Teores de ligninas, nitrogênio e taninos em folhas de espécies típicas do mangue

Abstract

IntroduçãoOs manguezais constituem comunidades vegetais muito conhecidas por sua riqueza em taninos (ver p.ex. Janzen 1974). Rizzini & Mors (1976) comentam que Rhizophora mangle, conhecida por mangue-vermelho, pode apresentar até 40% de taninos catequínicos na casca, um teor equivalente ao da acácia-negra, ou "wattle" (Acacia decurrens), considerada a planta tanífera mais importante do mundo. Além do mangue-vermelho, o mangue-branco (Laguncularia racemosa) é também espécie dos manguezais fornecedora de taninos. Os mencionados autores comentam ainda que os manguezais constituem "a maior reserva de tanino do mundo". É precisamente a riqueza em taninos com alto valor comercial, em alguns de seus representantes dominantes, que vem sendo uma das ABSTRACT -(Contents of lignins, nitrogen and tannins in leaves of typical species of mangroves). The contents of lignins, total N and tannins were measured in leaves of Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle. The leaves were collected in mangrove areas of Suape, Madre de Deus island (a highly polluted site in Bahia), Cananéia and two localities of Bertioga, one of them with high levels of pollution, in which no individuals of Rhizophora occur, and the other being an area adjacent to the latter. The leaves of Laguncularia and Rhizophora contain high contents of tannins, the former presenting from three to four times as much tannins as the latter. Leaves of Avicennia are devoid of tannins and possess the highest contents of N. The contents of lignins increase in general along the sequence Avicennia<Laguncularia<Rhizophora. The contents of N, for all species, were practically the same, comparing the samples from Suape and Cananéia. However, the leaves from Bertioga presented higher levels, which reached a maximum in samples from the most polluted area. The leaves of Laguncularia and Rhizophora collected in Suape presented less tannins and more lignins than the samples from Cananéia. The contents of tannins of the leaves of Laguncularia were higher in the samples of Bertioga than those of Cananéia, but the opposite is observed in Rhizophora. The amount of tannins in leaves of Laguncularia from Madre de Deus were the lowest among the localities investigated. The contents of lignins seem to be strongly influenced by pollution, a regular decrease being observed along the series Cananéia>Bertioga/adjacent area>Bertioga/polluted area. It seems that the levels of N and lignins are affected by pollution, the former assuming higher values in polluted areas and the latter lower values. The leaves of Laguncularia from Madre de Deus presented also relatively low levels of lignins, probably as a consequence of environmental impact. A possibility is raised that a decrease in the production of lignins may be one of the reasons for the replacement of Rhizophora by Laguncularia in the most polluted areas. RESUMO -(Teores de ligninas, nitrogênio e taninos em folhas de espécies típicas de mangue).Mediram-se os teores de ligninas, N total e taninos em folhas de Avicennia...

Mangrove habitat partitioning by Ucides cordatus (Ucididae): effects of the degree of tidal flooding and tree-species composition during its life cycle

“…These phenolic compounds (polyphenols and tannin) can disrupt digestion and form complexes that resist digestion by this species (Rhoades and Cates 1976;Lacerda et al 1986). Linton and Greenaway (2007) mentioned that leaves with high tannin content are not easily digested by crabs, confirming their anti-herbivory property (Godoy et al 1997;Kandil et al 2004); this explains the preference of some sesarmid crabs for mangrove leaves with lower concentrations of this alkaloid (Micheli 1993;Guerrero-Ocampo 2002). Data obtained by Nordhaus and Wolff (2007) suggest that the capacity of U. cordatus to digest leaves is not hampered by tannins, but also indicate that this species prefers R. mangle over Avicennia germinans leaves, due to a higher nitrogen content and lower C/N ratio and tannin content.…”

“…Although leaves of L. racemosa contain high concentrations of polyphenols (Lacerda et al 1986;Christofoletti 2005), in more-flooded L. racemosa forests, these compounds significantly decrease with oxidation on soil (Godoy et al 1997). Moreover, in more-flooded mangrove forests, the microbial decomposition process is more efficient, increasing the C:N rates and reducing the astringency of the leaves (Alongi 1997;Christofoletti 2005).…”

Leaf-litter decomposition of the mangrove speciesAvicennia schaueriana,Laguncularia racemosaandRhizophora mangle

“…Also for the same genus, Avicennia officinalis L. showed a decomposition coefficient four to five times higher than those of Rhizophora apiculata Blume, Rhizophora mucronata Lam. Avicennia leaves tend to decompose faster than other species because they are thinner and have a high N content and low concentrations of lignin and tannin (Godoy et al, 1997;Wafar et al, 1997;Kathiresan & Bingham, 2001;Bernini et al, 2006). Avicennia leaves tend to decompose faster than other species because they are thinner and have a high N content and low concentrations of lignin and tannin (Godoy et al, 1997;Wafar et al, 1997;Kathiresan & Bingham, 2001;Bernini et al, 2006).…”

“…and Sonneratia alba J. Smith, probably as a consequence of its thinner leaves, which fragment easily and accelerate decomposition (Wafar et al, 1997). Comparing the two remaining species, Moura (1997) found that the lower decomposition rate of R. mangle compared with L. racemosa is probably because of the thick waxy cuticle and epidermis, which impede shredders (Cundell et al, 1979), besides the higher lignin content (Godoy et al, 1997). Comparing the two remaining species, Moura (1997) found that the lower decomposition rate of R. mangle compared with L. racemosa is probably because of the thick waxy cuticle and epidermis, which impede shredders (Cundell et al, 1979), besides the higher lignin content (Godoy et al, 1997).…”

“…Avicennia schaueriana Stapf & Leechman, Laguncularia racemosa C.F. They have different chemical constituents, especially the concentrations of nutrients and secondary metabolites (Godoy et al, 1997;Bernini et al, 2006). They have different chemical constituents, especially the concentrations of nutrients and secondary metabolites (Godoy et al, 1997;Bernini et al, 2006).…”