EFFECTS OF ABSCISIC-ACID ON THE ORIENTATION AND COLD STABILITY OF CORTICAL MICROTUBULES IN EPICOTYL CELLS OF THE DWARF PEA

The effects of abscisic acid (ABA) on the orientation and cold stability of cortical microtubules (MTs) in epidermal cells of epicotyls of the dwarf pea, Pisum sativum L. cv. Little Marvel, were examined by immunofluorescence microscopy. The effect of ABA on the elongation of epicotyls and on the orientation of cortical MTs was opposite to that of gibberellin A3 (GA3). Treatment with ABA, which reduced the promotion of epicotyl elongation by GA3, eliminated the GA3-induced predominance of transverse MTs and resulted in a predominance of longitudinal MTs. The effect of ABA on the cold stability of cortical MTs was also opposite to that of GA3. ABA increased the cold stability of MTs, while GA3 decreased it. The predominance of longitudinal MTs brought about by ABA may have some relationship to ABA-induced inhibition of the elongation of the epicotyl. ABA may alter membrane proteins to stabilize cortical MTs and induce cold hardiness of plants. © 1990 Springer-Verlag.