Biology Reference
In-Depth Information
nectar; the nectary can be cylindrical or conical (Thiv, 2004). In
Gesneri-
aceae
, nectar is produced by glands between the base of the ovary and the
corolla; the nectary is either continuous (annular, cylindrical, or cup-shaped)
or consists of one to five separate glands, which can be free or adnate to the
ovary (Cronquist, 1981; Maldonado & Otegui, 1997; Perret et al., 2001; We-
ber, 2004); sometimes, they can be reduced and non-functional. The nectary
shape is of great importance in defining genera, and trends in shape charac-
terize evolutionary lines in the Neotropical Gesneriaceae: in Beslerieae from
a complete ring to a single dorsal gland (through steps involving a dorsally
thickened ring and a semilunar structure), and in Gloxinieae, Sinningieae,
and Episcieae from a ring to a single dorsal gland (through a sequence in-
cluding a five-lobed ring, five glands of unequal size, connation of the dorsal
glands, and stepwise reduction of the lateral and ventral glands; Weber,
2004). In addition, the quantity and disposition of the glands may show in-
tra- and interspecific variation (SanMartin-Gajardo & Sazima, 2004, 2005).
These nectaries are receptacular intrastaminal rather than gynoecial, but de-
velopmental studies have to be done to determine their origin properly. In
Lamiaceae
, nectaries are annular at the ovary base, from entire to four-
lobed, sometimes with the anterior lobe longer than the others (Cronquist,
1981; Kumari, 1986; Dafni et al., 1988; Zer & Fahn, 1992; Petanidou et al.,
2000). In
Lentibulariaceae
, a nectariferous spur is developed from the ante-
rior corolla lobe (Narayana & Satyavathi, 1988; Vogel, 1997). In
Martyniaceae
, the superior ovary is surrounded by an annular hypogynous
nectary (Ihlenfeld, 2004a); Thieret (1976) reported that glandular trichomes
located on the stamen bases produce nectar.
Phrymaceae
presents the charac-
teristic ovarian nectary of the order (Galetto, 1995b; Hazle & Canne-Hilliker,
2005). In
Plocospermataceae
, the ovary has an annular nectary at its base
(Struwe & Jensen, 2004); in addition, functionally male flowers were re-
ported to lack nectaries (D'Arcy & Keating, 1973). In
Scrophulariaceae
,
nectaries are as typical for the order and may be unilateral (Cronquist, 1981;
Galetto, 1995b; Gaffal et al., 1998). In this family, oil flowers can also exist
(Vogel, 1974; Sérsic & Cocucci, 1999). In
Verbenaceae
, the ovary is supe-
rior and has the typical basal nectariferous ring (Brown, 1938; Fahn, 1979;
Cronquist, 1981; Smets, 1986; Bernardello et al., 2000), as also occurs in
Oleaceae
(Fahn, 1979; Cronquist, 1981), although some members are wind-
pollinated (
Fraxinus
,
Olea
,
Phillyrea
; Green, 2004).
Orobanchaceae
(Fischer, 2004b; Bekker & Kwak, 2005),
Paulowniaceae
(Fischer, 2004b),
Pedaliaceae
(Cronquist, 1981; Ihlenfeld, 2004b; Wortley et al., 2005),
Schlegeliaceae
(Fischer, 2004b), and
Stilbaceae
(Linder, 2004) have annular
nectaries at the base of the ovary. In addition, in some Pedaliaceae taxa nectar
glands recorded at the base of the pedicel are considered to be modified flow-
ers (Monod, 1986).
