Table IV.

Percentage of ¹⁴C-labeled photosynthate exuded from cut petioles and retained in the leaf at 20 h after photosynthetic labeling with ¹⁴CO₂

Four mature adult leaves were excised and photosynthetically labeled with ¹⁴CO₂. Phloem exudation into EDTA-containing solution was collected and analyzed by scintillation counting. Label remaining in leaves in soluble and insoluble fractions was also established, and label distribution is expressed as a percentage of the total. Experiments in the top and bottom portions of the table were carried out on different days and with different plants. Average and sd values are from four (top three entries) or three (bottom two entries) sibling plants.

Line	Cumulative Percentage 14C Exudation					Soluble Residual	Insoluble Residual
	0 h	2 h	4 h	9 h	20 h
AtSUC2 +/+	0.0 ± 0.0	20.8 ± 4.1	36.7 ± 6.5	56.4 ± 6.2	70.1 ± 6.2	19.4 ± 4.9	10.5 ± 2.2
KD1039	0.1 ± 0.2	16.6 ± 5.3	31.4 ± 8.7	52.8 ± 6.5	66.5 ± 5.7	21.4 ± 1.8	12.1 ± 5.3
KD1294	0.1 ± 0.0	19.3 ± 4.1	29.9 ± 6.2	45.7 ± 6.8	59.4 ± 5.0a	18.7 ± 4.1	21.9 ± 3.1a
AtSUC2 +/+	0.0 ± 0.0	30.0 ± 2.9	47.2 ± 4.9	63.5 ± 3.7	75.3 ± 2.5	17.2 ± 0.8	7.5 ± 2.5
AtSUC2 −/−	0.0 ± 0.0	16.3 ± 5.8a	31.3 ± 10.2	52.2 ± 9.4	73.6 ± 3.8	18.1 ± 1.6	8.3 ± 2.7

^aStudent's t test, P < 0.05, relative to AtSUC2 +/+, performed separately on different experiments.