SC.3.L.14.2 Investigate and describe how plants respond to stimuli (heat, light, gravity), such as the way plant stems grow toward light and their roots grow downward in response to gravity.Scott Foresman science book pages 110-113, 2007

How Plants Response to Stimuliby: Emily Ellingsen

  • A plants embryo will not sprout if it is too cold, or too dry.
  • Different plants have different needs because of there DNA.
  • Such as a bush being short, or a oak tree being tall.
  • These also show how there branches grow.
  • Plants don't just grow due to it's DNA it also grow partly to the enviroment.
  • With perfect conditions the plant will grow faster than dry or cool soil.
  • Plants will still grow at different rates due to it's DNA.

Tropisms:Plants will grow different ways such as the leaves growing towards the sun, and the roots towards the water source. This occurs when cells in the plant are changed on different sides of the plant. The stem on the plant will bend because one side will grow longer and faster than the other. One reason is because one side may have different amounts of growth hormones. Plants make their own growth hormones. This chemicals more cells to grow in the plant, aswell as make the plant grow larger. Cells may grow different because of changes in it's water. Water fills up the vacuoles and make the cells grow larger.
Gravitropism: When this occurs in the roots and stem. The roots will grow downward because of gravity. Then the stem grows against gravity and grows upward. If you were to take a plant and put it on it's side it would begin to bend to it right position. The plants hormones stimulate the plant to reach for the sky, but the hormones prohibits cells in the plant which causes the plants roots to bend into the ground. The plant will react to gravity no matter what position it is in.

Phototropism:(Hint Photo = light) Phototropism comes in different ways. One way is the stem will grow towards the light or just the life will turn to the light.

Thigmotropism: Thigmotropism happens in the stem and will grow on post, fences, and trellises. This gives support to grow tall and reach sunlight. To get away from rocks and hard soil the roots will curve and bend.


embryo- rudimentary plant usually in the seed
tropism- a way thta plants change their growth because of something outside of them
gravitropism- the growth of a plant or plant part in relation to the pull of gravity
phototropism- a plant's reaction to a source of light
thigmotropism- a plant's growth in response to touching an object
growth hormone- a chemical that causes more cells to grow and helps cells to grow larger(also know as auxin)
vacuoles- part of plant that stores water