Effects of Seed Aging on Germination Characteristics and on Catalase and Peroxidase Activities in Two Canola Cultivars (Brassica napus L.)

Deterioration of seed is one of the most important limiting or even hindering factors in its germination. An evaluation and understanding of the factors responsible for/ and enhancing seed deterioration is of paramount importance. The main aim of this study was to determine the effects of seed deterioration on its germination and as well on the activities of antioxidant enzymes in canola culitvars. The experiments were carried out at seed and biotechnology laboratories of College of Agriculture, University of Tehran during 2004-2005. A completely randomized design of three replications was employed. The canola cultivars Licord (winter variety) and Option 500 (spring variety) were the ones studied. The seeds were aged through accelerate-aging and then germination characteristics measured. Such characteristics as germination percentage (%), germination index as well as germination speed were assessed in all the experiments. Moreover, the levels of antioxidant enzymes, catalase and peroxidase, on these cultivars both under the aging and non-aging treatments and at three imbibition stages were measured. The results revealed that seed aging or deterioration reduced the percentage of germination, germination index and speed of germination in either one of the cultivars. For Licord cultivar, under the accelerate-aging test, all the aforementioned traits were higher than those of Option cultivar. Seed aging reduced the activity of enzymes. Extending seed hydration intervals increased catalase and peroxidase activities. However, the aged seeds had lower levels of enzymes as compared to non-aged ones. Licord, with a higher vigor benefited from a more enzyme activity than Option 500.