Thats a fabulous question! I had not thought
of that before. Here is my guess: These plants
have a mutation in the geotropism genes. They
still have the hydrotropism and phototropism
genes. So the roots grow into the wet bag, and
the shoots grow toward the light, even though its
below the plant. How would you test my guess?
Thanks for asking.
If a plant has grown right-side-up for a while
and grown good roots, it could then be turned
upside down and still be anchored to the soil with
its roots.This is how Topsy Turvy works -- the
tomato plants are first grown normally, and then
they are flipped upside down. The roots probably
continue to try to grown down, but there's no dirt
beyond the bottom of the container. The plant
leaves/stems also try to grow up (because of
phototropism), so the plant is probably a little
confused. I don't think Topsy Turvy would work if
you started from seeds.