Biology Reference
In-Depth Information
Figure 3.
Common types of nectar secretion and presentation. In A, B, and C, parenchyma
cells produce and secrete nectar. In G and H, the secretory function is performed by epider-
mal/epithelial cells, and by trichomes in D, E, and F. Nectar may be presented as drops (A, D,
E) or as a continuous layer of variable depth (B, F, G). Nectar may be presented outside the
nectary (secondary presentation) in a spur (C) or at the end of a nectary duct (nd) as in H.
A:
Fatsia japonica
(Araliaceae; Nepi & Pacini unpublished data); B:
Cucurbita pepo
(Cucur-
bitaceae; Nepi et al., 1996a, b); C:
Linaria vulgaris
(Scrophulariaceae; Nepi et al., 2003); D:
Lonicera japonica
(Caprifoliaceae; Fahn, 1979a); E:
Zeyheria
(Bignoniaceae; Bittencourt &
Semir, 2004); F:
Hibiscus
(Malvaceae; Sawidis, 1987a); G:
Helleborus
(Ranunculaceae;
Vesprini et al., 1999); H:
Aloe
(Asphodelaceae; Nepi et al., 2006).
foraging pathways of pollinators. Figure 3 illustrates the main types of nectar
secretion and presentation.
Pacini et al. (2003) proposed the new term
nectar presentation
in analogy
to the better-known term
pollen presentation
(Faegri and van der Pijl,
1979), to indicate how and where nectar is offered for consumption. Nectar
presentation can be further subdivided into
primary presentation
, when nec-
tar is offered in the nectary itself, and
secondary presentation
when it is
presented elsewhere, e.g., stored in spurs or other reservoirs.
Spurs are cavities commonly derived from the corolla and are present in
at least 15 angiosperm families (Hodges, 1997; Bernardello, 2007). In certain
families, such as Scrophulariaceae, spurs are typical of almost all members; in
other families, such as Ranunculaceae, they may occur in some members
only (the genera
Aconitum
,
Aquilegia
,
Delphinium
,
Consolida
, and
Nigella
).
