I think that this discussion is really fascinating. A couple of questions: are fruit or country wines made from juice (no fruit cap) to be treated more like white wines rather than reds? or are they best treated as a different beast entirely when it comes to whether to begin the primary fermentation in an open bucket or a sealed carboy? And the second question is if O2 is really important for yeast in the first stage of its reproduction why is it that no one recommends or uses something to continuously pump air into the must.
I will let the fruit wine people answer the first part.
In some situations, a pump is used to do what is called a pump over. It is more to keep the cap down than just to add O2 but it certainly will also oxygenate the wine. (As a side, even up front, the must is now really considered wine. Legally speaking, it is wine as soon as the yeast is added.) O2 is good up front, but like in life, too much of a good thing can cause problems. The yeast need O2 to multiply, but the wine, itself, doesn't necessarily require it.
Generally speaking, for home wine making, just stirring the wine and lifting some in a spoon and letting it splash back into the fermenter provides enough O2. Just remember that at some point during the fermentation cycle, the yeast will switch to not needing/wanting any O2 at all.
That being said, there are situations where wine is purposely oxygenated - micro-oxygenated (M.O.). This is not something the typical home wine maker would need to do, other than the M.O. that takes place in an oak barrel, which can do wonders for some wines.
