Acta Botanica BrasilicaPrint version  ISSN 0102-3306

Acta Bot. Bras. vol.18 no.4 São Paulo Oct. / Dec. 2004

http://dx.doi.org/10.1590/S0102-33062004000400004 

Tracheary elements of five taxa of Cactaceae of Pernambuco savanna, Brazil

 

Traqueary elements of five taxa of Cactaceae of the calabash from Pernambuco State, Brazil

 

 

Emilia Cristina Pereira de Arruda I, * ; Marccus Alves II ; Flavia Gladys Melo-de-Pinna III

I Master's student at the University of São Paulo II Department of Botany, Institute of Biology, Federal University of Pernambuco, Av. Moraes Rego s / n, Ciudad Universitaria, CEP 50632-970, Recife, PE, Brazil III Institute of Biosciences, University of São Paulo, C. Postal 4005, CEP 0161-970, São Paulo, SP, Brazil

 

 

ABSTRACT

This paper presents the morphological characterization of vessel elements and WBT ("tracheid with wide thickening") root and cladodes five taxa of Cactaceae ( Harrisia adscendens (Gurke) Britton & Rose, melocactus× horridus Wedermann Notizbl., M . zehntneri ( Britton & Rose) Luetzelb., Tacinga inamoena (Schumann) NP Taylor & Stuppy and T . palmadora (Britton & Rose) NP Taylor & Stuppy) occurring in a stretch of caatinga of Pernambuco State, Brazil. The vessel elements in roots as much in the cladodes have practically identical among the taxa studied, pits alternate, opposite and scalariform being observed, and simple transverse and oblique perforation plates. The tracheids (WBT) were recorded only in the cladodes four taxa studied, except Harrisia adscendens . The WBTs have annular or spiral thickening and thickening occurs only in mixed melocactus . The tracheal elements were measured, showing that in melocactus both the root and the cladodes, feature elements of long vessel and the WBT as these are higher in cladodes of melocactus .

Keywords: anatomy, Cactaceae, calabash, tracheal elements

ABSTRACT

This work brings the morphological characterization of traqueary elements (vessels and tracheids) in root and cladode of five taxa of Cactaceae ( Harrisia adscendens (Gurke) Britton & Rose, melocactus × horridusWedermann Notizbl., M . zehntneri (Britton & Rose) Luetzelb. , Tacinga inamoena (Schumann) NP Taylor & Stuppy and T . palmadora (Britton & Rose) NP Taylor & Stuppy) occurent in the caatinga of Pernambuco State, Brazil.The vessels Observed elements in the roots and cladodes seem almost the same among Studied taxa, were Observed alternate, opposite and scalariform pitting, and simple perforation plate oblique or transverse. The tracheids (WBT) were exclusively Noted in the cladodes of four Studied taxa, except adscendens Harrisia . The WBTs with annular and helical thickening are present in all taxa and the mix thickening is present only inmelocactus . The vessel elements and tracheids were showing Measured and que the vessel elements are longer in roots and cladodes of melocactus and the longest WBTs were Observed only in cladode of melocactus .

Key words: anatomy, Cactaceae, calabash, traqueary elements

 

 

Introduction

The vascular system of the Cactaceae is basically constituted by conducting cells of the xylem and phloem as in other groups of vascular plants. But in Cactaceae usually the xylem tissue have the highest proportion of parenchyma cells compared to cells lignified walls (vessel elements and fibers) thus composing the aquifer called parenchyma (Soffiatti & Angyalossy 2003; Mazzoni-Nurseries & Costa 2003).

Some of the main characters of the vessel elements of Cactaceae include pits scalariform, alternating the presence of irregular and simple perforation plates (Metcalfe & Chalk 1950, Gibson 1973, 1977; Gibson & Nobel 1986; Soffiatti & Angyalossy 2003).

In addition to vessel elements, fibers and parenchyma cells, some species of Cactaceae may present in the xylem, a special type of tracheid called "wide-band tracheid" - WBTs (Metcalfe & Chalk 1950; Gibson 1973; Mauseth 1999). This cell type is characterized by the absence of perforations in their walls, bands of rigid secondary thickening, which may be annular, helical or double helix, directed to the heat cell (Gibson, 1977; Mauseth 1989; Landrum 2001).

There are still few studies conducted with WBT, so that its origin and function are still uncertain (Conde 1975), although some researchers relate their occurrence with juiciness (Boke 1944; Mauseth 1993). However, few studies have been developed to demonstrate that these cells may be important for the phylogenetic relationships of the Cactaceae (Mauseth et al 1995;. Mauseth & Landrum 1997; Landrum 2002). The dimensions of vessel elements and fibers, some work has been done (Mauseth 1993; Mauseth & Plemons-Rodriguez 1998). Nobel & Gibson (1986) reported a correlation between length and diameter of these cells with habit of plants.

The aim of this work is to characterize the tracheal elements (vessel elements and WBT) five taxa of Cactaceae occurring in a stretch of caatinga of Pernambuco State, and through these observations, seek these cells detect diagnostic differences between the organs (roots and cladodes) and between the taxa studied.

 

Material and methods

This work was developed in the city of Alagoinha (08 ° 29'' S and 36 º 47'' W), about 780m.sm (FIAM 1994), Cashew Farms in Dry and Lagoa Seca, located on a stretch of caatinga of Pernambuco, in boundary between the Central and the Wasteland Hinterland as proposed by Andrade-Lima (1957, 1960) classification. Excursions were made to the study area for collection of vegetative organs (roots and cladodes) of selected taxa and reproductive well as field observations.

The selection of taxa was done through consultation with the collections available in local herbaria (Herbarium of the Federal University of Pernambuco - UFP; Herbarium of the Federal Rural University of Pernambuco - PEUFR and Herbarium Pernambucana Agricultural Research Corporation - IPA). Due to the abundance in the study area, variety of ways and in different subfamilies these species were chosen: adscendens Harrisia (Gurke) Britton & Rose, with procumbent habit; melocactus × horridus . Wedermann Notizbl, M .  zehntneri (Britton & Rose) Luetzelb, both globular habit;. Tacinga inamoena (Schumann) NP Taylor & Stuppy and T . palmadora . (Britton & Rose) NP Taylor & Stuppy both with a shrub H. adscendens , melocactus × horridus and M. zenhtneri are representatives of the subfamily Cactoideae while inamoena Tacinga and T. palmadora subfamily Opuntioideae (Hunt & Taylor 1990). The classification of the habit of the taxa studied follows the proposal by Gibson & Nobel (1986) for the Cactaceae family.

After collection of the material was intended for the manufacture of dried specimens, according to the usual rules (Mori et al. 1989) and deposited in the Herbarium UFP. Part of plant material (roots and cladodes) was collected and fixed in FAA 50, after 24 hours, transferred to 70% ethanol (Johansen 1940), for its preservation. From this material, the technique of dissociation, both roots of cladodes, with a solution of hydrogen peroxide and acetic acid 1:1 (Franklin 1945) was used. After the material loose natural color, it was washed with distilled water until complete removal of the dissociation solution and stored in 70% ethanol (Franklin 1945). Fragments of this material were macerated on histological slide, with added drops of 1% safranin in 50% ethanol (Kraus & Arduin 1997) for staining and mounted in 50% glycerin (Purvis et al . 1964).

The analysis of vessel elements and WBT was performed under a light microscope. The measurement was made in the light microscope coupled millimeter eyepiece. For registration of the cells, the slides were photographed in the light microscope and schematic representations were made on camera lucida attached to a light microscope.

Statistical analysis was performed with BioEstat 2.0 software (Ayres et al. 2000).

 

Results

The vessel elements of the taxa analyzed, both in roots and in cladodes, are characterized by having simple perforation plates with transverse or oblique, scalariform pits, alternate and opposite and also pontoados appendages ( Fig. 1A-C , 2A- U ). In Figures 3 and 4 it is possible to observe the variation in length of these cells in roots and cladodes, respectively.

 

 

 

 

 

 

Statistical tests showed that longer vessel elements observed in the roots belong to melocactus , and this difference was statistically significant (p <0.05) in almost all combinations performed, except between H.adscendens and T. inamoena ( Fig. 3 ). In cladodes, the highest values found for the vessel elements occur in H.adscendens and melocactus , in particular M. zehntneri , which is also statistically significant relationship in almost all combinations performed, except between M. × horridus and M. zehntneri ( Fig. 4 ).

Only in the xylem of cladodes of melocactus × horridus , M. zehntneri , inamoena Tacinga and T. palmadora , which are among the most succulent taxa studied, WBT were observed, in adscendens Harrisia , the cladodes is less juicy. The rigid bands of secondary thickening present in these cells are shown of three types: spiral ( Fig. 1D ), annular ( Fig. 1D ) and mixed ( Fig. 1F ), the annular thickenings and helical occur in the same cell. The WBT with spiral and annular thickening were observed in melocactus × horridus , M. zehntneri , inamoena Tacinga and T. palmadora , while mixed with thickening were registered only in the cladodes of melocactus . You can also notice variations on the length of WBT among the taxa studied ( Fig. 5 ), and the longer occur inmelocactus , especially in M. × horridus . This relationship is statistically significant for all combinations performed.

 

 

Discussion

The vessel elements of cladodes and roots of the taxa analyzed are presented essentially as described in the literature of Cactaceae (Metcalfe & Chalk 1950; Gibson 1977; Soffiatti & Angyalossy 2003), with no specificity types among the taxa studied.

As for dimensional patterns, it was observed that the length of the vessel elements of the taxa analyzed in this study is within the range expected for Cactaceae (100-500μm) as mentioned by Metcalfe & Chalk (1950) values.

Gibson & Nobel (1986), through analysis of 119 species of 50 genera of the subfamily Cactoideae and 35 species from 17 groups Platyopuntias, found the correlation between the lengths of vessel elements and fibers with plant size, and these Longer the greater the size of the plant cells. However, Carlquist (1975) and Zimmerman (1983) showed the occurrence of vessel elements shorter shrub species in arid regions, such as is found in most of the Cactaceae. In taxa studied there seems to be a correlation between the length of vessel elements and plant habit, and in view of a tendency of these cells were longer in both roots and in cladodes in melocactus , smaller plants analyzed. Although H. adscendens plant larger study, using arguments longer vase in the cladodes, it is possible to observe similar pattern in M. zehntneri .

Earl (1975) showed length of elements of relatively constant vessel in five species of Opuntia analyzed by him.According to the author, this may be due to the relative similarity between species. This may in part be corroborated in the present study compared the two taxa Tacinga ( Tacinga inamoena -132μm and T. palmadora- 161μm) and the two of melocactus ( × M. horridus - 185μm and M. zehntneri - 198μm), although the number of representatives of each gender is small.

Bailey (1957) mentioned general evolutionary trend of reducing the length of vessel elements and fibers in Cactaceae. Based on this character plants of this study, which would be derived from the Tacinga are actually derived as less than melocactus (Hunt & Taylor 1990) Elements which have longer vessel. According Mauseth (1993), short glass elements prevent embolism and the consequent interruption of driving, especially on plants of dry environments, such as those studied here.

The occurrence of WBT in Cactaceae is mentioned by several authors (Metcalfe & Chalk 1950; Gibson & Nobel 1986; Mauseth 1999; Landrum 2002). The origin and function of these cells are still uncertain (Conde 1975), although some authors correlate their occurrence with the degree of succulence of the plant (Boke 1944; Gibson 1977; Fahn & Cutler 1992; Mauseth 1993), while others with the same evolution (Mauseth et al. 1995; Landrum 2002). According to Gibson (1977), when these cells are present so there is a tendency to reduce the proportion of vessel elements, and to the absence of xylem fibers. Although WBT have allowed the distinction of taxa analyzed, bearing in mind its absence only in H. adscendens , the claims made by the authors cited above suggest that studies should be conducted in these and other taxa to prove the real function of these structures.

Due to WBT occur in excessively succulent tissues, possible because of the strict bands of secondary thickening is strengthening this tissue, aiding in support (Bailey, 1966, cited in Conde 1975). According Mauseth et al.(1995), these bands prevent the collapse of the primary cell walls keeping fit to drive even in periods of water stress fire. Also according to the author, because of these properties, WBT may represent important adaptations to succulent plants in xeric environments. The thickening occurring in these cells may be annular, helical or double-stranded (Metcalfe & Chalk 1950; Gibson & Nobel 1986; Landrum 2001). Gibson (1977) mentioned the occurrence of WBT typically narrow and slender and with spiral thickening Cactoideae, although the annular thickening can occur in small representatives of that subfamily. Have the Opuntioideae, although presenting narrow and fusiform WBT, the thickening of these cells in these species is annular or, rarely, ring-worm. There is no specificity between types of thickening of WBT among the taxa studied, since all have annular and helical thickening, except for the ring-worm, described here as mixed, which occurs only in melocactus .

Based on the results, we suggest that the tracheal elements observed here corroborate the results for forms and types described for the Cactaceae. Due to the similarity of these elements in roots and cladodes, as well as among the taxa studied, it is not possible to diagnose the same based on this character. As the WBT are absent in the roots of all taxa studied and cladodes of H. adscendens , these may represent a diagnosis or even be related to the juiciness character. Regarding the pattern of thickening, restricted to cladodes mixed typemelocactus also allows the diagnosis of the taxa studied.

However, it should be emphasized that the small number of taxa analyzed, necessitates the expansion of studies on the tracheal elements in other family representatives, aiming to fix the characters observed in these taxa, and establish other also useful to diagnosis.

 

Thanks

The authors thank Dr. Nigel Taylor, for his kindness in identifying botanical material; PIBIC / CNPq / UFPe (Proc. 20310), the granting and renewal of scientific initiation scholarship granted to the first author.

 

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