I've been planning an experiment that maybe you might want to try. In Diana Walstad's book she talks about a "siesta" lighting regimen on low-tech tanks. Basically she turns the light on for 4 hours, off for 4 (during which the tank gets a lot of natural light), and back on for 4. She has a graph in her book that shows that CO2 gets depleted almost to zero in the first 4 hours, but rebounds while the lights are off. So the theory is that low-tech tanks on a siesta regimen will get more CO2 and thus grow better. I think the big question mark is in the latter part of that statement -- do they actually grow better?
An experiment you could try is setting up two identical tanks -- same everything including the size/shape, substrate, water source, dosing, type and number of plants, temperature, water flow/filter, etc. (and I would keep it to one type of plant so that plant interactions don't impact your results) -- except one tank is on a 12-hour constant-on lighting regimen, the other on a siesta regimen. You can measure the height of the plants and number of leaves (assuming you don't use something really tedious to count like myrio), and then re-measure after a 2 or 3 month period.
Practical real-world application? None really, but you could argue that if the method is "better" for plants, and every planted tank enthusiast then switched to using a siesta regimen, then it would reduce electricity usage by a third, making the hobby more eco-friendly.