Natural ageing of wheat seeds

Seed natural ageing is accompanied by the loss of the ability to germinate and by a reduction in viability. Viability loss is associated with damage to the DNA, changes in the synthesis of RNA and in enzymatic patterns. The loss of viability, in Triticum durum, is accompanied in imbibed seeds, among other components, by a reduced synthesis and poly(A) polymerase activity. Both young and aged germinating endosperms showed a different pattern of proteolytic activities. Among the factors which influence the longevity of seeds, the most important ones are temperature and moisture content, thus seed ageing is closely linked to storage conditions. In Triticum durum the protective action of low temperature against the degradation process during storage has been shown. A close correlation between the germination rate and capability to synthesise poly(A)+RNA and the integrity of the rRNA molecules may be considered to exist in embryos. Recent data show that the seed viability loss is associated with a progressive membrane deterioration in parallel with changes in RNases and nucleases activities. The damage observed in embryos and endosperms of aged seeds is not found in the cold stored seeds of the same age.