Comparative Embryology of Angiosperms

Abstract

AINtrgct. Attention has been drawn to selected examples of unusual features in the embryology of angiosperms. The study of reproductive processes through raicrocinematography reveals sequentiai stages in living material which add a new dimension to our investigations.

Ovule ontogeny of Tabebuia pulcherrima Sandwith (Bignoniaceae): embryo sac development

“…In all the species investigated by Mauritzon (1935) and in Bignonia megapotamica (Swamy 1941), Kigelia pinnata (Govindu 1950), Oroxilum indicum (Ghatak 1956) and Tabebuia ochracea (Bittencourt Jr. 1992) the antipodals are ephemeral, degenerating soon after cellularization of the embryo sac. However, in the species studied by Mehra & Kulkarni (1985), as well as in Jacaranda mimosifolia, Parmentiera cerifera, Tecoma stans (Johri et al 1992) and in the species presented here, the antipodals persist until the first developmental stages of the endosperm. The high cytoplasmatic density and the conspicuous nucleoli in the antipodals of Tabebuia pulcherrima suggest a strong metabolic activity, which is usually associated with the functions of translocation and secretion sometimes attributed to these cells (Jensen 1972, Kapil & Bhatnagar 1981, Tilton & Lersten 1981, Willemse & van Went 1984, Mansfield et al 1991.…”

“…Only the distal portion of the synergid lateral walls is in direct contact with the embryo sac envelope (synergids and egg cell are hooked). Such features were also observed in the synergids of other Bignoniaceae (Mauritzon 1935, Swamy 1941, Govindu 1950, Gathak 1956, Davis 1966, Mehra & Kulkarni 1985, Johri et al 1992. The shape of the egg cell is similar to the synergids, but in Tabebuia rosea, Stereospermum chelonoides and Dolichandrone falcata a spherical shape for the egg cell was reported (Mehra & Kulkarni 1985).…”

“…Subsequent studies were performed in Bignonia venusta (= Pirostegia venusta) (Duggar 1899), Bignonia tweediana, B. bungei, Campsis radicans, C. chinensis, Catalpa bignonioides, Crescentia macrophylla, Incarvillea olgae, Jacaranda mimosifolia, Phaedrantyus sp., Tecoma sambucifolia (Mauritzon 1935), Bignonia megapotamica (Swamy 1941), Jacaranda mimosifolia, Parmentiera cereifera, Kigelia pinnata, Tecoma stans (Govindu 1950), Oroxilum indicum (Ghatak 1956), Tabebuia rosea, Millingtonia hortensis, Dolichandrone falcata, Heterophragma adenophylum, Stereospermum chelonoides (Mehra & Kulkarni 1985) and Tabebuia ochracea (Bittencourt Jr. 1992). Schnarf (1931), Davis (1966) and Johri et al (1992) organized taxonomically the existing literature.…”

Poliembrionia e aspectos da embriogênese em Tabebuia ochracea (Chamisso) Standley (Bignoniaceae)

“…Os tipos de embriogenia para dicotiledôneas diferem-se quanto aos planos das primeiras divisões do zigoto e quanto à sua seqüência, observando-se os produtos da célula terminal do embrião bicelular e a participação da célula basal na formação do embrião (Johri 1984). O significado evolutivo desses tipos não está totalmente estabelecido, porém eles têm sido utilizados para fins taxonômicos (Esau 1985).…”

“…A poliembrionia consiste na presença de mais de um embrião em uma mesma semente (Johri 1984). Piazzano (1998) detectou este fenômeno, pela primeira vez, na família Bignoniaceae, ao realizar estudos citogenéticos em Tabebuia chrysotricha (Mart.…”