Senescence is not a good word to describe what happens when leaves and other plant organs get to the terminal stage of life.

It has echoes of "senile", and we're all too aware of what that means for humans.  It means deterioration, declining viability and approaching oblivion.

But take leaf senescence as an example: foliage turning from green to yellow, gold, red or purple, is experiencing neither a failure of vital processes nor a one-way ticket to death.

On the contrary - a leaf won't be able to senesce properly, or even at all, if its viability is interfered with.

And under the right conditions a leaf can wind the clock back  and go from yellow to green, in some cases running there and back again over several cycles.

It's better to think of senescence as a change of function rather than a loss of function.

Moreover, senescence is a natural event in the life-cycle at every level, from the cell to the tissue to the organ to the whole plant and even the population.  You could say it's hard-wired into the developmental circuitry of plants and their parts.

In fact, I would argue that senescence is such a fundamental event in growth and development that plants as we know them could not have survived and evolved without it.

Plants are ruthless recyclers.  They dismantle and rebuild as they grow.  The germinating seed is stripped of its contents which are used for making roots and shoots.  Materials salvaged from leaves support the growth of flowers and seeds.

The recycling economy of plants is powered by senescence.  This throw-away lifestyle   enables plants to survive in a hostile environment, deal with limited resources and evolve a huge range of forms and adaptations.

Follow the links on this page for more on the highlighted topics - and use your browser's return button to get back here.