AGE-RELATED-CHANGES IN THE ULTRASTRUCTURE AND MEMBRANE-PROPERTIES OF BRASSICA-NAPUS L SEEDS

The ultrastructure was studied of imbibed non-aged winter rape (Brassica napus L.) seeds in comparison with that of artificially aged seeds in which viability was partially or completely impaired. In parallel, measurements were made of lipid-phosphorus content, the leakage of phosphate from the seeds and their vigour and germinability. Decreases in lipid-phosphorus which accompanied the loss of viability corresponded to an increase in phosphate leakage, suggesting damage to cellular membranes. Three ultrastructural symptoms possibly related to age-induced membrane deterioration were observed: (i) the lowering of electron contrast in all cellular membranes excluding plasmalemma; (ii) coalescence of small storage lipid bodies to larger units presumably as a result of the degradation of enclosing half-unit membranes; and (iii) the appearance of protoplasmic inclusions inside the storage protein bodies, possibly resulting from rupture of the enclosing unit membranes.It is suggested that the presence of enlarged fibrillar centres in nucleoli of low viability seeds observed here for the first time in aged seed material may be the morphological manifestation of age-induced damage to nucleic acids. © 1992 Annals of Botany Company.