Morphological and developmental investigations of the underground system of ...

CSIRO PUBLISHING

www.publish.csiro.au/journals/ajb Australian Journal of Botany, 2007, 55, 749–758

Morphological and developmental investigations of the undergroundsystem of Erythroxylum species from Brazilian cerrado

Alexandre Antonio AlonsoA and Silvia Rodrigues MachadoA,B

APO Box 510, 18618-000 Botucatu, Sao Paulo, Brazil.BCorresponding author. Email: [email protected]

Abstract. Brazilian cerrado, a neotropical savanna, is characterised by a strongly seasonal climate with distinctive wetand dry seasons, and deep and well drained soils that are acidic and with high aluminium content. Recurrent fires in the dryseason place additional stress on the survival of plants, which exhibit an array of strategies of survival. The purpose of thiswork was to study the underground system of Erythroxylum nanum A.St-Hil. and E. campestre A.St-Hil., two sub-shrubbyspecies, and E. tortuosum Mart., a shrubby species, verifying the possible relationship between the morphology of theunderground organs and the resprouting ability of these plants. Anatomical analyses followed the usual techniques of plantanatomy. The cotyledons of the three species were green, foliaceous and photosynthesising. The two sub-shrubby species(Erythroxylum nanum and E. campestre) showed slow development of the aerial shoot system and extensive growth of theprimary root in the initial stage of development. E. tortuosum presented the most pronounced development of the aerialsystem and a poorly developed primary root compared with the sub-shrubby species. The sub-shrubby species occurredin clumps and had underground systems interlinked, consisting of a deep axial primary root system besides soboles inE. nanum and xylopodium in E. campestre. Plants of the E. tortuosum were isolated, highly branched and their undergroundsystem consisted of a superficial primary root system. Abundance of reserves and the bud-forming potential of the soboles,xylopodium and roots resulted in production of vigorous branches that are highly valuable in the regeneration of the aerialbiomass following fire or seasonal dry in cerrado.

Introduction

The Brazilian savanna, better known as cerrado (meaning‘closed’ in Portuguese), is a complex vegetation characterised bya mosaic of habitats ranging from pure grasslands through openscrubland to dense woodlands (Mantovani and Martins 1988).The typical climate of cerrado regions is seasonal tropical,characterised by alternating dry (usually April–September) andrainy seasons (October–March). The soils of these areas areancient, deep, sandy, acidic and poor in organic matter andmineral salts, and with high levels of aluminium and iron(Oliveira and Marquis 2002). Water availability, soil conditionsand fire are the determinant factors in this ecosystem (Mistry1998).

Many woody species of the cerrado possess pyrophyticcharacteristics expressed by a strong ability to form newbranches from adventitious buds after fires, resulting in intensivesympodial stem growth (Eiten 1982, 1994). Other adaptationsto fire include the ability to produce vigorous branches fromunderground roots after the complete carbonisation of the aerialsystem (Rachid-Edwards 1956). Many perennial species in theherbaceous stratum develop thickened underground structuresfor storage or vegetative propagation (Appendix 1).

Morphological studies of the underground systems ofBrazilian cerrado plants were performed for several species(reviewed by Appezzato-da-Gloria 2003). Among differentorgans types described are the tuberous root of Pfaffia jubata

Mart. (Menezes et al. 1969), the xylopodium of Brasilia sickiG.M.Barroso (Paviani 1977), Styrax camporum Pohl. (Machado1991) and Brosimum gaudichaudii Trecul. (Palhares et al. 2006);the xylopodium and tuberous roots of Mandevilla Lindl. species(Appezzato-da-Gloria and Estelita 2000); the xylopodium andadventitious roots (Vilhalva and Appezzato-da-Gloria 2006);and tuberous bud-forming roots (Vilhalva and Appezzato-da-Gloria 2006a) of Asteraceae species. Rhizophores andadventitious roots were studied in Smilax polyantha Griseb.(Martins and Appezzato-da-Gloria 2006), Vernonia herbaceaand V. platensis (Hayashi and Appezzato-da-Gloria 2005). Allthe subterranean organs have a strong bud-forming potentialand produce vegetative or reproductive branches above groundafter unfavourable periods (Coutinho 1982; Palhares et al. 2006;Vilhalva and Appezzato-da-Gloria 2006). Protection against fireappears to increase the presence of plants highly branched at thebase (Eiten 1994) and sub-shrubs distributed in clumps in theopen cerrado form (Sambuichi 1991). Vegetative reproductionis widespread among cerrado species and facilitates populationgrowth following fire (Raw and Hay 1985; Hoffmann andMoreira 2002).

Erythroxylaceae is a pantropical family and comprises fourgenera and ∼250 predominantly shrub or tree, but rarely sub-shrub, species. One of the species that stands out in this familyis coca (Erythroxylum coca), a native plant of Andean countrieswhose leaves are used locally as a stimulant and to mitigate

© CSIRO 2007 10.1071/BT07060 0067-1924/07/070749

750 Australian Journal of Botany A. A. Alonso and S. R. Machado

the effects of high altitudes. In Brazil, only ErythroxylumP.Browne occurs with ∼100 species (Mendonca and Amaral2002). In a comprehensive review of Erythroxylum genus,Mendonca and Amaral (2002) reported that in the cerrado, sub-shrub species are distributed in clumps and usually have aninterlinked underground system, whereas the shrub and smalltree species occur as solitary plants. Therefore, an associationbetween the morphology of the underground system and thespatial distribution pattern appears to be present in theseplants. However, morphological and anatomical studies on theunderground system for Erythroxylum species from cerrado areinexistent.

In the present study, we investigated the morphology andanatomy of the underground system of three species ofErythroxylum commonly found in cerrado vegetation, includingtwo sub-shrubs (E. nanum and E. campestre) and one shrub(E. tortuosum), with notes on the plants’ initial developmentunder natural conditions. These three species are native in opencerrado forms known as campo sujo (‘dirty field’ by Oliveiraand Marquis 2002) characterised by scattered trees and shrubsand a large proportion of grassland, and are capable of strongresprouting after injury.

Material and methodsThe study involved natural populations of two sub-shrubbyspecies (Erythroxylum nanum and E. campestre) and oneshrubby species (E. tortuosum) occurring in open cerrado in themunicipality of Botucatu, state of Sao Paulo, Brazil (22◦51′S,48◦26′W). Vouchers were deposited in the BOTU Herbariumof the Department of Botany at Sao Paulo State University(UNESP), registered under the Numbers 24011 (E. campestre),24256 (E. tortuosum) and 24484 (E. nanum).

Morphological observationsField observations were made on six specimens of each speciesfrom August 2003 to July 2006. Selection of the specimens wasbased on a range of morphological features, including height,thickness and number of branches, and vegetative growth stage.The ground was dug up periodically to analyse the morphologyof the underground system and to collect samples for anatomicalstudies.

To verify the bud-forming potential of the roots, 10–20-cm-long fragments were removed from the most developed rootsand were buried at 5–10 cm in experimental beds containing soilfrom the area of occurrence of the plants, at the Department ofBotany, Instituto de Biociencias–UNESP, Botucatu, Sao Paulo,Brazil.

To study the initial development of the underground system,50 seeds of each species were planted in experimental bedscontaining soil from the area of occurrence of the plants. Afterthe appearance of cotyledons, three specimens of each specieswere collected at 3-month intervals during a 1-year period,making 12 plants for each species.

Anatomical studySamples from the soft regions of underground roots andstems were fixed in Karnovsky solution (Karnovsky 1965),dehydrated in 50, 70 and 80% alcohol, embedded in HistoResin(hydroxyethylmethacrylate; Leica, Germany), following the

manufacturer’s instructions, and cut in a semiautomaticmicrotome. The sections (10 µm) were stained in an aqueoussolution of toluidine blue at pH 4.7 (O’Brien et al. 1964) andmounted in new Entellan synthetic resin (Merck, Germany).

Samples extracted from old, lignified regions were fixed inFAA 50 (1 part formaldehyde : 1 part glacial acetic acid : 18 parts50% ethanol, v/v) for 48 h (Johansen 1940) and then preserved in70% ethanol. This material was cut into sections manually witha Ranvier microtome (Pika, Japan). The sections were clarifiedin 20% sodium hypochlorite, washed in distilled water, stainedwith 1% aqueous astra blue and 1% aqueous safranin (Bukastch1972) and mounted in an aqueous glycerin solution (1 : 1).

Hand-cut sections of fresh material were subjected toa Sudan IV reaction to detect lipid substances (Johansen1940), an aqueous solution of 0.02% ruthenium red to verifypolysaccharides and pectins (Jensen 1962), an aqueous solutionof 10% ferric chloride to detect phenolic compounds (Johansen1940) and lugol’s reagent to observe starch grains (Johansen1940).

Results

Initial development of the plants

In the three species studied, the cotyledons emerged aboveground level ∼30 days after planting, persisting for up to12 months in E. nanum and E. campestre, and ∼3 months inE. tortuosum.

Twelve months after the appearance of the cotyledons(Fig. 1A–C), plants presented a relatively short epicotyledonaryaxis, with congested leaves arranged alternately and an elongatedhypocotyl. In E. nanum (Fig. 1A), the basal portion of thehypocotyl was chlorophyllous and slightly thickened, originatingstem branches. In E. campestre, a large portion of thehypocotyl (∼3/4 of the length) was chlorophyllous and thickened(Fig. 1B), whereas in E. tortuosum, the hypocotyl was elongated,although the basal portion, albeit chlorophyllous, did not presentthickening (Fig. 1C). The root system of these plants, comprisingthe primary axial root and its ramifications, was more developedthan the aerial system at this developmental stage. The primaryroot of E. nanum was long, twisted around its own axis, with thin,short lateral roots distributed along its entire length (Fig. 1A).E. campestre had a long, thick primary root, which was straighter,with thin, short lateral roots on the proximal portion and longer,more abundant roots on the distal portion of this root (Fig. 1B).The root system of E. tortuosum consisted of a short, thickprimary root that was stiffer than the long, thin lateral rootsabounding on the distal portion of the primary root (Fig. 1C, D).At 15 months of development (Fig. 5E), E. tortuosum plantsdisplayed a natural death of the aerial system and the emergenceof new stem branches on the basal portion of the hypocotyls andin the proximal region of the primary root. In this phase, theprimary root presented areas of contraction (Fig. 1E).

Underground system of adult plants

Erythroxylum nanum

These were sub-shrubby plants with aggregate distributionat the cerrado vegetation, with aerial branches up to 60 cmin height. The underground system consisted of numerousinterlinked, woody, cylindrical, plagiotropic stem branches.

Underground system of the Erythroxylum species Australian Journal of Botany 751

A B C E

D

Fig. 1. Initial development of (A) Erythroxylum nanum, (B) E. campestre and (C–E) E. tortuosum. (D) Proximal portion of the root system below groundlevel (dashed line). (E) Dead cauline system and new stems formed in the basal portion of the hypocotyl and in the proximal portion of the root. Notethe areas of contraction (arrowhead) in the root. Cotyledons (arrow) and hypocotyl (HY). Scale bars = 1.2 cm (A), 1.4 cm (B), 1.5 cm (C), 0.3 cm (D) and0.8 cm (E).

The superficial underground ramification was located ∼2–5 cmabove ground level (Fig. 2B–D). This kind of an undergroundsystem was a typical sobole and originated from the basal regionof the hypocotyls. Each of the branches had a variable thicknessof 1–5 mm at the terminal internodes and 10–15 mm at the basalnodes, and presented a sympodial ramification pattern. The apexof the soboles produced straight aerial stems bunched togetherin one or more clusters (Fig. 2A–C). The extremity of the sobolewas covered with concentrically arranged cataphylls, and thenodes and internodes were well demarcated (Figs 2D, 3A).

A cross-section of the last internode subjacent to the terminalbud of the sobole showed a uniseriate epidermis with cells ofvaried shapes, thin walls covered by thin cuticle; the stomata,located at the same height as the other epidermal cells, displayedsparse distribution and well demarcated sub-stomatal chambers(Fig. 3A, B).

Internodes situated very close to the apex of the soboles andprotected by cataphylls showed the periderm already installed,with the phellem more developed than the phelloderm. The

phellem presented 3–12 layers of hexagonal to rectangular cells,with uniform deposition of lignin and suberin on the cell walls;the phelloderm was composed of a layer of tabular cells withthin cellulosic walls (Fig. 3C). The pericycle was multilayered,originating gelatinous fibres in the periphery of the primaryphloem (Fig. 3D). The primary xylem in the analysed materialwas not yet completely differentiated.

The root system of the specimens was characterised bythe presence of a primary axial root, twisting around its ownaxis, reaching up to 6 m in depth and 25 mm in thickness inits median region (Fig. 4A). Lateral roots were sparse andshort, reaching up to 0.8 mm in thickness. Adventitious roots,formed in the nodal region of the soboles, were more abundantat the end of the dry season, presenting a length of ∼50 cmand a thickness of up to 0.6 mm (Fig. 4B). The centripetalmaturation of the xylem confirmed the root origin of theseorgans. All the roots analysed here showed differentiation of thephellogen in the outermost layers of the multilayered pericycle(Fig. 4C, D).


A B

C

D

Fig. 2. Shoot system of Erythroxylum nanum: (A) aerial stems; (B) soboles with signs of fire-related injury (arrow); (C) soboles (arrow heads);and (D) terminal portion of soboles. Scale bars = 16 cm (A), 1.9 cm (B), 25 cm (C) and 0.5 cm (D).

Adventitious buds grew on the surface of the fragmentsremoved from the principal roots to 2-m depth in soil, and theyoriginated from the phloem parenchyma cells (Fig. 4E, F). Thesebuds formed aerial stems.

Erythroxylum campestre

These were sub-shrubs, with aerial cylindrical branches40–150 cm in height. The underground system consisted ofan orthotropic, woody and cylindrical organ ∼30–50 cm thickand 15–30 cm long (Fig. 5A, B), formed from the thickenedhypocotyl and the proximal portion of the primary root. Thisorgan was a typical xylopodium, which produced plagiotropic

cauline branches ∼10–20 cm thick and 5–20 cm long, on 3–5 cmbelow ground level (Fig. 5A). These branches producecylindrical, erect aerial stems of up to 1.50 m in height. Inspecimens whose underground system was more developed, theradicular portion of the xylopodium (Fig. 5B) showed cracks ofvariable depths and thickened woody lateral roots.

Anatomically, the proximal portion of the xylopodium(∼1/5 of the total length), cut transversally in the regionabove the dashed line in Fig. 5B, showed a cauline structure,which was confirmed by the centrifugal maturation of theprimary xylem (Fig. 5C, D). A very short hypocotyl–roottransition region (Fig. 5B, dashed line) was characterised by the


A

B

C D

Fig. 3. Anatomy of the terminal internodes of the soboles of Erythroxylum nanum: (A) longitudinal section of the terminal bud and axillary bud;(B–D) cross-sections; (B) epidermis with stoma (arrow head) and pericycle installed in a peripheral position on the vascular cylinder; (C) periderm, cortexand pericycle; and (D) gelatinous fibres. EP = epidermis, EN = endodermis, CT = cortex, PC = pericycle, PE = periderm, GF = gelatinous fibres. Scalebars = 200 µm (A), 50 µm (B, C) and 100 µm (D).

greater development of the reserve parenchyma, with abundantstarch grains and scant lignification of the vascular cylinder.This region showed predominance of cells filled with starchgrains and thickened cellulose cell walls (Fig. 5E, F). Theremaining portion of the xylopodium was radicular in origin;in this region, the secondary xylem was the most developed

tissue and composed of largely solitary vessels with a diffusedistribution, abundant thick-walled fibres arranged compactly,predominantly uniseriate rays and scarce axial parenchyma cells(Fig. 5G, H).

The root system was composed of a woody primaryorthotropic root, reaching up to ∼80–120 cm in length; the


A

B

C

D E

F

Fig. 4. Root system of Erythroxylum nanum: (A) median portion of the primary root, showing torsion (arrow); (B) adventitious roots originating fromsoboles (arrow); (C–D) cross-sections of the vascular cylinder of roots; (E) buds (arrows) formed in a fragment of the primary root; and (F) cross-sectionof a radicular shoot, showing buds of exogenous origin (arrows). FE = phellogen. Scale bars = 5 cm (A), 4.5 cm (B), 80 µm (C, D), 0.60 cm (E)and 100 µm (F).

lateral roots are 20–50 cm long and are mostly plagiotropic(Fig. 5B). The anatomical structure of the roots wasconfirmed by the centripetal maturation of the primary xylem.Adventitious-root and bud formation in the root system wasnot observed.

Erythroxylum tortuosum

These were shrubby plants with two or three tortuous stems,varying in height from 1.5 to 2 m. Its underground system hada short, woody, orthotropic primary root no more than 40 cmin length, which originated thick, tortuous and stiff plagiotropiclateral roots of up to 3 cm in diameter in the median portion and∼1.50 cm in length. The lateral roots were distributed aroundthe primary root in the uppermost layers of the soil (Fig. 6B).Cross-sections of these roots, with a primary structure (Fig. 6D),showed a uniseriate epidermis formed by tiny, spherical cells

covered with thin cuticle. The cortex consisted of 4–10 layers ofthin-walled parenchyma cells of varied shapes and sizes, whereasthe endodermis was composed of juxtaposed tabular cells full ofphenolic content; the pericycle was uniseriate and the vascularcylinder was diarchic. In an incipient secondary structure(Fig. 6E), the cells of the endodermis were easily identified bytheir tabular shape and abundance of phenolic compounds; thepericycle was pluristratified and from its outermost cell layersdifferentiated the phellogen, which gave rise to the first periderm(Fig. 6F). In roots with an established secondary structure(Fig. 6G), pericycle cells had proliferated such that the pericyclebecame a thick region occupying ∼3/4 of the bark in relation tothe secondary phloem. Pericycle cells contained abundant starchgrains.

The portions of roots that remained in the ground during theexcavation (∼0.5-m depth in soil) of the underground system


A B

C

D

E

F G H

Fig. 5. Vegetative system of Erythroxylum campestre: (A) aerial stems above ground level (dashed line), ramifications of xylopodium in the (a) proximalportion, (b) xylopodium and (c) roots; (B) stem portion of the xylopodium above the solid line and radicular below this line, (d) principal root and(e) lateral roots; (C–H) cross-sections of the xylopodium; (C) cauline structure of the proximal portion; (D) protoxylem (arrow); (E) hypocotyl–root region;(F) detail showing the central position of the metaxylem in the hypocotyl-root transition region; (G) root structure of the distal portion of the xylopodium;and (H) detail of the previous figure, showing the central position of the metaxylem. Scale bars = 2.5 cm (A), 6 cm (B), 100 µm (C, G), 40 µm (D),200 µm (E) and 80 µm (F, H).

produced aerial shoots (Fig. 6C) emerging from adventitiousbuds formed in the secondary phloem parenchyma.

Discussion

The morphological characteristics presented by the seedlings ofthe three species in the present study enabled their classificationas ‘epigeous leafy’ type, according to Miquel (1987). Thecotyledons of the three species were green, foliaceous andphotosynthesising. Such characteristics enable these plants toexploit the multiple possibilities of the cerrado, especially thoserelating to light, water and carbon allocation (Franco 2002).

The slow development of the aerial shoot system and theextensive growth of the primary root in the initial stage ofdevelopment of the two sub-shrub species are traits commonto different woody species from cerrado (Rizzini and Heringer

1962; Rizzini 1965; Arasaki and Felippe 1990; Machado 1991;Paulilo et al. 1993). According to Rizzini and Heringer (1962),high light levels, lack of water stress and low N availabilityare typical conditions of cerrado and favour carbon storage andbiomass partitioning to roots rather than leaves. At the plantlevel, root : shoot ratios of cerrado woody species are fairly high,and underground structures for storage or vegetative propagationare common. According to Franco (2002), the establishment ofseedlings in the cerrado depends on their ability to reach thedamper layers of soil and to form underground reserve organs,which enable them to reconstruct their aerial biomass followingfires or seasonal droughts.

Erythroxylum tortuosum, a shrubby species, presented themost pronounced development of the aerial system and a poorlydeveloped primary root compared with the sub-shrubby species


A D

BE

C F G

Fig. 6. Vegetative system of Erythroxylum tortuosum: (A) aerial system; (B) root system exposed after excavation; the dashed line indicates ground level;(C) stem formed from root portions that remained in the ground after excavation of the root system (arrow); (D, E) cross-sections of lateral roots; (D) primarystructure; (E) collapsed cortex and multiseriate pericycle with beginning of differentiation of the phellogen (arrow); (F) periderm; and (G) multiseriatepericycle and secondary phloem. CT = cortex, EN = endodermis, PC = pericycle, PE = periderm. Scale bars = 5 cm (C), 80 µm (D, F), 40 µm (E)and 100 µm (G).

studied here. E. tortuosum presented strong suberisation of thestems and dormant apical and axillary buds which sprout afterfire, resulting in sympodial growth of the highly branched stems(A. A. Alonso and S. R. Machado, unpubl. data). Superficial rootsystem, as observed in E. tortuosum, may be important providinga large quantity of mineral nutrients after fire. According toCoutinho (1982, 1990), the immediate effects of burning incerrado result in a temporary increment at the soil surface inconcentrations of mineral nutrients such as calcium, magnesium,phosphorus and potassium, and the complete disappearance of

aluminium; the ash deposited on the topsoil is highly beneficialto the growth of plants with superficial root systems.

Erythroxylum nanum and E. campestre—both cespitose sub-shrubby species—exhibited subterranean stems. As for theshoot system, considering both aerial and subterranean stems,E. nanum was classified as a soboliferous plant. This plant typeis characterised by the presence of a diffuse underground systemand by the production of aerial stems springing from creepingunderground branches interlinked on the surface of the ground(Angely 1959; Rizzini and Heringer 1966). This type of diffuse


underground system was described for different species of theBrazilian cerrado, mostly sub-shrubs having a long primary rootand an aerial stem poorly developed or systematically destroyed(Rizzini and Heringer 1966). These authors found that sobolesgenerally originate from the cotyledonary node in hypogeousspecies. In E. nanum, an epigeous species, we noted that thesoboles form at the thickened base of the hypocotyl.

On the basis of our morphological and anatomical studyand observations of the plants’ initial development, wehave adopted the name ‘xylopodium’ in the present paperto denote the thickened, woody axis of the undergroundsystem of E. campestre. This xylopodium has a mixedstructure and includes the base of the hypocotyl, the root–stem transition region, and the proximal portion of the mainroot, as described for different species from cerrado (Rizzini1965; Paviani 1977; Machado 1991; Appezzato-da-Gloria andEstelita 2000; Vilhalva and Appezzato-da-Gloria 2006). Thepresence of xylopodium is widely reported in cerrado species(reviewed by Appezzato-da-Gloria 2003), and xylopodium hasbeen interpreted as an organ of resistance against fire andseasonally dry conditions (Coutinho 2002). The xylopodiumof E. campestre, in its proximal portion, presented plagiotropicramifications with the formation of aerial stems. The presenceof a scar caused by fire and of remains of carbonised branches,together with new formed branches in E. campestre plants,points to the importance of the xylopodium in reconstruction ofthe aerial shoot after cerrado burning. A ssimilar behaviour inother cerrado species possessing xylopodium with plagiotropicramifications was observed (Rawitscher and Rachid 1946;Rizzini 1965; Paviani 1977).

Erythroxylum tortuosum, albeit devoid of an undergroundstem, formed adventitious buds in the hypocotyl and proximalportions of the roots, enabling the production of new stemsafter the natural death of the shoot. It is worth noting that theformation of adventitious buds in this species occurred undernatural conditions in the absence of mechanical injury. Thishas been observed also in other cerrado species (Appezzato-da-Gloria 2003). There is strong evidence that root-bud formationwas associated with the reduction in auxin content, resultingfrom the loss of aerial biomass during the dry season (Peterson1975; Hoffmann and Moreira 2002).

The abundance of starch grains in the subterranean stemsand roots, and the bud-forming potential of the soboles,xylopodium and roots in the species studied were traitswidespread among cerrado plants (Rizzini 1976; Raw and Hay1985; Mistry 1998; Hoffmann 1999; Coutinho 2002; Hoffmannand Moreira 2002). Reserves stored in bud-bearing organscould be utilised for resprouting and maintenance expensesof parent plants (see Klimesova and Klimes 2007) and mayfacilitate population growth following fire and seasonallydry conditions in cerrado vegetation, as described by severalauthors (Mistry 1998, Oliveira and Marquis 2002; Hayashi andAppezzato-da-Gloria 2005). Therefore, buds forming, reservesand regrowth in these plants appear to be correlated events.Nevertheless, experimental assessment within and amongindividuals in different seasons must be conducted in orderto verify whether buds and storage are aligned (see Vesk andWestoby 2004).

Differences in location and protection of buds in the studiedspecies were clearly shown in the present work, as reported byVesk and Westoby (2004) for other species. The two sub-shrubErythroxylum species possessed below-ground buds protectedby soil, which sprout to re-establish the aerial shoots followingclipping or burning. On the other hand, above-ground budsprotected by thick bark enabled rapid recovery of multi-stemmedshoot system in E. tortuosum.

According to current knowledge on the role of bud banksin vegetative regeneration (Vesk and Westoby 2004; Klimesovaand Klimes 2007), we suggest that soboles, xylopodium androot-adventitious buds in the studied species can be consideredimportant bud banks in cerrado, increasing the probability ofsurvival after fire and seasonal dry. It appears reasonable tohypothesise that the costs of making and maintaining buds areminimal relative to their value to Erythroxylum species, whichsurvive in severely, and repeatedly disturbed cerrado habitat.

Acknowledgements

We thank Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP,Process 03/00957-1) for a doctoral grant awarded to the first author andfor financial support (Process 00/12469-3), and to CNPq (Brazil) for aproductivity grant awarded to S. R. Machado.

References

Andreata RHP, Menezes NL (1999) Morfoanatomia do embriao,desenvolvimento pos seminal e origem do rizoforo de Smilaxquinquenervia Vell. (Smilacaceae). Boletim de Botanica daUniversidade de Sao Paulo 18, 39–51.

Angely A (1959) ‘Dicionario de botanica.’ (Instituto Paranaense de Botanica:Curitiba)

Appezzato-da-Gloria B, Estelita MAM (2000) The developmental anatomyof the subterranean system in Mandevilla illustris (Vell.) Woodsonand M. velutina (Mart. ex Stadelm.) Woodson (Apocynaceae). RevistaBrasileira de Botanica 23, 27–35.

Appezzato-da-Gloria B (2003) ‘Morfologia de sistemas subterraneos:historico e evolucao do conhecimento no Brasil.’ (A. S. Pinto: RibeiraoPreto)

Arasaki FR, Felippe GM (1990) Crescimento inicial de Kielmeyera coriacea.Ciencia e Cultura 42, 715–720.

Bukastch F (1972) Bemerkungen zur dopplfarbung astrablau-safranin.Mikrokosmos 8, 255.

Coutinho LM (1982) Ecological effects of fire in Brazilian cerrado.In ‘Ecology of tropical savannas: ecological studies’. (Eds BJ Huntley,BH Walker) pp. 273–291. (Springer Verlag: Berlin)

Coutinho LM (1990) Fire ecology of the Brazilian cerrado. In ‘Fire in tropicalbiota’. (Ed. J Goldammer) pp. 82–105. (Springer Verlag: Berlin)

Coutinho LM (2002) O Bioma do cerrado. In ‘Eugen warming e o cerradobrasileiro: um seculo depois’. (Org. AL Klein) pp. 77–91. (UniversidadeEstadual Paulista: Sao Paulo)

Dutta AC (2000) ‘A class-book of botany.’ (Oxford University Press: Oxford)Eiten G (1982) Brazilian savannas. In ‘Ecology of tropical savannas:

ecological studies’. (Eds BJ Huntley, BH Walker) pp. 25–47. (SpringerVerlag: Berlin)

Eiten G (1994) Vegetacao. In ‘Cerrado: caracterizacao, ocupacao eperspectives’. (Ed. M Novais-Pinto) pp. 17–73. (UNB: Brasılia)

Franco AC (2002) Ecophysiology of woody plants. In ‘The cerradosof Brazil: ecology and natural history of a neotropical savanna’.(Eds PS Oliveira, RJ Marquis) pp. 178–197. (Columbia University Press:New York)


Hayashi AH, Appezzato-da-Gloria BA (2005) The origin and anatomy ofrizophores in Vernonia herbacea and V. platensis (Asteraceae) from theBrazilian cerrado. Australian Journal of Botany 53, 273–279.doi: 10.1071/BT04094

Hoffmann WA (1999) Fire and population dynamics of woody plantsin a neotropical savanna: matrix model projections. Ecology 80,1354–1369.

Hoffmann WA, Moreira AG (2002) The role of fire in population dynamicsof woody plants. In ‘The cerrados of Brazil: ecology and natural historyof a neotropical savanna’. (Eds PS Oliveira, RJ Marquis) pp. 159–177.(Columbia University Press: New York)

Jensen WA (1962) ‘Botanical histochemistry: principles and practice.’(WH Freeman: San Francisco)

Johansen DA (1940) ‘Plant microtechnique.’ (McGraw-Hill: New York)Karnovsky MJA (1965) Formaldehyde-glutaraldehyde fixative in high

osmolality for use in electron microscopy. Journal of Cell Biology 27,137–138.

Klimesova J, Klimes L (2007) Bud banks and their role in vegetativeregeneration—a literature review and proposal for simple classificationand assesment. Perspectives in Plant Ecology, Evolution and Systematics8, 115–129. doi: 10.1016/j.ppees.2006.10.002

Lindman CAM (1906) ‘A vegetacao do Rio Grande do Sul.’ (Loefgren: PortoAlegre)

Machado SR (1991) Morfologia e anatomia dos orgaos vegetativos de Styraxcamporum Pohl. (Styracaceae) em desenvolvimento. Brasil. PhD Thesis,Universidade de Sao Paulo, Brazil.

Mantovani W, Martins FR (1988) Variacoes fenologicas das especies docerrado da Reserva Biologica de Moji Guacu, Estado de Sao Paulo.Revista Brasileira de Botanica 11, 101–112.

Martins AR, Appezzato-da-Gloria B (2006) Morfoanatomia dos orgaosvegetativos de Smilax polyantha Griseb. (Smilacaceae). RevistaBrasileira de Botanica 29, 555–567.

Mendonca JO, Amaral AJr (2002) Erythroxylaceae. In ‘Flora Fanerogamicado Estado de Sao Paulo. Vol. 2’. (Eds MGL Wanderley, GJ Shepherd,AM Giulietti, TS Melhem) pp. 107–119. (Hucitec-Fapesp: Sao Paulo)

Menezes NL, Handro W, Campos JFBM (1969) Estudos anatomicos emPfaffia jubata Mart. Boletim da Faculdade de Filosofia. Ciencias e Letrasda Universidade de Sao Paulo 331, 195–237.

Miquel S (1987) Morphologie fonctonnelle de plantules d’especesforestieres du Gabon. Bulletin du Museum National di Histoire Naturelle,Sect. B. Adansonia Botanique 1, 101–121.

Mistry J (1998) Fire in the cerrado (savannas) of Brazil: an ecological review.Progress in Physical Geography 22, 425–428.

O’Brien TP, Feder N, Mccully ME (1964) Polychromatic staining of plantcell walls by toluidine blue. Protoplasma 59, 368–373.doi: 10.1007/BF01248568

Oliveira PS, Marquis RJ (2002) ‘The cerrados of Brazil: ecology andnatural history of a neotropical savanna.’ (Columbia University Press:New York)

Appendix 1. Glossary on terms related to underground organs commons in cerrado plants

Rhizophores. Thickened underground cauline system in plants that have bipolar cauline ramification systems; that is, both aerial (plumule origin) andsubterranean systems (cotyledonary bud origin). They increase the plant rhizosphere as well as function for storage and resprouting (Rocha and Menezes1997; Andreata and Menezes 1999; Hayashi and Appezzato-da-Gloria 2005).Soboles. Perennial subterranean interlinked horizontal branches, usually slender, which produce news horizontal shoots from their axillary buds constitutinga sympodial system at the soil surface; few roots developed at the nodes. Their distal parts, including nodes, internodes and axillary buds, are covered bycataphylls. The apical buds produce orthotropic aerial branches. This system was classified as ‘diffuse system’ by Rizzini and Heringer (1966).Tuberous root. Belowground orthotropic or horizontal swollen root; tap or adventitious root, without a definite shape or fasciculate, nodulose, moniliformor annulated roots; in some plants they produce adventitious buds spontaneously or after injuries (Dutta 2000; Appezzato-da-Gloria 2003).Xylopodium. Wooden foot (‘pe de madeira’ in Portuguese by Lindman 1906); perennial thickened woody organ with numerous buds and high resproutcapacity, formed from tuberisation of the hypocotyl or the root-stem transition region and of the proximal portion of the main root (Rizzini 1965).

Palhares D, De Paula JE, Santos Silveira CE (2006) Morphology of stemand subterranean system of Brosimum gaudichaudii (Moraceae). ActaBotanica Hungarica 48, 89–101. doi: 10.1556/ABot.48.2006.1-2.12

Paulilo MTS, Felippe GM, Dale JE (1993) Crescimento e desenvolvimentoinicial de Qualea grandiflora. Revista Brasileira de Botanica 16, 37–46.

Paviani TI (1977) Estudo morfologico e anatomico de Brasilia sickii GMBarroso. II. Anatomia da raiz, do xilopodio e do caule. Revista Brasileirade Biologia 37, 307–324.

Peterson RL (1975) The initiation and development of root buds. In ‘Thedevelopment and function of roots’. (Eds JG Torrey, DT Clarkson)pp. 125–161. (Academic Press: London)

Rachid-Edwards M (1956) Alguns dispositivos para protecao de plantascontra a seca e ao fogo. Boletim de Botanica da Universidade de SaoPaulo 13, 35–68.

Raw A, Hay J (1985) Fire and others factors affecting a populationof Simarouba amara in cerradao near Brasılia. Revista Brasileira deBotanica 8, 101–107.

Rawitscher FK, Rachid M (1946) Troncos subterraneos de plantasbrasileiras. Anais da Academia Brasileira de Ciencias 18, 261–280.

Rizzini CT (1965) Estudos experimentais sobre o xilopodio e outros orgaostuberosos de plantas de cerrado. Anais da Academia Brasileira deCiencias 37, 87–113.

Rizzini CT (1976) ‘Tratado de fitogeografia do Brasil: aspectos ecologicos.’(Hucitec-Edusp: Sao Paulo)

Rizzini CT, Heringer EP (1962) Studies on the underground organs oftrees and shrubs from southern Brazilian savannas. Anais da AcademiaBrasileira de Ciencias 34, 235–247.

Rizzini CT, Heringer EP (1966) Estudo sobre os sistemas subterraneosdifusos de plantas campestres. Anais da Academia Brasileira de Ciencias38(Suppl.), 85–112

Rocha DC, Menezes NL (1997) O sistema subterraneo de Dioscoreakunthiana Uline ex R.Knuth (Dioscoreaceae). Boletim de Botanica daUniversidade de Sao Paulo 16, 1–13.

Sambuichi RHR (1991) Efeitos de longo prazo de fogo periodico sobre afitossociologia da camada lenhosa de um cerrado em Brasılia. Brasil.Dissertacao de Mestrado, Universidade de Brasılia, Brazil.

Vesk PA, Westoby M (2004) Funding the bud bank: of the costs of buds.Oikos 106, 200–208. doi: 10.1111/j.0030-1299.2004.13204.x

Vilhalva DAA, Appezzato-da-Gloria B (2006) Morfo-anatomia dosistema subterraneo de Callea verticillata (Klatt) Pruski e Isostigmamegapotamicum (Spreng.) Sherff-Asteraceae. Revista Brasileira deBotanica 19, 39–47.

Vilhalva DAA, Appezzato-da-Gloria B (2006a) Morfoanatomia da raiztuberosa de Vernonia oxylepis Sch. Bip. in Mart. ex Baker—Asteraceae.Acta Botanica Brasilica 20, 591–598.doi: 10.1590/S0102-33062006000300009

Manuscript received 4 April 2007, accepted 28 June 2007

http://www.publish.csiro.au/journals/ajb

Morphological and developmental investigations of the underground system of ...

Documents

Transcript of Morphological and developmental investigations of the underground system of ...