AP BIOLOGY

Detailed explanation-1: -Ethylene is regarded as a multifunctional phytohormone that regulates both growth, and senescence. It promotes or inhibits growth and senescence processes depending on its concentration, timing of application, and the plant species.

Detailed explanation-2: -Ethylene (plant hormone responsible for ripening and senescence), Abscisic acid-ABA (stress hormone), and Auxin (growth hormone) all play a symphony and cause ‘Abscission-falling/separation of leaf tissue’ from the plant.

Detailed explanation-3: -As most developmental processes in plants, the regulation of abscission involves the plant hormone auxin.

Detailed explanation-4: -SHOOT-DERIVED AUXIN CONTRIBUTES TO ROOT ORGANIZATION Auxins, a class of essential plant hormones, orchestrate almost every aspect of plant growth and development (Woodward and Bartel 2005; Vanneste and Friml 2009).

Detailed explanation-5: -Auxin is known to exert an inhibitory role on primary root growth. An auxin gradient, established by local auxin biosynthesis and transport, is important for primary root growth. Auxin synthesized in roots via the IPyA pathway is crucial in normal root elongation and root gravitropic responses [43].