Desiccation stress in recalcitrantQuercus roburL. seeds results in lipid peroxidation and increased synthesis of jasmonates and abscisic acid

In a series of experiments the desiccation-sensitive seeds of Quercus robur were exposed to drying conditions both before and after a period of moist storage. Viability loss occurred at higher moisture contents in stored seed than in newly harvested seeds. Measurements were made at intervals during desiccation. In both stored and unstored seeds viability loss was preceded by an increase in the rate of ethane evolution, a commonly used indicator of lipid peroxidation, and by an increase in electrolyte leakage indicative of membrane damage. Jasmonic acid (JA), its methyl ester (MeJA) and ABA were quantified in the same extracts from both cotyledonary and axis tissues. The concentration of all three hormones was higher in the axis than in the cotyledons of untreated seeds and were within the range of concentrations quantified elsewhere in seed tissues from other species. The concentration of JA, MeJA and ABA progressively increased during drying in both cotyledons and axes of whole seeds and in excised axes prior to viability loss and then subsequently declined. The concentration of these hormones increased earlier during drying in stored seeds in line with their enhanced desiccation sensitivity. 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 induced senescence-like deterioration. The results presented are discussed in relation to the nature of desiccation sensitivity and viability loss in Q. robur seeds.