Aging in an herbaceous plant: increases in mortality and decreases in physiology and seed mass

1. Little is known about plant age-dependent trait expression and how environmental conditions might affect aging in the wild. This study evaluates age variation in multiple traits of a short-lived perennial herb using a manipulative field experimental design.
2. Two different-aged cohorts were followed in a field plot for over a year to evaluate trait expression in response to a competition treatment and seasonal stress. Traits measured included size, mortality, reproduction, and physiology, including photosynthetic efficiency and chlorophyll content (SPAD). We hypothesized that the stress of competition and seasonal changes would accentuate age-dependent trait declines in older plants.
3. The results highlight consistent age differences in plant size, mortality, and seed size with older plants being smaller, more likely to die, and producing smaller seeds. Some of the aging declines were sensitive to environmental conditions such that it was only during certain seasons when older pl...