The influence of light, darkness, and lack of CO2 on phloem translocation in detached maize leaves.

Longitudinal strips from leaf blades of Zea mays L., with veins continuous along their whole length, proved to be a very uniform and convenient material for translocation experiments. Under normal photosynthetic conditions a very strong basipetal assimilate movement was shown. In the dark this movement persisted as long as starch reserves were available. Parts of the strips exposed to darkness or to CO2-free air, i.e. nonphotosynthetic conditions, became strong sinks which attracted assimilates, darkness having the strongest effect. Microradioautographs showed that transport of assimilates took place in the sieve tubes of the phloem.