Q.Give a brief account on Programmed Cell Death (PCD)

Step 1. Senescence in plants runs under the plant's own genetic programme, and when this controlled process is carried through to completion at the level of the whole plant, an organ, or an individual cell, the result is called Programmed Cell Death (PCD); at the single-cell level, this is sometimes simply described as that cell's senescence.

Step 2. The enzymes that actually carry out PCD in plants are proteolytic enzymes called phytaspases, distinct from the caspases that perform the equivalent role in animal cells.

Step 3. PCD is not simply destructive - nutrients and other substrates recovered from the dying cells or tissue are remobilised and reallocated to other, still-surviving parts of the plant, so it functions as a recycling mechanism as much as a demolition one.

Step 4. PCD is also used constructively during entirely normal development: the protoplasts inside developing xylem vessels and tracheids deliberately die and disappear once these cells mature, which is exactly what makes them efficient, unobstructed water-conducting tubes. …

Define PCD, name the enzymes responsible, and give its dual role in nutrient rem …

• Describing PCD as purely destructive without mentioning its nutrient-remobilisation and normal-development roles. …