Adenine derivative is

Explanation:

• The plant growth regulators (PGRs) are small, simple molecules of diverse chemical composition.
• They could be indole compounds (indole-3-acetic acid, IAA); adenine derivatives (N6 -furfurylamino purine, kinetin), derivatives of carotenoids (abscisic acid, ABA); terpenes (gibberellic acid,GA3) or gases (ethylene, C2H4).
• Adenine derivatives are a class of plant hormones that include cytokinins. These compounds are derived from the adenine molecule, which is one of the four nucleotides in DNA and RNA.
• Cytokinins are involved in various plant growth processes such as cell division, shoot and root growth, and the delay of senescence (aging).
• Kinetin is one of the most well-known cytokinins and was the first to be discovered. It is used in tissue culture to stimulate cell division.

Other Options:

• ABA (Abscisic Acid): This is a plant hormone involved in many plant developmental processes, including seed dormancy, leaf senescence, and response to environmental stress. It is a derivative of carotenoids.
• Auxin: This is another class of plant hormones that play a critical role in the regulation of plant growth and development, particularly in cell elongation and the directional growth of roots and shoots. 
• GA (Gibberellins): These are a group of plant hormones that regulate growth and influence various developmental processes, including stem elongation, germination, and flowering. It is classified as a terpene.