I've always been told to make sure the light I use is close to the 65000k, because that emits a larger amount of usable light for plants than other lighting options(fairly sure that was the lighting instructions for dummies version). Because I didn't really want to go into too much depth about researching light, I just went with that simplistic approach. I have never used any form of UVA/B lighting until recently and my plants have always done fairly well. Just wanted to specify that you do not need UVA lighting to keep plants in your tank, just a bulb close to 6500k.
A large part of plant growth is also providing enough nutrients like nitrogen, phosphorus, and potassium, as well as micro-nutrients. Without sufficient nutrients, plants will not grow well regardless of lighting, at least with aquatic plants.
A quick google search about whether UVA adds extra benefits to plants led me to a growing sight for an illegal substance, but many users claimed that using UVA increased the potency of said substance. Maybe providing UVA add's something extra? I'll be interested to see if my plants do any better with UV lighting.