A fatal growth pattern and ways suspected of postponing death: corm dynamics in the perennial herb Corydalis cava

The forest herb Corydalis cava is the only known species with a corm where tissue is added annually as a layer on the outside, and where the older central parts rot away, i.e. the corm becomes an expanding sphere. This growth pattern creates energetic problems for ageing plants. However, older corms change their shape in a way that saves biomass. Growth of corm with age was here modelled introducing different corm traits saving mass and thus postponing death. The largest corm in the study patch had a volume of 60 ml. If such a corm had remained a solid sphere, its age would be estimated to be 8.3 years. In reality, 4 year old corms became hollow and later an opening appeared in their basal part. In addition, corms ≥ 7 years became more conical. A conical corm with a volume of 60 ml was estimated to be 15.9 years old. Volume and shape of corm thus made it possible to age individual plants. The age structure of the plants in the study patch was described and discussed in relation to the overall dynamics of the metapopulation. The patch consisted of a few strong age classes (from 5 to 7 years old). Any recruiting juvenile age classes were almost completely missing.