Pollen Evolution in the Early‐Divergent Monocot Order Alismatales

A developmental study of pollen dyads and notes on floral development inScheuchzeria(Alismatales: Scheuchzeriaceae)

“…Variations in tetrad types are described for Arum L. (Araceae; Pacini & Franchi, ), Arisaema Mart. (Araceae; Maheshwari & Khanna, ), Butomus L. (Butomaceae; Furness & Banks, ), Thalassia Banks ex K.D.Koenig (Hydrocharitaceae, Pettitt, ), Triglochin L. (including Lilaea Bonpl . , Juncaginaceae; Agrawal, ; Furness & Rudall, ,b), Potamogeton L. (Potamogetonaceae; Nunes et al ., ), Zannichellia L. (Potamogetonaceae; Schwanitz, 1967, cited in Furness & Banks, ).…”

Paisia, an Early Cretaceous eudicot angiosperm flower with pantoporate pollen from Portugal

“…Among monocots, members of Alismataceae and Limnocharitaceae are characterised by having pantoporate pollen (Argue 1973(Argue , 1974(Argue , 1976Chanda et al 1988;Furness & Banks 2010) and pollen in some genera such as Sagittaria and Hydrocleys has spiny supratectal elements scattered over the tectum and surrounding the apertures in a similar way as seen in the pollen of Paisia. However, in Paisia, the elements appear compound and constricted at the base, while the microechinate-echinate pollen of Alismataceae and Limnocharitaceae has more conical and non-constricted supratectal elements.…”

“…The dispersed pollen record documents pantoporate/polyporate pollen already in the Aptian and by the Albian this pollen type is almost globally distributed and represented by a diversity of forms (Chlonova 1986;Ibrahim et al 2017). Among early diverging angiosperms pantoporate pollen is reported for Trimeniaceae (Austrobaileyales) and Chloranthaceae (Sampson & Endress 1984;Endress 1986), and in early diverging monocots pantoporate pollen characterises all extant Alismataceae and Limnocharitaceae (Argue 1973(Argue , 1974(Argue , 1976Chanda et al 1988;Furness & Banks 2010). Pantocolpate and pantoporate pollen grains are also common in early diverging lineages of eudicots including the Ranunculales and Buxales.…”

Flowers and inflorescences of the seagrass Posidonia (Posidoniaceae, Alismatales)

“…11 ) occurs in only three families of seagrasses (Cymodoceaceae, Posidoniaceae, and Zosteraceae) and is absent from other Alismatales and all other angiosperms ( Ducker et al, 1978 ;Dahlgren et al, 1985 ;Takhtajan, 2009 ;Furness and Banks, 2010 ;Kamelina, 2011 ). These three families do not form a clade in most molecular phylogenetic trees (e.g., Les et al, 1997 ;Chen et al, 2004 ;Iles et al, in press ).…”

“…This feature, previously considered primitive (e.g., Takhtajan, 1987 ;Cronquist, 1988 ) is now commonly regarded as derived at the level of monocots ( Doyle and Endress, 2000 ;Chen et al, 2004 ;Endress and Doyle, 2009 ;Remizowa et al, 2010 ;Sokoloff et al, in press ). The core Alismatales include the seagrasses, which are unique in possessing underwater pollination and fi liform pollen grains (the latter reviewed by Ducker et al, 1978 andFurness andBanks, 2010 ). The seagrasses are adapted to permanently saline underwater habitats, where they can occupy large areas, forming underwater meadows that play a signifi cant role in the functioning of marine ecosystems.…”