Geographia Technica, No. 2/2012, pp. 59 - 67

ETUDE DE LA CONDUCTIVITE HYDRAULIQUE DES TRONCS D’HEVEA : CAS D’UNE PLANTATION EN COTE D’IVOIRE (II) RESULTATS ET DISCUSSION

Jerzy J. NIZINSKI, Gérard GALAT, Anh GALAT-LUONG

ABSTRACT: The necrosis of the rubber tree is an affection of the stem, being expressed by a deterioration of the cortical tissues on the level of which are located the conducting latex tissues. We studied the water relations in a mature rubber tree plantation (clone PB 260; planted in January 1996), in Côte d’Ivoire (May and September 2004), on «healthy» and on «necrosed» trees: mean height 15.0 m; mean circumference at 1.3 m level 59.6 cm; stand density 333 trees ha-1; leaf area index 3.2; rooting depths 4 m; field capacity, RFC = 412 mm; permanent wilting point, RWP = 225 mm; available water content, RAW = 187 mm. Measurements of water potential allow us to appreciate resistances along the continuum roots - trunk - leaves: the resistances between the trunk and the leaves are identical for «healthy» trees (0.3±0.1 cm3 H20 s-1 bars-1) and «necrosed» trees (0.2±0.1 cm3 H20 s-1 bars-1); on the other hand, concerning the resistances between the roots and the trunk the two types of trees differentiate radically: 0.2±0.1 cm3 H20 s-1 bars-1 for «healthy» trees and 1.1±0.3 cm3 H20 s-1 bars-1 for «necrosed» trees, it is thus on the level of the junction of grafting that resistance is exceptionally high for «necrosed» trees. The results seem to show a difference in functioning between «healthy» and «necrosed» trees in the regulation of transpiration flux. Measurements were made here in optimum conditions for water availability; these measurements would have to be continued in conditions of water shortage for the plant, we could then provide more contrasting results.


Keywords: Hevea brasiliensis, clone PB 260, Côte d’Ivoire, bark necrosis, transpiration, hydraulic conductance of a stem.

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