There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
We evaluated hypotheses of senescence in old trees by comparing putative biomarkers
of aging in Great Basin bristlecone pine (Pinus longaeva) ranging in age from 23 to
4713 years. To test a hypothesis that water and nutrient conduction is impaired in
old trees we examined cambial products in the xylem and phloem. We found no statistically
significant age-related changes in tracheid diameter, or in several other parameters
of xylem and phloem related to cambial function. The hypothesis of continuously declining
annual shoot growth increments was tested by comparing trees of varying ages in regard
to stem unit production and elongation. No statistically significant age-related differences
were found. The hypothesis that aging results from an accumulation of deleterious
mutations was addressed by comparing pollen viability, seed weight, seed germinability,
seedling biomass accumulation, and frequency of putative mutations, in trees of varying
ages. None of these parameters had a statistically significant relationship to tree
age. Thus, we found no evidence of mutational aging. It appears that the great longevity
attained by some Great Basin bristlecone pines is unaccompanied by deterioration of
meristem function in embryos, seedlings, or mature trees, an intuitively necessary
manifestation of senescence. We conclude that the concept of senescence does not apply
to these trees.