Effects of Temperature on Rubber Accumulation by the Guayule Plant

Abstract

1. Young greenhouse-grown plants of guayule showed marked difference in rubber formation according to the temperature conditions to which the plants were subjected. 2. Plants grown in the greenhouse or outdoors in the summer contained in general 0.50% or less rubber. When such plants were transferred to a greenhouse at a constant temperature of 80⚬ F., rubber concentration either remained at the initial low level or dropped slightly. 3. Similar plants subjected to an 8-hour day at 80⚬ and a 16-hour night at 45⚬ or 40⚬ increased in percentage of rubber. This increase amounted to 0.7-1.0% over a period of 1 month. 4. Night temperatures of 50⚬ appeared to be less effective than night temperatures of 40⚬-45⚬ in causing increase of rubber percentage. Night temperatures of 55⚬-60⚬ were ineffective. 5. Young plants continued to respond to night temperatures of 45⚬ with increased rubber production over a period of 4 months. 6. Older plants, which had already been subjected to one winter in the field, responded to low night temperatures in a manner qualitatively similar to that of young plants. The older plants, however, were more effective in rubber accumulation than the young plants, both at high and at low night temperatures.