The Effect of Petiole Temperature on the Translocation of Carbohydrates from Bean Leaves.

The present controversial status of the problem of transport rate as related to temperature is briefly summarized in a recent paper by WENT and HULL (8). As pointed out by these authors, the reported Qlo values for translocation range from less than 1 (7, 8), to essentially 1 (5), to values greater than 1 (3, 4). The effects of temperature are multiple and greatly complicate an analysis of this problem. It is to be expected, though little data exist for its substantiation, that the effect of temperature on rate of conduction of carbohydrate materials through petioles, will be influenced by temperature effects on numerous other processes occurring in various parts of the plant, such as respiration and assimilation, and the effect these processes have on concentration gradients between regions of export and import. Studies, therefore, in which the entire plant is subjected to different temperatures (4), although contributing much data of value, do not permit a clear analysis of the temperature effect on the process of translocation per se. In the present experiments, therefore, only the petiole temperature was varied, the rest of the plant in all treatments being maintained at a temperature of 20 ± 10 C.