Referencing the book Biology, Robert J. Brooker et al. 1st Ed. ISBN 978-0-07-295620-7. 2008.
This is the current Biology book most Universities are using for General Biology I & II.
Chapter 36: Flowering Plants: Behavior.
Plant behavior refers to internal and external stimuli. The external stimuli is the sun being directly above the Apical Meristem (Cola). The Phototropism is the cellular perception of light and the growth response of stem tissue. The plant responds to the light location and releases the hormone auxin. Look up Auxin if your not familiar. This is what will keep your plant standing straight up or lean over.
This next group of hormones are kinda complex. But if you have a good general understanding you will be able to better understand the YouTube videos put out by the Advanced Nutrients guy (can't remember his name).
But definatelly look into Cytokinins, Gibberellins, ETHYLENE, Abscisic Acid and Brassinosteroids.
Ethylene is important during curing. etc... I hope this will help. lol
Too much crap... ha? Anyways have fun... Just try my method once and see what you think. Peace......
Section 36.2 talks about the phenotypic plasticity