No shit, Sherlock

From the BBC:

Plants grown in pots never reach their full potential, images of their roots show. A medical imaging technique called magnetic resonance imaging (MRI) has been used by researchers to capture plant pot root snapshots. The pictures reveal that the roots "sense the size of the pot" and restrict the growth of the plant. The findings have been presented at the Society for Experimental Biology's annual meeting in Salzburg, Austria...

Within as little as two weeks of seeds being sown, the scientist explained, a plant's roots would stretch to the edge of the pot and then, "the trouble starts".

"When they reach the edge, they send some kind of signal to the shoots to say, 'there's a problem - stop growing'. Each plant appeared to be trying to escape its pot; more than three quarters of the root system was in the outer half of the container. The inside of the pot is hardly used," explained Dr Poorter.