survival and response

• stimulus 

  detectable change in the internal or external environment
• taxes

  directional movement in response to a stimulus
• kinesis

  non-directional movement  (speed and rate) in response to the stimulus
• tropism

  plants response to a stimulus
• IAA

  indoleacetic acid - made in the tip of roots and shoots can control cell elongation or inhibit elongation.
• phototropism (shoots)

  need light for LDR (photosynthesis) positive phototropism

  IAA produces in tips of shoots and diffuses to the shaded side of the shoot when there's light. causes cell elongation and plants to bend towards light
• phototropism (roots)

  does not require light negative phototropism

  high conc of IAA in roots inhibits cell elongation 

  roots bend away from light source
• gravitropism (shoots)

  IAA diffuses to the lower side of the shoot 

  causes cells to elongate and grow upwards 

  negative gravitropism
• gravitropism (roots)

  IAA diffuses to the lower side of roots 

  causes it to bend downwards

  positive gravitropism