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1998), they recorded differences in the phloem supply of median and lateral
nectaries and in the sugar composition of both nectary types. These results
show that it is fundamental to determine the morphological variability of
nectary structure within a single species. Without doubt, these analyses will
have a great impact on the taxonomy of the studied groups, but unfortu-
nately, most published nectary research is based on single individuals and
only one or a few flowers.
3.5.3
Cucurbitaceae
In the cosmopolitan gourd family, which is mainly insect-pollinated, there
are two different types of nectaries: hypanthial and epidermal.
Hypanthial nectaries are mesenchymatous, exude nectar through stomata,
and are typical of most members of subfamily Cucurbitoideae (Brown, 1938;
Vogel, 1990, 1997; Nepi et al., 1996; Ashworth & Galetto, 1999; Fahn &
Shimony, 2001). The family has characteristic unisexual flowers, and the
hypanthial nectaries of male and female flowers show differences in position
and size. In male flowers, the nectary forms a concealed nectar chamber at
the base of the filaments; in female flowers, it is a circular channel surround-
ing the style and is usually larger than in male flowers (Nepi et al., 1996;
Ashworth & Galetto, 1999; Fahn & Shimony, 2001). The nectary size differ-
ences found in species of
Cucumis
and
Cucurbita
are correlated with the
comparatively larger volume of nectar secreted by female flowers (Nepi
et al., 1996; Ashworth & Galetto, 1999). On the other hand, in a species
of
Ecballium
staminate flowers secrete more nectar than pistillate flowers
(Dukas, 1987; Fahn & Shimony, 2001), which, accordingly, have an incon-
spicuous nectary. In species of
Momordica
,
Lagenaria
, and
Luffa
no
nectaries were reported for pistillate flowers (Bahadur et al., 1986; Iyer et al.,
1989). One can conclude that in species of this and other families with gen-
der dimorphism, sexual differences in nectaries have to be carefully checked
and interpreted, because they may be important in the understanding of plant
reproductive biology.
The other type of nectary in Cucurbitaceae is epidermal, in the form of
glandular trichomes, especially in genera with male flowers with synandria
(Vogel, 1981b, 1990, 1997). Nectaries form conspicuous carpets, either on
the receptacle or on the hypanthium, and characterize subfamily Zanonioidae
and tribes Cyclanthereae and Scycieae of subfamily Cucurbitoideae (Vogel,
1997). The trichomes show a variety of distribution patterns (from loose,
sparsely distributed to dense, well-circumscribed cushions, either continuous
or separated with different shapes) and composition (from two-celled to
