The specialised meanings of senescence in plant science

Enter the term “senescence” into Google Scholar and, at the time of writing, the search returns close on 300000 entries. A glance through the first dozen or so search results reveals papers on leaf senescence in Arabidopsis, mammalian cell senescence related to multistep tumorigenesis, evolutionary significance of senescence in populations, replicative senescence in human cell cultures, memory loss in senescent rats, senescence in yeast mutants with altered telomere elongation, senescence in Drosophila life-history...

It is reasonable to ask whether this vast range of biological behaviours could possibly have anything in common in terms of process, regulation or outcome. The answer is clearly no, other than the casual application of the word senescence to it. In this sense, senescence has been hollowed out of precise meaning in the context of general comparative biology, and in recent times some in the biomedical community researching the cellular basis of gerontology have tended to avoid using the term because of its imprecision.

In the plant sciences semantic issues around the application of the term senescence remain. One still finds senescence being used in the fields of ecology and evolution to describe declining fitness and as a general synonym for ageing. In this context it generally refers to phenomena at the whole plant to population to community level. There is a separate question concerning senescence in organs, tissues and cells, relating to genetic programming and the extent to which senescence processes represent a subset of the programmed cell death syndrome in the plant life-cycle.

The scope and organisation of SenWiki allow these issues to be explored in (it is hoped) a constructive way that goes beyond semantics and engages with the shared and diverse biological mechanisms underlying the senescence of plants and their parts.