NEET BIOLOGY

Detailed explanation-1: -Abscisic acid (ABA) is the sole plant hormone known to maintain seed dormancy; it acts through a gene expression network involving the transcription factor ABSCISIC ACID INSENSITIVE 3 (ABI3).

Detailed explanation-2: -Embryonic ABA plays a central role in induction and maintenance of seed dormancy and also inhibits the transition from embryonic to germination growth. Therefore, the ABA metabolism must be highly regulated at both temporal and spatial levels during phase of dessication tolerance.

Detailed explanation-3: -Abscisic acid (ABA) reversibly arrests embryo development at the brink of radicle growth initiation, inhibiting the water uptake which accompanies embryo growth. Seeds which have been kept dormant by ABA for several days will, after removal of the hormone, rapidly take up water and continue the germination process.

Detailed explanation-4: -Induction and release of seed dormancy is mainly under the control of abscisic acid (ABA) and gibberellic acid (GA). ABA promotes seed dormancy and germination inhibition. Action of ABA is counteracted by GA, which promotes seed germination at appropriate time.

Detailed explanation-5: -Plant hormones, mainly abscisic acid (ABA) and gibberellin (GA), are the major endogenous factors that act antagonistically in the control of seed dormancy and germination; ABA positively regulates the induction and maintenance of dormancy, while GA enhances germination.