Translocation of 11C from leaves of Helianthus, Heracleum, Nymphoides, Ipomoea, Tropaeolum, Zea, Fraxinus, Ulmus, Picea, and Pinus: comparative shapes and some fine structure profiles
A 3-min pulse of 11CO2 was fed to leaves of various plant species to allow us to compare the patterns of movement of 11C translocate over 90 min. Three groups of profiles were found. (1) In Helianthus, Nymphoides, Tropaeolum, Ipomoea, and Fraxinus, a mass flow passed successive detectors, rising steadily over a 90-min period. (2) In Zea and Triticum, the mass flow remained at a peak for 5–10 min and fell steadily thereafter. (3) In Picea and Pinus, no obvious mass-flow pattern was detected in 90 min but rather a series of waves or packets. In every case, the activity opposite certain positions accumulated faster than others, suggesting that points of local buildup of translocate occur along a stem or petiole.By using high activity 11CO2 counting times of 5 s or 1 s, and the five-point mean technique of analysis of data, we have been able to detect aberrations in the tracer profile opposite each detector. These aberrations are due in part to the movement of tracer at different speeds in parallel veins, in part to the superposition of reverse flow of tracer, and in part to apparent discontinuities of flow or small waves of tracer. We conclude that some pulsatory sucrose loading mechanism is possible in the leaves, but a nonsteady-state translocatory mechanism is also possible. We have developed techniques for detecting the points of time of the onset of mass flow and the method of following small peaks of tracer activity past successive detectors. Waves of translocate moved at 0.2 cm min−1 in pine and spruce and 0.5–10 cm min−1 in ash and the angiosperms. Some synchrony of flow causes activity reinforcement or interference to occur in transient fashion.