

Origin and development of the cryptic shoot meristem in Zeylanidium lichenoides (Podostemaceae)

“…The adventitious root creeps on the rock surface, forming adventitious shoots one after another. The root-bome shoots also lack obvious shoot apical meristems and show determinate growth (Hammond, 1936;Rutishauser and Grubert, 2000). Since Podostemaceae is sister to Hypericaceae with typical shoot architectures (Soltis et al, 2000;Savolainen et al, 2000;Ruhfei et al, 2011), the novel determinate shoot of Podostemoideae is likely to have evolved from the conventional shoot prevailing in Hypericaceae and other eudicots ( Fig.…”

“…IA;Kita and Kato, 2001;Cook and Rutishauser, 2007;Koi et al, 2012a). In Podostemoideae, the shoot is one of the most characteristic organs because it is determinate and devoid of an obvious apical meristem (Hammond, 1936;Rutishauser and Grubert, 2000;Imaichi et al, 2005;Koi et al, 2005). Investigating the genetic basis for the development and evolutionary process of the unique shoot 'Manuscript received 29 October 2012; revision accepted 22 January 2013.…”