I'm not sure if it's right to post an answer like this but anyway, seeing is believing!
Three days ago, I (finally) gathered enough resources to do this experiment.
I'm testing on a pea plant as it comes in handy. I have set up two samples, one for the test and the other for reference.
Today's Day 3, and the results have started to show up. I thought it would be nice for you to see it yourself. The experiment is not over, it's still going on; so I would update the news every three days from now on.
Everything was done in my study room, which is not a laboratory, so the results may not be accurate. I have tried to bring uniformity in the amount and type of soil used, water content, no. of seeds in each sample, seed spacing and other parameters.
I'm providing the link here.
EDIT: Today's only day 5, but the test plant has grown out of my simulator box!
I have modified the setup and started a fresh experiment.
The updated record here.
Maybe I should give an update for future readers. I asked this question a couple of years ago and forgot about it. I did this experiment when I was in high school, and I am currently an undergrad in science :).
I can confirm that this experiment was seriously flawed, be it the control parameters or the theory used. The plants grew bigger just because they received more light.
My past self was too enthusiastic about the results that he forgot to think about any of these. I am not deleting this answer as I want it to serve as a reminder for myself how not to do an experiment.