Question: Do plants with cell division only occurring in meristems have a totally different control over senescence? Cell senescence appears to me to be localised rather than general in plants (leaf fall, xylem development etc) I would like to think that cell mechanisms predate the evolution onto plants animals etc

David Christensen answered on 6 Jan 2014:

Hi, thanks for the really interesting and really tough question!

I’ll be honest and start by saying that I know very little about plant biology, so my answer is going to be based on guess-work and a quick google.

I would expect the specific control over senescence and programmed cell death to be quite different in plants compared with animals because of the large differences in the way plants and animals grow and develop. I’d agree though that basic mechanisms of cell aging are likely to have arisen before plants and animals separated.

In fact, it seems that scientists are studying plant telomeres and find that telomerase, the enzyme that extends the telomeres to delay aging, is not expressed in most plant tissues. This would suggest that those cells must age and senesce in a basically similar way to animal cells. Scientists studying programmed cell death in plants have also found a similar mechanism for control of cell death, which suggests again that the basic controls of aging, senescence and death, on a cellular level, are actually quite similar.

If plants and animals are all descended from the first multicellular lifeforms (which I’d say is more likely than multicellular life beginning twice; once for animals and once for plants), then the basic controls to make sure the cells work together efficiently, including cell senescence and programmed cell death, should be the same, or very similar, in plants and animals, as these controls are likely to have arisen quickly in the first multicellular eukaryotes.

I hope this answers your question!