Light and Translocation of C14 in Detached Blades of Sugarcane

Abstract

Polarity of transport and percentage of translocation were affected by the time of day when the blades were detached, the duration and intensity of illumination. Darkening the apex plus the fed part during translocation, reversed polarity after 2-3 hours. The factor controlling polarity was saturated at 50 ft-c, and the factor controlling basipetal translocation was 100 ft-c. The photosynthetic assimilation of CO2 in similar blades, measured with the infrared analyzer, saturated at 6000 ft-c, and the compensation point was located at 120-125 ft-c. Because light affected translocation at intensities which allow no net uptake of CO2, the mechanism of translocation is apparently independent of the assimilation of CO2. So the effect of light upon translocation is not due merely to a washing out by further photosynthesis in C12O2. These results suggest that the initiation of translocation of sucrose from the blade may be under photocontrol, and that the transport of sugar in the phloem may be a photo translocation.