Growing tomatoes upside down and gravitropism

[tony873004]

I noticed the latest craze is to grow tomatoes upside down, so I though I'd try it. But in Biology of Plants class, we learned that roots only grow downward due to gravitropism. So if I plant the seedlings at the bottom of the pot, how will they ever develop a big root system that fills the container? I figured I could always start the plants right-side up, wait until they've developed a healthy root system throughout the container, and then turn them upside down. But nothing I read suggests doing it this way.

 

[mishrashubham]

http://www.cheapvegetablegardener.com/2009/04/make-your-own-upside-down-tomato.html