Viability and vigour of freshly collected 1, 2 and 3 years old seeds of the winter wheat cv. Jana were determined, on the base of the rate of germination, germinative capacity and the mean germination time, as well as the length of the shoot after 4, 7 and 10 days of the germination test. The intensity of respiration of whole caryopses, of isolated embryos and of the mitochondria was also measured. It was shown that the seed vigour and viability decreases with ageing. In seeds stored over longer periods the respiratory activity decreases as consequence of disturbance of the biogenesis of mitochondria, decline of oxidative phosphorylation and a decrease of the ability to oxidize the respiratory substrate.
Exposure of winter wheat (Triticum aestivum L.) to various combinations of flooding and freezing stresses induces much greater damage than the individual stresses. Cold-hardened plants flooded for 1 week or exposed to -6°C for 1 week show 100% survival, while survival of plants exposed to both stresses simultaneously is reduced by 20 to 30%, and cold hardiness decreases by several degrees. The level of nonstructural carbohydrates increases in crown tissue during cold acclimation, but decreases when the plants are exposed to flooding or to -6°C for 1 week. The respiratory capacity of crown tissue segments declines when the plants are stressed. Uptake of Rb by the roots of intact seedlings declines after exposure to either freezing or flooding, whereas passive efflux of amino acids is observed after freezing but not following flooding. This study has shown that detectable stress-induced metabolic changes occur in winter wheat before the applied stress is severe enough to reduce survival.