Hoehnea 45(4): 669-676, 19 fig., 2018
http://dx.doi.org/10.1590/2236-8906-44/2018
Morphological analysis of pollen grains from heterodynamous stamens
of some Aeschynomene L. (Leguminosae: Papilionoideae - Dalbergieae)
Higor Antonio-Domingues1,2,4, Angela Maria da Silva Corrêa2, Monica Lanzoni Rossi3,
Adriana Pinheiro Martinelli3 and Cynthia Fernandes Pinto da Luz2
Received: 4.05.2018; accepted: 21.08.2018
ABSTRACT – (Morphological analysis of pollen grains from heterodynamous stamens of some Aeschynomene L. (Leguminosae – Papilionoideae – Dalbergieae)). Flowers with heterodynamous stamens can present differences in the pollen
grains of each stamen size group. Species of Aeschynomene L. present didynamous stamens (five long and five short) but
little is known about their pollen dimorphism. The objective of this study was to increase the knowledge about the pollen
characteristics in Aeschynomene and emphasize the possible morphological differences between the pollen grains of long
and short stamens in order to contribute to ecological and taxonomic studies. Pollen grains from the two groups of stamens
size of ten species were analyzed separately, according to the standard methodology for studies of pollen morphology. In
addition, analyses of variance, comparison of means and base index were performed. The results showed that the amb,
shape, endoaperture type and sexine ornamentation did not vary in the pollen grains of the long and short stamens in the
same specimen, but they varied among the species. However, in relation to the size of the pollen grains of the two groups
of stamens, four species presented significant differences regarding the size of the polar and equatorial axes. The pollen
morphological data obtained considering the heteromorphism of the stamens can contribute to the knowledge of the reproductive dynamics of the genus, and to the systematic studies.
Keywords: Fabaceae, heteromorphism, Dalbergia subclade, Palynology, pollen morphology
RESUMO – (Análise morfológica dos grãos de pólen de estames heterodínamos de algumas Aeschynomene L. (Leguminosae:
Papilionoideae - Dalbergieae)). Flores que apresentam androceu com estames de alturas diferentes (heterodínamos) podem
também apresentar características distintas entre os grãos de pólen em cada tamanho de estame. As espécies de Aeschynomene
L. apresentam estames didínamos (cinco longos e cinco curtos), mas até o momento pouco se sabe sobre o dimorfismo polínico.
Diante da carência de estudos palinológicos do gênero, o objetivo do presente trabalho foi de incrementar o conhecimento
sobre as características polínicas do gênero Aeschynomene L., enfatizando as possíveis diferenças morfológicas entre os
grãos de pólen dos grupos de estames longos e curtos, contribuindo com os estudos ecológicos e taxonômicos. Os grãos de
pólen dos dois grupos de tamanho de estames de 10 espécies foram analisados separadamente utilizando-se a metodologia
padrão em morfologia polínica, além de análises de variância e de comparação da média e índice de base. Os resultados
inéditos mostraram que as características de âmbito, forma, tipo de endoabertura e ornamentação da sexina não variaram
entre os grãos de pólen dos estames longos e curtos num mesmo espécime, mas sim entre as espécies. No entanto, com
relação ao tamanho dos grãos de pólen dos dois grupos de estames, quatro espécies apresentaram diferenças significativas
quanto ao tamanho dos eixos polar e equatorial. Os dados morfopolínicos adquiridos com relação ao heteromorfismo dos
estames podem contribuir para o conhecimento da dinâmica reprodutiva do gênero e para os estudos sistemáticos.
Palavras-chave: Fabaceae, heteromorfismo, morfologia polínica, Palinologia, subclado Dalbergia
Introduction
The tribe Dalbergieae sensu latu Klitgaard
and Lavin (2005) in Papilionoideae subfamily of
Fabaceae comprises 49 genera, wich Aeschynomene
L. as the third most representative of the tribe .
The Aeschynomene genus presents pantropical
distributions, with approximately 180 species in the
1. Instituto de Botânica, Programa de Pós-Graduação em Biodiversidade Vegetal e Meio Ambiente, Avenida Miguel Stéfano, 3687,
04301-902 São Paulo, SP, Brasil
2. Instituto de Botânica, Núcleo de Pesquisa em Palinologia, Avenida Miguel Stéfano, 3687, 04301-902 São Paulo, SP, Brasil
3. Universidade de São Paulo, Centro de Energia Nuclear na Agricultura, Laboratório de Histopatologia e Biologia Estrutural de Plantas,
Avenida Centenário, 303, 13400-970 Piracicaba, SP, Brasil
4. Corresponding author: higor.domingues@hotmail.com
670
Hoehnea 45(4): 669-676, 2018
world (Rudd 1981, Lewis et al. 2005). Brazil is a
centre of diversity, with 49 accepted species, from
which 26 are endemic (Lima et al. 2015). The genus’
habit varies from herbaceous to shrubby and is divided
into two sections and nine series (Rudd 1955, 1959,
Fernandes 1996). However, the combined analysis by
Ribeiro et al. (2007) and others (Lavin et al. 2011)
demonstrated the paraphyly of genus. Aeschynomene
presents papilionoid corolla, which is related to the
co-evolution between the hymenopterans and the
Papilionoideae (Arroyo 1981, Judd et al. 2007),
whose flowers’ androecium has heterodynamous
stamens (five long and five short) and uniform anthers
(Rudd 1955). Tucker (1996) studied many species
of Leguminosae and pointed out that stamens with
dimorphisms are commonly found in this family,
possibly differing in size, filament length, anther
shape and moment of dehiscence. The presence of
different stamen sizes was diagnosed in Aeschynomene
in research carried out by Burkart (1939), Fernandes
(1996), Sampaio (2005), Silva & Antunes (2014).
Carvalho & Oliveira (2003) found significant
differences in the pollen grains-dimensions among
heteromorphic anthers of Senna sylvestris (Vell.)
H.S. Irwin & Barneby (Leguminosae) and Luo et al.
(2008) describe differences in sexine ornamentation
among long and short stamens of the same specimen
of Melastoma malabathricum L. (Melastomataceae).
It is also known that polymorphism occurs
in the size of the pollen grain of longistylous and
brevistylous flowers (Furtado et al. 2014), in the
number of apertures (Stanski et al. 2016) and sexine
ornamentation of Psychotria capitata (Ruiz & Pav.)
(Rubiaceae) (Ganders 1976, Stanski et al. unpublished
data). These characters that change depending on the
floral morphology, such as the number and aperture
type and sexine ornamentation are important in
the delimitation of pollen types in ecological and
palynotaxonomic studies (Salgado-Labouriau 1973,
Lorscheitter 2006).
There are studies available concerning pollen
morphology of Aeschynomene, such as Sharma
(1968), Ohashi (1971), Salgado-Labouriau (1973),
Pire (1974), Mitra and Mondal (1982), von der Ohe
and Dustmann (1996), Souza et al. (2004), Buril et al.
(2011) and Antonio-Domingues et al. (2015, 2016a,
2016b). However, these authors did not describe the
pollen grains separately from long and short stamens.
Studies on genus concerning the morphological
differences between pollen grains from heterodynamous
groups of stamens are inexistent. In this context, the
aim of this research was to carry out an unprecedented
analysis of the pollen morphology of ten species from
the genus Aeschynomene L.; with attention to the
possible morphological differences between long and
short stamens of the same specimen to contribute to
the studies of reproductive biology, pollination and
taxonomy to the genus.
Materials and methods
Flower buds were collected from herbarium
specimens of ten Aeschynomene L.: Aeschynomene
americana L.: BRAZIL. São Paulo: São Paulo, Anel
Viário, 27-II-2015, Shirasuma RT 4032 (SP488201).
Aeschynomene brevipes Benth.: BRAZIL. Mato
Grosso: Pontes e Lacerda, 18-IV-2012, Borges L.M.
& Oliveira CT 757 (RB608259). Aeschynomene
denticulata Rudd.: BRAZIL. Mato Grosso do
Sul: Porto Mourinho, Rodovia Bonito, 14-XI-2002,
Hatschbach M. et al. 74233 (MBM276632).
Aeschynomene elaphroxylon (Gillies & Perrr.) Taub.:
BRAZIL. Rio de Janeiro: Rio de Janeiro, Jardim
Botânico do Rio de Janeiro, 20-XIII-1984 Faria
S.M. & Lima H.C. 119 (RB335688). Aeschynomene
fluminensis Vell.: BRAZIL. Mato Grosso do Sul:
Campo Grande, Anel Viário, 14-XIII-2001, Lima
L.C.P. et al. 105 (SP367488). Aeschynomene martii
Benth.: BRAZIL. Bahia: Livramento do Brumado,
25-III-1991, Lewis G.P. & Andrade A.S.M.M. 1972
(MBM147346). Aeschynomene montevidensis Vogel:
BRAZIL. Paraná: Guaíra, Parque Nacional de Sete
Quedas, 18-III-1982, Melo M.M.R.F. 328 (SP209299).
Aeschynomene rudis Benth.: BRAZIL. Maranhão:
Viana, 23-VII-1919, Carvalho O. 3 (SP3427).
Aeschynomene selloi Vogel.: ARGENTINA. Buenos
Aires: Belgramo Bajo, 10-I-1931, Burkart A. 3630
(SP28105). Aeschynomene sensitiva Sw.: BRAZIL.
Paraná: Paranaguá, Alexandra, 21-XII-1948,
Tassmann G. s.n. (SP58253).
Groups with long (+) and short (-) stamens
were segregated for palynological analysis. To avoid
contamination between groups (+) and (-) samples
were dissected under stereomicroscope, with sterilized
tweezers and just flowers with anthers in pre anthesis
were studied. These samples were prepared according
to Erdtman (1960) and Melhem et al. (2003).
For each stamen group (+) and (-) of each
specimen the polar and equatorial axes in equatorial
view were measured in 25 random pollen grains.
The measurements of length and width of colpus
and endoapertures, thickness of sexine layer
Antonio-Domingues et al.: Pollen from heterodynamous stamens of Aeschynomene 671
(tectum + columelae) and nexine layer, total exine
(sexine + nexine) and lumen length were based on ten
pollen grains. The description of pollen morphology
to the genus level followed Barth and Melhem (1988),
Punt et al. (2007) and Hesse et al. (2009).
For the 25 measurements we performed the
arithmetic mean (x), with the standard deviation
pattern (sx), the sample deviation standard (s) and the
coefficient of variation (V). The comparisons of means
were performed through the analysis of confidence
interval at 95% of probability (Vieira 1981), with
software Minitab 14. For the ten measurements the
arithmetic mean was calculated, except for lumen size
at which the variation range was used.
The values of axes were subjected to variance
analysis (ANOVA) and significant differences
between means were identified by the Tukey test at
5 % probability. The base index (BX) was calculated
and consists of the subtraction of each of the 25
measurements of an axis (MS) by the smallest value
of variation range (M). Classes were established:
with values lower than 2.0 considered as a low value
(< 2.0 = B-) and values higher than 2.0 as a high value
(> 2.0 = B+). This index was described along with the
sample standard deviation, coefficient of variability
and the statistical difference between the stamens
of the groups (+) and (-) per species, to establish a
standard among the four variables.
Photomicrographs were obtained using an
OLYMPUS BX 50 microscope with camera and
CellSens software for Windows. For the SEM images
the pollen grains were deposited in a metal stub,
coated by cathodic spray (Leica EM ACE 600) using
Au with thickness of 120 nm. Samples were observed
under the SEM JEOL JSM-IT300LV (Tokyo Japan)
operating with 20 kV electron beam and the images
were digitized.
Results and Discussion
Aeschynomene L. (figures 1-17, table 1)
The pollen grains from the two groups of
stamens of Aeschynomene presented the following
characteristics: monads, small to medium sized;
isopolar; amb varying from circular to triangular,
shape varying from oblate to prolate; 3-colporate
(figures 1-6), colpi with margin (figures 2, 7, 10-11),
colpi with pointed apices (figures 4, 8) or bifurcates
and united at the pole (parasyncolporate) (figures 5,
9), with operculum (figures 1-2, 10-11), operculum
presenting different patterns of ornamentation
(figures 10-11). Endoaperture varying from lolongate
(figure 1), to lalongate (figure 2) up to circular.
Nanoreticulate, microreticulate (figure 11) to reticulate
(figure 13) or rugulate (figure 12) exine; the lumens
vary from < 0.50 μm (nanoreticulate) to >1.0μm
(reticulate) (figure 13-15; table 1); simplicolumellate
muri. Sexine thicker than the nexine (figures 3, 6, 1617).
Pollen morphology of short and long stamen groups
These characteristics (polarity, amb, apertures,
ornamentarion) did not vary between the two sets of
stamens, but rather between the species. The pollen
grain differences among the species demonstrate that
the palynological characteristics can be used in the
segregation of the species with palynotaxonomic
value.
Although the pollen grains of the long and short
stamens are in the same size class in Aeschynomene
denticulata, A. elaphroxylon, A. montevidensis and A.
rudis, they present significant differences concerning
the size of their polar and equatorial axes, when
submitted to the analysis of variance and subsequent
Tukey’s test (table 1). When submitted to the same
analyses, the specimens of A. americana, A. brevipes,
A. fluminensis, A. martii, A. selloi and A. sensitiva they
did not present significant differences.
Carvalho & Oliveira (2003) report that the long
anther of Senna sylvestris has the largest pollen grains
when compared to those of the other short anthers.
Furtado et al. (2014) demonstrated that the longistylous
morpho of Psychotria capitata presented smaller
pollen grains (12.87 ± 1.28 μm) than the brevistylous
morpho (18.73 ± 0.60 μm). We did not observe here
the pattern long stamen/largest pollen grain axes in all
species. According to our study, the pollen grains of
the short stamens not necessarily present low values
of the axes, as in A. elaphroxylon (figures 16-17, table
1), whose pollen grains of the short stamens presented
a higher mean to polar and equatorial axes of pollen
grains from the long stamen group. In the case of A.
denticulata and A. montevidensis, the long stamens
presented the pollen grains with the largest polar axes,
whereas in A. elaphroxylon and A. rudis it was the
short stamens that presented the highest values for the
same axis (table 1). Concerning the equatorial axis,
the pollen grains from these four species, the short
stamens always had the highest values.
Considering a confidence interval at 95% for
the equatorial and polar axes, it can be observed that
672
Hoehnea 45(4): 669-676, 2018
Figures 1-17. Light (1-6, 16-17) and scanning electron micrographs (7-15) of the pollen grains of Aeschynomene. 1. A. brevipes, equatorial
view, detail of the operculate colpus and lolongate endoaperture. 2. A. sensitiva, equatorial view, detail of the operculate colpus and lalongate
endoaperture. 3. A. americana, equatorial view, optical section. 4. A. montevidensis, polar view, normal colporus (not parasyncolpate). 5.
A. americana, polar view, parasyncolpate colporus. 6. A. denticulada, polar view, optical section. 7-8. A. fluminensis. 7. equatorial view.
8. polar view, normal colporus (not parasyncolpate). 9. A. americana, polar view, parasyncolpate colporus. 10. A. elaphroxylon, equatorial
view, detail of the operculum and the reticulate-microreticulate sexine. 11. A. americana, equatorial view, detail of the operculum and
the nanoreticulate sexine. 12. A. brevipes, equatorial view, rugulate sexine. 13. A. martii, reticulate sexine. 14. A. selloi, nanoreticulate to
reticulate sexine. 15. A. denticulata, nanoreticulate to microreticulate sexine. 16-17. A. elaphroxylon. 16. pollen grain of the long stamen.
17. pollen grain of the short stamen. Scale bar = 5 μm (1-8, 16-17); 1 μm (9-15).
Antonio-Domingues et al.: Pollen from heterodynamous stamens of Aeschynomene 673
(figures 18-19, table 1): 1) at the polar axis (figure
18), A. americana (+ -) are different from the others
because presents the smallest pollen grains. From A.
montevidensis (-) up to A. brevipes (-), was formed a
continuous values group; within this group A. rudis
(-) and A. selloi (+) presented the widest range in
the confidence interval limits and largest values to
coefficient of variability. From A. martii (+) up to A.
fluminensis (-), another continuous values group was
formed. Aeschynomene fluminensis had the highest
values to polar axis. Aeschynomene martii (-) and
A. elaphroxylon (+) presented the widest range in
the confidence interval limits and largest values to
coefficient of variability. 2) at the equatorial axis
(figure 19), the pollen grains formed two continuous
groups with the lowest values; one smaller than 19 µm
from Aeschynomene sensitiva (+) up to A. rudis (+),
and another one larger than 19 µm from A. americana
(-) to A. martii (+). From the larger than 19 µm, A.
martii (-) presented the broader range in the confidence
interval limits among all species. Separating from
the other pollen grains, A. fluminensis (- +) grouped
together with intermediate values of the equatorial
axis and A. elaphroxylon (+ -) grouped together with
the largest values and broadest range on the interval
of confidence limits, corroborating the results pointed
out by the ANOVA procedure and subsequently
the Tukey’s test. Aeschynomene denticulata, A.
montevidensis and A. elaphroxylon, differently from
A. rudis, did not separate in the confidence interval,
but present significant differences.
The base index (B) demonstrated the difference
of the data values between the lowest sample values
compared with the other values measured for each axis
of the pollen grains (table 1). The highest B indexes
were found in A. elaphroxylon (≥ 3.3), followed by A.
martii (≥ 2.7), A. brevipes (≥ 2.2) and A. rudis (≥ 2.2).
In these species, the highest values for the standard
deviation of the sample and for the coefficient of
variation were also observed, however not all species
presented significant differences between the pollen
grain axis of the (+) and (-) stamens group (A. brevipes,
A. martii). Although they have B+, in A. martii, A.
brevipes and A. rudis, these values were found only
in one of the axes from one of the groups of stamens,
whereas the others axes were B-. The lowest B indexes
were found in A. montevidensis (≤ 0.7), followed by A.
denticulata (≤ 0.9), with significant differen between
stamen group (+) and (-). It is worth mentioning that
between the two groups of stamens, A. americana,
presented the highest index of the basis (B), standard
deviation of the sample and coefficient of variation
than some species with significant differences.
Therefore, it is not possible to establish a constant
pattern among the four variables compared.
Concerning their axes size and the B values, the
pollen grains of the long stamens of Aeschynomene
denticulata, A. elaephroxylon, A. montevidensis and
A. rudis presented significant differences in polar and
equatorial axes when compared to the short stamens.
The pollen grains of the other species studied did
not present statistically significant differences in
these axes. It is recommended that new statistical
treatments and models be used, as well as studing
more species and specimens of Aeschynomene aiming
to complement the data obtained. As the pollen
Figure 18. Representation of confidence interval of means at
95% of probability of Polar axis (μm) in equatorial view of
Aeschynomene pollen grains. The higher and lower boundaries
show the confidence interval; the average circle shows the
arithmetic mean.
Figure 19. Representation of confidence interval of means at
95% of probability of Equatorial axis (μm) in equatorial view of
Aeschynomene pollen grains. The higher and lower boundaries
show the confidence interval; the average circle shows the
arithmetic mean.
+-
+
A. brevipes
+
A. denticulata +
A. elaphroxylon +
A. fluminensis +
A. martii
+
A
.
+
montevidensis
A. rudis
+
A. selloi
+
A. sensitiva
+
A. americana
Polar axis (P)
CI- (x ± sx) CI+
Bx
17.0 (17.2a ± 0.1) 17.5 1.3
17.0 (17.3a ± 0.1) 17.6 1.5
20.8 (21.1a ± 0.2) 21.5 1.2
21.4 (21.7a ± 0.1) 22.0 2.2
20.4 (20.7a ± 0.1) 21.1 1.6
20.0 (20.2b ± 0.1) 20.5 1.1
26.7 (27.4a ± 0.3) 28.0 3.3
28.1 (28.5b ± 0.2) 28.9 2.6
27.5 (27.8a ± 0.2) 28.2 1.6
28.6 (28.9a ± 0.2) 29.2 1.5
26.4 (26.7a ± 0.1) 27.0 1.1
26.5 (27.0a ± 0.2) 27.5 2.7
s
0.5
0.7
0.8
0.7
0.8
0.6
1.6
1.0
0.9
0.8
0.7
1.2
V%
3.2
4.1
3.9
3.3
3.9
3.1
6.0
3.5
3.4
2.7
2.8
4.7
Equatorial axis (E)
CI- (x ± sx) CI+
Bx
18.8 (19.0a ± 0.1) 19.3
1.9
18.8 (19.1a ± 0.1) 19.3
1.5
17.1 (17.4a ± 0.2) 17.8
1.1
17.5 (17.8a ± 0.1) 18.1
1.4
17.1 (17.3a ± 0.1) 17.5
1.2
17.4 (17.6b ± 0.1) 17.8
0.9
28.2 (28.5a ± 0.5) 29.4
2.8
29.2 (29.8b ± 0.3) 30.3
3.5
24.3 (24.7a ± 0.2) 25.0
1.2
24.0 (24.5a ± 0.2) 24.9
1.7
20.3 (20.8a ± 0.2) 21.3
1.8
20.1 (20.6a ± 0.2) 21.2
1.0
s
0.6
0.6
0.9
0.7
0.5
0.5
2.6
1.3
0.8
1.0
1.1
1.3
V%
3.3
3.2
4.9
4.2
3.0
2.9
9.1
4.5
3.4
4.1
5.6
6.5
P/E
Colpus
x Lenght Width
0.9 3.02
0.9 3.08
1.2 18.01 3.44
1.2 18.28 2.94
1.2 16.56 3.12
1.1 16.37 3.35
0.9 21.72 5.51
0.9 22.10 5.48
1.1 22.47 4.86
1.1 23.82 5.01
1.2 23.76 3.87
1.3 23.88 3.53
Endoaperture
Lenght Width
5.80
6.19
6.22
6.56
8.70
5.20
8.15
4.55
5.56
6.53
5.87
6.99
10.37 10.85
10.41 11.87
8.81
8.56
8.95
8.86
10.40 7.49
10.85 8.27
Exine
Nex Sex Ex
Lum
0.45 0.801.32 0.30-0.75
0.45 0.911.36 0.25-0.55
0.53 1.371.90
0.53 1.261.78
0.47 0.801.27 0.40-0.60
0.45 0.851.29 0.30-0.60
1.19 1.332.42 0.85-1.65
1.20 1.422.58 0.50-1.50
0.78 1.392.16 0.50-0.65
0.71 1.472.17 0.35-1.00
0.49 0.921.41 0.35-0.80
0.54 0.961.50 0.25-0.70
19.7 (19.9a ± 0.1) 20.0
0.6 0.4 1.8
19.8 (20.0a ± 0.1) 20.2
1.0 0.4 2.0 0.9 15.06 3.37
5.07
7.55
0.75 1.492.23 0.30-0.60
19.2 (19.4b ± 0.1) 19.6
19.5 (19.8a ± 0.1) 20.1
20.2 (20.7b ± 0.2) 21.1
19.7 (21.3a ± 0.2) 22.8
21.2 (21.5a ± 0.0) 21.8
20.1 (20.4a ± 0.1) 20.7
19.8 (20.1a ± 0.1) 20.4
0.9
1.4
1.7
1.6
1.3
1.0
1.1
19.8 (20.0b ± 0.1) 20.1
17.9 (18.1a ± 0.1) 18.4
19.1 (19.5b ± 0.2) 19.8
19.1 (19.3a ± 0.1) 19.5
18.4 (19.2a ± 0.1) 20.3
17.1 (17.3a ± 0.1) 17.6
17.2 (15.5a ± 0.1) 17.8
0.7
1.0
2.2
0.9
0.7
1.7
1.6
5.65
7.11
7.41
6.86
6.87
5.20
5.20
7.68
7.02
7.63
7.41
7.36
5.78
5.78
0.69 1.492.18
0.49 1.011.49
0.55 0.961.51
0.53 1.020.53
0.59 1.121.70
0.57 1.111.68
0.55 0.941.49
0.4
0.7
1.0
0.9
0.7
0.7
0.7
2.3
3.8
5.0
4.0
3.3
3.4
3.6
0.4
0.6
0.2
0.5
0.5
0.6
0.7
1.9
3.3
4.4
2.5
2.7
3.2
3.9
0.9
1.1
1.0
1.1
1.1
1.1
1.1
14.36
16.01
15.54
17.38
17.78
15.02
15.02
3.78
3.41
3.57
3.87
3.84
3.37
3.37
0.45-0.62
0.35-0.55
0.25-0.60
0.35-1.25
0.25-1.30
0.35-0.60
0.40-0.60
Obs. Species in bold present significant differences concerning the size of their polar and equatorial axes by Tukey’s test. The means (x) followed by the same letter (a) in the same species
and on the same axis (P or E) were not differentiated by Tukey test at 5% of probability (p < 0.05).
Hoehnea 45(4): 669-676, 2018
Species
674
Table 1. Measurements (μm) in equatorial view of pollen grains of Aeschynomene L. (n = 25). Long stamen (+) and short stamen (-), confidence interval at 95% of
probability of the lowest sample values (CI-) and highest sample values (CI+), arithmetic mean (x), average standard deviation (sx), mean of base index (Bx), standard
deviation of sample (s), coefficient of variation (V%), ratio between polar and equatorial axes (P/E), arithmetic mean (n=10) of lenght and width of colpus, arithmetic
mean (n = 10) of length and width of endoaperture, thickness of nexine layer (Nex), thickness of sexine layer (tectum + columelae) (Sex), total thickness of exine (Ex)
and variation range of length of lumen (Lum).
Antonio-Domingues et al.: Pollen from heterodynamous stamens of Aeschynomene 675
grains showed variations in the characteristics of the
apertures and exine ornamentation between species
the results of which are of the utmost importance for
systematic studies.
Acknowledgements
We are grateful to the curators of the herbaria (SP,
RB, MBM) who provided exsiccates (see specimens
investigated). Master’s degree scholarship was
obtained from the Coordenação de Aperfeiçoamento de
Pessoal de Nível Superior (CAPES) to the first author.
The authors are thankful to the Conselho Nacional de
Desenvolvimento Científico e Tecnológico (CNPq) for
the fellowship of ‘‘Productivity in research’’ to the fifth
author (Process CNPq 302766/2016-2). The authors
also extend their thanks to the Me. Carin Stanski
of the Postgraduate program at the Universidade
Federal do Paraná who provided the MBM herbarium
flower buds, also to M.Sc. Vera Lygia El Id of the
Postgraduate program at the Instituto de Botânica
and Dr. Cláudio José Barbedo, scientific researcher
of the Instituto de Botânica, for the assistance in
statistical analysis and “Núcleo de Apoio à Pesquisa
em Microscopia Eletrônica Aplicada a Agricultura,
Escola Superior de Agricultura ‟Luiz de Queiroz”,
Universidade de São Paulo” to SEM images.
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