as for the comment about plants growing on land in the wild... i understand what you're saying... and completely agree... however... just want to clear something up. lots and lots and LOTS and LOTS of plants in the hobby are naturally land plants, not aquatic plants. it just so happens some are marginals that spend a season above or below water in the wild and a select few are actually obligate aquatics... still yet there are a lot of them that are non-aquatic terrestrials by nature but are hardy enough not to suffocate when grown completely submersed.
now the plants in tubes and thrown into tanks at any lfs are typically ashame. not only because they won't survive long term but also because most folks working at the f/s's either don't know they won't survive or will not tell a would be buyer they're about to purchase a guaranteed failure that will only degrade and foul the water over time.