THE EFFECT OF PETIOLE TEMPERATURE ON THE TRANSLOCATION OF CARBOHYDRATES FROM BEAN LEAVES

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Abstract
The effect of temp., in the range from 5 to 40[degree]C on the rate of carbohydrate transport in bean plants, was investigated. An indirect method was used rate of transport was measured in terms of rate of elongation of the stem and first trifoliate leaf. By means of specially devised temp. jackets, only the temp. of the petiole was varied, the other parts of the plant being maintained at 20 [plus or minus] 1[degree]C for all treatments. Growth during the exptl. period (65-135 hrs. duration for the different expts.) occurred in complete darkness, sucrose being supplied to the plants by immersion of the blade of the temp.-treated leaf in 0.75 [image] sucrose soln. Maximum sucrose transport (maximum elongation of stem and leaf) occurred at petiole temps. in the range of 20-30[degree]C. At petiole temps. of 5-7.5[degree]C, and 40-42[degree]C, rate of transport was reduced as much as 50% and 100%, respectively, compared with controls. At a petiole temp. of 20[degree]C, the rate of elongation of either stem or leaf remained essentially constant throughout the exptl. period (135 hrs. maximum). At lower temps., the retarding effect on translocation progressively decreased with time; at higher temps., progressively increased.