Translocation of Labelled Assimilates in the Soybean IV. Some Effects of Low Temperature on Translocation

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Abstract
Translocation of Cl4-labelled assimilate within the plant ceased when the plant was held at 2-3[degree]C. Chilling a short length of petiole to 1[degree]C prevented translocation of labelled assimilate past the chilled section of petiole. When the petiole was again warmed, translocation through it was resumed. The time between warming the petiole and the resumption of translocation varied between 5 and 20 min. The profile of labelled material developed in the stem 30 min after chilling and rewarming was shown to be of logarithmic shape. This shape was lost after 2 hr. A logarithmic profile was obtained for both mobile and fixed labelled material. The rate of movement of the front of detectable activity down the stem was of the order of 17 cm/hr. Movement of labelled assimilate in the vascular tracts running downward from a particular leaf was inhibited when the leaf was isolated from the stem (by chilling), and enhanced when the root was deprived of assimilate from other leaves (by defoliation).