Biology Reference
In-Depth Information
Fahn (1979a)
Durkee (1983)
Nepi (this chapter)
epidermis
epidermis
epidermis
directly involved
in nectar production
and secretion
parenchymatous
tissue
secretory
tissue
nectary
parenchyma
with vascular bundles
sub-glandular
parenchyma
sub-nectary
parenchyma
not directly involved
in nectar production
with vascular
bundles
with vascular
bundles
Figure 1.
Anatomical organization of the nectary according to Fahn (1979a) and Durkee
(1983), and that proposed in the present chapter.
On the other hand, in some species the anatomical structure of the nec-
tary can be recognized, but the nectary does not produce nectar. This is the
case of the so-called vestigial nectaries found in some Bignoniaceae (
Catalpa,
Clytostoma
,
Cydista
,
Phryganocydia
) (Rivera, 2000 and references therein).
The lack of a functional nectary has been associated with pollination by
deception in Bignoniaceae (Gentry, 1980).
Before discussing the structure of the different components of the nec-
tary, it is necessary to give some definitions and to clarify differences
between the terms nectar production, nectar secretion, and nectar release.
Nectar production is sometimes considered synonymous with nectar secre-
tion. In my opinion the two terms are different. Nectar production is a
phenomenon related to the nectary as a whole. It comprises different events
(sugar unloading from the vascular bundle, transport of molecules into the
nectary tissue, transformation of molecules, nectar release from the nectary)
leading to nectar release (or exudation) from the nectary. Nectar secretion
refers to the release of nectar from the protoplasm of the nectary parenchyma
cells, thus it describes a phenomenon at the cellular level.
2.1
Epidermis
Epidermal cells are generally smaller than parenchyma cells; they are poly-
hedric and may have an anticlinal orientation. The vacuole is generally
