Tropism

• Tropism is a plants response, via growth, to stimuli
• Tropism uses Indoleatic Acid (IAA), an auxin that controls cell elongation in shoots and inhibits growth in roots
• Phototropism in Shoots is positive, shoot tip produces IAA that diffuses to the shaded region, elongating and bending towards the light
• Phototropism in Roots is negative, high concentrations of IAA inhibits growth on the lighter region, roots grow down and anchor the plant
• Gravitropism in Shoots is negative, IAA diffuses to the lower region causing elongation and plant grows upwards
• Gravitropism in Roots is positive, IAA diffuses to lower region of roots so the upper region elongates and bends towards gravity, anchoring the root