Desiccation of imbibed and germinating pea axes causes a partial reversal of germination events

Abstract

During the first 20 h of imbibition, the viability of ungerminated pea seeds was progressively impaired by desiccation, although by no more than about 15%. However, a drastic reduction in radicle growth and viability resulted if the seeds were imbibed for 24 h or longer before dehydration to 5% moisture content (but not if drying was to 10% moisture content or greater). Therefore, pea seeds undergo a transition from a desiccation-tolerant to a desiccation-intolerant state between 20 and 24 h after the start of imbibition. Seeds initially imbibed for 8, 12, and 16 h and desiccated to their original moisture content completed germination in a shorter time than control (once-imbibed) seeds. However, a residual effect of the treatment was noted, in that the total imbibition time required before germination was longer in those seeds that had been subjected to desiccation between periods of imbibition. Hence, events occurring prior to water loss are not completely stable to desiccation and are partially reversed. Axes from germinating seeds interrupted by a desiccation treatment retained some of their capacity to synthesize proteins. This metabolic event thus responded to desiccation in a similar manner to a physiological parameter, i.e., the rate of germination.