objective 2.81 phototrpoism

• 'Photo' refers to light whereas 'tropism' refers to growth in response to the light
• When the plant grows towards the light, this process is considered positive.
• Phototropism takes place in stems.
• When the light hits the tip of the stem from all directions, it grows forwards and upwards
• When the light hits the stem from the side (known as lateral light source) the stem bends towards the light. This is also considered 'positive' as the plant is growing towards the light. The light from the other side causes the plant hormone and compound known as auxin, which causes more growth on the other side, causing the stem to bend towards the other side