Control in plants

Control in plants

1. Plants need water and light for photosynthesis. Their responses, called TROPISMS, help make sure that any growth is towards light and water

   • The Positive Tropism: the plant grows towards the stimulus
   • The Negative Tropism: the plant grows away from the stimulus
   • Phototropism is where light is the stimulus and geotropism is where gravity is the stimulus
     • Light Stimulus: The shoot will grow toward the light and the root will grow away from the light
     • Gravity Stimulus: the shoot will grow against the force of gravity and the root will grow towards the force of gravity

2. Auxins are a family of hormones found in plants. They are mostly made in the tips of the shoots and roots, and can diffuse into other parts of the shoots or roots

   • They change the rate of elongation in the plant cells, controlling how tall they will become. Shoots and roots respond differently to high concentrations of auxins
     • Cells in shoots grow more
     • Cells in roots grow less