Down in that healthy rootzone of yours, there lives a rather large and diverse colony of microbes; aerobic microbes... These guys are responsible for breaking down substrate and providing the plant with the right materials for success.. Molasses, since it comes from sugar cane, has the carbohydrates that MOST benefit these microbes, in the absence of food, so they continue to shuttle the bad byproducts of cellular respiration, and give the microbes a chance to produce some O2 (oxygen) and other positive stimuli for the plant to use in such a way, that it cannibalizes the nutes stored for later.. Think of it like a fat person only having water and crackers for a week; sure, not super healthy, but that fat person will shed some of their additional stored energy (READ: fat), to make way for some muscle growth and lypolysis..
Maybe I skewed that comparison a little, since one is getting fatter, while the other is getting thinner, but they are both catabolic, or breakdown reactions that are beneficial on both sides of the spectrum..
