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Nuptial nectary structure of Bignoniaceae from Argentina

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Rivera, G. L. 2000. Nuptial nectary structure of Bignoniaceae from Argentina.Darwiniana 38(3-4): 227-239.Nuptial nectary characteristics were investigated in 37 taxa of Bignoniaceae. A nuptial nectaryassociated to the floral axis was found in all species. Two main types can be distinguished according totheir degree of development and functionality: 1) vestigial and non-secretory and 2) well-developed andsecretory. The former is characteristic of Clytostoma spp., while the latter is found in the remainingspecies. Two subvarieties of the secretory type of nectary can be discerned according to their positionand shape: 1) annular, found in Adenocalymma, Amphilophium, Anemopaegma, Arrabidaea,Dolichandra, Eccremocarpus, Macfadyena, Melloa, Pithecoctenium, Tabebuia, and Tecoma, and 2)cylindrical, found in Argylia, Cuspidaria, Jacaranda, Mansoa, Parabignonia, Pyrostegia, andTynnanthus. Anatomically, two tissues are distinguished: 1) a single-layered epidermis covered by acuticle and a variable number of stomata, and 2) a secretory tissue composed of compactly arrangedparenchyma cells. Both nectary size and nectary/ovary ratio were usually larger in lianas (Bignonieae)than in trees (Tecomeae). Nectary type proved to be consistent among species of same genus but notamong genera of same tribe. Nectary features such as vascularization, presence of trichomes and nectarytype were constant within the analyzed species and therefore have a reliable taxonomic value
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Darwiniana
Instituto de Botánica Darwinion (IBODA)
rpozner@darwin.edu.ar
ISSN (Versión impresa): 0011-6793
ISSN (Versión en línea): 1850-1702
ARGENTINA
2000
Guillermo L. Rivera
NUPTIAL NECTARY STRUCTURE OF BIGNONIACEAE FROM ARGENTINA
Darwiniana, año/vol. 38, número 3-4
Instituto de Botánica Darwinion (IBODA)
Buenos Aires, Argentina
pp. 227-239
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
Universidad Autónoma del Estado de México
http://redalyc.uaemex.mx
227
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
ISSN 0011-6793DARWINIANA
38(3-4): 227-239. 2000
INTRODUCTION
Bignoniaceae Juss. is a family of woody vines,
shrubs and trees, and occasional herbs. It
comprises about 100 genera and 800 mostly
Neotropical species (Cronquist, 1988). The family is
commonly subdivided into eight tribes, five of
which are restricted to the New World: Bignonieae,
Crescentieae, Eccremocarpeae, Schlegelieae and
Tourrettieae. The Tecomeae is found both in the
Old and New World, while the Oroxylaeae and
Coleeae are localized in Southeast Asia and Africa
NUPTIAL NECTARY STRUCTURE OF BIGNONIACEAE FROM ARGENTINA
GUILLERMO L. RIVERA
Instituto Multidisciplinario de Biología Vegetal, Universidad Nacional de Córdoba, Casilla de Correo 495, 5000
Córdoba, Argentina. E-mail: rivera@imbiv.unc.edu.ar
ABSTRACT: Rivera, G. L. 2000. Nuptial nectary structure of Bignoniaceae from Argentina.
Darwiniana 38(3-4): 227-239.
Nuptial nectary characteristics were investigated in 37 taxa of Bignoniaceae. A nuptial nectary
associated to the floral axis was found in all species. Two main types can be distinguished according to
their degree of development and functionality: 1) vestigial and non-secretory and 2) well-developed and
secretory. The former is characteristic of Clytostoma spp., while the latter is found in the remaining
species. Two subvarieties of the secretory type of nectary can be discerned according to their position
and shape: 1) annular, found in Adenocalymma, Amphilophium, Anemopaegma, Arrabidaea,
Dolichandra, Eccremocarpus, Macfadyena, Melloa, Pithecoctenium, Tabebuia, and Tecoma, and 2)
cylindrical, found in Argylia, Cuspidaria, Jacaranda, Mansoa, Parabignonia, Pyrostegia, and
Tynnanthus. Anatomically, two tissues are distinguished: 1) a single-layered epidermis covered by a
cuticle and a variable number of stomata, and 2) a secretory tissue composed of compactly arranged
parenchyma cells. Both nectary size and nectary/ovary ratio were usually larger in lianas (Bignonieae)
than in trees (Tecomeae). Nectary type proved to be consistent among species of same genus but not
among genera of same tribe. Nectary features such as vascularization, presence of trichomes and nectary
type were constant within the analyzed species and therefore have a reliable taxonomic value.
Key words: Anatomy, Bignoniaceae, Flower, Nectary, Stomata
RESUMEN: Rivera, G. L. 2000. Estructura de nectarios nupciales en Bignoniaceae de Argentina.
Darwiniana 38(3-4): 227-239.
Se investigaron las características de los nectarios florales en 37 especies de Bignoniaceae. Se encontró
un nectario nupcial asociado al eje floral en todas las especies, pudiéndose distinguir dos tipos principales
de acuerdo a su grado de desarrollo y funcionalidad: 1) vestigial y no secretor y 2) bien desarrollado y
secretor. El primero es característico de las especies de Clytostoma mientras que el segundo está presente
en el resto de las especies estudiadas. Dos variedades del tipo secretor pueden discernirse de acuerdo a su
posición y forma: 1) anular, encontrado en Adenocalymma, Amphilophium, Anemopaegma, Arrabidaea,
Dolichandra, Eccremocarpus, Macfadyena, Melloa, Pithecoctenium, Tabebuia, y Tecoma y 2) cilíndrico,
presente en Argylia, Cuspidaria, Jacaranda, Mansoa, Parabignonia, Pyrostegia, y Tynnanthus.
Anatómicamente se distinguen dos tejidos: 1) una epidermis monoestratificada, cubierta por una cutícula
y con un número variable de estomas y 2) un tejido secretor compuesto por células parenquimáticas
dispuestas en forma compacta. Tanto el tamaño del nectario como la relación nectario/ovario fue
usualmente más grande en lianas (Bignoniaceae) que en árboles (Tecomeae). El tipo de nectario fue
invariable entre las especies de un mismo género, pero no así entre los géneros de una misma tribu. Las
características de los nectarios analizados en este estudio como la vascularización, la presencia de
tricomas y el tipo de nectario fueron constantes en las especies analizadas, adquiriendo por lo tanto un
importante valor taxonómico.
Palabras clave: Anatomía, Bignoniaceae, Flor, Nectario, Estomas
228
Darwiniana 38(3-4). 2000
respectively (Gentry, 1980). About 50 species grow
in Argentina belonging to 22 genera, and are
grouped into four tribes (Gentry, 1980; Gentry &
Bernardello, 1984).
Flowers are usually large and showy, with a
sympetalous, tubular-campanulate, commonly
slightly bilabiate corolla. They are visited mainly for
nectar by a diverse spectrum of pollinators, from
bees, hummingbirds, and butterflies, to moths and
bats (Gentry, 1980; 1990). Nectar is secreted by a
nectary located at the base of the ovary, although
the gland may be vestigial in some species. Nuptial
nectaries in the family vary enormously with respect
to anatomy, position, and secretion mechanisms
(Elias & Gelband, 1976; Subramanian & Inamdar,
1989; Thomas & Dave, 1992; Belmonte et al., 1994;
Galetto, 1995).
Nuptial nectary attributes were previously
investigated in 24 taxa of Bignoniaceae (Rao, 1971;
Elias & Gelband, 1976; Subramanian & Inamdar,
1986a, 1986b, 1989; Rudramuniyappa & Mahajan,
1991; Thomas & Dave, 1992; Belmonte et al., 1994;
Galetto, 1995; Rivera, 1996). Except for one work
(Galetto, 1995), they lack a comparative analysis
among the studied species.
This paper examines nuptial nectary
characteristics of 37 species, belonging to 18 gene-
ra, from 3 different tribes of Bignoniaceae, growing
in Argentina. The aims of this investigation are 1: to
observe and compare nectary characteristics, and 2:
to determine if nectary anatomical and/or
morphological features are relevant characters in
the taxonomy of the family.
MATERIALS AND METHODS
The complete species names with authorities and
the collections used in this study are listed in
Appendix 1. Voucher material is kept at CORD (Mu-
seo Botánico de Córdoba). No species authorities
are cited in the text to facilitate reading.
Material was fixed in FAA, and then transferred
to 70% ethanol. For light microscopy, only flowers
in the beginning of anthesis were used. Material
was dehydrated through an ethyl alcohol/xylol se-
ries and the flowers were embedded in paraffin wax
(Johansen, 1940). Sections, both cross and
longitudinal, were cut at 8-12 µm, mounted serially,
and stained with safranin-astral blue (Maácz &
Vágás, 1961). Photographs were taken under a Zeiss
Axiophot using Kodak T Max film, ISO 100.
Nectary volume was calculated with the non-
circular-section toroids’ formula: V = 2.P.s.r (s =
nectary sectional area; r = nectary radius measured
from the sections’ center of gravity). The nectary/
ovary ratio was expressed in percentage of surface.
This parameter was estimated with reference to the
weight of the drawings of the nectary in
longitudinal section and the ovary (style and
receptacle were excluded). The nectary/ovary ratio
was also calculated in order to estimate the relative
nectary size, independently of nectary volume. The
comparison was made with the ovary surface due to
the difficulty of calculating the volume of the ovary.
For scanning electron microscopy, material was
washed repeatedly in 70% ethanol and dehydrated
through an ethyl alcohol/acetone series (Cohen,
1974). Flowers were critical-point dried using CO
2
(Crang, 1988) and coated with approximately 250Å
of gold. Observations were carried out using a JEOL
35CF scanning electron microscope and photo-
micrographs were taking using AgfaPan APX 100.
RESULTS
A nuptial nectary in association with the floral
axis is found in all species (Figs. 1; 2 A, C, 4). Two
main different types can be distinguished according
to their degree of development and functionality:
vestigial, non-secretory, and well-developed,
secretory nectaries.
Vestigial, non-secretory nectary
Clytostoma callistegioides and C. binatum have
a reduced and poorly developed nectary around the
base of the ovary (Fig. 1 D, E). In these species, the
epidermis of the nectary has no stomata, and its
parenchyma cells are very similar to those found in
adjacent tissues. No secretion was found in the
flowers of any individual among the different
analyzed populations.
Well-developed, secretory nectary
These are the nectaries found in most of the
studied species. Two different varieties can be
found according to their position and shape:
Annular: an enlarged ring or disk usually
surrounding the base of the ovary, commonly five-
lobed. In longitudinal sections, a groove or furrow
is observed dividing the nectariferous tissue from
the base of the ovary, floral axis or gynophore (Figs.
229
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
Fig. 1.- Floral nectary types in Bignoniaceae. Photomicrographs showing partial views of longisections. A: Annular
nectary, Tabebuia ochracea. B: Cylindrical nectary, Jacaranda mimosifolia. C: Annular nectary, Dolichandra
cynanchoides. D-E: Vestigial nectary. Clytostoma callistegioides. References: c, corolla; n, nectary; o, ovary.
1 A, C, 2 A). In some cases, the ovary is raised far
from the secretory tissue by a long floral axis or
gynophore (Fig. 1 C). It is found in Adenocalymma
marginatum, Amphilophium paniculatum,
Anemopaegma flavum, Arrabidaea sp.,
Dolichandra cynanchoides, Eccremocarpus
scaber, Macfadyena sp., Melloa quadrivalvis,
Pithecoctenium sp., Tabebuia sp., and Tecoma sp.
Cylindrical: an enlargement of the floral axis or
gynophore and intimately related to it (Fig. 1 B). In
longitudinal sections, no groove is observed
between the nectary and the base of the ovary and
the floral axis or gynophore. The secretory tissue
displays different degrees of development. This
type is found in Argylia uspallatensis, Cuspidaria
convoluta, Jacaranda sp., Mansoa difficilis,
Parabignonia chodatii, Pyrostegia venusta, and
Tynnanthus micranthus.
The different types of nuptial nectaries
described in this work (vestigial, annular, cylindrical
and some subtle variations of these forms) were
always consistent for all the species within a genus.
Even in genera with different flower morphological
types and visited by different pollinators for nectar
(e.g. Tecoma), the type of nuptial nectary remained
the same (Table 1).
Considering the anatomy of the nectaries, two
tissues are distinguished: 1) a single layer of epider-
mis comprising cells covered by a cuticle and a
variable number of stomata, and 2) a secretory
tissue composed of compactly arranged
230
Darwiniana 38(3-4). 2000
Fig. 2.- Photomicrographs showing floral nectary structure of Arrabidaea corallina (Bignonieae). A: Flower partial
longisection. B: Flower cross-section. C: Detail of lower left portion of nectary in A. D: detail indicated in B. E-F: Starch
grains of secretory tissue cells observed at different magnifications with phase contrast microscopy. c: corolla, k: calyx,
n: nectary, o: ovary. Arrow indicates a stoma on the surface of the nectary.
231
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
Table 1.- Nuptial nectaries in Bignoniaceae. Types and morpho-anatomical features. Flower morphological types and
frequent flower visitors from Gentry 1974, 1980; Rivera 1997). Volume measurements are means taken from 3 flowers
at least, N/O = nectary ovary ratio. N.A.= not applicable.
Taxón Habit
Type of nuptial
nectary
Vascularization
Volume
(mm
3
)
N/O
Ratio
Flower
morphological
type
Frequent
flower visitor
Tribe Eccremocarpeae
Eccremocarpus scaber Shrub Annular Phloem 4.105 0.282 Campsidium Hummingbird
Tribe Bignonieae
Adenocalymma marginatum Vine Annular Phloem 6.125 0.766 Anemopaegma Bee
Amphilophium paniculatum Vine Annular Phloem 11.261 0.328 Amphilophium Bee
Anemopaegma flavum Vine Annular Phloem 7.508 0.626 Anemopaegma Bee
Arrabidaea chica Vine Annular Phloem 1.088 0.436 Anemopaegma Bee
A. corallina Vine Annular Phloem 4.456 1.301 Anemopaegma Bee
A. selloi Vine Annular Phloem 3.581 0.774 Anemopaegma Bee
Clytostoma binatum Vine Vestigial N.A. N.A. N.A. Cydista Bee
C. callistegioides Vine Vestigial N.A. N.A. N.A. Cydista Bee
Cuspidaria convoluta Vine Cylindrical Phloem 0.371 0.154 Anemopaegma Bee
Dolichandra cynanchoides Vine Annular Phloem 15.895 0.979 Pyrostegia Hummingbird
Macfadyena dentata Vine Annular Phloem 12.118 0.393 Anemopaegma Bee
M. uncata Vine Annular Phloem 2.834 0.409 Anemopaegma Bee
M. unguis-cati Vine Annular Phloem 8.061 0.261 Anemopaegma Bee
Mansoa difficilis Vine Cylindrical Phloem 7.046 0.419 Anemopaegma Bee
Melloa
q
uadrivalvis Vine Annular Phloem 1.561 0.153 Anemopaegma Bee
Parabignonia chodatii Vine Cylindrical Phloem 29.051 0.511 Anemopaegma Bee
Pithecoctenium crucigerum
Vine Annular Phloem 16.522 0.789 Pithecoctenium Bee/beetle
P. cynanchoides
Vine Annular Phloem 11.335 0.901 Pithecoctenium Bee/beetle
Pyrostegia venusta
Vine Cylindrical Phloem 3.066 0.428 Pyrostegia Hummingbird
Tynnanthus micranthus Vine Cylindrical Phloem 0.05 0.121 Tynnanthus Bee
Tribe Tecomeae
Argylia uspallatensis Shrub Cylindrical Phloem 0.352 0.121 Anemopaegma Bee
Jacaranda micrantha Tree Cylindrical Phloem 2.564 0.331 Anemopaegma Bee
J. mimosifolia
Tree Cylindrical Phloem 3.993 0.367 Anemopaegma Bee
Tabebuia alba
Tree Annular Phloem/xylem 2.464 0.211 Anemopaegma Bee
T. aurea
Tree Annular Phloem/xylem 7.668 0.248 Anemopaegma Bee
T. chrysotricha
Tree Annular Phloem/xylem 2.617 0.225 Anemopaegma Bee
T. heptaphylla
Tree Annular Phloem/xylem 0.305 0.118 Anemopaegma Bee
T. impetiginosa
Tree Annular Phloem/xylem 0.891 0.134 Anemopaegma Bee
T. lapacho
Tree Annular Phloem/xylem 7.643 0.213 Anemopaegma Bee
T. nodosa
Tree Annular Phloem/xylem 0.561 0.065 Anemopaegma Bee
T. ochracea Tree Annular Phloem/xylem 1.592 0.125 Anemopaegma Bee
T. pulcherrima Tree Annular Phloem/xylem 2.787 0.466 Anemopaegma Bee
Tecoma capensis
Shrub Annular Phloem 0.881 0.166 Pyrostegia Bee
T. garrocha
Shrub Annular Phloem 0.774 0.166 Pyrostegia Hummingbird
T. stans
Tree Annular Phloem 0.442 0.156 Anemopaegma Bee
T. tenuiflora
Tree Annular Phloem 0.686 0.142 Anemopaegma Hummingbird
232
Darwiniana 38(3-4). 2000
Fig. 3.- Photomicrographs showing floral nectary structure of Tabebuia sp. (Tecomeae) in longisection. A-C. Tabebuia
chrysotricha. A. Detail of nectary. B: detail of secretory tissue showing xylem. C: Detail of stoma indicated in A. D-E:
Tabebuia ochracea. D: Detail of nectary. E: Detail of secretory tissue showing xylem. c: corolla, n: nectary, o: ovary.
Arrows show xylem.
233
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
parenchyma cells (Fig. 2 A-D). Intensely stained
parenchyma cells have large nuclei and numerous
vacuoles as well as starch grains (Fig. 2 E-F). The
secretory tissue lacks intercellular spaces.
Generally it is supplied only by phloem traces,
which are distinguished by their distinct affinity to
stain (e.g. Fig. 2 C). However, the vascularization is
both by xylem and phloem in all species of
Tabebuia (Fig. 3 A, B arrow, D, E arrow).
The surface of the nectary is glabrous in most
species (Figs. 1; 2 A, C; 3 A, D, 4 C) except for that of
Pithecoctenium sp. (Fig. 4 A) and Tynnanthus
micranthus (Fig. 4 B). In these species, non-
secretory multicellular simple hairs similar to those
found on the surface of the ovary, cover the nectary
surface.
Nectary stomata were always anomocytic (Fig. 5)
and usually located at the apical portion of the
nectaries (Figs. 2 C arrow; 3 A arrow, C). Usually
they were found open (Fig. 5 A, C). Nevertheless
some stomata were barely open (Fig. 5 D) while
others were completely closed (Fig. 5 B, E, F). They
were always flush with the surface of the epidermis
except those found in Tabebuia aurea, T. chrysotri-
cha, T. nodosa, and T. ochracea whose stomata
were raised above the epidermal layer (Fig. 3 C).
An annular protuberance was found between the
perianth whorls in Parabignonia chodatii,
Macfadyena dentata, and Melloa quadrivalvis
(Fig. 4 C, D). The anatomy of this tissue showed
differences from a typical secretory tissue found in
Fig. 4.- Floral nectary of Pithecoctenium crucigerum, Tynnanthus micranthus, and Melloa quadrivalvis (Bignonieae).
A: Pithecoctenium crucigerum. SEM photomicrograph of lower portion of flower with sepals and petals partially
removed, showing ovary and nectary covered by hairs. B:. Tynnanthus micranthus. OM photomicrograph of lower
flower cross-section showing nectary covered by hairs. C-D: Melloa quadrivalvis. C: SEM photomicrograph of lower
portion of flower with sepals and petals removed, showing ovary, nectary and protuberance. D: OM photomicrograph
of flower partial cross-section showing protuberance. c: corolla, n: nectary, o: ovary, p: protuberance.
234
Darwiniana 38(3-4). 2000
Fig. 5.- SEM photomicrographs of nectary stomata in Bignoniaceae. A. Arrabidaea corallina. B. Macfadyena unguis-
cati. C. Parabignonia chodatii. D. Tecoma stans. E. Dolichandra cynanchoides. F. Tabebuia heptaphylla.
nectaries, and it appeared to be regular parenchyma
tissue similar to that found in the flower receptacle
(Fig. 4 D). Observations under SEM (Fig. 4 C) also
revealed lack of stomata on its surface, as is
customary in mesenchymatic secretory tissues. In
short, it was a structure not related to the nectary,
located between the petals and sepals, and made up
of non-secretory parenchyma cells and of unknown
function.
The nectaries of Bignonieae were usually larger
than those of Tecomeae, reaching almost 30 mm
3
in
Parabignonia chodatii and over 15 mm
3
in both
Dolichandra cynanchoides and Pithecoctenium
crucigerum (Table 1). The volume was variable
among species of the same genus. For example in
Tabebuia, some species attained a volume of over 7
mm
3
(T. aurea and T. lapacho), others ranged
between 1.5 a 2.7 mm
3
(T. alba, T. chrysotricha, T.
ochracea and T. pulcherrima), while some had a
235
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
very small nectary (0.3-0.9 mm
3
in T. heptaphylla, T.
impetiginosa and T. nodosa). This variability was
also observed among the species of Macfadyena.
In Tecoma sp., however, the volume was almost
constant (Table 1). The nectary/ovary ratio (N/O)
was also commonly larger in Bignonieae, with extre-
me cases in Arrabidaea sp. where the nectary area
in a longisection exceeded that of the ovary. In most
genera where more than one species was observed
(e.g. Tabebuia and Macfadyena) N/O ratios gave
more uniform results than did volume measure-
ments (Table 1).
DISCUSSION
According to a topographical classification
depicted by Fahn (1979a), annular secretory
nectaries found in Bignoniaceae would correspond
to type 4 (“nectary as a disk surrounding the base of
the ovary”), while cylindrical secretory ones, would
belong to type 3 (“nectaries on receptacles”).
However this classification (Fahn, 1979a), only
refers to the nectaries’ position and the fact that the
nectaries of Bignoniaceae fall into two distinct
categories, is simply due to a difference in their
degree of development and position.
Clytostoma sp., on the other hand, shows a
vestigial nectary. This type of gland is
characteristic of other genera of the family such as
Cydista and Phryganocydia (Gentry, 1980), but it
was also found in one species of Catalpa (Rivera,
1996). The lack of a functional nectary was
associated with pollination by deception and
multiple-bang-flowering phenology (Gentry, 1980),
which also holds true for the studied populations of
Clytostoma (Rivera, 1997).
Nectary anatomical characteristics found in the
studied species agree with those reported by
several authors in other species of Bignoniaceae
(Elias & Gelband, 1976; Subramanian & Inamdar,
1986a, 1989; Thomas & Dave, 1992; Belmonte et al.,
1994; Galetto, 1995; Rivera, 1996). No intercellular
spaces were found in the secretory parenchyma as
it is distinctive in mesenchymatic nectaries (Fahn,
1979a, 1979b; Subramanian & Inamdar, 1989;
Thomas & Dave, 1992). This could be explained by
the fact that these spaces appear at the end of the
secretion period, when the secretory tissue
becomes less dense (Subramanian & Inamdar,
1989), while the material used in this study was all
young flowers or buds near anthesis.
The vascularization of nectaries is always by
phloem, except for the species of Tabebuia whose
nectaries are supplied by both phloem and xylem.
Galetto (1995) had already reported this distinction
in T. heptaphylla while Thomas & Dave (1992) did
not comment on the nectary vascularization in their
study of T. serratifolia. According to Frey-
Wyssling (1955), a correlation exists between type
of vascularization of secretory structures and the
concentration of their secreted nectar. This
relationship however was not detected in a study of
nectar chemistry (Rivera, 1997).
Raised stomata, as those found in four species of
Tabebuia, are rare in the family, but have been
reported for Podranea ricasoliana (Rivera, 1996)
and Tecoma capensis (Subramanian & Inamdar,
1989). Stomata were always found on the apical
portion of the nectary, which corresponds to the
region of secretory activity in the nectary. The
apical location of stomata has already been noted in
Bignoniaceae and other families (Davis & Gunning,
1992; Galetto, 1995). According to some authors
(Davis & Gunning, 1992), nectary stomata are
modified in that their guard cells have lost their
ability to close completely. This theory has always
been suggested as a reason for the fact that nectary
stomata were always detected open. On the
contrary, other studies have confirmed the guard
cells capacity to alter the aperture regulating nectar
secretion (Zandonella, 1967; Davis & Gunning,
1993). Stomata in the nectaries of T. heptaphylla, T.
pulcherrima and Macfadyena unguis-cati revealed
an open ostiole in flowers just opened, while they
had a closed ostiole in 1-2 day-old flowers. The
stomata regulatory effect on secretion or resorption
was not corroborated.
Gentry (1980) reports that the trichomes on the
surface of the nectary of Tynnanthus micranthus
are responsible for the secretion of nectar in this
species but field observations and tests revealed no
secretion. On the other hand, it was also observed
that the nectary, although small, has a typical
secretory parenchyma and stomata on the epider-
mis, as is typical for functional secretory nectaries.
Gentry (1980) proposed the term «double» disk
to describe the secretory structure along with the
protuberance located between the perianthic
whorls in Melloa, also present in Macfadyena
dentata and Parabignonia chodatii. The expre-
ssion “double” probably arose from a macroscopic
236
Darwiniana 38(3-4). 2000
analysis of flowers without their corolla, in which
the nectary, resting on this protuberance would
appear as two stacked disks. Since this structure
does not perform any secretory function, nor is it
directly associated with the gland, it is
recommended that the term “double” disk be
abandoned.
The nectary volume was very variable as Galetto
(1995) reported. Nevertheless, there is a tendency in
the Bignonieae to form larger nectaries than those
present in Tecomeae. This propensity, as expected,
was also true for nectary/ovary ratios. The larger
nectary volume is probably related to the fact that
the flowers of lianas secrete more nectar than trees,
as was found in secretion studies (Rivera, 1997).
Nevertheless, the relationship between nectary
features and flower visitors is not apparent. Opler
(1983) reported a connection between flower size
and maximum secretion and different flower visitors
when analyzing several species of different families
in a tropical community. This relationship is not
apparent among the studied species when
comparing either nectary size or ovary/nectary
ratio, even when looking at different species of a
genus, visited by both hummingbirds and bees.
Although information of the taxonomic
distribution of nuptial nectaries in the family is far
from complete, it is apparent that structures similar
to those found in these species occur in members of
all Bignoniaceae. The nuptial nectary terms
proposed in this study provide a useful generic
character for future studies in other species, as the
types (secretory and vestigial) and the varieties of
the former (annular and cylindrical) remain constant
within a genus.
ACKNOWLEDGEMENTS
The author thanks E. Di Fulvio, A. E. Cocucci, A. A.
Cocucci, and two anonymous reviewers for constructive
comments to the manuscript, and R. Munch for
photographic assistance. CONICET (Consejo Nacional
de Investigaciones Científicas y Técnicas) and
CONICOR (Consejo de Investigaciones Científicas y
Técnicas de la Provincia de Córdoba) provided support
for this study.
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Appendix 1.- The species of Bignoniaceae included in the investigation are listed below. Department name and the site
of collection follow province name. N = number of specimens studied. The collectors were AAC= A.A. Cocucci, C= A.
Cabrera; GLR= G.L. Rivera; K= A. Krapovicas; L= R. Legname; PP= Pedro Prieto; wn= without collection number.
Taxon N Provenance, collectors, date
Tribe Eccremocarpeae Hogg.
Eccremocarpus scaber Ruiz & Pav. 1 Río Negro. Dpto. El Bolsón: Piltriquitrón, 9-I-1994. AAC 531
Tribe Bignonieae Dumort
Adenocalymma marginatum (Cham.) DC. 1 Misiones. Dpto. Igua: Cataratas, 2-II-1994. GLR 34
Amphilophium paniculatum DC. 1 Tucumán. Dpto. Burruyacu: El Cajón, 22-IX-1994. GLR 68
Anemopaegma flavum Morong 1 Santa Fe. Dpto. Obligado: Ocampo, 12-XI-1958. C 10487
Arrabidaea chica (Humb. & Bonpl.) Verl. 1
2
Misiones.
Dpto. Igua: Cataratas, 1-II-1994. GLR 32
Misiones.
Dpto. Igua: Yacuy, 2-II-1994. GLR 33
Arrabidaea corallina (Jacq.) Sandwith 1
2
3
Jujuy.
Dpto. Ledesma: Calilegua, 5-XI-1993. GLR 16
Jujuy.
Dpto. Ledesma: Urundel, 20-09-1994. GLR 62
Salta.
Dpto. On: Pichanal, 20-IX-1994. GLR 3
Arrabidaea selloi (Spreng.) Sandwith 1
2
Misiones.
Dpto. Igua: Cataratas, 1-II-1994. GLR 30
Misiones.
Dpto. Igua: Iguazú, 20-XII-1994. GLR 87
Clytostoma callistegioides (Cham.) Bureau ex Griseb. 1
2
rdoba.
Dpto. Capital: cultivada, 15-XI-1993. GLR 10
Jujuy.
Dpto. Ledesma: Calilegua, 5-XI-1993. GLR 14
Clytostoma binatum (Thumb.) Sandwith 1
2
Misiones.
Dpto. Igua: Cataratas, 1-II-1994. GLR 28
Misiones.
Dpto. Igua: Iguazú, 20-XII-1994. GLR 86
Cuspidaria convoluta (Vell.) A. H. Gentry 1 rdoba. Dpto. Colón: cultivada, 11-XI-1994. GLR 79
Dolichandra cynanchoides Cham. 1
2
rdoba.
Dpto. Colón: El Diquecito, 12-I-1994. GLR 40
rdoba.
Dpto. Capital: Villa Warcalde, 30-IV-1994. GLR 41
Macfadyena dentata K. Schum. 1
2
rdoba.
Dpto. Capital: cultivada, 15-X-1993. GLR 23
Misiones.
Dpto. Igua: Cataratas, 23-XII-1994. GLR 90
Macfadyena uncata (Andr.) Sprague & Sandwith 1 Misiones. Dpto. Igua: Ruta 101, 23-XII-1994. GLR 89
Macfadyena unguis-catis (L.) A. H. Gentry 1
2
3
Jujuy.
Dpto. Ledesma : Calilegua, 5-XI-1993. GLR 17
rdoba.
Dpto. Capital: Villa Allende, 20-X-1993. GLR 22
Salta.
Dpto. Sta. Victoria: Los Toldos, 21-IX-1994. GLR 65
Mansoa difficilis (Cham.) Bureau & K. Schum. 1 Misiones. Dpto. Igua: Ruta 101, 28-X-1994. GLR 75
Melloa
q
uadrivalvis (Jacq.) A. H. Gentry 1 Jujuy. Dpto. Ledesma: Calilegua, 5-XI-1993. GLR 15
Parabignonia chodatii (Hassler) A. H. Gentry 1 Jujuy. Dpto. Ledesma: Calilegua, 5-IV-1995. GLR 100
Pithecoctenium crucigerum (L.) A. H. Gentry 1
2
Misiones.
Dpto. Igua: Garganta Diablo, 26-X-1994. GLR 71
Misiones.
Dpto. Igua: Ruta 101, 27-X-1994. GLR 72
Pithecoctenium cynanchoides DC. 1
2
rdoba.
Dpto. Colón: Villa Warcalde, 15-I-1994. GLR 26
rdoba.
Dpto. Colón
: La Calera, 20-II-1994. GLR 56
Pyrostegia venusta
(Ker-Gawl.) Miers 1 rdoba.
Dpto. Capital
: cultivada, 18-V-1994. GLR 42
Tynnanthus micranthus
Corr. Méllo ex K. Schum. 1 Misiones.
Dpto. Igua
: Ruta 101, 22-XI-1994. GLR PP 80
Tribe Tecomeae Endlicher
Argylia uspallatensis DC. 1 Mendoza. Dpto. Uspallata: Uspallata, 14-XII-1994. AAC wn.
Jacaranda micrantha Cham. 1 Misiones. Dpto. Igua: Garganta Diablo, 22-XII-1994. GLR 91
Jacaranda mimosifolia D. Don 1 rdoba. Dpto. Colón: El Diquecito, 12-I-1994. GLR 39
Tabebuia alba Sandwith 1 Misiones. Dpto. Cainguás: Aristóbulo del Valle, 14-IX-1972. K 18612
Tabebuia aurea (Silva Manso) Benth. & Hook. 1 Maui. Kahului: Hawaii, U.S.A. cultivada. 20-III-1994. GLR 36
Tabebuia chrysotricha (Martius & DC.) Standl. 1
2
Tuc u mán .
Dpto. Burruyacú: 22-IX-1994. GLR 67
Misiones.
Dpto. Capital
: cultivada, 28-X-1994. GLR 76
239
G. L. RIVERA. Nuptial nectary structure of Bignoniaceae from Argentina
a
Native to South Africa, but commonly cultivated in the subtropics and in the Neotropics.
Taxon N Provenance, collectors, date
Tabebuia heptaphylla (Velloso) Toledo 1 rdoba. Dpto. Capital: cultivada, 4-X-1993. GLR 5
Tabebuia impetiginosa (Martius ex DC.) Standl. 1 Salta. Dpto. Capital: Cerro San Bernardo, 19-XI-1994. GLR wn
Tabebuia lapacho (K. Schum.) Sandwith 1 Salta. Dpto. Santa Victoria: Los Toldos, 21-IX-1994. GLR 64
Tabebuia nodosa (Griseb.) Griseb. 1 rdoba. Dpto. Ischilin: Cruz del Eje, 24-I-1995. GLR 92
Tabebuia ochracea (Cham.) Standl. 1
2
rdoba.
Dpto. Capital: cultivada, 14-IX-1993. GLR 2
Jujuy.
Dpto. Ledesma: Calilegua, 5-XI-1993. GLR 5
Tabebuia pulcherrima Sandwith 1 rdoba. Dpto. Capital: cultivada, 10-XII-1995. GLR 101
Tecoma capensis (Thunb.) Lindl.
a
1 rdoba. Dpto. Capital: cultivada, 18-V-1994. GLR 44
Tecoma garrocha Hieron. 1 La Rioja. Dpto. Capital: Los Sauces, 16-IX-1994. GLR 50
Tecoma stans (L.) Kunth 1
2
3
Tuc u mán .
Dpto. Tafí: San Javier, 2-XI-1993. GLR 12
Salta.
Dpto. La Caldera: La Caldera, 6-XI-1993. GLR 19
Jujuy.
Dpto. Ledesma: Calilegua, 5-IV-1995. GLR 96
Tecoma tenuiflora (DC.) Fabris 1 Salta. Dpto. Santa Bárbara: without locality, 15-10-1948. L 546
... Solanaceae Solanales buzz-pollination (Endress, 1998) Pyrostegia venusta (Ker Gawl.) Miers Bignoniaceae Lamiales ornithophily (Galetto et al., 1994;Rivera, 2000) ...
... In these species, orbicules may be spherical, sub-spherical or piriform, but they always have a smooth surface. Rauvolfia mattfeldiana, Allamanda cathartica (Apocynaceae); Geniostoma borbonicum, G. rupestre (Geniostomaceae); Mandevilla atroviolaceae (Apocynaceae) and Jacaranda mimosifolia (Bignoniaceae) are all examples of species that present the same pollination mode (Humeau et al., 2003;Castro & Robertson, 1997;Ehrenfeld, 1979;Löhne et al., 2004;Torres & Galeto, 1998;Rivera 2000) and orbicule morphology (Vinckier & Smets, 2002a, b;El-Ghazaly & Chaudhary, 1993;Hess, 1986;Huysmans et al., 1997;Galati & Strittmatter, 1999a, b). ...
... Pyrostegia venusta is an ornithophilous species (Galleto et al., 1994;Rivera 2000). Its pollen is dispersed by hummingbirds. ...
Article
Orbicules or Ubisch bodies are corpuscles of sporopollenin that appear in the anther locule during pollen grain development. Their size ranges from 0.14 μm to 20 μm. They present different shapes with a smooth or ornamented surface. Orbicules often form aggregates and sometimes have a plaque-like appearance. Ultrastructurally, they may present a central core with different degree of transparency to electrons. Those that do not have a central core are observed completely solid. Orbicules are resistant to acetolisis, autofluorescent when irradiated with ultraviolet light and have the same reaction to colorants that the exine of pollen grains. Their presence is generally associated with a tapetal membrane in species with secretor type tapetum and with a peritapetal membrane in species with intermediate or plasmodial type tapetum. Although the shed of orbicules out of the anther along with the pollen grains is cited, they are usually attached to the inner surface of the locule when the anther opens. Investigations suggest that orbicules appear in approximately 80 families of Angiosperms and Gimnosperms. It is not certain whether orbicules are not developed in the rests of the families or are just not informed. Researches on ontogeny and ultrastructure of orbicules are rare. However, their tapetal origin and their simultaneous formation with the pollen grain wall are well established. The systematic value of orbicules is known and considered in a few families, such as Loganiaceae, Gentianaceae, Apocynaceae, Rubiaceae and Oxalidaceae. Evolutionary studies on these bodies or on its relationship with the different modes of pollination are lacking. Even though orbicules are so common among angiosperms, their function is unknown and only speculations are made. On this report a review on orbicules is made and an analysis of their presence, ontogeny and morphology is presented. Our aim is to supply information that will help understand orbicules function. Therefore, the orbicules morphology in relation with the pollination mode is studied.
... Gentry (1980) señala la existencia de glándulas, pero sólo describe como nectario al disco que rodea la base del ovario. En la familia Bignoniaceae ha sido muy bien documentada la presencia y distribución de los nectarios florales, sin embargo el análisis de las estructuras secretoras que se encuentran en las hojas y otras partes vegetativas como tallo y pseudoestípulas sólo se realizó en algunas pocas especies (Elias & Prance, 1978;Rivera, 1996Rivera, , 2000. ...
... Anatómicamente los NEFs consisten de una epidermis secretora en empalizada y un estrato basal que puede estar formado por una sola célula o por un estrato de células cuboides, que permite su clasificación en simples y compuestos, términos propuestos por Rivera (2000) para los nectarios extranupciales de Bignoniaceae, ubicados en el cáliz y frutos y utilizados en el presente estudio. Esta estructura concuerda con la encontrada en nectarios descriptos en algunas especies de Bignoniaceae, tanto en NEFs ubicados en las hojas o nectarios extranupciales de cáliz y frutos (Elias & Gelband, 1976;Elias & Newcombe, 1979;Subramanian & Inamdar, 1989;Thomas & Dave, 1992;Rivera 2000). ...
... Anatómicamente los NEFs consisten de una epidermis secretora en empalizada y un estrato basal que puede estar formado por una sola célula o por un estrato de células cuboides, que permite su clasificación en simples y compuestos, términos propuestos por Rivera (2000) para los nectarios extranupciales de Bignoniaceae, ubicados en el cáliz y frutos y utilizados en el presente estudio. Esta estructura concuerda con la encontrada en nectarios descriptos en algunas especies de Bignoniaceae, tanto en NEFs ubicados en las hojas o nectarios extranupciales de cáliz y frutos (Elias & Gelband, 1976;Elias & Newcombe, 1979;Subramanian & Inamdar, 1989;Thomas & Dave, 1992;Rivera 2000). La presencia de NEFs simples o compuestos permite la identificación de las especies al estado vegetativo. ...
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A comparative anatomical study was undertaken on the leaves of 50 Argentinean Bignoniaceae species in order to investigate anatomical variations which may be useful in species identification and to evaluate their significance in the taxonomy of the family. Leaves were analyzed on surface view and in serial sections, cross and paradermal, using optical and scanning electron microscopy. Among the features that stand out for their diagnostic value are: position and anatomical structure of the extrafloral nectaries, trichome complement, number of layers of epidermis, mesophyll type and composition of leaf margin. These characteristic, alone or in combination may be useful in species identification. The results provide a comprehensive leaf anatomical character-set typical for the family.
... Fortunately, several authors have demonstrated the taxonomic and evolutionary value of floral nectaries in understanding the classification of many angiosperm groups. Examples of the groups that have been analysed with interesting and challenging results are: Apocynaceae-Asclepiadoideae (Christ & Schnepf, 1988), Bignoniaceae (Galetto, 1995a;Rivera, 2000a), Bromeliaceae (Böhme, 1988;Sajo et al., 2004), Costaceae (Newman & Kirchoff, 1992), Crossosomatales (Matthews & Endress, 2005a), Dipsacales (Wagenitz & Laing, 1984), Haemodoraceae (Simpson, 1993), Iridaceae (Rudall et al., 2003a), Lamiaceae (Dafni et al., 1988;Petanidou et al., 2000), Liliaceae (Khaniki & Persson, 1997), Malvales (Judd & Manchester, 1997;Vogel, 2000), Melastomataceae (Stein & Tobe, 1989), Melianthaceae (Decraene & Smets, 1999a;, Aizoaceae-Mesembryanthemoideae (Chesselet et al., 2002), Polygonaceae (Decraene & Smets, 1991a), Rhamnaceae (Medan & Aagesen, 1995), Solanaceae (Bernardello, 1987;, among others. More importantly, the survey publications on dicot groups by Smets (1986Smets ( , 1988 and Smets and Cressens (1988) and on monocot groups by Daumann (1970), Vogel (1981a), Endress (1995), and Smets et al. (2000) were fundamental to appreciation of the significant role of nectaries in systematics and evolution. ...
... The same situation is true for members of the mainly tropical Bignoniaceae-primarily centered in northern South America-most representatives of which have nectar as reward. The nectar is exuded from an annular ovarian nectary (Galetto, 1995a;Rivera, 2000a), a character that can be considered ancestral for the family. Nevertheless, in a few taxa from tribe Bignonieae (Cydista, Clytostoma, Phryganocydia, and some species of Lundia; Gentry, 1980Gentry, , 1982Rivera, 1996Rivera, , 2000a, the nectary is non-functional and the species are thought to be pollinated by deceit. ...
... The nectar is exuded from an annular ovarian nectary (Galetto, 1995a;Rivera, 2000a), a character that can be considered ancestral for the family. Nevertheless, in a few taxa from tribe Bignonieae (Cydista, Clytostoma, Phryganocydia, and some species of Lundia; Gentry, 1980Gentry, , 1982Rivera, 1996Rivera, , 2000a, the nectary is non-functional and the species are thought to be pollinated by deceit. As this tribe and the "mimetic clade" within it are considered to be derived (Lohmann, 2006), this condition can be regarded as derived as well and it seems to have evolved once in the group. ...
... Dolichandra chodatii is also characterized by woody tendrils, although this feature is shared with D. quadrivalvis and D. steyermarkii. The presence of a ring of tissue outside the corolla is also distinctive of D. chodatii but uncommon in other Dolichandra, shared only with D. quadrivalvis (Rivera 2000). This ring of tissue may be a vestigial calyx, in which case, the structure generally called calyx in D. chodatii would represent a pseudocalyx, composed of fused bracteoles or a second external calyx whorl. ...
... Dolichandra quadrivalvis is characterized by a thick, woody, oblong, and clearly four-parted fruit (Table 1). A ring of tissue outside the corolla is also distinctive of D. quadrivalvis, but uncommon in other Dolichandra; this feature is also found in D. chodatii (Rivera 2000). This ring of tissue may be a vestigial calyx, with the structure generally called calyx actually representing a pseudocalyx, composed of fused bracteoles or a second external calyx whorl. ...
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Dolichandra Cham. emend. L.G.Lohmann is a genus of Neotropical lianas in tribe Bignonieae (Bignoniaceae) that comprises nine species. It is centered in Paraguay, southern Brazil and northeastern Argentina, where six species occur and three are endemic. Species of Dolichandra are generally climbers of dry and wet lowland forests, also growing in swamps and gallery forest formations. The genus is characterized by four main synapomorphies: (i) stems with multiple dissected phloem wedges in cross-section, (ii) trifid and uncate tendrils, (iii) psilate and 3-colpate pollen, and (iv) capsules with four lines of dehiscense. Other features of the genus are the large and membranaceous calyces, dimorphic growth with the juvenile form attaching by its uncinate tendrils, lanceolate prophylls of the axillary buds, congested- cymose inflorescences, and a lobed nectary disk. In this taxonomic revision, we present detailed descriptions for all species recognized, taxonomic and nomenclatural comments, distribution maps and information on the habitat and distribution of each species, as well as information on their conservation status (i.e., IUCN categories), and illustrations of diagnostic characters. Thirty-five names are treated as synonyms, six of which are newly proposed. More specifically, Tecoma maximiliani Mart. ex DC. is synonymized under Dolichandra unguiculata (Vell.) L.G. Lohmann, Bignonia pseudounguis Desf., Bignonia unguis-cati var. radicans DC., and Macfadyena hassleri Sprague are synonymized under Dolichandra uncata (Andrews) L.G. Lohmann, while Bignonia tweediana Lindley and Dolichandra kohautiana Presl are synonymized under Dolichandra ungui-cati (L.) L.G. Lohmann. Lectotypes are proposed for 13 species names, namely Bignonia californica Brandegee, Bignonia gracilis G. Lodd., Bignonia inflata Griseb. Bignonia tweediana Lindley, Bignonia unguis-cati var. guatemalensis K. Schum. & Loes., Bignonia unguis-cati var. serrata Bureau & K. schum., Dolichandra cynanchoides Cham., Dolichandra fenzliana Miq. Macfadyena hassleri Sprague, Parabignonia steyermarkii Sandwith, Paradolichandra chodatii var. brachycalyx , Spathodea mollis and Tecoma maximiliani Mart. ex DC.
... Nectar has been considered the most important resource available to anthophilous animals in angiosperms (Galetto & Bernardello 2005;Willmer 2011). Bignoniaceae species are predominantly zoophilous (Gentry 1974;Alcantara & Lohmann 2010) and the fl oral nectar production has been commonly attributed to a conspicuous nectary, characterized as a disk that surrounds the ovary base (Gentry 1992;Galetto 1995;2009;Rivera 2000). Th is nectariferous disk is usually composed by a secretory epidermis and secretory parenchyma, predominantly supplied by phloem (Galetto 1995;Thomas & Dave 1992;Rivera 2000;Guimarães et al. 2016). ...
... Bignoniaceae species are predominantly zoophilous (Gentry 1974;Alcantara & Lohmann 2010) and the fl oral nectar production has been commonly attributed to a conspicuous nectary, characterized as a disk that surrounds the ovary base (Gentry 1992;Galetto 1995;2009;Rivera 2000). Th is nectariferous disk is usually composed by a secretory epidermis and secretory parenchyma, predominantly supplied by phloem (Galetto 1995;Thomas & Dave 1992;Rivera 2000;Guimarães et al. 2016). However, in some genera as Clytostoma, Cydista, Phryganocydia (now treated as Bignonia according to Lohmann & Taylor 2014) and Lundia the nectariferous disk is absent, and these nectarless flowers are supposed to be pollinated by deceit (Gentry 1980). ...
Article
Full-text available
The genus Zeyheria (Bignoniaceae) comprises only two species, both of which have been described as possessing a reduced and non-functional nectary disk. Despite the importance of this evolutionary change in the floral nectary, these functional assumptions have been based on disk size and on the distribution, abundance and histochemistry of corolla-borne trichomes. By combining methods on light and electron microscopy, here we investigated the functionality of the reduced nectary disk and describe all of the tissues and structures of the nectar chamber in order to determine the sites of floral nectar secretion in both Zeyheria species. . Our data find the floral nectary traits of both species to be very similar, although differing in their cellular contents. Subcellular evidence in both species indicated that disk, stipe and petal axils were, predominantly, involved in hydrophilic secretion, while capitate glandular trichomes produced lipophilic secretion and papillae produced mixed secretion. Our study shows that in spite of its reduced size, the reduced disk functions in nectar secretion in both species of Zeyheria. This kind of nectary system is a novelty for Bignoniaceae, since it comprises several tissues and structures functioning in an integrated fashion.
... El segundo mecanismo que favorece la asociación mutualística entre las plantas y los insectos son los nectarios extraflorales (NEFs), mediante los cuales las plantas brindan alimento a las hormigas y en compensación, éstas brindan protección contra los fitófagos (Bentley, 1977;Rogers, 1985;Heads, 1986;Oliveira et al. 1987;Oliveira & Pie, 1998). La lista de Bignoniaceae con NEFs fue actualizada por Keeler (2010), registrando de la literatura la presencia de NEFs en 176 de unas 800 especies de la familia, la mayoría de los cuales son nectarios extranupciales ubicados en cáliz y frutos (Rivera, 2000) con escasas observaciones de NEFs en hojas. Tal vez el único trabajo realizado en órganos vegetativos de esta familia sea el de Seibert (1948) quien reconoció la presencia de glándulas en diversas posiciones, entre las que describe bajo la categoría de glándulas neuro-axilares a los domacios o "coeliac glands" y a los campos glandulares, ambos ubicados en la axila de las venas laterales. ...
... Autores como Grose & Olmestead (2007) o Zapater et al. (2009) los describieron como escamas o tricomas glandulares; sin embargo por su estructura anatómica y producción de néctar muy atractivo para las hormigas se los considera aquí como nectarios extraflorales (Gonzalez, trabajo en preparación). Su estructura anatómica concuerda con la encontrada en nectarios extraflorales descriptos por Elias & Gelband (1976), Elias & Newcombe (1979, Subramanian & Inamdar (1989), Thomas & Dave (1992) y los descriptos como extranupciales por Galetto (1995) y Rivera (2000), ubicados en el cáliz y frutos. ...
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Plants have mutualistic relationships with insects in two ways: through domatia provide housing of predators, and extrafloral nectaries secreting nectar and provide food in exchange for control of herbivores or fungal pathogens. The foliar anatomy of 52 species of Bignoniaceae was examined by light and scanning electron microscopy, in order to describe the different types of domatia and extrafloral nectaries. Two types of domatia were observed: small hair-tufts and pockets; the presence and type of domatia represents important taxonomic characters in Bignoniaceae. Extrafloral nectaries are found in all studied species. They are located in different positions: along the midvein, associated with domatia, or grouped in glandular fields, either in leaf or interpetiolar. The Bignoniaceae have simultaneously domatia and extrafloral nectaries on their leaves, these features are described as plant components in a probable mechanism of indirect defense.
... Bignoniaceae is known by the presence of zoophilous flowers (Gentry, 1974), with most species presenting nectar as trophic resource, which is produced by a conspicuous nectariferous annular disk that surrounds the ovary base (Galetto, 1995). However, some Bignoniaceae species may present nectarlessness flowers, which has been associated with the absence of a disk (Hauk, 1997), or with the presence of vestigial and non-secretory disks (Rivera, 2000) and with pollination by deceit (Umaña et al., 2011). In spite of Jacaranda oxyphylla Cham. ...
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The presence of nectarless flowers in nectariferous plants is a widespread phenomenon in angiosperms. However, the frequency and distribution of nectarless flowers in natural populations, and the transition from nectariferous to nectarless flowers are poorly known. Variation in nectar production may affect mutualism stability, since energetic resource availability influences pollinators’ foraging behavior. Here, we described the spatial and temporal nectar production patterns of Jacaranda oxyphylla, a bee-pollinated species that naturally presents nectarless flowers. Additionally, we compared nectariferous and nectarless floral disks in order to identify histological, subcellular and chemical changes that accompanied the loss of nectar production ability. For that we used standard methods for light and transmission electron microscopy, and gas chromatography coupled to mass spectrometry for chemical analyses. We verified that 47% of flowers did not produce nectar during the whole flower lifespan (nectarless flowers). We also observed remarkable inter-plant variation, with individuals having only nectarless flowers, others only nectariferous ones and most of them showing different proportions of both flower types, with variable nectar volumes (3–21 μl). Additionally, among nectariferous flowers, we registered two distinct rhythms of nectar production. ‘Early’ flowers produced nectar from 0 to 24 h, and ‘late’ flowers produced nectar from 24 to 48 h of anthesis. Although disks from nectariferous and nectarless flowers displayed similar histological organization, they differed strongly at subcellular level. Nectariferous (‘early’ and ‘late’) flowers exhibited a cellular apparatus typical of nectar secretion, while nectarless flowers exhibited osmophoric features. We found three aliphatic and one aromatic compound(s) that were detected in both the headspace of flowers and the disks of nectarless flowers, but not the disks of nectariferous flowers Although the remarkable variation in nectar availability may discourage pollinator visits, nectarless flowers might compensate it by producing volatile compounds that can be part of floral scent, acting as chemical attractants. Thus, nectarless flowers may be helping to maintain pollination in this scenario of trophic resource supply scarcity. We suggest that J. oxyphylla can be transitioning from a nectar-based pollination system to another resource-based or even to a deceit mechanism of pollination.
... Algunos trabajos abordan temas tales como la estructura de los nectarios y la química del néctar. La mayoría de los nectarios nupciales descriptos para especies chaqueñas se encuentran en la base del ovario o rodeando al mismo, y la salida del néctar tiene lugar usualmente por medio de estomas (Galetto et al., 1990;Galetto, 1995;Lin y Bernardello, 1999;Rivera, 2000b). En cambio, en las Bromeliáceas los nectarios son septales (Bernardello et al., 1991). ...
... Although L. tulipifera nectar is secreted through nectarostomata, the L. tulipifera flower nectary structure is very different than that of Brassicaceae flowers (Kram and Carter, 2009) and even that of Magnolia stellata in the same Magnoliaceae family (Erbar, 2014). As an apocarpous gynoecium flower, the nectary of L. tulipifera flowers was located on the modified orange-yellow part of petals, as in flowers of Helleborus and Symphyglossum (Vesprini et al., 1999;Stpiczynska and Davies, 2006), whereas in most species, it encircles the ovary (Brown, 1938;Zer and Fahn, 1992;Rivera, 2000;Konarska, 2010;Nocentini et al., 2012;Stpiczyñska et al., 2012;Lüttge, 2013;Stephens, 2013). Although this result was consistent with previous findings in plants in the Ranunculaceae family (Kosuge, 1994), it was different from what has been seen in M. stellata in the same family (Erbar and Leins, 2013). ...
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Nectar is a primary nutrient reward for a variety of pollinators. Recent studies have demonstrated that nectar also has defensive functions against microbial invasion. In this study, the Liriodendron tulipifera nectary was first examined by scanning electron microscopy, and then the nectar was analysed by two-dimensional gel electrophoresis and liquid chromatography–tandem mass spectrometry, which led to identification of 44 nectar proteins involved in various biological functions. Bioinformatic analysis was then performed on an identified novel rubber elongation factor (REF) protein in L. tulipifera nectar. The protein was particularly abundant, representing ~60% of the major bands of 31 to 43 kDa, and showed high, stage-specific expression in nectary tissue. The REF family proteins are the major allergens in latex. We propose that REF in L. tulipifera nectar has defensive characteristics against microorganisms.
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The purpose of fixation is twofold: to bring about the rapid cessation of biological activity and to preserve the structure of the cell. Ideally, the colloidal Suspension of the cytoplasm and organelles within a cell is turned into a gel that maintains the spatial relationship of the components while providing sufficient stability for them to survive the solvent action of aqueous buffers, dehydration agents, and plastic resins. The objective is to process tissues and cells without significant changes in size, shape, and positional relationships of the cellular components and to preserve as much of the biological activity and chemical nature of cellular constituents, such as enzymes and antigenic proteins.
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The structure and anatomy of floral trichomes and nectaries of 4 species of Tecomeae (Bignoniaceae) are studied. All taxa exhibit pluricellular glandular trichomes of different forms and distribution in calyx, corolla and ovary wall and bear a conspicuous floral nectary except for Catalpa bignonioides Walter. In this species the floral nectary is reduced and appears to be a vestigial organ without a secretory function. The nectary of Argylia radiata (L.) D. Don, Podranea ricasoliana (Tanfani) Sprague and Pandorea jasminoides (Lindl.) K. Schum. comprises epidermis and secretory parenchyma without intercellular spaces. Secretory tissue is supplied by phloem. Raised nectarial stomata were found only in P. ricasoliana, whereas they are at the same level of the epidermis in the remainder species. Extrafloral nectaries were found in flowers of P. jasminoides and P. ricasoliana in the outer surface of the calyx. Those of P. jasminoides are cupular and vascularized while those of P. ricasoliana are patelliform and nonvascularized.
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