REFOLIATION OF ERYTHROXYLUM COCA VAR. COCA. IT. EFFECT OF TEMPERATURE

after being stripped of its leaves. Leaf regrowth may depend on past environmental conditions as well as current ones. The purpose of this study was to determine Ca) how temperature affected the refoliation process and leaf yield and Cb) whether there was any after effect of temperature on subsequent refoliation and yield. Coca plants grown under near optimum temperatures were defoliated and placed in controlled environment chambers at constant day/night temperatures of 17, 18, 19, 20 or 21°C. Some plants remained in the greenhouse at a mean daily temperature of 21.9°C. The number of leaves per growing point was closely associated with leaf yield. The change in canopy cover was a three parameter, logistic function of time with two temperature-sensitive parameters: canopy cover at the end of a flush and the time required for 50 % canopy cover. Coca refoliation was similar for temperatures~19°C but fell off sharply at 18°C and practically stopped at 1TC. After the second defoliation, plants were placed under similar environ· mental conditions. Plants previously grown at low temperatures had higher canopy cover 11 d after defoliation than other plants but this difference quickly disappeared. All plants initiated similar numbers of leaves by the end of the first flush. The rate of leaf initiation and the completion of the second flush were similar for all plants. However, the beginning of the second flush was a linear function of prior temperature treatment. Plants from the lowest temperature began the secohd flush earliest. This ability to eliminate yield differences caused by low temperature by the next harvest suggests that coca plants are resilient to sub-optimal temperatures and that annual yields may be relatively stable even though yields for individual harvests throughout the year may fluctuate. Key words: narcotic, leaf yield, canopy cover, yield assessment