Getting the Light Right - Part 2

How We Determine a Plant's True Light Requirements

Although our plants are in roughly the right position (we hope), how do we really know?

Simple. We watch them - they 'communicate'. They move themselves around until the light fits just right, just as we do on the beach. This movement is called 'phototropism'.


LEAF MOVEMENT

If light is too LOW

This mint has gone leggy (become etiolated, stretching vertically) and is also bending towards the light. It is thus clearly asking for more light.

Plants also grow larger leaves in low light; it helps them produce enough food. This is why it is best to keep coriander leaf (cilantro) out of too bright light.



If light is too HIGH

We have already seen how a begonia turns its leaves away from the sun. This fuchsia is doing the same thing. I'm not sure if you can see, but the leaves are all different sizes, reflecting to some extent the different light levels to which it has been exposed.



ROOT MOVEMENT

Roots exhibit negative phototropism. That is, they move away from the light. You would have seen this with your coriander roots, although I didn't mention it at the time.