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Plant Adaptations and Tropisms. Adapt or Die!  Plants dominate the surface of the Earth. There are not many areas where you can’t find at least a few.

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Presentation on theme: "Plant Adaptations and Tropisms. Adapt or Die!  Plants dominate the surface of the Earth. There are not many areas where you can’t find at least a few."— Presentation transcript:

1 Plant Adaptations and Tropisms

2 Adapt or Die!  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!

3 Desert Plants  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.

4 Wet Plants  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.

5 Fire! Fire! Fire!  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!

6 Cold Plants  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.

7 TROPISMS

8 Tropisms  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.

9 Phototropism  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.

10 Gravitropism  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.

11 Thigmotropism  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.

12 Chemotropism & Hydrotropism  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.

13 That’s All I Got…


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