The germination response to heat and salt stress in evaluating vigour loss in aged wheat seeds

Wheat seeds were aged under different conditions of moisture content, temperature and storage time, without any apparent change in germination percentage and rate. To improve the seed vigour pattern prediction of a standard germination test, this was conducted by including stress factors prior to the radicle emergence phase: treatments with 40 degrees C or 40-45 degrees C temperature regimes, as well as imbition in 0.4-0.6M NaCl solutions, during 16-24 h germination at 20 degrees C induced a progressive variation of germination percentage and mean germination time in deteriorating seeds. Moreover, close relationships between germination parameters of treated aged seeds and leachate conductivity and embryo [H-3] leucine incorporation, measured in corresponding untreated aged seeds, were established while the magnitude of correlation coefficients indicated that mean germination time was the most sensitive parameter in monitoring induced hear and salt tolerance in relation to the progress of deterioration. The combined effects of two processes opposing a normal germination behaviour may amplify ageing symptoms in wheat seeds, hence the relative germination test appears to be suitable for evaluating seed quality before a large decline in viability.