The chemical composition of exudate obtained from incisions made in the bark of the stem of actively growing Ricinus plants has been determined. The exudate had a high dry matter content (100-125 mg/ml), a high sugar content (80-106 mg/ml) which was solely sucrose, reducing sugars being absent. The amino acid composition was mainly glutamic and aspartic acids and threonine with a total amino acid concentration of 35.2 mM. The exudate had a pH of 8.0-8.2. Potassium was the major cation (60-112 mM) with sodium present at a lower concentration (2-12 mM). Of the divalent cations, calcium was at a low concentration (0.5-2.3 mM) and magnesium relatively higher (4.5-5.4 mM). Chloride was the major inorganic anion (10-19 mM). Phosphate concentration was relatively high (3.7-5.7 mM) and low concentrations of sulphate (0.3-0.5 mM) and bicarbonate (1.7 mM) were also present. Nitrate was absent. The ionic balance was maintained by the presence of relatively large quantities (30-47 meq/l) of organic anions, mainly malate. Bioassays revealed auxin, gibberellin and cytokinin activities in chromatographed exudate. Adenosine triphosphate was found in the exudate (0.40-0.60 mM). The analysis is dicussed with respect to the composition of phloem sap reported for other plant species.

On intact, 3-week-old plants of Phaseolus the larger bud in the axils of the primary leaves shows slow, continuous elongation growth. Release from correlative inhibition can be detected within 30 min following decapitation. When 0.1% indoleacetic acid in lanolin is applied to the decapitated stem stump, the lateral bud shows slow growth during the first 7 h, then stops completely for a further 15 h but after 2 days a further gradual increase in length is observed.The movement of (14)C-labelled assimilates from the subtending primary leaf into the lateral bud increases following removal of the shoot apex. When indole acetic acid is applied to decapitated plants the ability of the buds to import (14)C increases for 5-7 h and then declines to a negligible amount. Little or no radioactivity from tritiated indoleacetic acid is transported into the lateral buds of decapitated plants during the first 48 h following removal of the apex and it appears that rapid metabolism of the compound occurs in the stem tissues.

No abstract