Embryological studies in some grasses and their taxonomic significance

Abstract

BHANWRA, R. K., KAUR, N., KAUR, N. & GARG, A., 1991. Embryological studies in some grasses and their taxonomic significance. The species investigated are Lolium multiftorum Lam (tribe Poeae), Rostraria cristata (Linn.) Tzevlev (tribe Aveneae), Cenchrus setigerus Vahl, Digitaria abludens (Roem. et Schult.) Veld, and D. ciliaris (Retz.) Koel (tribe Paniceae). Apart from the number of microsporocytes in a median longitudinal section of each anther lobe, microsporogenesis and male gametophyte development are similar. However, members of subfamilies Pooideae and Panicoideae show marked differences in structure of the ovary, ovule and post‐fertilization development. Lolium multiftorum and R. cristata vary in the structure of the dorsal ovary wall, degree of curvature in the megagemetophyte in relation to the longtitudinal axis of the ovule, and structure of the pericarp. Cenchrus setigerus is an aposporic apomict and differs markedly from species of Digitaria in this respect, in the extent of development of the inner integument and in the constitution of the dorsal ovary wall. The two species of Digitaria show minor embryological differences.

Homologies of the flower and inflorescence in the early‐divergent grass Anomochloa (Poaceae)

“…Endothecium morphology also differs between Anomochloa and many other Poaceae. In Anomochloa , the endothecium apparently lacks prominent thickenings and degenerates, whereas in other grasses the endothecium is persistent and possesses prominent fi brous thickenings on the inner tangential wall ( Bhanwra, 1988 ;Bhanwra et al, 1991Bhanwra et al, , 2001. A reduced endothecium was also reported for Pharus ( Sajo et al, 2007 ) and Streptochaeta ( Sajo et al, 2009 ). In Anomochloa , most microsporocytes undergo two consecutive meiotic divisions to form isobilateral tetrads, as in other Poaceae ( Sajo et al, 2007 ).…”

“…In contrast, anther-wall development in most other Poaceae is reported as the monocot type ( Bhanwra, 1988 ;Bhanwra et al, 1991Bhanwra et al, , 2001, in which the outer secondary parietal layer develops directly into an endothecium, and the inner layer divides periclinally to form the tapetum and a single middle layer. Endothecium morphology also differs between Anomochloa and many other Poaceae.…”

Microsporogenesis is simultaneous in the early‐divergent grass Streptochaeta, but successive in the closest grass relative, Ecdeiocolea

“…A reduced endothecium was also reported for Pharus (Sajo et al, 2007). In other grasses, the endothecium is persistent and possesses fibrous thickenings on the inner tangential wall (Bhanwra, 1988;Bhanwra et al, 1991). Three different types of thickening occur in other Poaceae; baseplates, annular and U-shaped (Manning & Linder, 1990).…”

“…Meiosis does not appear to be synchronous within a locule in Ecdeiocolea, since Furness & Rudall (1999) and references therein, also Bromeliaceae (Sajo et al, 2005), Prionium (Munro & Linder, 1997), Cyperaceae (Simpson et al, 2003), Joinvilleaceae (Bayer & Appel, 1998), Ecdeiocoleaceae, Anomochlooideae (this paper), Pharoideae (Sajo et al, 2007), other Poaceae (Bhanwra, 1988;Bhanwra et al, 1991 Linder & Rudall (2005). Anther wall development type from: Bromeliaceae (Sajo et al, 2005), Typha (Asplund, 1972), Sparganium (Mü ller-Doblies, 1969), Rapateaceae (Tiemann, 1985;Venturelli & Bouman, 1988), Prionium (Munro & Linder, 1997), Cyperaceae (Khanna, 1963;Makde, 1982), Juncaceae (Munro & Linder, 1997), Mayaca (Venturelli & Bouman, 1986), Xyris (Rudall & Sajo, 1999), Eriocaulaceae (Monteiro-Scanavacca & Mazzoni, 1978;Arekal & Ramaswamy, 1980), Abolboda (Tiemann, 1985), Restionaceae (Krupko, 1962), Centrolepidaceae (Hamann, 1975), Flagellaria (Munro & Linder, 1997), Anomochlooideae (this paper), Pharoideae (Sajo et al, 2007), other Poaceae (Bhanwra, 1988;Bhanwra et al, 1991 dyads and tetrads are present together, which is unusual. Among other monocots, such reversals in microsporogenesis type can occur occasionally, for example, most lower asparagoids (Asparagales) are simultaneous, with a reversal to the successive type in Hypoxidaceae and within Iridaceae (Rudall et al, 1997;Penet et al, 2007).…”

“…Anther wall development in Streptochaeta spicata is of the reduced type (with only three layers), in common with another early-divergent grass Pharus (Sajo et al, 2007), but in contrast to most other grasses, in which the monocot type occurs (Bhanwra, 1988;Bhanwra et al, 1991). The monocot type also characterises most other Poales, with a few exceptions (Table I); for example, both basic and monocot types have been reported in Rapateaceae (Tiemann, 1985;Venturelli & Bouman, 1988), the basic type in Mayaca (Venturelli & Bouman, 1986) and the reduced type in Xyris (Rudall & Sajo, 1999).…”