Photomorphogenesis and Plant Tropic Responses
chemical energy that the plant will use for growth and development. The
perception of sunlight is necessary for plant development. The absence of light
also elicits growth responses in plants. Examine the text and movies listed
below and answer the questions.
Follow the navigation links and the instructions provided below. Questions
answered will be submitted as part of Lab 6 on Photosynthesis.
Click on: Ticket to Enter Site
Read: Introductory Text
NOTE: You will need QuickTime 5.0 to view movies
If you don?t have it download it now.
Click on: Photomorphosis
Read: Introductory Text
Click on: Sunflower dark and light
Read: Text with each movie (NOTE: Movie may take a few minutes to load on some
Create a Table:
Across the top of the table put light and dark. Down the side put:stem
elongation; leaf (cotyledon) development, chlorophyll production; hooked stems.
As you read text fill-in the table indicating how light grown and dark-grown
plants respond in each category listed.
Click on: Movie for Dark Grown Seedlings (right facing triangle) You may drag
circular slider back to the beginning to view again. The triangles with lines
next to them allow you to move forward or backward step-by-step through the
Answer these questions.
Q-1 How did the movies provide support for the table that you developed?
Q-2 Which plant is most prepared to start photosynthesizing? Explain.
Q-3 Prior to starting to photosynthesize, what was the energy source for the
young plants? By what process did the plants get energy from this source?
Q-4 The dark-grown plants had longer stems. What is a possible reason that the
longer stems might be an advantage to the plants in the dark?
Click on: Dark-grown Arabidopsis
Q-5 Compare the Arabidopsis with the dark- grown sunflower movie.
Click on: Tropisms
A positive tropism is when the plant grows toward the stimulus and a negative
tropism is when the plant grows away from the stimulus.
Click on: Arabidopsis shoot phototropism
Read: Text with both movies
View: Blue-light induced phototropism movie
View: Red-light enhanced phototropism movie
Q-6 Which plants responded most quickly to the blue light? Why?
Q-7 Were the plants displaying a positive or negative phototropism?
Click on: Tomato Phototropism
Click on: Corn Phototropism
Click on: Cool Corn Plants
Click on: Sunflower phototropism
Click on: Arabidopsis shoot Gravitropism
Click on: Coleus Sh oot Gravitropism
Click on: Sunflower Gravitropism
Q-8 Summarize your observations of plant stems response to gravity.
Q-9 What is the adaptive value of plants responding in this way?
Click on: Corn root gravitropism
Q-10 Make a statement regarding the adaptive value of plant roots displaying a
positive gravitropic response.