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The biological mechanisms controlling Hevea brasiliensis rubber yield

Jacob J.L., Prévôt J.C., Lacote R., Gohet E., Clément A., Gallois R., Joët T., Pujade-Renaud V., D'Auzac J.. 1998. In : Symposium on natural rubber (Hevea brasiliensis) : Vol II : Physiology and exploitation and crop protection and planting methods sessions = [Symposium sur le caoutchouc naturel (Hevea brasiliensis) : Vol II : sessions physiologie et exploitation, prot. Brickendonbury : IRRDB, p. 1-11. Symposium on Natural Rubber (Hevea brasiliensis), 1997-10-14/1997-10-15, Ho Chi Ming City (Viet Nam).

The production of rubber by the laticiferous system of Hevea brasiliensis depends on two major limiting factors: the latex flow after tapping and the latex regeneration between two tappings. Physiological mechanisms are able to control the functioning of these two limiting factors. Latex flow depends on several parameters: turgor pressure, the characteristics of hydric transfer from phloem tissues to laticifers after tapping and processes involved in latex coagulation. These processes are antagonistic: some induce coagulation (hevein, glucanase..), and others slow it down (alfa-glucosminidase, chitinase..). Latex regeneration is controlled by four essential mechanisms. The first concerns the sucrose loading of the laticifers. Sucrose is effectively the fundamental element of the cellular metabolism in general, and more specifically of the isoprenic metabolism. It depends on the carbohydrate availability of elaborated sap flow and bark reserves, but also of its plasmalemmic transfer inside the laticiferous syncitium. The second mechanism implies the regulation of limiting enzymatic activities in the laticiferous metabolic pathways involved in latex regeneration (ie the invertase step). The third mechanism is linked to the availability of biochemical energy and its regeneration in situ. The quantity and the turnover of the adenylic pool have a fundamental importance on the latex flow and latex regeneration, and consequently on rubber yield. The fourth mechanism is concerned with two topics: on the one hand reactions inducing senescence phenomena, which generate toxic molecules of active oxygene species, AOS, are responsible for laticifer fatigue and dry bark; whilst on the other hand, biochemical processes involving antioxidant reactions fight against AOS and detoxify the laticiferous tissues and preserve the latex production capacity.

Mots-clés : hevea brasiliensis; latex; rendement; physiologie végétale; saignée; régénération; métabolisme; saccharose; activité enzymatique; vieillissement; laticifère; Écoulement du latex

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