In this article, we review allelopathy studies conducted in Brazil or involving plant species that occur in the country. Conceptions and misconceptions associated with allelopathy, as well as some international criteria to be applied in allelopathic research, are presented and discussed. We observed a sharp increase in the number of papers on this subject conducted in Brazil between 1991 and 2010. However, most studies are conducted under laboratory conditions, lack a clear hypothesis or a solid justification, and typically make use of target species that do not co-exist with the donor species under natural conditions. We also found that most studies do not take the additional steps in order to purify and identify the bioactive molecules. We recommend that further studies be conducted in order to explore the potential of plant biodiversity in Brazil. Such studies could lead to the development of new molecular structures (allelochemicals) that could be used in the control of pests and weeds, thereby reducing the use of the harmful synthetic herbicides that are currently being widely employed.

Adventitious rooting is essential for vegetative propagation of woody species. We studied the effects of auxin and light on the development of adventitious roots in cuttings obtained from seedlings of Eucalyptus saligna Smith and E. globulus Labill in an attempt to characterize the adventitious rooting process and identify factors controlling rhizogenesis. Root development was scored as rooting percentage, root density (roots per rooted cutting), mean rooting time and root length. In both species, rooting time was reduced in the presence of auxin. Cuttings from 2-month-old E. saligna seedlings were responsive to lower auxin concentrations than comparable cuttings from E. globulus seedlings. Cuttings from 3-month-old E. saligna seedlings rooted promptly and rooting was not significantly affected by light conditions. In contrast, rooting of cuttings from 3-month-old E. globulus seedlings exhibited recalcitrant behavior and no roots were formed if illuminated during the root formation phase. Effective root regeneration of E. globulus cuttings was obtained by a 4-day exposure to 10 mg l(-1) IBA and culture in darkness during the root formation step. Loss of rooting capacity with seedling age was more pronounced in E. globulus than in E. saligna. The possibility of switching adventitious rooting off and on by manipulating light regime and exogenous auxin supply in E. globulus, and the constitutive nature of rooting in E. saligna may provide useful models for examining the rooting process at the biochemical and molecular levels in Eucalyptus.

RESUMOA família Myrtaceae é muito bem representada na flora do estado do Rio Grande do Sul, região sul do Brasil. Frutos e sementes de seis espécies foram examinados quanto ao tamanho, cor, massa, teor de água. As espécies são: Acca sellowiana (Berg.) Burnet; Campomanesia guazumifolia (Camb.) Berg.; Campomanesia xanthocarpa Berg.; Eugenia rostrifolia Legr.; Myrcianthes pungens (Berg.) Legr. e Psidium cattleyanum Sabine. Avaliou-se o comportamento germinativo das sementes, tendo sido usada como substrato areia de rio autoclavada umedecida com água destilada, colocada em caixas gerbox (11 x 11cm) nas temperaturas constantes de 15, 20, 25 ou 30°C ou na alternada de 15°C -30°C, com 14 horas na temperatura mais alta. Os experimentos foram efetuados na presença e ausência de luz. Acca sellowiana, Myrcianthes pungens, Psidium cattleyanum mostraram sementes fotoblásticas positivas. Todas as espécies germinaram em noventa dias, exceto Campomanesia guazumifolia, que levou cerca de cento e cinqüenta dias. O conteúdo de água das sementes variou de 9% em Campomanesia guazumifolia até 68% em Myrcianthes pungens, ocorrendo sementes de intermediárias a recalcitrantes em relação à dessecação. Os embriões tipo eugenoide mostraram germinação criptocotiledonar, enquanto os embriões tipo mircióide e pimentóide apresentaram comportamento fanerocotiledonar. Palavras-chave: Acca sellowiana; Campomanesia guazumifolia; Campomanesia xanthocarpa; Eugenia rostrifolia. ABSTRACTMyrtaceae family is well represented in the flora of Rio Grande do Sul, in the Southern region of Brazil. The seed and the fruits from six trees species of this family were examined concerning their size, color, mass and water content. The species were the following: Acca sellowiana (Berg.) Burnet; Campomanesia guazumifolia (Camb.) Berg.; Campomanesia xanthocarpa Berg.; Eugenia rostrifolia Legr.; Myrcianthes pungens (Berg.) Legr and Psidium cattleyanum Sabine. The germinative behavior of the seeds was evaluated and the substratum used was autoclaved, which was placed in gerbox (11 x 11cm), at constant temperatures 15, 20, 25 or 30°C or in alternate ones 15°C/ 30°C, with fourteen hours period, in the highest temperature. The experiments were also carried out in the dark. The seeds of Acca sellowiana, Myrcianthes pungens, Psidium cattleyanum showed positive photoblastic behavior. All species germinated in 90 days except Campomanesia guazumifolia which took around 150 days to germinate. The water content ranged from 9% in Campomanesia guazumifolia to 68% in Myrcianthes pungens and the seeds varied from intermediate to recalcitrant ones. The eugenoid embryos had a cryptocotylar germination, however the myrciod and the pimentoid had a fanerocotylar germination.

Recebido em 15/08/00. Aceito em 26/04/01 RESUMO -( RESUMO -( RESUMO -( RESUMO -( RESUMO -( Germinação de sementes de Asteraceae nativas no Rio Grande do Sul, Brasil) ) )) ) Aquênios (sementes) recém coletados, de treze espécies nativas de Asteraceae comuns nos ambientes abertos da região sul do Brasil foram testados quanto à germinação em temperaturas alternadas ( 20/10; 25/15; 30/20; 35/25ºC) com a temperatura e o regime de luz; podendo prover uma base inicial para interpretação de efeitos sazonais sobre a germinação e estabelecimento a campo. Em adição, comentários sobre o substrato ágar ou areia são feitos.Palavras-chavePalavras-chavePalavras-chavePalavras-chavePalavras-chave -Germinação, temperatura, luz, Compostas, Senecio, Baccharis, Eclipta, Elephantopus, Eupatorium, Mikania, Stenachenium, Sumphyopappus, Tagetes, Trixis. ABSTRA ABSTRA ABSTRA ABSTRA ABSTRACT -CT -CT -CT -CT -(Germination of seeds of Asteraceae natives of Rio Grande do Sul, Brazil). Achenes of thirteen native Asteraceae species common to the natural grassland or weeds of the southern region of Brazil were tested for germination over a range of alternating temperatures ( 20/10; 25/15; 30/20 and 35/25ºC), and under constant temperatures ( 20; 25 and 30ºC) with light or not .Only fresh collected achenes (herein = seeds) were used. The optimum temperature for germination differed among the species, with Elephantopus mobillis; Eupatorium

No abstract

RESUMO -(Efeitos alelopáticos de extratos aquosos de Aristolochia esperanzae O.Kuntze sobre desenvolvimento de plântulas de Sesumum indicum L.). Aristolochia esperanzae é uma trepadeira que ocorre no cerrado do sudeste do Brasil. Os objetivos deste trabalho foram de identifi car 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 -(Allelopathic effects of aqueous extracts of Aristolochia esperanzae O.Kuntze on development of Sesamum indicum L. seedlings).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.

Pedaliaceae) sob diferentes temperaturas). Alelopatia pode ser definida como o efeito maléfico ou benéfico que uma planta exerce sobre a outra por meio de compostos químicos liberados no ambiente. Diversas espécies do gênero Solanum apresentam evidências de propriedades alelopáticas. S. lycocarpum A. St.-Hil (lobeira) é espécie de ampla distribuição em ambientes perturbados do Cerrado. No presente trabalho foram investigados efeitos alelopáticos de extratos de folhas de lobeira na germinação e no crescimento do gergelim (Sesamum indicum L.). Extratos aquosos das folhas foram preparados nas concentrações de 1%, 2%, 3%, 4% e 5% (p/v). A osmolaridade dos extratos foi medida e soluções de polietileno glicol (PEG 6000), de osmolaridade similar, foram preparadas para avaliar possíveis efeitos osmóticos dos extratos aquosos. Nos testes de germinação, as sementes de gergelim foram colocadas em placas de Petri forradas com papel de filtro com a solução a ser testada e observadas a cada 8h. Para os experimemtos de crescimento, sementes de gergelim foram germinadas em água e posteriormente dispostas para crescimento nos extratos. Após 5 dias, foram medidos os comprimentos da parte aérea e radicular das plântulas. Todos os experimentos foram conduzidos a 22ºC, 30ºC e 38ºC. Observou-se que os extratos de folhas não afetaram a germinabilidade, mas aumentaram o tempo médio de germinação em uma relação próxima à dose-dependente, nas três temperaturas. Quanto ao crescimento, a parte radicular foi a mais afetada pelos extratos aquosos, apresentando redução no tamanho, necroses, ausência de pêlos absorventes e formação de raízes laterais. Os efeitos dos extratos no crescimento das plântulas foram mais evidentes a 38ºC. Os experimentos conduzidos com soluções de PEG 6000 mostraram que os efeitos observados na presença dos extratos não são de natureza osmótica. Palavras-chaves: alelopatia, crescimento, germinação, lobeira, temperaturaABSTRACT -(Allelopathic effect of Solanum lycocarpum A. St.-Hil. leaves on the germination and growth of Sesamum indicum L. (Pedaliaceae) under different temperatures). Allelopathy should be defined as any stimulatory or inhibitory effect by one plant on another through production of chemical compounds released into the environment. Several Solanum species have shown some allelopathic property. S. lycocarpum is largely distributed on disturbed areas of the Brazilian Cerrado. In the present study the effects of aqueous extracts of S. lycocarpum leaves on the germination and growth of Sesanum indicum L. (sesame) were investigated. Aqueous leaf extracts at concentrations of 1%, 2%, 3%, 4%, and 5% (w/v) were prepared. The osmolarity of the extracts were measured and solutions of polyethylene glycol (PEG 6000) of similar osmolarity were prepared to evaluate osmotic effects of the extracts on sesame germination and growth. The experiments were carried out on petri dishes lined by two layers of filter paper plus the solutions to be tested. For the germination experiments the number of germinated seeds was chec...

The activities of the enzymes chalcone synthase (CHS) and phenylalanine ammonia-lyase (PAL) were measured in leaf extracts obtained from four cultivars of the common bean (AB 136, Rio Tibagi, Carioca and Macanudo). Two stages of plant development were examined: plantlets (V2) and the onset of blooming (R6). Initially, the plants were either treated with salicylic acid or inoculated with the delta race of Colletotrichum lindemuthianum (inductive fungus) and after three days they were evaluated for enzyme activity. Afterwards, all plants were inoculated (challenged) with the virulent pathotype 33/95 of C. lindemuthianum except for the water control. Five days later, the activities of PAL and CHS were evaluated. There were significant changes in the activities of both enzymes three days after treatment with salicylic acid or inductive fungus when compared to the control. Five days after inoculation with with the virulent pathotype 33/95 of C. lindemuthianum CHS activity in the Macanudo was similar to control plants that were not treated with salicylic acid or the inductive fungus but inoculated with 33/95 C. lindemuthianum. The increase in enzyme activity after challenge with 33/95 C. lindemuthianum was greatest for the salicylic acid treatment in the cultivar AB 136, followed by Rio Tibagi and Carioca.