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Senescence and Abscission
Concepts tested here
- Senescence as a programmed process
All Questions
2008 AIPMT 1 question
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Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in:Senescence is the period between reproductive maturity and death, in which degenerative changes take place in cells, organs or the whole plant.
It is not a passive wearing out; it is an active, genetically programmed and hormonally controlled developmental process.
Leaf abscission is the best example: before a leaf falls, chlorophyll and proteins are broken down and the nutrients are withdrawn into the plant body.
An abscission layer is then actively formed at the base of the petiole, where enzymes such as cellulase and pectinase dissolve the cell walls and middle lamella.
This process is promoted by abscisic acid and ethylene and delayed by auxins and cytokinins, which shows that it is an active, regulated cellular process.
So senescence as an active developmental process is indicated in leaf abscission, as given in the answer key.