14. Which one of the following statements related to components/features of senescence in plants is INCORRECT?

(1) Programmed cell death in plants may generate functional cells or tissues.

(2) Senescence can be induced by application of cytokinins and delayed by overexpression of salicylic acid.
(3) Plants defective in autophagy demonstrate accelerated plant senescence.
(4) Leaf senescence is regulated by NAC and WRKY gene families.

The incorrect statement is: (2) Senescence can be induced by application of cytokinins and delayed by overexpression of salicylic acid.

Why option (2) is incorrect

• Cytokinins generally delay senescence, maintaining chlorophyll, photosynthetic proteins, and leaf function; they are widely used experimentally and horticulturally to keep leaves green.​

• Salicylic acid (SA) typically promotes or accelerates senescence at normal/high levels, often via WRKY‑ and ROS‑dependent signaling; low SA can under some conditions mitigate JA‑induced senescence, but SA is not a general senescence‑delaying hormone.​
  So the direction in statement (2) is reversed, making it incorrect.

Why the other statements are correct

(1) Programmed cell death in plants may generate functional cells or tissues

• Plant PCD is integral to development: differentiation of tracheary elements, sieve elements, aleurone layer modulation, and aerenchyma formation all involve PCD that creates functional conductive or aerating tissues.​

• Therefore, PCD can indeed yield functional cells/tissues, not just dead remnants.

(3) Plants defective in autophagy show accelerated senescence

• Autophagy mutants (e.g., atg lines) often display early leaf yellowing and faster age‑related or stress‑induced senescence, because autophagy is required for recycling damaged components and sustaining metabolism during aging and stress.​

• Loss of autophagy compromises this recycling, accelerating senescence.

(4) Leaf senescence is regulated by NAC and WRKY gene families

• Many NAC (e.g., ORE1, NAC016) and WRKY (e.g., WRKY53, WRKY75) transcription factors act as major positive or negative regulators of leaf senescence, integrating hormonal (ABA, SA, ethylene) and stress signals.​

• Large NAC and WRKY senescence‑associated gene networks have been documented, so this statement is correct.