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Figure 2. A capitate trichome of the Cyclanthera pedata (Cucurbitaceae) nectary at the be-
ginning of nectar secretion. Nectar ( asterisk ) accumulates in a subcuticular space, stretching
the cuticle. Bar = 2 µm.
Nepi et al. (1996) hypothesized that the thin cuticle of Cucurbita pepo
nectaries contains very little wax because it is not stained by auramine O, a
specific dye for this substance (see Table 2). Nectar may possibly exude
through a permeable cuticle. Cuticle permeability to secretory products
has been also postulated in nectaries of the orchid Maxillaria coccinea
(Stpiczyńska et al., 2003).
In some species of the genus Euphorbia the cyathial nectary is covered
by a cuticle that is not uniform in thickness, being thinner in the “secretory
pits” through which the nectar exudes (Arumugasamy et al., 1990a). Kronestedt
et al. (1986) reported pores in the cuticle above the nectar secreting
trichomes of Abutilon sp. (Malvaceae).
The cuticle may have microchannels from which the nectar exudes
(Davis et al., 1988; Stpiczyńska, 2003). In Platanthera chlorantha (Orchidaceae),
the microchannels appear as fibrillar outgrowths of the outer epidermal
cell wall (Fig. 3), as also observed in Abutilon sp. (Kronestedt et al.,
1986). In Helleborus foetidus (Ranunculaceae), microchannels are narrow
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