The biological mechanisms controlling Hevea brasiliensis rubber yield. - (:unkn) unknown (My University)
The biological mechanisms controlling rubber yield are reviewed. The production of rubber by the H. brasiliensis laticiferous system depends on 2 major limiting factors: latex flow after tapping and latex regeneration between 2 tappings. Physiological mechanisms are able to control the functioning of these 2 limiting factors. Latex flow depends on several parameters: turgor pressure, the characteristics of water transfer from phloem tissues to laticifers after tapping, and processes involved in latex coagulation. These processes are antagonistic: some induce coagulation (hevein, glucanase, etc.) others slow it down (alphaglucosaminidase, chitinase, etc.). Latex regeneration is controlled by 4 essential mechanisms. The first concerns sucrose loading of the laticifers. Sucrose is effectively the fundamental element of cellular metabolism in general, and more specifically of isoprene metabolism. It depends on the carbohydrate availability of elaborated sap flow and bark reserves, but also on plasmalemmal transfer inside the laticiferous syncytium. The second mechanism concerns the regulation of limiting enzymatic activities in the laticiferous metabolic pathways involved in latex regeneration (i.e. 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 adenylate pool play a major role in latex flow and latex regeneration, and consequently in rubber yield. The fourth mechanism concerns 2 aspects: on the one hand, reactions inducing senescence phenomena, which generate toxic molecules of active oxygen species (O2, H2O2, OH), are responsible for laticifer fatigue and dry bark, whereas biochemical processes involving antioxidant reactions fightagainst active oxygen species and detoxify the laticiferous tissues, preserving their latex production capacity.
The biological mechanisms controlling rubber yield are reviewed. The production of rubber by the H. brasiliensis laticiferous system depends on 2 major limiting factors: latex flow after tapping and latex regeneration between 2 tappings. Physiological mechanisms are able to control the functioning of these 2 limiting factors. Latex flow depends on several parameters: turgor pressure, the characteristics of water transfer from phloem tissues to laticifers after tapping, and processes involved in latex coagulation. These processes are antagonistic: some induce coagulation (hevein, glucanase, etc.) others slow it down (alphaglucosaminidase, chitinase, etc.). Latex regeneration is controlled by 4 essential mechanisms. The first concerns sucrose loading of the laticifers. Sucrose is effectively the fundamental element of cellular metabolism in general, and more specifically of isoprene metabolism. It depends on the carbohydrate availability of elaborated sap flow and bark reserves, but also on plasmalemmal transfer inside the laticiferous syncytium. The second mechanism concerns the regulation of limiting enzymatic activities in the laticiferous metabolic pathways involved in latex regeneration (i.e. 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 adenylate pool play a major role in latex flow and latex regeneration, and consequently in rubber yield. The fourth mechanism concerns 2 aspects: on the one hand, reactions inducing senescence phenomena, which generate toxic molecules of active oxygen species (O2, H2O2, OH), are responsible for laticifer fatigue and dry bark, whereas biochemical processes involving antioxidant reactions fightagainst active oxygen species and detoxify the laticiferous tissues, preserving their latex production capacity.
Keywords: antioxidants; biochemistry; Biosíntesis.; chitinase; enzyme activity; enzymes; Látex.; oxidation; plant physiology; rubber plants; sucrose; tapping; toxicity; translocation; tropical crops; vascular system; yields; Antioxidants; Biochemistry; Biochemistry; Biochemistry; Chitinase; Enzymes; Enzymes; Oxidation; Plant physiology; Plant physiology; Rubber plants; Sucrose; Tropical crops; Cardiovascular system