I don't know about rotating your hydroponic plants - that sounds difficult!  But I do know that there is considerable literature showing that vibration can reduce plant stature, which may also lead to an increase in flowering.  You would find this under the old "thigmotropism" literature.  You could start with a couple of articles by Telewski and Jaffe, (1986) in Physiol. Plantarum vol 66. or by Janet Braam in Cell (1990) Vol 60 357-364. Maybe you could just give the bench they are growing on a good shake several times a day!

Two thoughts on this:

1. There's a rotational hydroponics wheel which was developed I think originally by NASA (or so the legend goes?) - a video on an extension called the volksgarden here: https://www.youtube.com/watch?v=84zh7XL15n8 (apologies for the annoying infomercial type for the growlamp but at least gives an interesting idea)

2. Introducing production methods which intrinsically cause significant stress to me sounds quite risky. If we are looking at commercial production, stressed plants are much more susceptible to diseases, pest attacks etc. which obviously can have disastrous effects on farm operations. It is probably a utopia to avoid any kind of stress during crop cycle but building it into the methodology? (related question, does anybody know if Kratky-method for growing leafy greens is being used commercially and if there are any such stress-induced problems with pests?)

Leaf hairs and growing tips sense pressure and in several plants like on tomatoes was clear an effect just blowing air or passing a brush by hand  as given for leaflet closure in Albizia that is thigmotropism, the main sensors for gravity are in root tips and usually the experiments are done decreasing gravity by clinostatic equipement that is described in http://www.unoosa.org/pdf/sap/hsti/ZGIP/Teachers_Guide_Plant_s.pdf Several treatments have been used for decreasing apical dominance like Alar, TIBA, CCC, are active on branching and flowering by Auxin inhibition. You may searh Horticultural applications in flower production industries

Philip Lintilhac,

Considering the amount of labour, machinery and cost needed to prepare one whole set-up, yeah it is a bit problematic. However if it really does increase the growth rate and yield significantly, then I guess it is worth trying. I don't know if rotating will have the same effect with vibration, but thanks I'll keep that factor in mind too! 

Jonas Eichhorst,

Yeah, I am currently questioning the viability and practicality of the Volksgarden wheel and a few other products in the market that utilize the rotating method. However according to them, the aren't much open research going on regarding the microgravity, gravitropism and their relationship with yield.

Guido Bongi,

Thank you for your suggestion. Right now I haven't look into any chemical treatments yet. I am still wondering whether clinostatic rotation upon plants have any significant effect in growth. Apical dominance is controlled by auxin distribution towards lower lateral buds and according to Nigel G. Ball in "Analysis of Growth: Behavior of Plants and Their Organs VA" by F.C Steward, he stated that apparently rotating (clinostat rotation) the plants will help with the distribution of Auxin equally in the hypocotyl and roots. Maybe there is a clear relationship to this, but I am still having trouble finding a proper research that conclude this theory.