ABSCISIC-ACID ENHANCES THE ABILITY OF THE DESICCATION-TOLERANT FERN POLYPODIUM-VIRGINIANUM TO WITHSTAND DRYING

Detached fronds of Polypodium virginianum L. survived loss of 65-70% o f their fresh weight over 10 d of slow-drying. Drying over silica gel resulted in a faster rate of water loss, to a lower fresh weight, whic h the fronds did not survive. When fronds were incubated in abscisic a cid for 24 h prior to silica-drying, the amount of water lost was redu ced, resulting in survival of the fronds upon subsequent rehydration. Incubation in abscisic acid for at least 18 h was necessary for surviv al. Fronds in which the final fresh weight after drying was below a cr itical amount (i.e. to less than 25% original fresh weight) did not su rvive. A reasonable correlation could be drawn between electrolyte lea kage upon rehydration and survival of some desiccation treatments, alt hough this was not always clear-cut, especially in fronds incubated in abscisic acid for an insufficient time to ensure survival. Several po lypeptides were synthesized during slow- and silica-drying, and in res ponse to abscisic acid. No novel polypeptides were identified that wer e unique to the desiccation regimes which resulted in survival. Nor di d ABA induce specific proteins in fronds desiccated after preincubatio n in this regulator for 24 h.