The Effect of Soil Temperature on Guayule Plants.

The work of several investigators, including BONNER (2), WHITEHEAD and MITCHELL (18), has shown that low air temperatures greatly reduce the growth rate of guayule plants and at the same time bring about an increase in their rubber percentage and, conversely, that high air temperatures increase the growth and decrease the rubber percentage. However, aside from two brief unpublished reports (4, 6) little information is available as to the effect of soil temperatures on the growth, carbohydrate and rubber production of guayule. This paper presents results obtained where guayule plants were grown at the same air temperature but at different soil teimiperature levels.