Differences in lead tolerance between Allium cepa plants developing from seeds and bulbs

Tolerance to lead of three of Allium cepa L. varieties grown from seeds and bulbs was compared. In all cases plants developing from bulbs were found more tolerant to lead than those developing from seeds. During 10 days of exposure to lead, the difference in the tolerance index between adventitious and seedling roots was 24% on average (7-61% depending on the plant variety and the dose of lead), which was significant. In all cases, the seedlings contained more lead in their tissues than the plants that had developed from bulbs. This observation may explain a difference in lead tolerance between these developmental phases of Allium cepa.