Aims: In order to achieve a good and sustainable harvest of Hevea brasiliensis rubber, the effect of exogenous hormonal stimulation on the metabolic partition growth-production of clones according to the class of metabolic activity was made. Place and Duration of Study: The study was conducted for 9 years in the San-Pedro region in south-west Ivory Coast, precisely in the experimental industrial plantations of the former HEVEGO, now Southwestern Agricultural Civil Society Société (SCASO). Methodology and Results: The rubber trees were planted at a density of 510 trees/ha in a completely randomised system. They were bled in S/2 d4 and stimulated to 2.5% Etephon at annual frequencies of 0, 1, 2, 4, 6, 8, 13, 18, 26, 39 and 78. The parameters measured were rubber production, trunk circumference, sucrose content, inorganic phosphorus, thiol groups and dry notch rate. The results showed that productivity increased with the intensity of stimulation (58.96 - 68.49 g.a-1.s-1 ; 39.83 - 66.69 g.a-1.s-1) over the intervals [0.6] and [0.26] stimulations respectively in clones with active and slow metabolism. The circumference of the trunk was marked by a less pronounced decrease in growth in slow metabolizing clones (0.52%) with good protection of the laticigene system (R-SH : 0.815 mmol.l-1) and low sensitivity to dry notching (1.6). Whatever the classes of metabolic activity of the clones, the agrophysiological parameters were strongly correlated with each other by a degree 2 polynomial function. Conclusion: This polynomial function seems to reflect the existence of a good state of equilibrium between laticigenic metabolism and vegetative growth according to the class of metabolic activity of the Hevea brasiliensis clones.

Rubber growing is one of the most important industrial crops in Ivory Coast. In order to achieve a good sustainable rubber crop of Hevea brasiliensis in Ivory Coast, the effect of bleeding at unstimulated d4 frequency on radial vegetative growth was evaluated with 16 clones of Hevea brasiliensis divided into three classes of vegetative growth and metabolic activity, planted in a completely randomized block pattern. Agronomic (vegetative growth and rubber production) and physiological (sucrose and inorganic phosphorus levels) parameters were assessed over nine years. The results obtained showed that bleeding in d4 had a significant impact on the mean annual increase in circumference of bleeding trees (3.04 cm.yr -1 ) relative to that of non-bleeding trees (5.29 cm.yr -1 ). The reduction in growth expressed as a percentage of the vegetative growth potential was estimated at 42.53%. Mean annual circumference increments of unbleeded trees of clones of active (MAC; 5.46 cm.yr -1 ) and moderate (MMC; 4.96 cm.yr -1 ) vegetative and metabolic growth classes are significantly greater than those of bleeding trees of clones of the same classes (3.00 and 2.80 cm.yr -1 ). On the other hand, the average annual increments of the slow vegetative and metabolic growing clones (SMC) are hardly affected by bleeding. The production and reduction in growth were 58.96 g.a -1 .s -1 , 45.06% for MAC, 56.2 g.a -1 .s -1 and 43.55% for SMC, and 39.83 g.a -1 .s -1 and 23.8% for SMC, respectively. A very highly significant polynomial relationship (R 2 = 1) between percent reduction in increment (%RedAcc), rubber production and P/Sac and Pi/Sac ratios was found. The percentage of vegetative growth potential below 50% is a sign that bleeding at the unstimulated d4 frequency is a good indicator for improving the productivity of rubber clones without damaging the physiological state.