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This chapter consists mainly of examination of the major limiting factors — flow and regeneration — and study of the physicochemical and biochemical parameters of latex which account for them. A certain stability in the measurement of parameters from September to the end of November makes it a suitable period for using the latex diagnosis. Flow plays a major role in latex production. Ecoclimatic conditions, tapping systems, the utilization of stimulating agents, and also the characteristics of the laticiferous system and its relation with surrounding tissue in the bark govern the mechanisms of flow. The two primary limiting factors in production are first, flow, which governs the quantity of latex collected at tapping, and second, in situ regeneration of cell material between two tappings. Overexploitation implies a low pH reflecting disturbed metabolism following too great a demand on the laticiferous tissue. The values of the physiological parameters of latex are in general of clonal origin.

Brown Bast is the main phenomenon which limits production in Hevea brasiliensis plantations, lying ahead of fungal diseases affecting roots, leaves, or tapping panel tissue. The disease is in effect mainly associated with too intensive exploitation of trees, leading to physiological imbalance and the stopping of latex flow. This physiological imbalance, aggravated by tapping, may also follow poor ecological conditions. The effect of ecological conditions, climate, and soil on the onset of the disease are examined in turn. This mainly concerns experimental or accidental traumatisms and the effect of tapping methods which enable Hevea to modulate outflow of latex and hence yield. Shortly after the establishment of selected populations, it appeared that high sensitivity to Brown Bast was a hereditary feature. In 1969, Milford defined the plugging index, clonal feature linked with production and thus to sensitivity to bark dryness.