<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
Dismiss
Skip Navigation

Plant Responses

Plants use receptors to respond to changes in the environment.

Atoms Practice
Estimated3 minsto complete
%
Progress
Practice Plant Responses
Practice
Progress
Estimated3 minsto complete
%
Practice Now
Turn In
Plant Responses

So what happens to a vineyard in the middle of winter?

The vines cannot die each year. Instead, the plants go into a state of dormancy, almost as if they are taking a long nap.

Plant Responses

Like all organisms, plants detect and respond to stimuli in their environment. Unlike animals, plants can’t run, fly, or swim toward food or away from danger. They are usually rooted to the soil. Instead, a plant’s primary means of response is to change how it is growing. Plants also don’t have a nervous system to control their responses. Instead, their responses are generally controlled by hormones, which are chemical messenger molecules.

Plant Tropisms

Plant roots always grow downward because specialized cells in root caps detect and respond to gravity. This is an example of a tropism. A tropism is a turning toward or away from a stimulus in the environment. Growing toward gravity is called geotropism. Plants also exhibit phototropism, or growing toward a light source. This response is controlled by a plant growth hormone called auxin. As shown in Figure below, auxin stimulates cells on the dark side of a plant to grow longer. This causes the plant to bend toward the light.

Phototropism response

Phototropism is controlled by the growth hormone auxin.

Daily and Seasonal Responses

Plants also detect and respond to the daily cycle of light and darkness. For example, some plants open their leaves during the day to collect sunlight and then close their leaves at night to prevent water loss. Environmental stimuli that indicate changing seasons trigger other responses. Many plants respond to the days growing shorter in the fall by going dormant. They suspend growth and development in order to survive the extreme cold and dryness of winter. Dormancy ensures that seeds will germinate and plants will grow only when conditions are favorable.

Responses to Disease

Plants don’t have immune systems, but they do respond to disease. Typically, their first line of defense is the death of cells surrounding infected tissue. This prevents the infection from spreading. Many plants also produce hormones and toxins to fight pathogens. For example, willow trees produce salicylic acid to kill bacteria. The same compound is used in many acne products for the same reason. Exciting new research suggests that plants may even produce chemicals that warn other plants of threats to their health, allowing the plants to prepare for their own defense. As these and other responses show, plants may be rooted in place, but they are far from helpless.

KQED: Plant Plague: Sudden Oak Death

Devastating over one million oak trees across Northern California in the past ten years, Sudden Oak Death is a killer with no cure. But biologists now are looking to the trees' genetics for a solution. See http://www.kqed.org/quest/television/plant-plague-sudden-oak-death for more information.

Summary

  • Like all organisms, plants detect and respond to stimuli in their environment. Their main response is to change how they grow.
  • Plant responses are controlled by hormones. Some plant responses are tropisms.
  • Plants also respond to daily and seasonal cycles and to disease.

Explore More

Use this resource to answer the questions that follow.

  1. Describe the various plant responses:
    1. Tropisms
    2. Nastic Movements
    3. Circadian Responses
    4. Photomorphogenesis

Review

  1. What is the primary way that plants respond to environmental stimuli? What controls their responses?
  2. Define tropism. Name one example in plants.
  3. State ways that plants respond to disease.
  4. Why is it adaptive for plants to detect and respond to daily and seasonal changes?

Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes
Please to create your own Highlights / Notes
Show More

Vocabulary

auxin

Plant growth hormone that controls phototropism.

dormant

Condition where plants suspend growth and development in order to survive the extreme cold and dryness of winter.

geotropism

Growing toward gravity response of a plant.

hormone

A chemical messenger molecule.

phototropism

The growing toward a light source by a plant.

tropism

Turning by an organism or part of an organism toward or away from an environmental stimulus.

Image Attributions

Explore More

Sign in to explore more, including practice questions and solutions for Plant Responses.
Please wait...
Please wait...