I wonder, terms like "Auxin", "Cytokinin", "Gibberellin" etc means NOT a single compound; but a class of compound.
For example "Auxin" does-not mean a single compound, but several compounds such as : natural auxin (IAA in all plants*, 4-Cl-IAA in pea*, IBA in mustards*) and their synthetic analogs like NAA, 2,4-D, 2,4,5-T, dicamba ( * ), etc.
Similarly there are more-than one natural compounds under the group "Gibberellin" (such as GA1, GA3, GA4, GA7 etc),
and similarly more-than one compounds under cytokinins: natural: cis-Zeatin, 9RiP ( * ) etc. and their artificial analogs such as kinetin ( * ), 6-BAP , etc
Now, my question is, would all the auxins work in exactly the same way? or would there be slightest difference (qualitatively) between their actions? and similarly, Would all the cytokinins work the same way? and would all the gibberellins work in the same way?
(So far I heard that they have difference in their 'strength' i.e. in which concentrations they are undetectable/optimal/toxic to a cell. (i.e. quantitative difference), but don't have any references for this.)
But beside that; my question is, would there be ay qualitative difference?
So far I haven't found anything clear-cut about this in any book or on the web.
Any help welcome
( * ) (ref. Plant Physiology/ Taiz and Zeiger, ed3; chapter 19, fig. 19.3, fig. 19.4)
In one source, Plant Tissue Culture: Theory and Practice/ Bhojwani and Razdan, (edition= ? ) 3.2.3. Growth hormones; , it is told that "IBA and IAA are widely used for rooting, and with a interaction with a cytokinin, for shoot proliferation. 2,4-D and 2,4,5-T are very effective for the induction and growth 2,4-D and 2,4,5-T are very effective for the induction and growth of callus. 2,4-D is also an important factor for the induction of somatic embryogenesis."
However there I could not found, is this difference is really due to a difference in biological (signaling-path) process, or due to some-other superficial difference (solubility, binding with same receptors, etc) of these applied molecules.