Aging in wheat seeds: biochemical changes associated with loss of vigour and viability

The maximum germination potential is realized when seeds reach physiological maturity. From that time until planting only deterioration of seed quality occurs. The gross physiological symptoms of this phenomenon are delayed germination, reduced growth of seedlings and increased sensitivity to environmental stress. Such seed characteristics, which are generally grouped under the term of «seed vigour », are the consequence of different bio­chemical events, i.e. decline in respiratory and enzymatic activity, damages on macromolecular syntheses and membranes. Both physiological and biochemical changes are currently obiect of extensive work with the aim to devise laboratory means for a reliable evaluation of seed quality. However, essential to this goal is a better understanding of the fundamental processes occurring during germination with particular regard to their role in determining the loss of potential performance and, ultimately seed death. On this regard, much of the literature is concerned with structural or biochemical changes occurred in embryonic cells while non-embryonic tissue deterioration and its possible relationship to differences in seed vigour and viability has received little attention. In the present paper, we describe the physiological condition of both embryonic and non-embryonic tissues in wheat seeds (T. durum L., cv. Appulo) at different viability levels.