SciELO - Scientific Electronic Library Online

 
vol.24 issue2Synopsis of the species of Croton L. (Euphorbiaceae) in Pernambuco state, BrazilVariation of floral architecture and reproductive success of two Helicteres (Malvaceae) species in southwestern Mato Grosso author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Acta Botanica Brasilica

Print version ISSN 0102-3306

Acta Bot. Bras. vol.24 no.2 São Paulo Apr./June 2010

http://dx.doi.org/10.1590/S0102-33062010000200016 

ARTIGOS

 

Allelopathic effects of aqueous extracts of Artistolochia esperanzae O.Kuntze on development of Sesamum indicum L. seedlings

 

Efeitos alelopáticos de extratos aquosos de Aristolochia esperanzae O.Kuntze sobre desenvolvimento de plântulas de Sesumum indicum L.

 

 

Ana Beatriz GattiI; Alfredo Gui FerreiraII,1; Marcos ArduinIII; Sonia Cristina Gualtieri de Andrade PerezIII

ISão Carlos Federal University, Graduate Program in Ecology and Natural Resources. São Carlos, SP, Brazil
IIRio Grande do Sul Federal University, Biosciences Institute, Botany Department. Porto Alegre, RS, Brazil
IIISão Carlos Federal University, Center for Biological and Health Sciences, Botany Department. São Carlos, SP, Brazil

 

 


RESUMO

Aristolochia esperanzae é uma trepadeira que ocorre no cerrado do sudeste do Brasil. Os objetivos deste trabalho foram de identificar os efeitos dos extratos aquosos de A. esperanzae sobre a germinação, crescimento da raiz e de células do xilema de plântulas de gergelim. Extratos de folhas, caule e raiz foram preparados nas concentrações de 1,5 e 3,0%. Os extratos causaram alterações na germinação e no crescimento das plântulas com inibição maior causada pelos extratos de raízes. Observou-se mudanças morfológicas e decréscimo no crescimento e desenvolvimento das plântulas de gergelim. Os extratos de A. esperanzae causaram uma inibição de até 50% no tamanho das células do xilema das raízes e mudanças na raiz primária e no número de raízes secundárias.

Palavras-chave: Papo-de-perú, alelopatia, crescimento de raiz, desenvolvimento de xilema, cerrado


ABSTRACT

Aristolochia esperanzae is a climbing plant that occurs in the savanna regions of Brazil. The aim of this work was to identify the effects of aqueous extracts of A. esperanzae on germination, root growth and xylem cell development of sesame seedlings. Leaf and shoot extracts were prepared at concentrations of 1.5 and 3%. Extracts caused marked changes in germination and seedling growth with greatest inhibition produced by root extracts. Morphological changes and decreased growth and development of seedlings were also observed. The extracts of A. esperanzae caused a reduction of 50% in the size of root xylem cells and marked changes in the primary root and in the number of secondary roots.

Key words: "Papo-de-perú", allelopathy, root growth, xylem development, savanna


 

 

Introduction

Allelopathy is defined as the beneficial or harmful influence of chemical substances released by plants that can alter the growth and development of nearby plants or microorganisms. Allelochemicals may be present in all plant organs, including leaves, flowers, fruits, roots, rhizomes, stems and seeds (Putnam & Tang 1986), some of which can store these compounds. However, the quantity and emission pathway varies from species to species (Friedman 1995).

Typical allelopathic inhibitory effects result from the action of groups of allelochemicals that collectively interfere in various physiological processes altering the growth patterns of plants (Einhellig, 1996; Parvez et al. 2004; Kil & Shim 2006). In most cases the organic compounds that are inhibiting at higher concentration and they are stimulating at smaller ones (Rice 1984). The action of allelochemicals can affect the respiration, photosynthesis, enzyme activity, water relations, stomatal opening, hormone levels, mineral availability, cell division and elongation, and structure and permeability of cell membranes and walls (Chou 1999; Reigosa et al. 1999).

Many studies have found that roots are more sensitive to allelochemicals than aerial parts of seedlings (Bagchi et al. 1997; Hamdi et al. 2001; Parvez et al. 2003; Rahman 2006; Punjani et al. 2006; Oliveira & Campos 2006; Ercoli et al. 2007). The inhibition of root growth and development by allelochemicals can be due to changes in DNA synthesis in cells of apical root meristem, alteration of the mitochondrial metabolism (Abrahim et al. 2000) or changes in cell mitotic indices (Dayan et al. 1999; Romagni et al. 2000; Pires et al. 2001; Iganci et al. 2006).

Kaur et al. (2005) demonstrated that benzoic acid produces irregularities in mustard root cells, which were disorganized, inhibiting root growth. Cells at the root tips of Phaseolus vulgaris also were stunted and compacted when the seedlings of this species were grown under the influence of aqueous extracts of Sicyos deppei (Cruz-Ortega et al. 1998). Morphological changes are signs of previous changes that occur at the cellular and molecular level (Ferreira & Áquila 2000). Alterations in the cell membranes can be considered one of the first effects caused by allelochemicals, and these effects may then trigger secondary effects (Barkosky et al. 2000).

Aristolochia esperanzae, known popularly in Brazil as papo-de-peru (turkey crop) and mil-homens (thousand-men), among other names, is a pioneer species and is considered the most frequent among members of the genus in the savanna regions of the state of São Paulo (Cappelari 1991). Various works have reported the presence of terpenes, diterpenes, lignans and aristolochic acid in Aristolochia species, including A. esperanzae (Priestap et al. 1971; Lopes et al. 1988 and Lopes & Bolzani 1988). Stem and root extracts of A. esperanzae caused abnormalities and inhibited root growth of Lactuca sativa and Raphanus sativus seedlings (Gatti et al. 2004). By releasing allelochemicals, this species can influence the succession of plants in savanna grasslands because it is a pioneer species and widely distributed in the environment.

Most studies on allelopathy are focused on invasive species and plants of agricultural interest, or on identifying and isolating chemical substances with potential use as herbicides. Little is known of allelopathic interference in biomes such as savannas, which have been suffering rapid degradation. Besides this, the succession of species can be affected by allelopathy, permitting pioneer species to establish themselves thanks to the release of allelochemicals (Reigosa et al. 1999). However, allelochemicals can be selective in their actions and plants can be selective in their responses. For this reason, it is difficult to determine the action of these compounds (Seigler, 1996). Many studies have shown changes in germination and growth of target seedlings, but few have evidenced the physiology and method of action of allelochemicals (Reigosa et al. 1999; Inderjit & Duke, 2003). In this study sesame seeds were used since they have very uniform germination and seedling development.

Therefore, the aim of this study was to examine the effects of leaf, stem and root aqueous extracts of Aristolochia esperanzae to identify effects on the germination of sesame seeds and if they alter the morphology and anatomy of the target seedlings.

 

Material and methods

Plant material – Leaves, stems and roots of Aristolochia esperanzae O.Kuntze (Aristolochiaceae) were collected on the campus of São Carlos Federal University (São Paulo, Brazil) in April 2005. The material was kept frozen until preparation of the extracts.

Aqueous extracts – The plant material was weighed and ground with distilled water in an industrial blender and the homogenate was left to settle for three hours in the dark. Then each extract was filtered using a vacuum pump coupled to a Büchner funnel covered with qualitative filter paper and immediately utilized. The extracts were prepared at concentrations of 1.5 and 3.0% (1.5g/100 mL and 3.0 g/100 mL) of dry material, at which time the percentage of water in these materials was obtained. The target species used in the bioassays was sesame (Sesamum indicum L., Pedaliaceae) and the effects of the leaf, stem and root extracts of Aristolochia esperanzae were compared to those of the control group (grown in distilled water).

Germination bioassay – Thirty sesame seeds were placed in Petri dishes (9 cm diameter) containing a double layer of filter paper moistened with 5 mL of A. esperanzae extracts or distilled water, on which 30 sesame seeds were placed. The plates with the seeds were kept in BOD chambers at 28ºC (± 2) and 12-h. photoperiod. The germinated seeds were counted at 12-h intervals during the first seven days and every 24 h thereafter until ten days had elapsed. Those seeds that had emerged a 2 mm radicle were considered germinated. The parameters analyzed were percentage and speed of germination (Labouriau 1983; Borghetti & Ferreira 2004). The experimental setup was totally random with four repetitions for each treatment.

Growth bioassay – Clear plastic boxes (11 x 29 x 9.5 cm) were lined with two sheets of filter paper moistened with 40 mL of extract (or water), covered and placed in clear plastic sacks. Thirty sesame seeds germinated in water (2- to 4-mm-long rootlet) were distributed in the plastic boxes and kept in the climate-controlled chamber under the same conditions as for the germination test. After four days the length of the aerial part and primary root was measured with a digital caliper.

Examination of xylem elements – For this evaluation the seedlings were grown in the same temperature and light conditions as in the other bioassays. After four days, the seedlings were removed from the boxes, the primary root segment was detached and immersed in 70% ethanol.

The modified Fuchs method of staining was used (Kraus & Arduin, 1997), where the roots remained immersed in alcohol (70%) for seven days and then were placed in a solution of 25% NaOH for 24 to 48 h until the material was clarified. Then the root segments were immersed in a 2% solution of glacial acetic acid for 30 min., 30% ethanol for 5 min., following by safranin in a water-alcohol medium (50%) for 30 min., then a solution of 30% ethanol + 0.5 mL of acetic acid for 5 min., and finally 30% ethanol for 5 min.. After staining, the material was mounted on glass slides with the roots in Apathy’s syrup (Kraus & Arduin 1997) for observation under an optical microscope (Olympus–BX41) coupled to a camera (Sony CCD-IRIS). Four primary roots were used from sesame seedlings grown in water or the different extracts of Aristolochia esperanzae. One-half of the length of each root was photographed, from the central region upward. From each photograph ten central cells of the metaxylem with 20X magnification (Image Pro Plus program) were measured.

Data treatment and statistical analysis – The experimental setup and bioassays were totally random, with four replicates for each treatment. The percentage values were transformed into arc sin (√%). The Kolmogorov-Smirnov (Lillifors) test for normality was applied to all the groups of values obtained (treatments). The data were submitted to variance analysis (single criterion), and depending on the distribution, the Kruskal-Wallis (non-parametric) or Tukey (parametric) test was used at 5% significance (Santana & Ranal 2005). The statistical analyses were run in the BioEstat 3.0 program.

 

Results and discussion

Germination bioassay – The leaf and stem extracts did not cause any changes in the germination percentage of the sesame seeds at any of the concentrations tested. However, the 3.0% root extract caused a significant reduction in the germination percentage. Regarding germination speed, all the extracts caused a delay in germination except for the 1.5% stem extract (Fig. 1).

 

 

Alterations in germination patterns can be caused by changes in the permeability of cell membranes, transcription and translation of RNA, integrity of secondary messengers, respiration, conformation of enzymes and receptors, or a combination of these changes (Rizvi & Rizvi 1992; Ferreira & Áquila 2000). For example, 6-methoxy-2-benzoxalinone (MBOA) inhibits the germination of lettuce seeds by impeding inducement of α-amylase synthesis, which mobilizes the stored reserves and maintains seed respiratory activity (Kato-Noguchi & Macias, 2005). Baleroni et al. (2000) showed that p-coumaric and ferulic acids increased total lipid content in the cotyledons of canola seeds and suggested that this change is due to reduced mobilization of reserves during germination in the presence of these phenolic compounds.

Often the allelopathic effect is not observed in the final germination percentage, but rather in the speed of germination, which can provide important indications of the allelochemical (Ferreira 2004). Delays in seed germination of any species can have important biological implications, because this will affect the establishment of seedlings in natural conditions (Escudero 2000; Chaves et al. 2001) and their chances of competing for resources with neighboring species (Xingxinag et al. 2009).

Aristolochia esperanzae extracts altered the germination process of the sesame seeds, demonstrating that these changes can also occur in nature. Among the extracts from the different organs used, those from the root inhibited germination the most. This effect varied depending on the concentrations used, with total suppression at 3% concentration (Fig. 1).

Growth bioassay – Growth of the shoot was stimulated when the sesame seedlings were grown in the presence of leaf and stem extracts (1.5 and 3.0%), but in the presence of the root extracts (1.5 and 3.0%) it did not differ statistically from the control group (Fig. 2 – top). Other studies have also identified stimulated plant growth in the presence of extracts. Extracts of Euphorbia serpens stimulated growth of the aerial parts and roots of Lactuca sativa (Dana & Domingo 2006), and leaf extracts of Phytolacca americana stimulated growth of the aerial parts and roots of Cassia mimosoides (Kim et al. 2005).

 

 

The leaf extract had no significant effect on growth of the primary root. However, the stem and root extracts caused a significant reduction in growth. They were darkened and rotted when kept in the 3.0% root extract. These results reveal that regarding initial growth, the primary root of the sesame seedlings was more sensitive to the root extracts of Aristolochia esperanzae than was the aerial part (Fig. 2). Others authors have also reported that roots are more sensitive to allelochemicals than aerial parts (Hamdi et al. 2001; Parvez et al. 2003; Punjani et al. 2006; Abdelgaleil & Hashinaga, 2007; Ercoli et al. 2007). Extracts of alfalfa (Medicago sativa) and coumarin increased the diameter of alfalfa roots (Chon et al. 2002). According to the authors, this was due to the expansion of the central vascular cylinder and changes in cortex cell layers. In another study, the monoterpenes camphor, eucalyptol, limonene and α-pinene inhibited the growth of corn roots, and the authors demonstrated that this happened because of changes in the mitochondrial metabolism, thus altering various other physiological and metabolic processes associated with growth and development of the plants (Abrahim et al. 2000). Corn seedlings showed a reduced mitotic index in the presence of Leucena leucocephala mulch and the authors observed that the absence of cell division and root thickening was due to the increased activity of the enzyme peroxidase in these seedlings (Pires et al. 2001). Other authors have also reported changes in mitotic indices in the presence of allelopathic substances (Dayan et al. 1999; Jacobi & Fleck 2000; Pires et al. 2001; Iganci et al. 2006). Concentrations of 0.1 and 0.15mM of sorgoleone provoked changes in the formation of cell walls and caused deformation of vessel elements, besides discontinuity in the starch sheath (Hallak et al. 1999).

In line with these findings and similar to the results of the germination bioassay, the root extracts of A. esperanzae had the greatest inhibiting effect, causing morphological changes and reduced growth of the seedlings. Root exudates and residues are commonly known as the two main sources of allelochemicals released into the soil (Yu et al. 2000). These compounds are generally stored in root cells for subsequent release (Rice 1984). This is the probable route by which the allelochemicals of A. esperanzae are released into the soil, explaining the greater inhibitory activity (both on germination and growth) of the root extracts.

Xylem elements - The average size of the metaxylem cells of the seedlings grown in water was 150.89 µm (±54.11). Those grown in the leaf, stem and root extracts of Aristolochia esperanzae had statistically smaller average of metaxylem cell sizes than the control group (around 50% smaller) (Fig. 3 - 4). The data on the percentage of cells distributed in size classes showed that the control group had homogenous cell size distribution, with the highest percentage (37.70%) found for cells between 101-150 µm long. There were no cells lower than 50 µm in the control group, but there were cells longer than 151 µm. In contrast to the control group, the cells of seedlings grown under the influence of the extracts were more homogeneously distributed regarding size. The cells of seedlings grown with the leaf and stem extracts were predominantly (60%) between 51-100 µm. For the root extracts (1.5 and 3.0%), the majority of cells were also in this size interval (78.8 and 79.5%, respectively). None of the cells from plants grown under the influence of the root extracts were longer than 151 µm (Fig. 5).

 

 

 

 

 

A. esperanzae extracts inhibited the growth of sesame roots as was shown above. This indicates the probable interference of allelochemicals present in the extracts with concentrations of different categories of hormones like auxins and cytokinins

Aliotta et al. (2004) demonstrated that the expansion of root cells was reduced in the presence of different concentrations of parts of Olea europea and this reduction resulted in thickening of the root tip in comparison to the control. According to Al-Wakeel et al. (2007), inhibition of cell elongation can be related to the direct action of allelochemicals, by interfering in the process of cell division and thus altering the balance of the different hormones. In the present study, sesame plants grown under the influence of extracts in general showed stunted primary root growth and reduction of 50% in the size of root xylem cells.

The results obtained in this study show that different extracts of A. esperanzae caused changes in germination and growth of sesame seedlings. Among the extracts of the different organs utilized, those from the roots had the strongest inhibitory effect on germination and growth, and this inhibition depended on the concentration used, causing morphological changes and diminished growth and development of the seedlings, with total suppression of germination and growth at 3% concentration. Exudation from the roots can be the way the allelochemicals of A. esperanzae are released into the soil, explaining the greater inhibitory effect with use of the root extracts. Moreover, the extracts altered the number and size of the lateral roots. Therefore, it is not possible to determine the principal action or direct action of the allelochemicals present in the A. esperanzae extracts. However, it is probable they are related to the biosynthetic metabolism, concentration and/or sensitivity of the various plant hormones. Chemical studies are under way to analyze the constituents of the extracts to enable determination of which substances function as allelochemicals.

 

Acknowledgments

The authors thank the National Research Council (CNPq) for the grants (471135/2006-2) and for the scholarships to the authors and, to the lab technician Maristela Imatomi for her experimental help.

 

References

Abdelgaleil, S.A.M. & Hashinaga, F. 2007. Allelopathic potential of two sesquiterpene lactones from Magnolia grandiflora L. Biochemical Systematics and Ecology 35(11): 737-742.         [ Links ]

Abrahim, D., Braguini, W. L., Kelmer-Bracht, A. M. & Ishii-Iwamoto, E. L. 2000. Effects of four monoterpenes on germination, primary root growth, and mitochondrial respiration of maize. Journal of Chemical Ecology 26: 611-624.         [ Links ]

Aliotta, G.; Ligrone, R.; Ciniglia, C.; Pollio, A.; Stanzione, M. & Pinto, G. 2004. Application of microscopic techniques to the study of seeds and microalgae under olive oil wastewater stress. Pp. 289-314. In: F.A. Macias; J.C.G. Galindo; J.M.G. Molinillo, H.G. Cutler. Allelopathy – Chemistry and mode of action of allelochemicals. Washington, CRC Press.         [ Links ]

Al-Wakeel, S.A.M.; Gabr, M.A.; Hamid, A.A. & Abu-El-Soud, W.M. 2007. Allelopathic effects of Acacia nilotica leaf residue on Pisum sativum L. Allelopathy Journal 19: 411-422.         [ Links ]

Bagchi, G.D.; Jain, D.C.; Kumar, S. 1997. Arteether: A potent plant growth inhibitor from Artemisia annua. Phytochemistry 45: 1131-1133.         [ Links ]

Baleroni, C.R.S.; Ferrarese, M.L.L.; Souza, N.E & Ferrarese-Filho, O. 2000. Lipid accumulation during canola seed germination in response to cinnamic acid derivatives. Biologia Plantarum 43: 313-316.         [ Links ]

Barkosky, R.R.; Einhellig, F.A. & Butler, J.L. 2000. Caffeic acid-induced changes in plant-water relationships and photosynthesis in leafy spurge Euphorbia esula. Journal of Chemical Ecology 26: 2095-2109.         [ Links ]

Borghetti, F.; Ferreira, A. G. 2004. Interpretação de resultados de germinação. pp. 209-222. In: A.G. Ferreira, F. Borghetti (eds.). Germinação: do básico ao aplicado. Porto Alegre, Editora Artmed.         [ Links ]

Capellari, L.J. 1991. Espécies de Aristolochia L. (Aristolochiaceae) ocorrentes no estado de São Paulo. Dissertação de Mestrado. Campinas, Universidade de Campinas.         [ Links ]

Chaves, N., Sosa, T. & Escudero, J.C. 2001. Plant growth inhibiting flavonoids in exudate of Cistus ladanifer and in associated soils. Journal of Chemical Ecology 27: 623-631.         [ Links ]

Chon, S.U.; Choi, S.K.; Jung, S.; Jang, H.G.; Pyo, B.S. & Kim, H.G. 2002. Effects of alfafa leaf extracts and phenolics allelochemicals on early seedling growth and root morphology of alfafa and barnyard grass. Crop Protection 21: 1077-1082.         [ Links ]

Chou, C.H. 1999. Roles of allelopathy in plant biodiversity and sustainable agriculture. Critical Reviews in Plant Science 18: 609-636.         [ Links ]

Cruz-Ortega, R.; Anaya, A.L.; Hernández-Bautista, B.E. & Laguna-Hernández, G. 1998. Effects of allelochemical stress produced by on seedling root ultrastructure of Phaseolus vulgaris and Cucurbita ficifolia. Journal of Chemical Ecology 24: 2039-2057.         [ Links ]

Dana, E. D. & Domingo, F. 2006. Inhibitory effects of aqueous extracts of Acacia retinodes Schltdl., Euphorbia serpens L. and Nicotiana glauca Graham on weeds and crops. Allelopathy Journal 18(2): 323-330.         [ Links ]

Dayan, F.E.; Watson, S.B.; Galindo, J.C.G.; Hernández, A.; Dou, J.; Mcchesney, J.D. & Duke, O. 1999. Phytotoxicity of quassinoids: physiological responses and structural requirements. Pesticide Biochemistry and Physiology 65: 15-24.         [ Links ]

Einhellig, F.A. 1996. Interactions involving allelopathy in cropping systems. Agronomy Journal 88: 886-893.         [ Links ]

Ercoli, L., Masoni, A., Pampana, S. & Arduini, I. 2007. Allelopathic effects of rye, brown mustard and hairyn vetch on redroot pigweed, common lambsquarter and knotweed. Allelopathy Journal 19: 249-256.         [ Links ]

Escudero, A., Albert, M.J., Pita, J.M. & Pérez-Garcia, F. 2000. Inhibitory effects of Artemisia herba-alba on the germination of the gypsophyta Helianthemum squamatum. Plant Ecology 148: 71-80.         [ Links ]

Ferreira, A.G. & Áquila, M.E.A. 2000. Alelopatia: uma área emergente da ecofisiologia. Revista Brasileira de Fisiologia Vegetal 12: 175-204. Edição Especial.         [ Links ]

Ferreira, A.G. 2004. Interferência: competição e alelopatia. Pp 251-262..A.G. Ferreira, F. Borghetti (eds.). In: Germinação: do básico ao aplicado. Porto Alegre: Editora Artmed.         [ Links ]

Friedman, J. 1995. Allelopathy, autotoxicity, and germination. pp. 629-644. In: J. Kigel; G. Galili. (eds.). Seed Development and Germination. New York, Marcel Dekker.         [ Links ]

Gatti, A.B., Perez, S.C.J.G.A. & Lima, M.I.S. 2004. Atividade Alelopática de extratos aquosos de Aristolochia esperanzae O. Ktze na germinação e crescimento de Lactuca sativa L. e Raphanus sativus L. Acta Botanica Brasilica 18: 459-472.         [ Links ]

Hallak, A.M.G.; Davide, L.C.; Gavilanes, M.L & Souza, I.F. 1999. Efeito de exsudatos de raiz de sorgo (Sorghum bicolor L.) sobre características anatômicas do caule do feijoeiro (Phaseolus vulgaris L.). Ciência a Agrotecnologia 23: 317-322.         [ Links ]

Hamdi, B.A., Inderjit, Olofsdotter, M. & Streibig, J.C. 2001. Laboratory bioassay for phytotoxicity: an example from wheat straw. Agronomy Journal 93: 43-48.         [ Links ]

Hao, Z. P., Wang, Q., Christie, P. & Li, X.L. 2007. Allelopathic potencial of watermelon tissues and root exudates. ScientiaHorticulturae 112: 315-320.         [ Links ]

Iganci, J.R.V.; Bobrowski, V.L.; Heiden, G.; Stein, V.C. & Rocha, B.H.G. 2006. Efeito do extrato aquoso de diferentes espécies de boldo sobre a germinação e índice mitótico de Allium cepa L. Arquivos do Instituto Biológico 73: 79-82.         [ Links ]

Inderjit & Duke, S.O. 2003. Ecophysiological aspects of allelopathy. Planta 217: 529-539.         [ Links ]

Jacobi, U.S. & Fleck, N.G. 2000. Avaliação do potencial alelopático de genótipos de aveia no início do ciclo. Pesquisa Agropecuária Brasileira 35: 11-19.         [ Links ]

Kato-Noguchi, H & Macias, F. A. 2005. Effects of 6-methoxy-2-benzoxazolinone on the germination and α-amylase activity in lettuce seeds. Journal of Plant Physiology 162: 1304-1307.         [ Links ]

Kaur, H.; Inderjit & Kaushik, S. 2005. Cellular evidence of allelopathic interference of benzoic acid to mustard (Brassica juncea L.) seedling growth. Plant Physiology and Biochemistry 43: 77-81.         [ Links ]

Kil, J.H. & Shim, K.C. 2006. Allelopathic effects of Tagetes minuta L. and Eupatorium rugosum Houtt. Aqueous extracts on seedling growth of some plants. Allelopathy Journal 18: 315-322.         [ Links ]

Kim, Y.O.; Johnson, J.D. & Lee, E.J. 2005. Phytotoxicity of Phytolacca Americana leaf extracts on the growth, and physiological response of Cassia mimosoides. Journal of Chemical Ecology 31: 2963-2974.         [ Links ]

Kraus, J. E. & Arduin, M. 1997. Manual básico de métodos em morfologia vegetal. Seropédica, EDUR.         [ Links ]

Labouriau, L.G. 1983. A germinação de sementes. Washington, Secretaria Geral da Organização dos Estados Americanos. 175p.         [ Links ]

Lopes, L.M.X. & Bolzani, V.S. 1988. Lignans and diterpenes of three Aristolochia species. Phytochemistry 27: 2265-2268.         [ Links ]

Lopes, L.M.X.; Bolzani, V.S. & Trevisan, L.M.V. 1988. Lignans from Brazilian Aristilochiaceae. Revista Latioamericana de Quimíca 19: 113-117.         [ Links ]

Oliveira, S.C.C & Campos, M.L. 2006. Allelopathic effects of Solanum palinacanthum leaves on germination and seedling growth of Sesamum indicum L Allelopathy Journal 18: 331-338.         [ Links ]

Parvez, S.S., Parvez, M.M., Fujii, Y. & Gemma, H. 2003. Allelopathic competence of Tamarindus indica L. root involved in plant growth regulation. Plant Growth Regulation 41: 139-148.         [ Links ]

Parvez, S.S., Parvez, M.M., Fujii, Y. & Gemma, H. 2004. Differential allelopathic expression of bark and seed of Tamarindus indica L. Plant Growth Regulation 42: 245-252.         [ Links ]

Pires, N.M.; Souza, I.R.P.; Prates, H.T.; Faria, T.C.L.; Pereira Filho, I.A.& Magalhães, P.C. 2001. Efeito do extrato aquoso de leucena sobre o desenvolvimento, índice mitótico e atividade da peroxidase em plântulas de milho. Revista Brasileira de Fisiologia Vegetal 13: 55-65.         [ Links ]

Priestap, H.A.; Ruveda, E.A.; Mascaret, O.A. & Deulofeu, V. 1971. Aristolochic acids from aristolochia-argentina gris and Aristolochia esperanzae O. Kuntze. Anales de la Asociación Quimica Argentina 59: 245.         [ Links ]

Punjani, B.L., Patel, K.M. & Patel, U.A. 2006. Allelopathic influence of Prosopis cineraria leaf extracts on germination and seedling growth of rice. Allelopathy Journal 18: 339-344.         [ Links ]

Putnam, A.R. & Tang, C.S. 1986. Allelopathy: state of the science. Pp. 1-19. In: A.R. PUTNAM; C.S. TANG. The Science of Allelopathy. New York, John Wiley & Sons.         [ Links ]

Rahman, A. 2006. Allelopathic potential of Parthenium hysterophorus L. on Cassia sp. Allelopathy Journal 18: 345-354.         [ Links ]

Reigosa, M.J.; Sánchez-Moreiras, A. & Gonzáles, L. 1999. Ecophysiological approach in allelopathy. Critical Reviews in Plant Science 18: 577-608.         [ Links ]

Rice, E. L. 1984. Allelopathy. New York, Academic Press. 353 pp.         [ Links ]

Rizvi, S.J.H. & Rizvi, V. 1992. Allelopathy: Basic and Applied Aspects. London, Chapman & Hall. 480 pp.         [ Links ]

Romagni, J.G., Allen, S.N. & Dayan, F.E. 2000. Allelopathic effects of volatile cineoles on two weedy plant species. Journal of Chemical Ecology 26: 303-313.         [ Links ]

Santana, D.G. & Ranal, M. A. 2004. Análise da germinação: um enfoque estatístico. Brasília, Editora Universidade de Brasília. 247 pp.         [ Links ]

Seigler, D. S. 1996. Chemistry and mechanisms of allelopathy interactions. Agronomy Journal 88: 876-885.         [ Links ]

Xingxinag, G.; Li, M Zongjung G, Changsong L. & Zuowen S. 2009 Allelopathic effects of Hemisterpa lyrata on the germination and growth of wheat, sorghum, cucumber, rape and radish seeds .Weed Biology and Manangement 9: 243 - 249        [ Links ]

Yu, J.Q.; Shou, S.Y.; Qian, Y.R.; Zhu, Z.J. & Hu, W.H. 2000. Autotoxic potential of cucurbit crops. Plant and Soil 223: 147-151.         [ Links ]

 

 

Recebido em 27/10/2009
Aceito em 4/03/2010

 

 

1 Author for correspondence: ferreira@unb.br

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License