Senescence refers to all of the many changes that inevitably lead to the death of part or all of a plant. Two related terms, aging and longevity, are also often used when senescence and eventual death are being discussed. Aging means all of the changes that occur over time, whether or not these changes lead to death, and longevity refers to how long a seed, or plant, or part of a plant, survives.

Senescence occurs in all plants and at all stages of the life cycle. Even in a young bean seedling, senescence processes have begun. The cotyledonary leaves, which were present in the dry seed, will rapidly give up their nutritive reserves to the growing plant, undergo senescence, and fall off.

At the same time, root hairs and root cap cells are dying and being continuously replaced as the root grows. Elsewhere in the plant, cells are...