Re: What vitamin or vitamins will help most plants grow at a quicker rate.

In general plants do not require vitamins as do most animals. Plants 
synthesize many of the vitamins that animals require.  There is some 
evidence that plants benefit from vitamins, though.  When growoing plants 
in tisssue culture, it is often helpful or even necessary to add some of 
the B vitamins.  Specifically B1, B6, niacin and B12 are used.