Loss of telomere function in metazoans results in catastrophic damage to the genome, cell cycle arrest, and apoptosis, Here we show that the mustard weed Arabidopsis thaliana can survive up to 10 generations without telomerase. The Last five generations of telomerase-deficient plants endured increasing Levels of cytogenetic damage, which was correlated with developmental anomalies in both vegetative and reproductive organs. Mutants ultimately arrested at a terminal vegetative state harboring shoot meristems that were grossly enlarged, disorganized, and in some cases, dedifferentiated into a callusoid mass. Unexpectedly, Late-generation mutants had an extended Life-span and remained metabolically active. The differences in plant and animal responses to dysfunctional telomeres may reflect the more plastic nature of plant development and genome organization.