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Master's Dissertation
DOI
https://doi.org/10.11606/D.59.1998.tde-13032005-181922
Document
Author
Full name
Mara Patrícia Pais
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 1998
Supervisor
Committee
Varanda, Elenice Mouro (President)
Claro, Kleber Del
Godoy, Silvana Aparecida Pires de
 
Title in Portuguese
Valor Nutritivo e Investimento em Defesas em Folhas de Didymopanax vinosum E. March. e sua Relação com a Herbivoria em Três Fisionomias de Cerrado.
Keywords in Portuguese
cerrado
Didymopanax vinosum
herbivoria
trips
Abstract in Portuguese
O estudo teve por objetivo verificar se existe um gradiente de estresse nutricional entre fisionomias distintas na ARIE Pé-de-Gigante e verificar se às plantas de cerrado podem ser aplicadas (1) a hipótese da disponibilidade de recursos (Coley et al., 1985), segundo a qual plantas em ambientes com menos recursos investem mais em defesas e (2) a hipótese de que plantas sob estresse abiótico tornam-se mais susceptíveis a insetos herbívoros (Rhoades, 1979; White, 1969, 1984). Além disso, pretendeu-se verificar a composição da fauna de insetos herbívoros e de predadores e parasitóides associadas à planta. Foram comparados os padrões de herbivoria foliar, bem como a fauna de insetos herbívoros e de predadores e parasitóides associada a Didymopanax vinosum E. March. em fisionomias de campo cerrado, cerrado e cerradão, relacionando-os com possíveis variações nutritivas, da dureza foliar e dos teores de celulose, ligninas e taninos. Foi constatado que as folhas jovens de D. vinosum possuem maior conteúdo de água e nitrogênio, menor dureza e menores teores de celulose, ligninas e taninos. As análises de solo não apontaram diferenças entre as áreas em termos de composição química, indicando a ausência de um gradiente de estresse nutricional. No entanto, as plantas do cerrado e do cerradão apresentaram folhas mais ricas em água e nitrogênio e menor dureza que as plantas do campo cerrado. As plantas das duas primeiras áreas investem mais em taninos e menos em ligninas, os principais tipos de defesas quantitativas. Outros fatores abióticos podem exercer grande influência nas concentrações destes compostos, como a luminosidade, cuja deficiência parece colocar as plantas do sub-bosque do cerrado e do cerradão em situação de estresse. Desse modo, a hipótese 1 aplica-se a D. vinosum apenas quando se considera o investimento em taninos, mas não em ligninas. A herbivoria por insetos mastigadores foi muito baixa tanto em folhas jovens quanto em adultas (inferior a 2 e 5%, respectivamente). Em folhas adultas, foi maior apenas no cerradão, corroborando parcialmente a hipótese 2. Por outro lado, a herbivoria por insetos sugadores em folhas jovens foi intensa, principalmente no campo cerrado e no cerradão, sendo Lyothrips didymopanacis (Thysanoptera) a principal espécie responsável pelos danos foliares. As populações desta espécie demonstraram ser influenciadas primariamente pela disponibilidade de folhas jovens da planta. Populações de aranhas e coccinelídeos acompanharam parcialmente as flutuações das populações de L. didymopanacis.
 
Title in English
Nutritive value and defence investment in Didymopanax vinosum E. March. leaves and its relationship with herbivory in three cerrado physiognomies
Keywords in English
cerrado
Didymopanax vinosum
herbivory
trips
Abstract in English
This study aimed at verifying the existence of a nutritional stress gradient among distinct physiognomies at Pé-de-Gigante Relevant Ecological Interest Area (ARIE), and in such case, verifying whether the following hypotheses can be applied to cerrado plants: (1) the resource availability hypothesis (Coley et al., 1985), according to which plants in environments with fewer resources invest more in defence strategies, and (2) the hypothesis stating that plants under abiotic stress become more susceptible to herbivorous insects (Rhoades, 1979; White, 1969, 1984). In addition, the study also aimed at verifying the composition of the herbivorous insects fauna as well as those of predators and parasitoids associated with the plant. The leaf herbivory standards were compared and so were the faunas of herbivorous insects, predators and parasitoids associated with Didymopanax vinosum E. March in physiognomies of “campo cerrado", “cerrado" and “cerradão". Such standards were then related to possible variations in leaf nutrition, toughness and levels of cellulose, lignins and tannins. It was observed that young leaves of D. vinosum had more water and nitrogen content, less hardness and smaller levels of cellulose, lignins and tannins. Soil analyses did not show differences among the areas as to chemical composition, which indicates the absence of a nutritional stress gradient. However, cerrado and cerradão plants presented leaves with greater water and nitrogen contents as well as less toughness than campo cerrado plants. The plants in the two first areas invested more in tannins and less in lignins, which are the two major types of quantitative defences. Other abiotic factors can exert great influence on the concentration of these compounds, such as luminosity, whose deficiency seems to place cerrado and cerradão understory plants in a stressing situation. Therefore, hypothesis 1 applies to D. vinosum only when the investment in tannins is taken into account, but not that in lignins. Herbivory in chewer insects was low both in young and adult leaves (lower than 2 and 5%, respectively). As to adult leaves, it was higher only in cerradão, which partly supports hypothesis 2. On the other hand, herbivory by sucking insects on young leaves was intense, especially in campo cerrado and cerradão where Lyothrips didymopanacis (Thysanoptera) was the mainly responsible species for leaf damage. This species’ population showed to be primarily influenced by the availability of the plant’s young leaves. Populations of spiders and Coccinelideae partly followed L. didymonopacis population flows.
 
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Publishing Date
2005-03-15
 
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