Which way roots and shoots grow

Let bean or gram seeds germinate on a moist cloth until each has a small root and a small shoot. Tie each seedling to a glass plate with wet blotting paper and stand it in a beaker:

• Beaker A: upright, with sunlight from all sides.
• Beaker B: turned upside down: shoot pointing down, root pointing up.
• Beaker C: upright, inside a cardboard box that lets light in from one side only, through a small hole.

Results:

• A: the root grows downwards; the shoot grows upwards.
• B: the root bends and grows downwards; the shoot bends and grows upwards. The seedling 'knows' which way is down!
• C: the shoot grows towards the light coming through the hole; the root keeps growing downwards.

So shoots grow upwards and towards sunlight, and roots grow downwards. Growing and moving like this is how a plant responds to its surroundings.

The Indian scientist Jagadish Chandra Bose did fascinating experiments with plants. He built a machine called a crescograph to record how plants respond to light, heat, electricity and gravity. With it, he could measure how fast plants grow, and he showed that plants can sense and respond to stimuli.