Amborellales 1 1 Nymphaeales 3 2 Austrobaileyales 3 2 Chloranthales 1 1 Magnoliids Cannellales 2 Piperales 5 3 Laurales 7 2 1 Magnoliales 6 3 1 Monocots Acorales 1 Alismatales
13 2 Petrosaviales 1 Dioscoreales 5 2 Pandanales 5 2 Liliales 10 4 Asparagales (incl.
The latest classification system (known as APG system: Angiosperm Phelogeny Group system), of the families and orders of the flowering plants which based largely on DNA sequences of the chloroplast, nuclear ribosomal, and mitochondrial genes, In this system the order Alismatales
put in monocot clad (Fig.
, many Araceae (including Lemnaceae) have unicarpellate flowers (also the basal genus Gymnostachys; Buzgo, 2001), and some have unistaminate flowers (Mayo et al.
These occur in Alismatales (or Alismatidae) mostly.
After Acorales (= the genus Acorus),which is the sister to the remaining monocots and is discussed separately below, the next node leads to Alismatales.
The clearest examples of this trend are in the submersed aquatics of the Alismatales such as Aponogetonaceae or Zosteraceae, in which vessels may have been lost simply because so little xylem is produced.
Araceae Amorphophallus albispathus Hett.
As a result of more intensive sampling and analysis of a larger data set, both in molecular and combined molecular-morphological studies, additional groups, most prominently Tofieldiaceae, Araceae, and other families of Alismatales sensu Angiosperm Phylogeny Group (APG, 1998), came into focus as comparatively basal taxa and separated as the next clade (after Acorus) from the remainder of monocots (Chase et al.
SIEVE-ELEMENT PLASTIDS OF ACORALES AND ALISMATALES SENSU APG (1998)
Because of their many similarities and the ease of accessibility to material, the Alismatales (monocots) and Nymphaeales (dicots) have been the subject of numerous comparative studies.
More important, Kudraishov agreed with an earlier interpretation by Meier (reference in Kudraishov, 1964; original not seen) that in Nymphaeaceae, beginning with the third leaf, development follows the pathway seen in the Alismatales.
Among early-branching monocot taxa, Acorus and Tofieldia have secretory tapeta, whereas Araceae and Alismatales
are uniformly plasmodial.