Translocation in the Giant Kelp Macrocystis I. Rates, Direction, Quantity of C14‐labeled Products and Fluorescein

SUMMARY C14 tracer and fluorescein dye experiments on translocation through the stipes of Macrocystis are reported. Both dye and C14‐labeled products move mainly in the sieve tubes acropetally and basipetally in variable amounts and at variable rates, frequently entering young developing blades en route. The maximum rate of transport of organic products of photosynthesis may reach 65‐78 cm/hr, while that of fluorescein rarely exceeds 1.0 cm/hr in intact fronds. By their behavior, fluorescein and the C1J′‐labeled products(s) resemble phloem translocation in vascular plants.