Pollen morphology of Vochysiaceae tree species in the State of Santa Catarina , Southern Brazil

Tropical Vochysiaceae includes mainly trees, and also shrubs and subshrubs. Three genera and seven species are present in the Brazilian state of Santa Catarina. The pollen morphology of six species of trees, belonging to three genera of the Vochysiaceae A. St-Hil. family, was studied. Herbaria samples were obtained, processed and treated by standard methods. The pollen grain morphology of Callisthene, Qualea and Vochysia is distinct. Medium sized pollen grains occur in Vochysia species, and small ones in Callisthene and Qualea. Specific characteristics were considered at species level [C. castellanosii H. F. Martins, C. kuhlmannii H. F.Martins, Qualea cordata Spreng var. cordata, Q. cryptantha (Spreng) Warm. var. cryptantha, Vochysia magnifica Warm. and V. tucanorum Mart.]. The presence of a fastigium (vestibulum) and a thin space devoid of nexine fixing the boundary of the apertural area is characteristic of Qualea and Vochysia species only. Rev. Biol. Trop. 62 (3): 1209-1215. Epub 2014 September 01.

The family of Vochysiaceae includes mainly trees, and also shrubs and subshrubs, being mainly tropical.It presents six genera and about 200 species.In the state of Santa Catarina three genera and seven species are present.The two species of Callisthene Mart.and Vochysia bifalcata Warm.are preferentially found in lowland areas near the coast, while the species of Qualea Aubl., Vochysia magnifica Warm.and V. tucanorum Mart.are found in higher regions above 500m (Vianna & Martins, 2001).
Trees of Callisthene and Qualea have very restricted distribution in the State of Santa Catarina, as well as Vochysia magnifica and V. bifalcata.According to Vianna and Martins (2001), excicata of V. tucanorum have not yet been collected in the state of Santa Catarina, but occur throughout the neighboring state of Paraná.
The species of the lowlands are part of the Rain Forest in the Atlantic hill side, and can occur up to an altitude of 400m, while in higher regions, up to 1 500m, they reach the "Matinha Nebular" (fog forest), and Q. cryptantha (Spreng.)Warm.may go down to 250m.
The pollen grain morphology of 20 Brazilian species of the genus Vochysia Aubl.was described by Vianna, Mendonça, Franklin, Pereira, and Gonçalves-Esteves (2002), including excicata occurring from Paraíba to Paraná States.Previously, Watanabe (1995) examined two species of Qualea from the "Reserva do Parque Estadual das Fontes do Ipiranga", São Paulo.The other species from Southern Brazil were considered in the present paper.

MATERIAL AND METHODS
The list of species presented in the present paper was taken from Vianna and Martins (2001).The pollen material was obtained from herbarium specimens deposited in the Vochysia bifalcata Warm occurs in the state of Santa Catarina also.The pollen grain morphology of the specimen available (Brazil.Paraná: Paranaguá, G. Hatschbach 6627, GUA 10649) was formerly described and illustrated in Vianna et al. (2002).
Pollen material of the previously cited species was submitted to acetolysis (Erdtman 1952(Erdtman , 1960) ) and embedded in glycerin jelly.Light micrographs (LM) were obtained using a Zeiss Axiophot microscope coupled to a digital AxioCam camera, and were digitally processed in the AxioVision 4.6.3Zeiss program.
Measurements were performed using n=25 for the polar and equatorial diameters, and n=10 for sexine and nexine measured at the mesocolpium.The terminology used follows Barth and Melhem (1988) and Punt, Hoen, Blackmore, Nilsson, and Le Thomas (2007).

RESULTS
The descriptions of the pollen morphology of six tree species occurring in the state of Santa Catarina, Brazil are presented.Morphometric data of pollen grains, comprising the polar and equatorial axis and the exine layer thickness, are shown in table 1. Fig. 1,Fig. 2,Fig. 3,Fig. 4 and Fig. 5 Pollen grains small, isopolar, spheroidal, ambitus subtriangular, 3-colporate, longicolpate, psilate, sexine of variable thickness, nexine thin.

Qualea cordata var. cordata
The colpi are narrow and invaginate, however prominent over the endoapertures and with smooth margins.The endoapertures are lalongate, large, variable-sized.There is a small fastigium.The tectum of the sexine is slightly thicker than the nexine, perforate and present small protrusions of columellae over the tectum, giving an ornate surface appearance.Pollen grains small, isopolar, suboblate to oblate spheroidal, ambitus triangular with rounded corners, 3-colporate, surface microreticulate, sexine about twice the thickness of the nexine.

Qualea cryptantha var. cryptantha
The colpi are short and not invaginate.The endoapertures are lalongate, large, variable-sized.There is a fastigium.The tectum of the sexine is as thick as the nexine.The perforations in the tectum look like a microreticulate surface.
Size and shape of pollen grains are quite variable, since nexine offers little rigidity leading to wrinkling of the pollen grains.The colpi are not invaginate and are partially covered by sexine, except over the endoapertures.These are lalongate with pointed ends and well defined.The apertural area is highlighted by narrow longitudinal lines (tracks) parallel to the colpi, and defined by the absence of nexine.There is a wide-ranging fastigium.The sexine of pseudocolpi is less thick than of mesocolpia, presenting a granular ornamentation Vochysia tucanorum Fig. 34,Fig. 35,Fig. 36,Fig. 37,Fig. 38 and Fig. 39 Pollen grains of medium size, isopolar, oblate spheroidal to spheroidal, ambitus subcircular, 3-colporate, longicolpate, surface irregularly microreticulate or foveolate, sexine with about three times the thickness of the nexine.
Size and shape of pollen grains are quite variable, since nexine offers little rigidity leading to wrinkling of the pollen grains.The colpi are narrow and not invaginate.The endoapertures are narrow and lalongate.There is evidence of the formation of an apertural area bounded by tracks of lack of nexine in some parts of the pollen grains, as well as pseudocolpi, though not always observable.There is a small fastigium.

DISCUSSION
Each one of the three genera of Vochysiaceae (Callisthene, Qualea, Vochysia) examined in the present paper showed a distinct pollen morphology.
The pollen grains of the two species of Callisthene examined are very similar, with no morphological distinct features, conferring with the description of C. fasciculata (Salgado-Labouriau, 1973).All of them showed small sized pollen grains, subtriangular, with invaginated colpi and protruding over the endoapertures, psilate ornamentation, thus characterizing the pollen type Callisthene.
Significant variation of pollen grain morphology was observed in Qualea.Ambitus subcircular to circular, invaginated long colpi, and a very delicate ornamentation characterize Q. cordata.The most striking feature of the pollen grains of the Q. cryptantha sample studied was well defined microreticulate ornamentation.Erdtman (1952) and Carreira (1976) examined respectively pollen grains of Q. pilosa and Q. retusa, establishing the Qualea pollen type, characterized by the presence of a small fastigium in the equatorial part of the apertures and large, lalongate and hardly defined endoapertures, which was corroborated here.The largest variation of the morphological characteristics was found in the genus Vochysia.
The strongest variation in pollen grain morphology was observed in Vochysia magnifica, presenting distinct pseudocolpi and large apertural areas with significant demarcation of their boundaries through the tracks devoid of nexine.In V. bifalcata (Vianna et al., 2002) and V. tucanorum these features were more attenuated.The detailed study of 20 species of Vochysia, richly illustrated and including a literature review (Vianna et al., 2002), reflects the variability of pollen morphology within this genus.
The pollen grains of the genus Qualea, corresponding to the two species described in this paper, present a morphological approach to the genus Callisthene, on another side to the genus Vochysia.The similarities with Callisthene comprise the small, narrow and invaginate colpi and surfaces tending to be psilate in Q. cordata.They approach to Vochysia while presenting a fastigium, distinct perforations in the tectum, and small prominences of columella mainly in Q. cordata Erdtman (1952) studied the pollen morphology of some Brazilian species of three genera of Vochysiaceae addressed in this work, as Callisthene fasciculata, Qualea pilosa, Vochysia chapadensis, V. maxima and V. petraea, none occurring in Southern Brazil.Regarding morphological characteristics they are in agreement regarding trends in the formation of oblate spheroidal pollen grains and delicate ornamentation of the surfaces.Some morphological characteristics of pollen grains of Vochysia magnifica are similar to species of Aspidosperma Mart.& Zucc., Apocynaceae (Barth & Luz, 2008), in particular by the presence of pseudocolpi and apertural areas bounded by narrow tracks devoid of nexine.Similar pseudocolpi and tracks devoid of nexine were observed in Verbenaceae species also (Punt & Langewis, 1988).Further studies of pollen grain morphology of Vochysiaceae species from other countries may improve additional informations.

ACKNOWLEDGMENTS
We are grateful to Maria Celia Vianna, FEEMA, Rio de Janeiro, by obtaining herbarium and identified pollen material.Financial support was got by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for providing research grants to the authors.

TABLE 1
Morphometric data of pollen grains (µm).Arithmetric average and standard deviation are presented in P and E. Amplitude is presented between parentheses E=equatorial axis (equatorial view), P=polar axis (equatorial view), P/E=ratio between polar axis and equatorial axis, S=thickness of sexine, N=thickness of nexine.longicolpate, psilate, sexine of variable thickness, nexine thin.