The effect of low temperatures on the phloem transport of radioactive assimilates in the stolon of Saxifraga sarmentosa L.

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Abstract
The movement of naturally assimilated 14C down the stolon of Saxifraga sarmentosa under the influence of localized cold treatments (0°‐10°C) applied over lengths up to 10 cm was followed by finding the distribution of tracer at the termination of the experiment. Inhibition is slight at 10°C and very considerable at 0°C. It is very dependent on the length treated, but is definite even when this is only 0.8 cm. Cooling the daughter plantlet to 0°C has a smaller inhibitory effect than might be expected. This is difficult to understand if ‘unloading’ is metabolic; perhaps the concentration free energy of the sucrose or other solute can be utilized in the sink terminals on the lines of the chemi‐osmotic hypothesis. If so the same source of non‐respiratory free energy might be available to energize an active sieve‐tube mechanism in mid‐path chilling experiments.