NEET BIOLOGY

Detailed explanation-1: -Ethylene is a plant hormone which is present in gaseous form. It is formed by the breakdown of methionine, which is in all cells. Thus, methionine is called as the precursor of ethylene hormone.

Detailed explanation-2: -close precursor of methionine, was also found to be converted to ethylene. Since the conversion of lhomoserine to etlhylene is less efficient than that of methionine, it is concludedthat homoserine is not a closer precursor of ethylene than is methionine.

Detailed explanation-3: -This is because methionine is the immediate precursor of S-adenosylmethionine (AdoMet), which plays numerous roles of being the major methyl-group donor in transmethylation reactions and an intermediate in the biosynthesis of polyamines and of the phytohormone ethylene.

Detailed explanation-4: -1-Aminocyclopropane 1-carboxylic acid (ACC) is the direct precursor of the plant hormone ethylene. ACC is synthesized from S-adenosyl-L-methionine (SAM) by ACC synthases (ACSs) and subsequently oxidized to ethylene by ACC oxidases (ACOs).

Detailed explanation-5: -The gaseous hormone ethylene plays a key role in plant growth and development, and it is a major regulator of stress responses. It inhibits vegetative growth by restricting cell elongation, mainly through cross-talk with auxins.