Effect of moisture stress on abscisic acid levels in Ricinus communis L. with particular reference to phloem exudate.
Abscisic acid (ABA) increased considerably in stem apices attached to Ricinus plants during a moisture stress but only slightly in stem apices which were detached and then allowed to lose water. A very marked rise in ABA also occurred in phloem-sap of moisture-stressed Ricinus plants. These results suggest that in apices of moisture-stressed plants the increased ABA does not arise in situ but is translocated to the apex after synthesis in the mature leaves.
Long Ashton Research Station, University of Bristol, Long Ashton, BS18 9AF, Bristol, UK.
G V
GV
Hoad