Generally after the final drying stage of maturation, a seed is in a condition of maximum vigor (see, however, Grzesink and G6recki, l9g9; Ellis and pieta Filho, 1992) and from this point gradually deteriorates toward ultimate viability loss.
It has been suggested that this reflects progressive impairment of the potential of the seed to synthesize lipids. proteins, and all the classes of ribonucleic acid (osborne, l9g2).
The enzymes involved in DNA repair are thought also to become impaired with time (Elder ei al., 1993; vdzquez et al., l99l), leading to morphological abnormalities and chromosomal aberrations.