^ Those aren't exactly true intended purposes for using blackstrap molasses, or kelp. Kelp (seaweed, usually ascophyllum nodosum) produces compounds such as plant growth hormones and regulators in abundance; is also a good organic source of potassium and trace elements. Because of the content of plant hormones (plant cytokines and auxins), it has been suggested that kelp should not be used during flowering or the mid to late bloom period especially.
Blackstrap molasses contains some sucrose and other carbohydrates that can be utilized by soil biota, however, taste a little blackstrap and you'll find it more bitter than sweet. This is because it has higher concentrations of various minerals, and it also has a decent amount of potassium (K).
The purpose of the biota is to keep the plant roots happy, and the purpose of the medium\soil is to keep the biota happy...pretty much. They all require nutrients (including carbon, biota need nutrients for cell structure as well) and they all require energy. Keep in mind that any limiting nutrient will result in a plant growing slower and\or not up to full genetic potential.
As a general rule and simply put most microbes in the rhizosphere are directly benefiting the plant to some degree, or in some capacity...and they also benefit directly from the plant (symbiosis). Plant roots produce exudates (various substances from simple sugars to complex compounds) to attract certain microbes and allow them to proliferate. The energy the plant expends doing this is usually recovered in some way (and then some), typically by means of direct access to nutrients, or protection from disease or predation. The simple sugars are an ideal source of energy for bacteria, which are capable of more rapid proliferation at higher concentrations.
Not that I haven't thought about injecting shit into the stems, out of curiosity, back when I had some syringes around (was either an IV drug user or a diabetic, which are you?). Ultimately this is pointless for improving flavor or whatever if you ask me, and.... vanilla? I am not sure how that would blend with the more natural, complex floral-fruity bouquet of my soil grown head stash. On a larger scale I think it would be borderline just wrong.
