 Plants dominate the surface of the Earth.
There are not many areas where you can’t find at least a few plants. Given that the Earth has a vast array of different environments, each with its own characteristics and challenges, it would make sense that plants either adapt to the areas they live in or die trying.
 Remember, unlike the animals, once a plant is in place, it is not going anywhere!

 To save water…
 Leaves are small – needles – so to minimize water loss. Thick cuticle to keep water inside.
 Stems are modified to store water.
 Roots are extensive to maximize water absorption.
 Seeds germinate quickly in short rainy season.

 Plants that live in swamps or wetlands must:
 Float leaves and stems to surface for gas exchange. Oxygen is needed for cellular respiration (making ATP).
 Hollow stems can move oxygen downward for use in parts below the water-line.
 Plants also limit water intake in various ways so cells do not swell and rupture the cell walls.

 Fires happen and they kill some plants in the forest. But, fires can also be a good thing…
 It removes old and dead trees that take up room that new growth would like to use.
 The ashes enrich the soil and can make acidic soils a little less acidic.
 Some seeds, while in the ground, require a lot of heat to germinate. When they final punch through the surface, the competition for soil and nutrients is gone!

 Cold areas have tough temperatures, tough soils and they tend to have short growing seasons.
 To overcome this a plant may…
 Lose the leaves – too much energy needed to keep them and they will only weigh you down in the snow.
 Rely on needles – less surface area to gather ice and they minimize water loss.
 Undergo a very short reproductive and growing season.

 A tropism is a plant growth response to an external/environmental stimulus.
(Basically, a change in plant growth because of something around it.)
 There are positive tropisms in which the plant grows toward a stimulus and negative tropisms in which the plant grows away from the stimulus.

 A phototropism is a plants bending and growth of its stem toward the sunlight.
(Photo = Light)
 Photosynthesis is needed so get your leaves up and at the sun.
 Roots show a negative response to light.
 Auxins help the plant bend toward or away from the sun.

 A gravitropism is a plants growth response to gravity.
 Stems show a negative response while roots show a positive response to gravity.
 Helps in seed orientation when planted.
 Also known as geotropism.

 Thigmotropisms are plant growth responses to touch.
 Leaner plants will often use the stronger plants around it to gain height without growing the thick stem/trunk.

 Chemotropisms are plant growth patterns directed by chemicals in the environment.
 Think of what fertilizers do to plants – they fluorish.
 Acids or toxins added to soil by industry can alter plant growth dramatically.
 A hydrotropism is a plants growth toward water.
 This is a great example of a positive tropism.