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% of 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, which the fronds did not survive. When fronds were incubated in abscisic acid for 24 h prior to silica-drying, the amount of water lost was reduced, resulting in survival of the fronds upon subsequent rehydration. Incubation in abscisic acid for at least 18 h was necessary for survival. Fronds in which the final fresh weight after drying was below a critical amount (i.e. to less than 25% original fresh weight) did not survive. A reasonable correlation could be drawn between electrolyte leakage upon rehydration and survival of some desiccation treatments, although this was not always clear-cut, especially in fronds incubated in abscisic acid for an insufficient time to ensure survival. Several polypeptides were synthesized during slow- and silica-drying, and in response to abscisic acid. No novel polypeptides were identified that were unique to the desiccation regimes which resulted in survival. Nor did ABA induce specific proteins in fronds desiccated after preincubation in this regulator for 24 h.