The Biologist
(Lima)
ISSN Versión Impresa 1816-0719
ISSN Versión en linea 1994-9073 ISSN Versión CD ROM 1994-9081
ORIGINAL ARTICLE /ARTÍCULO ORIGINAL
ADVANCES ON THE FLORAL MORPHOLOGY OF CAESALPINIA SPINOSA
(FEUILLÉE EX MOLINA) KUNTZE “TARA”, A NATIVE TREE TO PERUVIAN FLORA
AVANCES EN LA MORFOLOGÍA FLORAL DE CAESALPINIA SPINOSA (FEUILLÉE EX
MOLINA) KUNTZE “TARA”, UN ÁRBOL NATIVO DE LA FLORA PERUANA
1 1 2 1
Carlos Sánchez Ocharan ; Eduardo Molinari-Novoa ; Elena Núñez-Linares & Ana Arista
1“Augusto Weberbauer” MOL Herbarium, La Molina National Agrarian University. Correspondent author (EAMN):
20090095@lamolina.edu.pe
2Instituto de Biotecnología, La Molina National Agrarian University.
The Biologist (Lima), 14(1), jan-jun: 35-43.
35
ABSTRACT
Keywords: Fabaceae – floral biology – keeled flower – melittophily – Peruvian flora –pollination syndrome.
Descriptive research was conducted on the floral morphology of Caesalpinia spinosa (Feuillée
ex Molina) Kuntze “tara” (Caesalpinioideae: Fabaceae), a tree native to the Peruvian flora and an
important source of tannins. Flowers were found to be 13,3±1,2 mm long and 11,6±2,1 mm wide,
yellow colored, and highly zygomorphic. The keel had nectar guides, and the nectar gland was
surrounded by the stamens, which formed a tight barrier except for the fenestrae. Melittophily
was suggested the most probable pollination syndrome, given the morphological characteristics
exhibited by the flower.
RESUMEN
Palabras clave: Fabaceae – biología floral – flores con quilla – melitofilia – flora peruana – síndrome de polinización.
Se llevó a cabo una investigación descriptiva de la morfología floral de Caesalpinia spinosa
(Feuillée ex Molina) Kuntze “tara” (Caesalpinioideae: Fabaceae), un árbol nativo de la flora
peruana, e importante fuente de taninos. Las flores son de 13,3±1,2 mm de largo y 11,6±2,1 mm
de ancho, de color amarillo, muy cigomorfas. La carina presenta marcas de miel, y el nectario está
rodeado por los estambres, que forman una barrera densa, interrumpida por las ventanas. Se
propone que la melitofilia es el síndrome de polinización más probable, dadas las características
morfológicas exhibidas por la flor.
number, however, is very limited, as only some
species have been studied regarding this
subject (cf. Endress 1996, Rodríguez-Riaño et
al. 1999, Borges et al. 2009), especially in the
pea family, Fabaceae, which is considered to
be the third most diverse family out of the
angiosperms, and the second in economic
Studies on floral biology are important as they
are a key tool to understand the evolution of
plants and their diversification (Barret et al.
1996, Barret 1998, Li et al. 2004). Their
INTRODUCTION
36
The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
inclusion as a regular crop so that a sustainable
treatment can be developed (cf. Calizaya
2009).
The goal of this study is to describe and to
analyze the floral morphology of C. spinosa in
order to set the basis of future research on the
ecology of its pollination, and innovation on
the agronomical treatment of the species, as
well as to ensure the creation of suitable
strategies for its conservation in wild.
The study was conducted on the fields of
Fundo Canchacalla, an estate located at the
District of Ambo, Provice of Ambo, Huánuco
Region, Peru between 2200 and 3215 masl.
Flowers were collected from the individuals of
C. spinosa cultivated in the estate.
Measurements were made using a digital
caliper given the small size of the flowers.
Thirty racemes were collected at random from
which flowers totally open were measured.
Length and diameter of each flower were
recorded. Also, measurements of every single
piece of the floral whorls were taken.
Univariate analysis was performed in order to
obtain average mearsurements (Hammer et al.
2001).
Collected material was deposited in the
“Augusto Weberbauer” (MOL) Herbarium of
the La Molina National Agrarian University, in
Lima, Peru. The vouchers are the following:
PERÚ: Huánuco, Ambo. Distrito de Ambo.
Arbusto. Flores amarillas, dispuestas en
racimos. Nombre vulgar: “tara”. Hábitat:
Campo de cultivo. Fundo Canchacalla. 2500
m.s.n.m. Domingo, 8 de junio de 2014.
Sánchez-Ocharan 1, con Molinari-Novoa.
(MOL! N° 1229 ×2).
importance (Rodríguez-Riaño et al. 1999)
since many important crops belong in it.
Particularly, the genus Caesalpinia L. sensu
lato, which includes about 60 (Bustamante &
Bustamante, 2009) to 150 species (Gagnon et
al. 2013), is an important genus with several
plants used either in industry (v.g., C. echinata
“Brazilwood”, C. spinosa “tara”) due to the
production of tannins in their pods (Macbride
1943, cf. De la Cruz 2004, Villanueva 2007,
Bustamante & Bustamante 2009; Stronati et al.
2009), or as ornamental plants (v.g., C. gilliesii
“bird of paradise”, C. pulcherrima
“flamboyant-de-jardin”) (Stronati et al. 2009).
Nevertheless, as has happened with many
other genera within the pea family, the
morphology has been poorly studied, as well as
many other aspects of their floral biology (Li et
al. 2004; Borges et al. 2009).
The present study aims to firstly understand the
floral morphology of one of those species, C.
spinosa (Feuillée ex Molina) Kuntze,
popularly known as “tara”, a species native to
Peru that has been used to obtain the tannins of
its pods (Garro Gálvez et al. 1997; Villanueva
2007; Bustamante & Bustamante 2009) and
the gum of its seeds (Villanueva 2007;
Bustamante & Bustamante 2007). The tannins
are known because of their use in the fur and
leather industries, and also because of their
medicinal properties; the gum is currently used
as a stabilizer and emulsifier of both drugs and
foods, and even as a fixator of flavors and
aromas in sodas (Villanueva 2007; Bustamante
& Bustamante 2007). Even so, the treatment of
the species as a crop is quite recent, and it is
still exploited directly from wild (Calizaya
2009, Ramos 2010). Furthermore, C. spinosa
is included as a vulnerable species (VU) by
Peruvian law (DS N° 043-2006-AG; Reynel et
al. 2007), for many natural woods made up
mainly of this species are being affected by
both urban spawn and over exploitation. A
better comprehension on the floral
characteristics will lead to an appropriate
Sánchez Ocharan et al.
MATERIALS AND METHODS
37
The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
free from one another. They all are
perpendicular to the symmetry axis, with the
arc directed adaxially, very close to each other
so that a barrier is formed except for two little
splits at both sides of the base of the first
stamen known as fenestrae (Figure 5), which
lead to the nectar gland. The base of the
filaments is pubescent, and the anthers show
longitudinal dehiscence. As it occurs in all
species of pea family, stamens are formed in
two whorls that lose differentiation after
development, and appear as one unique whorl.
Ginoecium
The pistil is monocarpic, half-inferior, inserted
in the receptacle and surrounded by the nectar
gland (Figure 3). Style is curved, with a 5,74 ±
0,71 mm long arc, and the ovary is 4,03 ± 0,58
mm long. Up to eight ovules are found per
flower, with an average of 6,31 ± 0,73 ovules.
Results suggest that the flowers of C. spinosa
are quite constant in their dimensions, with a
similar average size of that in other species of
the genus such as C. nuga (Aluri 1990).
However, the flowers are considerably smaller
than those of many other species (Cruden &
Hermann-Parker 1979, Lewis & Gibbs 1999,
Moré et al. 2006, Borges et al. 2009). The
hypanthium is considered a common feature of
some genera whithin the Fabales order (Bello
et al. 2010).
The color yellow and the presence of nectar
guides suggest an adaptation to bee
pollination, syndrome known as melittophily,
as stated by Endress (1996), Borges et al.
(2009), and Leite & Machado (2009) who
observe also that these features are very
attractive to bees; these same characteristics
are found in many other species of the genus
where melittophily is either suggested or
proved to occur (Aluri 1990, Lewis & Gibbs
PERÚ: Huánuco, Ambo. Distrito de Ambo.
Arbolito espinoso. Con frutos. Este espécimen
es fe de la tesis de licenciatura “ESTUDIO DE
L A B I O L O G Í A F L O R A L Y
REPRODUCTIVA EN Caesalpinia spinosa
(MOLINA) KUNTZE 'TARA'”, del B. Sc.
Carlos Sánchez. Fundo Canchacalla, Silva
Team (-10.128363 m E, -76.176507 m S). 2500
m.s.n.m. Domingo, 8 de junio de 2014.
Molinari-Novoa 84. (MOL! N° 2012).
The flower of C. spinosa is pentamerous,
zygomorphic, bisexual and dichlamydeous.
Both the calyx and the corolla have free parts.
The stamens are arranged in two whorls,
although indistinguishable from one another,
and there is one single, monocarpic pistil.
Flowers are 13,3 ± 1,19 mm long and 11,62 ±
2,07 mm wide. Receptacle is cup-shaped, and
the first three whorls (i.e., the calyx, the corolla
and the stamens) are inserted on the
hypanthium. There is little variation in the
length, while it was found that the width shows
some variability, which may be related to the
moment of blossoming at measuring time.
Perianth
The calyx is made up by five sepals as a general
rule, but there may be up to six in some cases.
Four of the sepals are pretty homogenous in
shape, while one of them – which we named
the “dissimilar sepal” – is rather different, as it
is larger, concave and laciniate; the concavity
is directed adaxially.
The corolla is highly zygomorphic, and petals
are very variable in length. The keel has nectar
guides, and it is arranged parallel to the
symmetry axis of the flower. These features
suggest their active participation in the process
of attracting visitors and potential pollinators.
Androecium
Stamens are ten, curved, similar in size and
Floral morphology of Caesalpinia spinosa
RESULTS
DISCUSSION
38
The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
As a final conclusion, melittophily is
considered to be the most probable pollination
syndrome in C. spinosa since all the
morphological characteristics of the flower are
similar to those found in species where bee
pollination has been proved to occur.
Moreover, this syndrome itself has been
suggested and/or confirmed in several other
species within the genus, with very few
exceptions, and it seems to be an ancestral
feature as stated by Endress (1996).
1999, Li et al. 2004, Moré et al. 2006, Borges
et al. 2009, Leite & Machado 2009). The
existence of a dissimilar sepal is rare but not
unique to C. spinosa (cf. Li et al. 2004).
The way how the stamens are arranged seems
very proper of the genus, as many other species
have the same tight conformation (Endress
1996, Borges et al. 2009, Leite & Machado
2009). Endress (1996) says that this is to
prevent the access to the nectar gland except
for the splits known as fenestrae so that pollen
is ensured to be placed on the body of the
visitor.
Sánchez Ocharan et al.
Table 1. Morphological features of Caesalpinia spinosa.
Mean Standard deviation Variation coefficient (%)
Length (in mm) 13.30 1.19 8.98
Diameter (in mm) 11.62 2.07 17.81
Perianth
length (in
mm)
# sepals 5.04 0.20 3.98
Dissimilar sepal 8.47 0.63 7.48
Basal petal 1 6.99 0.91 13.08
Basal petal 2 7.04 0.89 12.61
Lateral petal 1 6.62 0.98 14.80
Lateral petal 2 6.63 0.94 14.20
Keel 5.20 0.75 14.47
Arc of
stamens (in
mm)
Stamen 1 6.88 0.87 12.71
Stamen 2 6.97 0.76 10.84
Stamen 3 7.04 0.81 11.48
Stamen 4 6.91 0.74 10.73
Stamen 5 6.74 0.91 13.56
Stamen 6 6.94 0.79 11.39
Stamen 7 6.81 1.04 15.26
Stamen 8 7.03 1.06 15.04
Stamen 9 6.96 0.93 13.39
Stamen 10 7.23 1.01 13.99
Pistil length
(in mm)
Style 5.74 0.71 12.46
Ovary 4.03 0.58 14.34
Source: Self-made.
39
Figure 1. Floral formula and floral diagram specific to Caesalpinia spinosa. Dark green, bract; light green, sepals; yellow, lateral
(upper) and basal (lower) petals; red, keel; pink, stamens; aquamarine, pistil; gray, ovule. Upper sepals, as well as petals, are
imbricated. Placentation is marginal. Source: Self-made.
Figure 2. External morphology of the flower Caesalpinia spinosa. Lateral view of the flower of C. spinosa. Nectar guides are the
red lines on the yellow petals. The dehiscence of anthers is longitudinal. Zoom: 25x.
The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
Floral morphology of Caesalpinia spinosa
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The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
Sánchez Ocharan et al.
Figure 3. Possible arrangement of stamens of Caesalpinia spinosa Source: Self-made. Possible arrangement of stamens in the
whorls of the androecium. Inner whorl: 1, 4, 5, 8 and 9; outer whorl: 2, 3, 6, 7 and 10. The bract (b) marks the abaxial region; the
receptacle is indicated by t and the hypanthium by h. Zoom: 25x.Source: Self-made.
Figure 4. Floral structure of Caesalpinia spinosa. Left. Longitudinal section of the flower, where the receptacle (t), the
hypanthium (h), the sepals (k), the petals (c) and the stamens (a) are shown. Notice the position of the nectar gland (n). Right.
Position of the nectar gland (n) at the base of the androecium (a). The pistil (g) is inserted in the middle of the receptacle. The
arrow points to the stigma. Zoom: 25x.
t
h
k
c
a
g
n
n
a
k
t
41
Figure 5. View of the stamens of Caesalpinia spinosa. Adaxial (superior) view of the stamens. The arrows point to the fenestrae,
which are little splits granting access to the nectar gland. Notice the pubescence of filaments. Zoom: 25x. Source: Self-made.
Figure 6. Relative arrangement of the floral pieces of Caesalpinia spinosa. Perianth: d, dissimilar sepal; b1 and b2, basal petals;
l1 and l2, lateral petals; c, keel. Androecium: from 1 to 10, stamens. Pistil: o, ovary; e, style.
The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
Floral morphology of Caesalpinia spinosa
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The Biologist (Lima). Vol. 14, Nº1, jan-jun 2016
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Floral morphology of Caesalpinia spinosa
