Tangpakdee J., Tanaka Y., Jacob Jean-Louis, D'Auzac Jean. 1999. Characterization of Hevea brasiliensis rubber from virgin trees: a possible role of cis-polyisoprene in unexploited tree. Rubber Chemistry and Technology, 72 (2) : 299-307.
Autre titre : Caractérisation du caoutchouc d'hévéas (Hevea brasiliensis) jamais exploités : un rôle possible du cis-polyisoprène chez les arbres non exploités
Résumé : The role of rubber in #Hevea brasiliensis# was analyzed based on the structural analysis of rubber in rubber trees as latex. The rubber obtained from a mature-tree which has never tapped before, so-called "virgin mature-tree" (Vir-NR), contained the gel fraction higher than 80%, while that from a regularly tapped mature-tree (Reg-NR) was less than 3%. The gel showed almost the same structure as a crosslinked rubber prepared from fresh latex in the presence of peroxide, with the molecular weight between crosslinks (Mc) of 3 x 10 puissance 3. This value is extremely low comparing with that of 7 x 10 puissance 5 observed for the soft-gel in rubber from high-ammonia latex and Pale crepe. The Sol fraction from Vir-NR was an oxidative degraded product containing aldehyde and epoxide groups. Aging properties of Vir-NR are much worse than those of Reg-NR. This indicates that rubber accepts free-radicals to form C-C crosslinking and partly oxidative scission of main-chains during storage in laticiferous tubes of Hevea trees. This suggests that a possible role of rubber is a scavenger of free-radicals in latex, due to lack of the naturally occurring antioxidants. The consecutive tappings of latex from the first opening mature-tree resulted in the formation of rubber similar to that obtained from Reg-NR, after six days. This modification indicates that the new regulation mechanisms in latex biosynthesis, which is induced by exploitation, can avoid the rubber chain crosslinkings and increase their elongations.
Mots-clés Agrovoc : Hevea brasiliensis, caoutchouc, latex, structure chimique, saignée, biosynthèse, réponse de la plante, radical libre
Classification Agris : F60 - Physiologie et biochimie végétale
Auteurs et affiliations
- Tangpakdee J.
- Tanaka Y.
- Jacob Jean-Louis, CIRAD-AMIS-AGRONOMIE (FRA)
- D'Auzac Jean
Autres liens de la publication
- Localisation du document : CD_PE425 [(Bibliothèque de Lavalette)]
Source : Cirad - Agritrop (https://agritrop.cirad.fr/391931/)
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