Displaced Coriander Seedling Shows Geotropism At Work

The main roots on both the coriander and the lettuce have now reached the bottom of their cups. No water given yet. We shall soon be returning to this for a fascinating insight. For now, I want to tell you about GEOTROPISM - a plant's growth response to gravity.

Shoots grow away from gravity and are said to be NEGATIVELY GEOTROPIC. But roots show POSITIVE GEOTROPISM, growth towards gravity.

Just a couple of weeks ago, all seemed lost for this germinating coriander seedling. The seed case had been pulled out of the compost during germination; the root lay prostrate on the surface, its tip facing upward.

Examine the seed's response in its struggle to survive (right). Notice how, 28 days later, the root hairs have anchored the root (radicle) to the surface of the compost, allowing its tip to be thrust downwards to access water and food from the compost. Meanwhile, the cotyledons (seed leaves of developing shoot) are struggling free from the seed case (testa) and are thrusting upwards towards the light.

It's amazing just how resilient, resourceful and determined plants are. It seems they will do everything they can to survive any situation. And I do mean ANY situation. If only they had a brain . . . .