Biology Reference
In-Depth Information
Caryophyllales.
This complex order shows a wide array of nectariferous
families, together with others that are anemophilous (
Achatocarpaceae
:
Bullock, 1994;
Simmondsiaceae
: Niklas & Buchmann, 1985), have pollen
flowers (
Rhabdodendraceae
: Nelson & Prance, 1984), or bear no nectaries
(
Drosophyllaceae
: Ortega Olivencia et al., 1995;
Physenaceae
: Dickinson
& Miller, 1993). The nectaries are predominantly receptacular, being typi-
cally intrastaminal or related to the basal part of the filaments of the stamens.
Zandonella (1977), in a comparative study, proposed an evolutionary trend
from nectaries surrounding the base of the ovary to nectaries around the an-
droecium. In
Aizoaceae
, a continuous ring of nectariferous tissue coats as
the inside of the perianth-stamen tube (Zandonella, 1977; Chesselet et al.,
2002). Ihlenfeldt (1960) holds that this nectary is part of the gynoecium, in-
stead of the androecium; the latter view is also held by Zandonella (1977).
Chesselet et al. (2002) proposed a new tribal classification supported by flo-
ral nectary morphology for the former Mesembryanthemaceae (now placed
within Aizoaceae
s.l.
). The basal group (Aizoaceae
s. str.
) has a ring-shaped an-
nular nectary (holonectary), whereas mesembryanthemums possess a hollow
or shell-shaped (koilomorphic)—not continuous—nectary (meronectary). On
the other hand, the more specialized Ruschioideae is characterized by the fol-
lowing four nectary types: (i) meronectary, (ii) broad, flat holonectary, (iii)
lophomorphic (crested or lobed) holonectary, which is considered the most
derived type, and (iv) nectary inconspicuous or absent.
In
Amaranthaceae
(including Chenopodiaceae), there is a trend towards
anemophily and many taxa possess no nectaries; nevertheless, when present,
they are located at the inner base of the filaments, either as a ring or as five
glands alternating with the filaments (Zandonella, 1977).
Basellaceae
shows
an annular nectary at the outer or inner base of the stamens (Zandonella,
1977). In
Cactaceae
, nectar is secreted by an annular receptacular nectary
(
Pereskia
,
Rhipsalis
), or along the basal portion of the hypanthium (Zan-
donella, 1977; Barthlott & Hunt, 1993; Nassar et al., 1997); in the latter case,
distinct nectar chambers may occur, formed by different organs (e.g., fila-
mental or hypanthial appendices).
Caryophyllaceae
shows nectariferous
tissue as a ring at the base of the filaments, or in the tube formed by the
bases of filaments and petals, or coating the inside of a receptacular cup
(Zandonella, 1977). In
Didieraceae
, the bases of the stamens are adnate and
form a ring-like nectary surrounding the ovary (Kubitzki, 1993b). For
Droseraceae
, Murza and Davis (2003) found no nectaries or nectar in
Drosera
species, although papillate cells that were reminiscent of secretory
tissue were observed at the apices of anthers and ovaries. As there are reports
of both the existence and absence of nectaries, it was suggested that the pres-
ence of floral nectaries may vary in
Drosera
(Murza & Davis, 2003). In
