To test the hypothesis that fructan structure can be used as a
taxonomic character for the Poaceae we examined
the accumulation of the linear, β-2,6-linked fructan series with a
terminal glucose residue within the tribes
Aveneae and Poeae. Only Dactylis glomerata L. (Poeae) has been
shown to contain this series, making it unique
among fructan structures and a potential taxonomic marker. To this end,
13 members of the tribes Aveneae and
Poeae were surveyed for the presence of this fructan series by comparing
extracts of water-soluble carbohydrate
by TLC with an extract of D. glomerata. The fructans of four species
were similar to those of D. glomerata, as
determined by TLC. Further comparison by anion-exchange chromatography and
linkage analysis demonstrated
that Phalaris aquatica L., Puccinellia stricta (Hook. f.)
C. H. Blom and Holcus lanatus L. contained a linear, β-2,6-linked
series of fructan with a terminal glucose residue but that Lagurus
ovatus L., although containing
predominantly β-2,6-linked fructan was composed of more than one series
of fructan, one with a terminal glucose
residue and one with an internal glucose residue. A linear β-2,6-linked
series of fructans with a terminal glucose
residue was the dominant fructan accumulated by some species of genera
belonging to both the Aveneae (Phalaris
and Holcus) and the Poeae (Dactylis and Puccinellia).
As both of these tribes also contain genera that accumulate
fructans with an internal glucose residue, e.g. Avena and Lagurus
(Aveneae) and Lolium (Poeae), structure of
fructan cannot be used to distinguish these tribes. Review of the literature,
however, showed that it is possible
to separate the supertribes Triticodae and Poodae on the basis of the
structure of the fructan that they accumulate.
