Abscisic Acid Changes in Primary Roots and Root Protoplasts of Zea Mays L. To Lanthanum Stress

Lanthanum ions antagonize calcium and are used as a Ca 2+  channel blocker but their direct effects are unknown. We investigated lanthanum effects on endogenous abscisic acid (ABA) levels in protoplasts and intact primary roots of  Zea mays  L. Application of 1 mM La 3+  reduced primary root elongation, caused swelling of root tips, and essentially doubled the ABA content in intact roots but decreased ABA in root protoplasts in a concentration-dependent manner. Osmotic stress increased ABA level in protoplasts more than in intact roots. Temporal ABA changes in response to La 3+  treatment indicate that La 3+  affects root growth at least partially via ABA pathway.