| Abstract: | In a series of experiments the desiccation-sensitive seeds ofQuercus robur were exposed to drying conditions both beforeand after a period of moist storage. Viability loss occurredat higher moisture contents in stored seed than in newly harvestedseeds. Measurements were made at intervals during desiccation.In both stored and unstored seeds viability loss was precededby an increase in the rate of ethane evolution, a commonly usedindicator of lipid peroxidation, and by an increase in electrolyteleakage indicative of membrane damage. Jasmonic acid (JA), itsmethyl ester (MeJA) and ABA were quantified in the same extractsfrom both cotyledonary and axis tissues. The concentration ofall three hormones was higher in the axis than in the cotyledonsof untreated seeds and were within the range of concentrationsquantified elsewhere in seed tissues from other species. Theconcentration of JA, MeJA and ABA progressively increased duringdrying in both cotyledons and axes of whole seeds and in excisedaxes prior to viability loss and then subsequently declined.The concentration of these hormones increased earlier duringdrying in stored seeds in line with their enhanced desiccationsensitivity. Exogenous JA, MeJA and ABA were shown to inhibit germination.However, none of these substances promoted ethylene evolution,which also inhibits germination of Q. robur seeds, or inducedsenescence-like deterioration. The results presented are discussed in relation to the natureof desiccation sensitivity and viability loss in Q. robur seeds. Key words: Quercus robur, seed, desiccation, jasmonates, abscisic acid |
