The root system is one thing, and the bushiness of the plant is another. Restricting the roots will not work, and would likely harm the plant. Depending upon the species, it will grow to a "normal" size, but this is influenced by the environment, which includes light intensity, nutrient availability, and to a lesser extent temperature.
Red-leaf plants require more intense light than green, and restricting the light (with floating plants or less intense light to begin with) will affect growth. The duration does not, except it has to be minimum for the needs of the plant. But aside from this, increasing or decreasing duration is not going to impact on the plant's growth.