Advantageous and Detrimental Effects of Osmotic Pre-Sowing Treatment on the Germination Performance ofAgrostemma githagoSeeds

Abstract

Dormant and after-ripened seeds of Agrostemma githago (corn-cockle) were pretreated in polyethylene glycol 400 (PEG) solutions at temperatures which would have allowed germination if the seeds had been imbibed in water, viz. 4°C or 20°C for after-ripened seeds, and 4°C for dormant seeds. Pretreated seeds germinated faster than untreated seeds. The maximum decrease of the T50 (time to 50% germination) was 66%. Furthermore, pretreated seeds were capable of germination at supra-optimal temperatures which otherwise had inhibited germination completely (20°C for dormant seeds and 30°C for after-ripened seeds). The percentage germination at a supra-optimal temperature was considerably higher when the seeds had been primed at a temperature at which they developed more extension power. The advantageous effects of the osmotic pretreatment were less than might be expected when the osmoticum had inhibited only cell elongation. This was largely, if not fully, due to a general detrimental effect of osmotic stress and not to a selective inhibition of the processes which occur during the pregerminative phase in preparation for growth. Thus, during priming seeds complete all or almost all processes which occur in water-imbibed seeds prior to radicle emergence.