Panel 3: Botanics

Panel leader: Christel Palmberg

PHENOTYPIC CHARACTERIZATION OF THE TAMARUGO BIOTYPES AT THE TAMARUGAL PAMPA

Carolina Briner
University of Chile

INTRODUCTION

This research study was carried out at the Tamarugal Pampa, located in Region I, Chile, with a highly specific desert ecosystem as regards climate, soils, flora and fauna.

The climate is characterized by low relative humidity during the day and relatively high humidity during the night, and a considerable difference between daytime and nighttime temperatures, ranging from 35° C to -5° C.

Rainfall and cloud cover are negligible, dryness prevailing, with over 250 totally cloudless days a year.

As regards soils, two sectors may be identified: the eastern sector, a great piedmont composed of aluvial fans with shallow soils, and the western sector, with salt flats which in ancient times used to be lakes, with a salt crust ranging from 0.1 m to 0.6 m in thickness, made up of sodium, magnesium, calcium and potassium.

Flora is poor, both from the vegetational and the floristic point of view. The following species may be mentioned: Prosopis strombulifera (Fortrena), Prosopis burkartii (Tamarugo argentino), Tessaria absinthioides (Brea), Distichlis spicata (Grama salada), Cressa cretica (Retamal), Atriplex spp (Pillaya), Euforbia tarapacana, Targetea minuta, Prosopis chilensis (algarrobo) and Prosopis tamarugo (tamarugo).

Tamarugo is a legume tree, Mimosaceae, usually reaching up to 18 m in height. Leaves are shed as new ones sprout, and the tree grows around the year.

As an evergreen it is potentially apt, in the deserts of the world, for year-round fodder production, even in highly saline areas. It yields nutritive and palatable fruit and leaves.

The main goals of this study were:

• to make a phenotypic description of tamarugo, through eleven parameters considered representative;

• to make a comparative grouping to select the biotypes with the highest fruit and leaf yield, with a view to providing animal feed.

MATERIALS AND METHODS

The trials were conducted at the Refresco Farm, presently in the hands of the National Forestry Corporation, CONAF. The Junoy 1 plot was selected within this property, with a 50-year-old stand in full production.

First a reconaissance tour was made to eliminate the two rows at the edges, in order to avoid the “border effect”. Then, seriously diseased, fallen or severely lopped individuals were discarded from count and observation.

309 trees remained to be considered in this study.

Each tree was described, graded and marked so as not to repeat measurements.

As regards each parameter, trees were sorted into three groups, considering the purposes of the study. For instance, a taller tree, with larger crown and thicker foliage, is better from the point of view of fodder yield and, consequently, received a higher rating.

Similarly, higher rates were assigned those trees whose greater amount of thorns made them more inaccessible to browse. On the contrary, those trees with fruit severely affected by insect attack, or those with small or few fruit, etc., were given low ratings.

The parameters considered were: 1. Height; 2. Crown diameter; 3. Amount of thorns; 4. Size of thorns; 5. Amount of fruit in crown projection area; 6. Amount of fruit on the branches; 7. Proportion of fruit damaged by insects; 8. Degree of ripeness of fruit in crown projection area; 9. Fruit thickness; 10. Fruit length; and 11. Foliage thickness.

As this was a preliminary study, the results were derived from visual observations. The classification made is arbitrary, as the purpose is to make a grouping of the trees suitable for our purposes: more or less apt for fodder production.

Both tree height and crown diameter were “measured” at the beginning by mere visual observation, identifying the taller, medium-sized and smaller ones, in one case, and the wider, medium and narrower ones in the other case.

The author marking tamarugo trees during the research work sponsored by the University of Chile.

Simultaneously, another research team measured both parameters with an instrument (Haga gun).

When data obtained by each method were statistically confronted, a considerably greater accuracy was observed when using instruments, as this made it possible to assess the visual observations and separate, objectively —although with certain arbitrary delimitations—, large trees from small and medium sized ones.

In the end, the data from instrumental measurements was used, whereby average height was found to be 10.9 m, with a minimum of 4 m and a maximum of 17.5 m; variation was 3.53 m and standard deviation 1.88 m. For crown diameters, the average was established as 14.4 m, minimum 5.4 m and maximum 23.3 m; variation was 7.51 m and standard deviation 2.74 m.

In terms of height, trees between 4 m and 7.9 m were rated as small; those from 8 m to 10.9 m were rated as medium-sized, and those from 11 to 17.5 m were rated as tall.

In terms of crown diameter, narrow trees were considered as those between 7 m and 12.9 m; medium-sized those from 13 m to 17.9 m, and large those 18 m and up.

All other observations were estimates and the classification was arbitrary, though careful.

RESULTS AND DISCUSSION

The findings of height, crown diameter and foliage density measurements, as per the above mentioned methods, are presented in Table 1 A, B, and C.

As regards height and foliage density, most individuals fall into category 3, the most favourable. In terms of crown diameter, the majority falls into the intermediate category, 2.

Table 1 (D, E, and F) shows the findings for the amount of thorns, fruit on the branches and on the crown projection area. In terms of amount of thorns and number of fruit on the crown projection area, most trees fall into category 3, the most favourable; as regards fruit on the branches, most fall into category 1.

TABLE 1

Number of trees and percentage into each category, crown diameter, foliage thickness, amount of thorns and fruit on the branches, amount of fruit on the crown projection area, length of fruit and thorns and fruit thickness for 309 tamarugo trees at the Junoy 1 Stand.

Most of the trees are concentrated in category 2, intermediate, in terms of fruit length and thickness. As regards thorn length, most fall into category 3, the longest thorns. These results are included in Table 1, G, H and I.

Table 2, in turn, shows the findings for the degree of fruit ripeness and the amount of fruit damaged by insect attack. As regards the first of these two items, most trees are concentrated in category 3, ripe. The amount of fruit damaged by insect attack is only mentioned as illustrative data, for this parameter was not grouped. The only fact that was clear in this respect, is that over half of the fruit within the crown projection area suffered from some degree of damage caused by insects.

TABLE 2

Fruit in crown projection area, degree of ripeness and percentage damaged by insects

Of the eleven parameters considered in this study, four were selected for their greater relevance on fodder yields: a. Tree height; b. Crown diameter; c. Amount of fruit within crown projection area; and d. Foliage density.

As each tree was rated from 1 to 3 for each parameter, 3 being the most favourable, those individuals whose characteristics added up to 12 points were rated as best.

In these terms, the trees showed a relatively low frequency with regard to biotype 12, as can be seen from Table 3. Predominant are those falling into biotype 10. Equally low is the frequency of biotype 5.

TABLE 3

Biotypology according to height, crown diameter, amount of fruit in crown projection area and foliage thickness grading limited to these four parameters

CONCLUSIONS

As most of the individuals studied (62.1%) fall into biotypes 9 to 11, the conclusion follows that this species is apt for fodder production.

Although the results are useful from a descriptive point of view, this research should be continued with more accurate measurements of the parameters considered here, in order to achieve a less arbitrary classification.

This classification should establish delimitations better supported by other experiences and criteria, in order to obtain a more fitted biotypification to make possible, later, a selection of the most outstanding biotypes for a genetic improvement program through vegetative propagation or gamete reproduction in a seed orchard.

REFERENCES

HABIT M.A. 1981. Prosopis tamarugo: Fodder tree for arid zones. FAO Plant Production and Protection Paper No. 25, FAO - Rome.

INSTITUTO FORESTAL 1981. Estudio de las especies del género Prosopis en la Pampa del Tamarugal. Tomo III. CORFO, Chile.

MEYNARD S.M., OBERPAUR W.C. 1982. Caracterización de una población y determinación de su fitomasa en tamarugo. (Unpublished).

FRUIT AND SEED MORPHOLOGY OF CHILEAN PROSOPIS (FABACEAE-MIMOSOIDEAE)

Sergio Trobok
Agricultural Production Department
University of Chile

INTRODUCTION

The genus Prosopis L. (Burkart 1940, 1976; Johnston 1962) groups some 44 species in 5 sections, spread through Southeast Asia, Africa and America. It is predominant in this latter continent, and occurs from Western North America down to the Patagonia, with a center of polymorphism at the Argentinian Central-Western region.

According to Reiche (1897), C. Muñoz (1960) and Burkart (1976), these are xerophytic trees or shrubs, usually thorny and frequently phreatophyte (Acevedo & Pastenes 1980). Leaves are 1–3 yugate with opposing pinnas; petiole with apical gland, but occasionally present on the rachis of the pinnas; folioles are small, numerous, linear and oblong. Flowers in spicate or clustered bunches, axillary and thick-flowered; they are small, actinomorphous, hermaphrodite and pentamerous; calyx is campanulate; the corolla has linear petals, more or less fused at the base, frequently pilous inside and towards the apex; androecium with 10 free stamens, excerpt and in two verticils; anthers are elliptical, dorsifixed and with connectival gland at the apex; ovary shaped like an inverted pyramid and frequently downy. Flowers are apparently protoginous, pollinated by insects.

The plants show an enormous variety in their growth habits and in their defenses, which may be represented by thorns, pricks (with no vascular tissue) or be entirely absent. The habit and stem or stipular origin of the thorns offer the best basis for dividing the genus into sections and classifying the species (Burkart 1976; C. Muñoz 1959, 1960, 1971), although, as stressed by the first of these authors, the terminology employed (e.g., stipular thorns) may be at times ambiguous and inaccurate.

Flower characteristics, such as certain features in the petals, ovary and connectival gland of the anther, among others, may also at times be considered relevant for separating the sections of the genus.

Within the genus, the fruit is essentially uniform, despite its variations in curvature and crimp. It is generally straight, falcate, anular or curled into a loose open spiral or tightly curled; the seeds are confined within segments of the endocarp. The lengthwise or crosswise arrangement of these segments in the fruit is a valid trait only in certain sections, such as Strombocarpa, in which it is possible to differentiate the series making it up, but in other cases it is reduced to its systematic value.

Six Prosopis species are recognized for Chile (Burkart 1976), two of which are endemic and included in two sections: Strombocarpa and Algarobia.

The only species in the section Strombocarpa, series Cavenicarpae, is the native tree Prosopis tamarugo Phil.; Prosopis strombulifera (Lam.) Benth. and the native shrub Prosopis burkartii Muñoz belong to the series Strombocarpae of the same section.

The species in this section are characterized, basically, by having stipules transformed into thorns and for their straight, falcate fruit, curved on the side or more frequently curled into one or two open rusks or giving shape to a tight spiral like a screw. The two series in this section are differentiated by the disposition of the endocarp segments: transverse and alternate in two rows in the series Cavenicarpae, and longitudinal in a single row in the series Strombocarpae.

The other three species, Prosopis chilensis (Mol.) Stuntz., Prosopis flexuosa DC. and Prosopis alba Gris., belong to section Algarobia, series Chilenses. In general, the species in this section have geminate axillary thorns originating from the stem, occasionally missing. The fruit is frequently tight, elongated, straight, falcate, ring-like or at the most curled into a loose open spiral with 1–3 rusks; stipe and acumen noticeable; endocarp segments more or less numerous, large, hard, coriaceous and always arranged into a single lengthwise line. In the series Chilenses, the fruit is, furthermore, linear and fleshy and with coriaceous to osseous segments, more or less subcuadrate-ovoid in shape.

The first two species in section Strombocarpae have been well characterized in Chile by Reiche (1897), but only in 1971 C. Muñoz first classified P. burkartii. The former of these authors included P. stenoloba Phil. in his work, probably considered as a synonim of P. alba, while the latter author included P. alpataco, native to Argentina.

Of the three Chilean species considered in section Algarobia, perhaps the one known as Algarrobo de Canchones, growing at the location bearing that name at the Tamarugal Pampa, Atacama Desert, in association with other Prosopis, is the one that offers the greatest difficulties in its classification. M. Muñoz (1981) indicates that it corresponds to P. nigra, native to Argentina, or to P. alba var. panta, whose pods can measure up to 30 cm in length.

The classification of the Chilean species (C. Muñoz 1959, 1960, 1971) is based primarily on traits such as the origin or location of the spines, size and number of pinnas and folioles and on the habits of the plants. Secondarily, size and shape of the fruit and shape and number of the seeds are described; as to this latter point, Reiche (1897) seems to have been the only one to consider the fruit as basis to differentiate these species.

The fruit of Prosopis corresponds to an indehiscent modified legume called drupe-like loment by Burkart (1952, 1976). In addition to what has been reported by this author, the fruit presents a tight section, cylindrical or outlined; epicarp externally straw yellow, brown-reddish or grayish with violet spots; mesocarp fleshy, fibrous or sugary, in some cases edible; endocarp divided into one-seed segments, closed or occasionally easy to open and generally longitudinal. Solbrig & Cantino (1975), in a study on reproductive adaptations of Prosopis in Argentina, add that the fruit has a thin epicarp with a single layer of cells, a multi-layered, fleshy, sweet and nutrivite mesocarp, and endocarp impervious to water, which must be removed to produce germination.

Palacios & Bravo (1981), in a work on natural hybridization of Prosopis growing at the Chaco region in Argentina, consider that the fruit traits having the greatest diagnostic value are the shape, color and presence of spots on the epicarp. These authors found interspecific hybrids of P. ruscifolia x P. alba; P. ruscifolia x P. nigra; and P. alba x P. nigra.

Burkart (1940, 1952), Boelcke (1946) and Palacios & Bravo (1974) have described the seeds of some species, particularly those of the section Algarobia in Argentina. The second of these authors, in a very thorough study including illustrations and taxonomic keys for various characters indicates, together with the other authors, the difficulty for differentiating them resulting from the hybridization produced. This may be valid for Chile, as in some places there are closely related ecotypes and species growing together.

According to Boelcke and Palacios & Bravo, the more valuable traits are the shape, color, length, width, thickness and characteristics of the fissural line and of the endosperm.

The seeds are generally ovoid, elliptical, oblong-elliptical, more or less quadrangular or at times irregular; hard; tight; light brown, brown-yellowish to reddish and more or less shiny.

The hillar end is frequently pointed, containing the hillum, funicle, micropil and the raphe; at the other vertex is the wide chalazal end, blunt or occasionally truncate. The hillum is small, circular or ovoid, superficial or sunk, apical or sub-apical, with the funicle inserted on it. The raphe is umbonate, furrowed or like a line, often whitish.

The seed cover is formed by the testa and the tegmen, which is generally brown and darker than the testa.

The fissural line is imprinted on the testa, in the shape of a horseshoe with the arms pointing towards the hillar end and sometimes around an umbon running along the center of the faces. This line is known also as pleurogram (Corner 1951) and ecusson, but its meaning is not clear, despite being a characteristic of Mimosoideae.

The transverse section is compressed, elliptical to broadly elliptical-transverse. Inside the tegmen is the endosperm, which is generally hard, mucilaginous, corny or vitreous, frequently surrounding the cotyledons. These are flat, flat-convex, round or elliptical, yellow, the base sagittate and frequently not covering the upper part of the radicle; epigeous when germinating.

This work aims at characterizing morphologically and illustrating the fruits and seeds of the Chilean Prosopis species in accordance with the material studied. Subsequently, this work will be continued with the chromosomic and phytochemical study of the material, with the purpose of obtaining the greatest amount possible of information on the individual, interspecific and populational variations of Prosopis.

MATERIALS AND METHODS

Fruit and seeds from various locations in Chile were studied. The material on Prosopis deposited at the National Museum of Natural History was consulted, together with the herbarium at the Faculty of Agricultural, Veterinary and Forest Sciences of the University of Chile, as well as some private collections.

The following traits were considered for the fruit: consistence, shape, number of fruits emerging from the peducle, color (visually), size (the length was taken from the end of the stipe to the end of the mucro), peduncle, section, characteristics of the fruit cover and number and features of the endocarp segments.

The traits considered in the study of the seeds included: shape, color, size, characteristics of the fissural line, chalazal and hillar ends, hillum and raphe, section, seed cover, endosperm and cotyledons. To this end, the indications of Boelcke (1946) and Palacios & Bravo (1974) were followed, but the opening and diameter of the fissural line were measured.

Tamarugo fruit (Prosopis tamarugo Phil.).

The material considered as more representative was drawn to scale and the various traits observed in fruit and seeds were used to make the taxonomic keys.

Identification key for the Chilean Prosopis species by means of their fruit.

Key to identify the Chilean Prosopis species by their seed.

F. Phil. 1886: 159; R. Phil. 1891, 8:21; K. Reiche 1897, 97: 292, 1898: 30; E. Maldonado 1918, 22: 66 plate 4; A. Burkart 1940: 80 fig. 4 tab. 7; C. Muñoz 1959: 252, 1960: 276, 1973: 46; J. Ortiz-Garmendia 1966: 40–44; C. Donoso 1974: 80; A. Burkart 1976: 469; M. Muñoz 1981a; R. Rodríguez, O. Matthei and M. Quezada 1983: 290 plate 69, 291 fig. 78.

Tree up to 15 m tall, occasionally reaching 25 m, pendulous or fastigiate with the crown globe-like and irregular in shape; fissured bark, dark gray; branches arched and gnarled; twigs flexuose, brown-reddish; thorns in pairs, stipular in origin, 0.5–3.8 cm, brown reddish; leaves often bipinnate, with 6–15 pairs of folioles; flowers in cylindrical spicate bunches, yellow-golden.

Figure 1. Prosopis tamarugo. a and b, two forms of the fruit; c, lengthwise section of the fruit showing the endocarp segments; d, cross section showing a seed and the lamellas of the mesocarp; e and f, two forms of the seed; g, cross section of the former seed; h, hillar end with the funicle on the upper side; i, radicle and base of the cotyledons. All drawings are originals. a-c × 1.2; d × 3.2; e and f × 7.2; g-i × 12.

Legume (Fig. 1) coriaceous, bulky, subtorulous, shaped like a ring (1a) or very crooked (1b), often solitary, brown-reddish, green-yellowish or straw yellow; diameter between 2.5 and 4 cm and 0.7–1 cm thick; sutures imprinted (1b), particularly on the concave side, which is puberulous; the apex has short subapical stipe and a round base with an acumen 1 mm in length. Sub-cylindrical section (ld); epicarp 0.5–1.5 mm thick; mesocarp thick, lamellate, brown-reddish, drying when ripe; 5–22 endocarp segments (lc), transverse in two irregular rows and separated by the mesocarp (ld), easy to open, containing 7–18 seeds.

Seeds are light brown to dark brown, smooth and more or less shiny, ovoid (le) to pear-shaped (lf), asymmetrical and more or less compressed; 3.8–5.2 mm in length by 2.6–3.2 mm wide and 1.1–1.4 mm thick. Fissural line shaped like an open horseshoe, short and assymmetrical on the seed faces. Chalazal end wide and oblique, located towards the dorsal suture of the fruit; hillar end pointed and prominent; hillum subapical in a slight depression (lh) and grayish umbonate raphe.

Seeds have elliptical to triangular section (lg), with thin blunt edges; the seedcoat is very thick, with tegmen somewhat thicker and lighter in color than the testa; endosperm is corny, hard and asymmetrical on both sides of the cotyledons (li), which are light yellow, flat and sagittate at the base but not surrounding totally the upper part of the radicle.

This endemic species covers a vast area at the Tamarugal Pampa, from the Tana Ravine to María Elena (Latrille & García 1969).

Material studied: Iquique, Pozo Almonte, La Tirana, Sulfatera Canchones (SGO 76216), Junoy Forest (SGO 80167), Refresco (SGO 80168), La Huaica, Pintados, Chuquicamata, Antofagasta, (Herbarium of the Agricultural School of the University of Chile).

Gay II 1846: 249; K. Reiche 1897: 292, 1898: 29–30; A. Burkart 1940: 71, 1976: 457; M. Muñoz 1981: 50, 1981a; Looser 1948: 6.

Shrub up to 1.5 m tall with gemiferous horizontal roots; bark is ash-colored; long, thin, drooping branches; thin and very decurrent stipular thorns, 0.5–3 cm long, white-ashen; leaves glaucous, with a pair of pinnas each and 3–6 pairs of small glabrous folioles; flowers are light yellow and arranged in small heads.

Legume (Fig. 2a) subcoriaceous, cylindrical, straight or somewhat arched and formed by 5–12 regular rusks tight like a screw, solitary or more frequently 8–9 radiating from a peduncle (2b) 1.5–4 cm in length. The fruit, 2–5 cm long and 0.6–1 cm wide, is lemon-yellow, shiny, or brown-ashen; stipe short and acumen very small and dark; rusks 2.5–5 mm thick and barely puberulous at the place they fuse. Epicarp thin, shelly, 0.4 mm thick; mesocarp fleshy, dark brown to reddish, drying when ripe into delicate lamellas (2c) which surround the endocarp segments; these are placed lengthwise in the fruit and are thin, oval-elliptical and easy to open; 5–12 seeds.

Seeds (2d) are yellowish-greenish, smooth, not very bright, ovoid, compressed; 3.2–5.4 mm in length, 2.3–2.8 mm wide (occasionally up to 3.7 mm) and 1.4–1.6 mm thick. Fissural line well imprinted in the center of the faces, somewhat darker than the testa and with arms of unequal length. Chalazal end blunt, symmetrical; hillar end (2f) pointed with a noticeable cleft under the raphe, which is clear and prominent; hillum subapical, circular; funicle short and cylindrical. Seeds (2e) with biconvex section and round edges; seedcoat thinner than in the case of P. tamarugo; tegmen slight and somewhat darker than the testa; endosperm corny and abundant; cotyledons (2g) yellow, sagittate and not covering the upper part of the radicle.

This range of this species covers the western part of Argentina and the north of Chile. In the latter country it occurs from Tarapacá to Aconcagua (M. Muñoz 1981), associated in its northern border with P. tamarugo, P. alba and P. burkartii.

Material studied: Tarapacá, La Huaica, Refresco, Lo Gatica, Tierra Amarilla (SGO 39960), Los Morteros (Atacama), Huasco Alto (SGO 49999), La Chimba (Ovalle).

Prosopis burkartii Muñoz

C. Muñoz 1971: 363–370, 365 plate 1,367 plate 2 and 368 plate 3; A. Burkart 1976: 468; M. Muñoz 1981: n.p.

Glabrous shrub up to 1.5 m tall, compact and branching out densely from the base; brown bark; thick branches, hard and somewhat flexuose; thorn stipular, fine, 0.2–2.5 cm long by 0.1–0.2 cm wide, brown yellowish; leaves bipinnate with pubescent petiole, 7–12 pairs of folioles, ellyptical oblong and ciliated at the edges; flowers in dense long spikes, brown or yellowish-reddish.

The fruit is a legume (Fig. 3a), subcoriaceous to coriaceous, torulous, with 1–2 irregular rusks, loose and puberulous; fruit are bunched into a globe-shaped compact set with up to 15 of them, some 4.5 cm in diameter; the peduncle (3b) is brown, grooved, with white pubescent punctuate apex up to 6 cm long; brown-reddish or yellowish or yellowish-ashen, opaque; 1–2.2 cm long by 0.8–1.5 cm wide, with short stipe and apical mucro up to 2.5 mm long. Each rusk (3c) is 5–8 mm thick, with sutures not easily noticeable and more or less triangualr in section; epicarp is shelly to coriaceous, 0.5 mm thick; mesocarp granulous, reddish, with delicate lamellas; endocarp segments located lengthwise in the fruit, elliptical, coriaceous but easy to open, 5–8 mm in length; seeds 4–9.

Figure 2. Prosopis strombulifera. a, fruit; b, fruit seen from the top; c, cross section at a rusk showing the seed on the right-hand side; d, seed; e, seed section; f, hillar end; g, radicle and base of the cotyledons. All drawings are originals. a × 1.2; b-c × 3.2; d × 7.2; e-g × 12; f somewhat enlarged.

Seeds (3d) are brown to light brown or brown-reddish, smooth, shiny, compressed, broadly ovoid to orbicular, 4.6–5.2 mm long by 3.8–4.2 mm wide and 1.4–1.6 mm thick. Fissural line slightly darker than the testa, with short straight arms which sometimes surround an umbon on one of the faces; chalazal end is wide, blunt, symmetrical; hillar end is fine, hillum flat, subapical; funicle flat; raphe small, not bulky, grayish (3f). Seed with elliptical section (3e), compressed; tegmen somewhat lighter in color and thicker than the testa; endosperm not very abundant, somewhat vitreous; cotyledons (3g) yellow and widely sagittate.

This species corresponds to a stabilized biotype (Burkart 1976), originated by the probable crossing between P. tamarugo and P. strombulifera, growing at the same locations as these species.

Material studied: Tarapacá, La Huaica, Refresco, El Gobierno (SGO 102417 and 101889), between La Huaica and Matilla.

Gay II 1846: 249; R. Phil. 1860: 192, 1869: 114; K. Reiche 1897: 293; A. Burkart 1940: 105, 1952: 131 & 1976: 495; H. Medina 1941: 27; C. Muñoz 1959, plate 132, 1960: 276 & 1973: 45 fig. 19; G. Looser 1962: 103; J. Ortiz-Garmendia 1966: 6–11; C. Donoso 1974: 79; E. Navas 1976: 180 plate 21 (d-e); M. Muñoz 1981: 50; R. Rodríguez, O. Matthei and M. Quezada 1983: 288, plate 68 and 289 fig. 77.

Fastigiate tree 3–10 m tall, wide globe-shaped crown and stem short and thick; brown-reddish bark, easy to break off and somewhat resinuous; branches arched and flexible, partially thorny; thorns originating from the stem, strong, geminate, whitish or dark brown, up to 6 cm long; leaves 1–3 yugate, with 13–28 pairs of linear folioles (Looser 1962), light green and separate from each other; flowers in cylindrical dense spicate bunches, 6–12 cm long, light green to yellowish.

Legume (Fig. 4) sub-ligneous to coriaceous, fleshy; sub-straight (4a), falcate (4b) or ring-shaped until it forms a loose spiral, sometimes strangled and with joints, linear or subtorulous, compressed; straw-yellow to brown-reddish or with purple spots when very dry; 8–18 cm long, 0.8–1.3 cm wide and 0.5–0.7 cm thick, with long stipe, subapical, 0.6–1.5 cm and strong acumen 0.3–0.6 cm long. Epicarp 0.3–0.4 mm thick, lined externally by thin veins, somewhat dichotomous; mesocarp fleshy, dense, sugary, light brown; endocarp segments (4c & d) transverse-right-angled, lengthwise in the fruit, wide rather than long, 9–12 mm wide by 4–6 mm long, subcoriaceous to thin, easy to open, 12–24 in number.

Seeds are brown-yellowish to brown-reddish, more or less shiny, smooth, ovoid (4e), elliptical-ovoid (4f) or rhomboidal, more or less compressed and asymmetrical; 5.4–7.8 mm long by 2.9–5.1 mm wide and 1.7–2.6 mm thick. Fissural line well imprinted, dark or light, with the ends of its arms tending to come together around a central umbon. Chalazal end blunt or wide and oblique, pointing towards the ventral suture of the fruit; hillar end pointed or blunt; hillum apical in a slight depression; flat funicle; raphe barely bulky, grayish.

Seeds with biconvex section, sides bulky and edges widely round; seedcoat thick, with testa somewhat darker than the tegmen; endosperm is very thick (4g), yellow-greenish; cotyledons (4h) yellow-greenish, not surrounding the radicle completely, which is elongated and darker at the end, sagittate-pointed at the base.

This species occurs in southern Peru, Bolivia, Argentinian Northeast and Central Chile (Burkart 1976). In the latter country it occurs from Atacama to Colchagua (K. Reiche 1897; M. Muñoz 1981). However, B. Contreras and other authors have placed the southern border at Isla de Maipo (1983). Looser (1962) reports that it is particularly abundant in the northern portion of the Santiago basin.

Material studied: San Pedro de Atacama, Desviación Río Loa, Río Huasco, Estancia Manflas, Valle de Puquíos, San Félix (Río del Carmen), Quebrada Marquesa, Marquesa to Condoriaco, La Serena to Vicuña, Río Turbio, Paihuano, Algarrobal, Huanta, Ovalle, Illapel, Salamanca, Los Andes, Río Blanco, Pocuro, Putaendo, San Felipe (SGO 39955), Rungue, Valparaíso, Til-Til, Polpaico, Batuco, Colina, Estación Colina, Quilicura, North Pan American Highway, El Yeso Reservoir, Rinconada de Maipú, Buin, Isla de Maipo.

Gay II 1846: 247; K. Reiche 1897: 293; A. Burkart 1976: 512; C. Muñoz 1971: 369.

Straight shrub 3–10 m tall or tree up to 18 m tall; crown shaped like a semi-globe; branches fanning out; twigs drooping and flexuose; thorns originating from the stem, axillary, geminate, 3–4 cm long, or absent; leaves 1–3 yugate, glabrous or somewhat puberulous, with 8–29 pairs of linear subcoriaceous folioles; bunches are spicate, 4–14 cm long.

Legume (Fig. 5a) is subcoriaceous, thick, subtorulous and more or less curved; light yellow or grayish with violet spots which may grow darker up to black-violet; 5–14 cm long by 0.8–1.5 cm wide and 0.5–0.8 cm thick; apical stipe short and thick, 5–7 mm long and basal mucro 3–5 mm. Section (5b) sub-compressed, more or less right-angled; epicarp thin; mesocarp thick, abundant, sweet, sticky, drying when ripe; longitudinal segments (5c & d), subcuadrate-rotund, hard, rugosule and umbonate on both faces, 7.5–9 mm long by 10–13 mm wide, closed, 10–18 in number.

Figure 3. Prosopis burkartii. a, three fruits from the glomerule; b, end of the peduncle (very enlarged), showing the pedicel with remains of the calyx at the lower part; c, cross section of a rusk showing the location of the seed; d, seed; e, section of the seed; f, hillar end (very enlarged); g, radicle and base of the cotyledons. All drawings are originals. a × 1.2; c × 2.4; d × 7.2; e and g × 12.

Seeds (5e) are brown-light brown to reddish, opaque, smooth, minutely punctuate; ovoid, somewhat asymmetrical, large, 6–6.6 mm long by 4.5–5.3 mm wide and 1.9–2.2 mm thick, well compressed. Fissural line more or less noticeable, accompanied by a lighter edge; chalazal end is wide, blunt and somewhat oblique; hillar end (5g) pointed and wide; hillum is dark, subapical; funicle flat, long; raphe somewhat protuberant, grayish. Section is biconvex (5f), very narrow, with thin edges; seedcoat thinner than in P. chilensis; endosperm is compact, symmetrical, corny; cotyledons (5h) light yellow to greenish, somewhat overlapping and not covering the short radicle.

Figure 4. Prosopis chilensis. a & b, two shapes of the fruit; c, longitudinal section showing the position of the seeds; d, three shapes of the endocarp segments; e & f, two shapes of the seeds; g, cross section; h, radicle and base of the cotyledons. All drawings are originals. a & b × 1.2; c & d × 3.2; e & f × 7.2; g & h × 12.

Material studied: San Pedro de Atacama, Lassana, El Cobre (northeast from Vallenar), San Félix (Río del Carmen), Huasco Alto, Chapilca (Río Turbio), Canto del Agua (on the road to Carrizal Bajo).

This species, subspontaneous in Chile in Regions III and IV, is native to the semi-arid Argentinian western region.

Gay II 1846: 245; R. Phil. 1891, 8: 20, 1893, 84: 444; A. Burkart 1940, 4: 119–121, fig. 14, plate 19; 1976: 520; H. Medina 1941, 8: 25–48; C. Muñoz 1960: 275; M. Muñoz 1981: 49, 1981a n/p; R. Rodríguez, O. Matthei and M. Quezada 1983.

Tree 5–15 m tall, with wide round crown; the bark is grayish and barely grooved; branches are thick and gnarled; twigs are pendulous, disarmed; thorns originating from the stem, in pairs or absent, 2–4 cm long, grayish; leaves 1–3 yugate, with 20–36 pairs of folioles with asymmetrical base; flowers in cylindrical spikate bunches, yellowish, 4–11 cm long.

Legume (Fig. 6a) sub-ligneous to coriaceous, falcate to ring-shaped, linear, very compressed, straw-yellow with no spots, 12 to 25 cm long by 1.2–1.8 cm wide and 0.4–0.5 cm thick; stipe 1 cm long and with acuminate-curved base, with both faces revealing the shape of the seeds, lying crosswise. The section (6b) is biconvex, with thin edges; epicarp 0.1–0.2 mm thick, with slender veins running on its outer part; mesocarp is fine, fleshy up to ripeness, light brown; longitudinal endocarp segments (6c), large, transverse-right-angled, wide rather than long, 5–7 mm long by 11–15 mm wide, subcoriaceous, umbonate on both faces, closed, easy to open and 18–30 in number.

The seeds (6d) are brown-light brown to reddish, smooth, dull gloss, oblong, right-angled, transverse-elliptical to obovoid, somewhat asymmetrical and widening at the hillar end, compressed, 6.6–7.5 (and up to 8.2 mm) long by 3.2–3.8 (up to 5.5 mm) wide and 2–2.8 mm thick. The fissural line is very long and running around an umbon on one of the faces, the same color as the testa, delicate or well imprinted and with lighter edge; chalazal end blunt to tapering with a crosswise cleft; hillar end widely pointed, somewhat asymmetrical and protuberant; hillum subapical, round; funicle short; raphe like a small light umbon.

Seeds with wide section (6e), biconvex to sub-rhomboidal, bulkier on one side, edges round and thick; seedcoat very thin with tegmen darker than the testa; endosperm is vitreous, asymmetrical and nearly missing at the edges; cotyledons (6f) are light yellow, folded like a stretched “S”, with asymmetrical base surrounding the upper part of the radicle more than in the foregoing species.

It is a scant species, subspontaneous, introduced from the northeast of Argentina, Eastern Gran Chaco, Peru and southern Bolivia. In Chile it grows in Regions I and II, associated at its northern border with P. strombulifera, P. burkartii and plantations of P. tamarugo (NAS 1979).

Palacios & Bravo (1981) have found interspecific hybridizations between P. alba × P. ruscifolia and P. alba × P. nigra, native to the Chaco Region in Argentina. In Chile, M. Muñoz (1981: 49) indicates that the tree known as Algarrobo de Canchones, growing at the location bearing this name in the Tamarugal Pampa, in reforestations with P. tamarugo, may correspond to P. alba var. panta Gris. or P. nigra (Gris.) Hieron.

The pods of var. panta are nearly straight, 30 cm long and over 1.8 cm wide; this latter dimension has not been possible to observe; P. nigra has a sub-falcate fruit, yellow with violet spots, very marked joints on the faces, 12–18 cm long by 1–1.5 cm wide and 0.5–1 cm thick, very similar as those reported for P. flexuosa.

Material studied: Mamiña, Canchones (SGO 76212-3), La Huaica, Pica, southern portion of Pintados Salt Flat, Quillagua, Río Salado (Antofagasta), Perales (Paposo mountain road), Loa River detour, Lassana, Toconao, San Pedro de Atacama.

Figure 5. Prosopis flexuosa. a, fruit; b, cross section showing an endocarp segment in the middle; c, two closed endocarp segments; d, an open segment with the seed in the middle; e, seed; f, cross section; g, hillar end; h, radicle and base of the cotyledons. All drawings are originals. a × 1.2; b-d × 3.2; e × 7.2; f-h × 12.

Figure 6. Prosopis alba. a, fruit; b, cross section of the fruit showing the seed inside the segment; c, two segments of the endocarp; d, two shapes of the seeds; e, a section of the seed; f, radicle and base of the cotyledons. All drawings are originals. a × 1.2; b-c × 3.2; d × 7.2; e & f × 12.

REFERENCES

1. ACEVEDO E. & PASTENES J. 1980. Distribución de Prosopis tamarugo Phil. en la Pampa del Tamarugal (Desierto de Atacama). In: International Congress on Arid and Semi-Arid Zone Studies. La Serena, Chile, Jan. 1980. Abstracts.

2. BOELCKE O. 1946. Estudio morfológico de las semillas de Leguminosas Mimosoideae y Caesalpinoideae de interés agronómico en la Argentina. Darwiniana 7: 240–321.

3. BURKART A. 1940. Materiales para una monografía del género Prosopis (Leguminosae). Darwiniana 4 (1): 57–128. 15 figs., 23 plates.

4. BURKART A.. 1952. Las leguminosas argentinas silvestres y cultivadas. 2nd ed. Acme Agency, Bs. Aires. 590 p.

5. BURKART A., 1976. A monograph of the genus Prosopis (Leguminosae subfam. Mimosoideae). Journal Arn. Arb. 57 (3–4): 217–249, 450–525.

6. CONTRERAS B. 1983. Diversidad morfológica en poblaciones de algarrobo (Prosopis chilensis, [Mol.] Stuntz) en la IV Región. Thesis for Forestry Eng. Deg., Universidad de Chile. 108 p.

7. CORNER E. 1951. The Leguminous Seed. Phytomorphology 1 (1–2): 117–150.

8. DONOSO C. 1974. Dendrología: Arboles y arbustos chilenos. Fac. de Ciencias Forestales, Universidad de Chile, Santiago. Manual N^o 2, 142 p.

9. GAY C. 1846. Historia Fisica y Política de Chile. Serie Botánica II-VIII. París. Museo Nacional de Historia Natural, Chile. II, 245–250.

10. JOHNSTON M.C. 1962. The North American mesquites, Prosopis sect. Algarobia (Leguminosae). Brittonia 14 (1): 72–90.

11. LATRILLE L., GARCIA X. 1969. Evaluación nutritiva del tamarugo (Prosopis tamarugo Phil.) como forraje para rumiantes. Partes I y II. Univ. de Chile, Fac. Agron., Depto. de Prod. Animal. Memoria Anual 1968.

12. LOOSER G. 1948. Prosopis strombulifera y Dodonaea viscosa en la provincia de Coquimbo. Rev. Universitaria, Universidad Católica de Chile. 33 (1): 5–8.

13. LOOSER G.. 1962. La importancia de algarrobo (Prosopis chilensis [Mol.] Stuntz) en la vegetación de la provincia de Santiago de Chile. Rev. Universitaria, Universidad Católica de Chile. 47 (25): 102–116.

14. MALDONADO E. 1918. Contribución al estudio del tamarugo. Rev. Chil. Hist. Nat. 22 (1): 65–71.

15. MEDINA V.H. 1941. Contribución al estudio del algarrobo chileno. Rev. Argentina Agron. 8 (1): 25–48. 2 fig.

16. MUÑOZ C. 1959. Sinopsis de la Flora Chilena. Claves para la identificación de Familias y Géneros. 1st Ed. Universidad de Chile. 840 p. 238 plates.

17. MUÑOZ C. 1960. Botánica Agrícola. Edit. Universitaria, 2 vol. Santiago. Tomo 1.344 p.

18. MUÑOZ C. 1971. Una nueva especie de Prosopis para el norte de Chile. Bol. Mus. Nac. Hist. Nat. 32: 363–370.

19. MUÑOZ C. 1973. Chile: Plantas en extinción. Ed. Universitaria, Santiago. 2nd Ed. 247 p 41 figs., 31 plates.

20. MUÑOZ M. et al. 1981. El uso medicinal y alimenticio de plantas nativas y naturalizadas en Chile. Mus. Nac. Hist. Nat. Publicación Ocasional N^o 33 91 p.

21. MUÑOZ M. 1981a Estudio de las especies del género Prosopis en la Pampa del Tamarugal. Análisis Dendrológico. Instituto Forestal, Chile. V. 3 n/p.

22. NATIONAL ACADEMY OF SCIENCES 1979. Tropical Legumes. Resources for the future. Washington D.C. 237 p.

23. NAVAS L.E. 1973–1976. Flora de la Cuenca de Santiago de Chile. Ed. Universidad de Chile, Santiago. 3 v. Vol. 2. 1976 Dicotiledoneae, Archichlamydeae. 559 p, 63 plates.

24. ORTIZ-GARMENDIA J. 1966. Algunos forestales chilenos de la estepa septentrional. Ministerio de Agricultura, Santiago. Bol. Técnico N^o 23 45 p.

25. PALACIOS R., BRAVO L. 1974. Estudio morfológico de las semillas de algunos Prosopis del nordeste argentino. Darwiniana 18 (3–4): 437–452. plate 1 figs. c, d, e.

26. PALACIOS R. 1981. Hibridación natural en Prosopis (Leguminosae) en la región chaqueña argentina. Evidencias morfológicas y cromatográficas. Darwiniana 23 (1): 3–35.

27. PHILIPPI F. 1886. Reise nach der Provinz Tarapacá. Verhandl. D. deutsch. wiss. Ver. Santiago 1: 135–163.

28. PHILIPPI R.A. 1860. Viaje al Desierto de Atacama hecho por el Gobierno de Chile, en el verano de 1853–54. Flórula Atacamensis I-IV, 1–236. 27 plates, 1 map.

29. PHILIPPI R.A. 1869. Elementos de Botánica para el uso de los estudiantes de Medicina y Farmacia en Chile. Imprenta Nacional, Santiago. 9, 1–571 p.

30. PHILIPPI R.A. 1891. Catalogus praevius plantarum in itinere ad Tarapacá a Federico Philippi lectarum. Anales. Mus. Nac. Hist. Nat., Santiago. I-VIII, 1–96, 2 plates. 2:21

31. PHILIPPI R.A. 1893. Plantas nuevas chilenas. Anales Univ. de Chile. 84 (15): 433–444.

32. REICHE K. 1894–1909. Estudios críticos sobre la flora de Chile. Anales Univ. de Chile, 88–125. 1897, 97: 292–294; Memorias Cient. y Lit. 1898, 2: 29–30.

33. RODRIGUEZ R., MATTHEI O., QUEZADA M. 1983. Flora arbórea de Chile. Ed. Universidad de Concepción, Chile. 408 p.

34. SOLBRIG O., CANTINO P. 1975. Reproductive adaptations in Prosopis (Leguminosae, Mimosoideae). Jour. Arn. Arb. 56 (2): 183–210.

ANATOMIC STRUCTURE AND ORGANOLEPTIC CHARACTERISTICS OF PROSOPIS TAMARUGO AND PROSOPIS ALBA GRIS. AT THE TAMARUGAL PAMPA

Iván Ulloa
Ramón Rosende
Juan Donoso
Emilio Cuevas
Faculty of Agricultural, Veterinary and Forest Sciences
University of Chile

INTRODUCTION

The genus Prosopis belongs to the sub-family Mimosaceae, family Leguminosae, and is represented by 44 species particularly well adapted to arid and semi-arid environments (Burkart 1976).

They are usually mid-sized trees, with a short stem and, mostly, gnarled, with limbs branching out from near the base, although they can reach 20-m height with a relatively straight stem.

Seven Prosopis species grow in Chile: P. tamarugo, P. strombulifera, P. chilensis, P. alpacato, P. alba, P. fruticosa, P. burkartii (Muñoz 1971), occurring geographically from Region I to Region VI, depending on the species.

By the end of last century, the Tamarugal Pampa was one of the zones most densely populated by tamarugo (P. tamarugo Phil.) and algarrobo (Prosopis alba Gris.). The intense and progressive felling practices applied brought about the present saline desert physiognomy observed in the area. In view of this, the Chilean Government started —in 1965— a vast tamarugo and algarrobo plantation program which, together with the remaining native forest, has come to cover approximately 25,000 ha (Contreras 1982).

In addition to reforestation at the Pampa, research studies have been encouraged —particularly by the Production Development Corporation (CORFO)— on the renewable natural resources existing in the region.

As there were no previous studies on genus Prosopis wood from the Tamarugal Pampa, and considering that data on the technological characteristics are limited to only a few species of the genus Prosopis, the Wood Technology Department of the Faculty of Agricultural, Veterinary and Forest Sciences of the University of Chile was encharged —through a request from the CORFO Agricultural Society Ltd.— with studying the fundamental technological properties of this wood, starting with the basic knowledge of its anatomic structure and organoleptic characteristics.

AIMS

The study of the anatomic structure requires the macroscopic and microscopic description of the anatomic elements and inclusions forming the ligneous tissue, the determination of the size of the various cellular elements and the determination of the organoleptic characteristics of the wood.

The above determinations will permit to confirm the taxonomic identification of these two species, broadening the understanding of the relationship between the properties and the behaviour of the wood during its processing and utilization.

MATERIAL AND METHODS

The material for the trial was collected at the Refresco Farm, locating four plots, two for the extraction of 50- and 22-year-old Prosopis tamarugo, and two for extracting Prosopis alba of the same age as Prosopis tamarugo.

Five trees of each species were selected from each age class, cutting 1.2 m sections at breast height, from which 2 × 2 cm cubes were prepared for the anatomic study, and 15 × 1 cm tablets for the macroscopic study.

180 microscopic slices and 80 macerations were prepared from the cubes, employing usual techniques for this kind of research.

Pores per mm², tangential diameter of the pores, intervascular punctuation diameter, amount of radii per mm, height and width of radii and thickness of parenchyma bands were measured at the microscopic slices, and fiber length and diameter, cell wall and length of vessel elements were measured at the macerations. The organoleptic and macroscopic characteristics were determined from the tablets.

Minimum, maximum and mean values were determined for the anatomic elements.

ANATOMIC STRUCTURE OF PROSOPIS TAMARUGO WOOD

a. Macroscopic Description

There is considerable difference in color between sapwood and heartwood. The former is white-yellowish, and the latter brown-reddish, turning dark reddish with the passage of time.

It is very heavy and very hard wood, lacking characteristic smell or taste.

Texture is medium and heterogeneous. Slanting grain is abundant with a tendency to interlace. The vein is derived mainly from the size of the vessels, which may be observed with the naked eye at the tangential slice, where they appear as dark-brown to blackish lines. Additionally, blackish stripes may be observed in the heartwood, distributed in a circular manner resembling a growth ring, due to the considerable cellular content of the vessels.

Its semi-circular porosity in the crossection is notorious under the magnifying glass, as well as abundant solitary pores and a few multiple ones in radial chains. Very thin lengthwise parenchyma stripes may be observed in sapwood, laid out in a circle and lighter in color than the rest of the fibrous tissue. These bands might be limiting the growth ring, which is not clearly distinguished, particularly in the heartwood.

Well polished wood has an intense gloss which, together with its texture and medium grain, make it attractive to the eye.

b. Microscopic Description

Vessels/Pores

Semi-circular porosity with a tendency to be diffuse. Solitary pores are abundant, with circular or oval shape. Multiple pores are fewer and are made up by 2 or 3 pores in radial lines, with flattened tangential walls.

Pores are range from few to numerous, 9 to 12 per mm², with maximum diameter of 240 μ, minimum 40 μ and an average of 100 μ. Most are between 60 μ and 160 μ. Short vessels range from 85 μ to 240 μ, most in the range of 125 μ to 200 μ.

Perforation plaques are simple, with horizontal to slightly slanted terminal walls. Intervascular punctuations are very small, 2 to 3 μ in diameter, and very abundant in alternate arrangement and ornamented.

Fibers

Fibers are thick-walled and narrow, the lumen accounting for ½ to ⅓ of its total diameter of 8 to 10 μ. As to their length, very short to short range from 600 μ to 1,300 μ. Each wall is 2 to 4 μ thick.

Ligneous Radii

Radii are homogeneous to slightly heterogeneous, following a somewhat sinuous or rectilinear path, and vary from not very numerous to numerous, 6 to 9 per mm, mostly 7 to 8 per mm.

The most abundant radii in 22-year-old Prosopis tamarugo are triseriated (30 to 37 μ thick); biseriated are fewer (20 to 29 μ). There are some tetraseriated ones (38 to 45 μ), but very scant uniseriated ones (10 to 19 μ). In 50-year-old trees most radii are biseriated (20 to 29 μ thick), with some triseriated ones and very few uniseriated ones.

Maximum height in number of cells is 60 (750 μ) in 22-year-old Prosopis tamarugo, and 38 cells (48 μ) in 50-year-old tamarugo. This number is most frequent in the range of 9 to 26 cells (130 to 350 μ).

Longitudinal Parenchyma

The most abundant type of parenchyma is the vessel-centered paratracheal parenchyma, at times aliform and confluent-striped in short stripes covering 3 or 4 vessels; the thickness of these bands is 6 to 8 cells. Apotracheal parenchyma can also be observed in circular lines 1 to 2 cells thick at regular intervals, associated generally with small pores, which would indicate it to be terminal and might be delimiting a growth period of one annual ring. In the microscopic slices this parenchyma line is observed both in sapwood and heartwood, and macroscopically —under magnifying glass— it can only be observed in sapwood. The tangential and radial cuts show cells of fusiform parenchyma and septum parenchyma.

Cell Content

The vessels show a large amount of gum inclusions, particularly in heartwood.

There are numerous rombhoidal crystals in the fibers, and a lesser amount in parenchymatic cells.

ANATOMIC STRUCTURE OF PROSOPIS ALBA

a. Macroscopic Description

There is a considerable difference in color between sapwood and heartwood. The former is white-yellowish, very similar to Prosopis tamarugo sapwood. Heartwood is brown-pinkish, and after felled, it becomes dark brown, in a bit lighter shade and less reddish than Prosopis tamarugo heartwood.

The wood is heavy to moderately heavy and hard, lacking any peculiar smell or taste.

Texture is medium and homogeneous, with abundant slanted and interlaced grain. Vein is soft to marked, mainly caused by the size of the vessels, visible to the naked eye. It is more evident in the tangential cut, in the form of dark brown to blackish lines. Dark-colored stripes of fibrous tissue, and other lighter ones of parenchymatic tissue, can be observed in heartwood, resembling growth rings due to their circular and uniform layout.

Blackish circular stripes caused by the abundance of cell content in the vessels may also be observed in heartwood.

The radii may be easily made out on the radial face, lending a mottled apearance to the wood.

Semi-circular porosity is notorious in the cross section under magnifying glass, with a great amount of solitary pores, some multiple ones and small clustered ones. Thin lengthwise parenchyma stripes laid out in a circle may be clearly distinguished, lighter in color than the remaining fibrous tissue, both in sapwood and heartwood.

Well-polished wood has a not very intense gloss which, together with its texture and medium grain, lend it a decorative appearance.

b. Microscopic Description

Vessels/Pores

Porosity is semi-circular with a tendency to be diffuse. Solitary pores are abundant, round to oval shaped; multiple pores occur in lesser proportion, and are formed by 2–3 pores in radial lines with flattened tangential walls. There are some small clustered pores.

Pores range from few to numerous, from 5 to 10 per mm². Average diameter is 120 μ in 22-year-old Prosopis alba and 150 μ in 50-year-old trees; maximum diameter is 260 μ, and the minimum is 40 μ.

Vascular elements are generally sinuous and very short, ranging from 80 to 240 μ. The most frequent length varies from 125 to 200 μ. Perforation plaques are simple, with horizontal to slightly slanted terminal walls.

Intervascular punctuations range from very small to small, 3 to 4 μ in diameter, and are ornamented, abundant and laid out in alternate arrangements.

Fibers

Fibers are arranged irregularly, with polygonal or round section and thick walls; they are narrow and the lumen is ½ to ⅓ of total diameter, which varies from 8 to 10 μ. Most frequent diameters are in the range of 800 to 1,000 μ. Walls are 2 to 3 μ thick.

Ligneous Radii

Radii are homogeneous, following a rectilinear or somewhat sinuous trajectory; few to not numerous, 4 to 6 per mm.

The most common radii are the multi-seriated ones, 4 to 9 cells wíde (36 to 95 μ), 5-cell ones predominant (46 to 55 μ). Triseriated ones (26 to 35 μ) and biseriated ones (16 to 25 μ) occur less frequently; uniseriated ones are scant (6 to 15 μ).

Maximum height expressed in number of cells is 75 (1,000 μ), the most frequent being 16 to 32 cells (185 to 400 μ).

Longitudinal Parenchyma

There is a considerable amount of longitudinal parenchyma, the volume of which is almost equal to that of fibrous tissue. They may be seen in confluent stripes 10 to 30 cells thick. There are also vessel-centered paratracheal parenchyma. Apotracheal parenchyma may be observed in lines 1–2 cell thick, which are easily mistaken for the paratracheal parenchyma confluent stripes, hard to tell apart in the microscopic slices, but clearly distinguishable macroscopically under the magnifying glass. These parenchyma lines indicate a certain regularity of growth.

Adult tamarugo at the Tamarugal Pampa. (Photo E. Acevedo.)

Abundant fusiform parenchyma is observed in the tangential and radial cuts, along with some series of 2–4-cell septum parenchyma.

Cell Content

Many gum inclusions may be seen in the vessels, particularly in heartwood, and occasionally in sapwood. Numerous rhomboidal crystals occur in the fibers and in a lesser proportion in longitudinal parenchyma. Additionally, large amounts of starch were observed in longitudinal and radial parenchyma cells.

DISCUSSION AND CONCLUSIONS

The analysis of the anatomic structure of Prosopis tamarugo and Prosopis alba wood shows the following:

Notorious semi-circular porosity with tendency to be diffuse; pores not numerous, solitary; multiple (2–3) radial pores and clustered ones are scant and small-sized. Vessel elements are very short, visible to the naked eye and with simple perforations, small intervascular alternate punctuations, generally ornamented.

Radii are homogeneous and vary from 1 to 3 cells in width for Prosopis tamarugo and from 1 to 9 cells for Prosopis alba. Their height varies from 50 to 1,000 μ. Ligneous fibers are very short, narrow and thick-walled. Longitudinal parenchyma is abundant, occurring either in greater or lesser amount than fibruous tissue; it is more so in Prosopis alba than Prosopis tamarugo. The most common types of parenchyma are the vessel-centered paratracheal, striped confluent, aliform and apotracheal in lines 1 to 2 cells wide.

There is a large amount of cell content in the vessels, particularly in heartwood and rhomboidal crystals in the fibers and in lesser proportion in the parenchyma. Growth rings are not very visible, possibly being entirely absent.

The anatomic characteristics observed in the analyzed species coincide with those characterizing this genus (Boureau 1957, Record 1949).

The comparison of Prosopis alba growing at the Tamarugal Pampa and Prosopis alba growing in Argentina (described by Tortorelli 1956), shows no significant differences in the anatomic structures.

This identification agrees with that made by Burkart (1976), based on the morphology of fruit, leaves and flowers, although the indications of variability within this species cannot be ruled out, since there are trees with different fruit shape and size.

The macroscopic and microscopic comparison of Prosopis tamarugo and Prosopis alba wood shows the former to be very heavy and hard, due to the fact that its fibers are thick-walled and with small lumen, low number of pores per mm² and few, narrow radii, while that of Prosopis alba is lighter in weight and not as hard, on account of its greater amount of longitudinal parenchyma and wider radii.

Another relevant difference is heartwood color: in Prosopis tamarugo it is brown-reddish, and in Prosopis alba brown-pinkish with light and dark stripes. The ligneous radii are clearly marked on the radial face of Prosopis alba, lending a mottled appearance to the wood.

Vain is soft to marked, stressed occasionally by the presence of blackish circular stripes derived from the high cell content of the vessels.

The gloss, texture and medium grain lend a decorative appearance to these woods.

If these woods are compared with wood from Prosopis occurring at other geographic areas, some very similar ones may be found, judging by their anatomic structure. For example, Prosopis alba Gris., Prosopis ruscifolia Gris., Prosopis nigra Gris., Prosopis algarrobilla Gris. —occurring in Argentina—and Prosopis juliflora (Swartz) DC occurring in North America are very similar, while Prosopis africana (Guill. & Perr.) Taub., occurring in Tropical Africa, is similar to Prosopis tamarugo Phil.

MACROSCOPIC CHARACTERISTICS

MICROSCOPIC CHARACTERISTICS

REFERENCES

BOLSA N., KEATING W.G. 1972. African timbers. The properties, uses and characteristics of 700 species. CSIRO, Div. Build Res. Melbourne, Australia.

BOUREAU E. 1954: Anatomie vegetale, V.l. Presses Universitaires de France. Paris, France.

BRAZIER J.D., FRANKLIN G.L. 1961. Identification of hardwoods, a microscope key. Department of Scientific and Industrial Research. Forest Products Research. Bulletin N^o 46. London.

BURKART A. 1976. A monograph of the genus Prosopis. Jour. of the Arnold Arboretum 57 (3): 219–249.

CARVALLO N., SUDZUKI F. 1983: Reforestación de la Pampa del Tamarugal (Chile) con Prosopis tamarugo Phil. Ministero Degli Affari Esteri. Instituto Agronomico per l'Oltremare - Firenze. Italy.

CONTRERAS D. 1982. Distribución, productividad y manejo de ecosistemas naturales y artificiales de tamarugo y algarrobo en Chile. Algaroba v. 2. Simposio Brasileiro sobre Algaroba. Empresa de Pesquisa Agropecuaria do Rio Grande do Norte S. A. Natal, Brazil.

FLAKER P. 1982. The Mesquite Wood Workshop. Mesquite Messenger 1 (1). Texas, USA.

FAO. 1981. Prosopis tamarugo: fodder tree for arid zones. Plant Production and Protection Paper 25. Rome, Italy.

FERREIRA C. 1982. Observaciones sobre ocurrencia y usos de especies del género Prosopis en Chile y Perú. Algaroba V. l. Simposio brasileiro sobre algaroba. Empresa de Pesquisa Agropecuaria do Rio Grande do Norte S. A. Natal, Brazil.

GOBIERNO DE LA PROVINCIA DE SANTIAGO DEL ESTERO. 1970. Maderas Santiagueñas. Ministerio de Economía, Direc. Gral. de Bosques, Argentina.

MUÑOZ C. 1971. Una nueva especie de Prosopis para el Norte de Chile, Bol. Mus. Nac. Hist. Nat. 32: 363–370. Chile.

ORTIZ J. 1966. Algunos forestales chilenos de la estepa septentrional, Ministerio de Agricultura, Direc. Agr. y Pesca, N^o 23, Santiago, Chile.

PEREZ C., ROBLES F., SIMENTAL A. 1979. Determinación de las características anatómicas y fisico-mecánicas de la madera de cuatro especies de leguminosas. Inst. Nac. de Investig. Forestales. Bol. Téc. N^o 61, México.

RECORD S.J., HESS R.W. 1949. Timbers of the New World. Yale University Press. New Haven, USA.

RODRIGUEZ R., MATTHEI O., QUEZADA M. 1983. Flora arbórea de Chile. Editorial de la Universidad de Concepción, Chile.

SALLANAVE P. 1955. Propriétés physiques et méchaniques des bois tropicaux de l'Union Francaise. Centre Technique Forestier Tropical. Paris, France.

TORTORELLI L. 1956. Maderas y bosques argentinos. Ed. Acme. Buenos Aires, Argentina.