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Latex diagnostic : warning of over-exploitation of Hevea brasiliensis in Thailand's non-traditional area

Vichitcholchai N., Kosaisawe J., Lacote R.. 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. 61-65. Symposium on Natural Rubber (Hevea brasiliensis), 1997-10-14/1997-10-15, Ho Chi Ming City (Viet Nam).

The Latex Diagnostic (LD: measurement of latex inorganic phosphate, reduced thiol, sucrose and dry rubber content) could allow the warning of over-exploitation, especially through over-stimulation, which leads quickly to the onset of transient TPD and progressively to the onset of definitive TPD. After 30 months of experiment, the concentrations of sucrose and reduced thiols in the latex from over-stimulated trees decreased to low levels, whilst a high concentration of inorganic phosphorus in the latex of over-stimulated trees revealed a very high metabolic activity, which consumed too much energy with a low extra-gain in production. In the case of daily tapping, there was no warning of real over-exploitation: the concentrations of sucrose and reduced thiols in the latex remained in the same range as those of the control, whilst inorganic phosphorus concentration remained significantly higher than the control, thus revealing high metabolic activity because of the high latex regeneration rate for such a short harvesting time.

Mots-clés : hevea brasiliensis; latex; diagnostic; rendement; Épuisement des ressources; méthode d'optimisation; saignée; physiologie végétale; thaïlande; diagnostic latex; stimulation; encoche sèche

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