Biology 2Plants keep track of the hours and the seasons!

Concept 22.3

Objectives

• Define circadian rhythm

• Explain how day length may affect plant flowering.

Long-Day Plants ~ Jacob Miller

Long - Day is the name given to plants that bloom when the longer days come in the summer. They bloom to receive the critical amount it needs to grow during its cycles.Some examples are…

• Lettuce• Spinach• Tomatoes• Black-eyed susans

Photoperiodism

• Photoperiodism is how the plant reacts to change of light or length of day or night.

Christian Whited

• *Phytochromes : (or pigmented proteins)is how the plant monitor the time of day.

• *Sunrise: the plant absorbs the red light from the sun and this triggers the plant. It also changes the shape of the plant to active.

• *Sunset : all of that was said in sunrise is reversed.

• By Teresa Mittermeier

Phytochromes

Day-Neutral Plants

Day Length and Seasons - Day-Neutral Plants - Plants that flower when they reach a particular stage of maturity. - These will flower during any day length. - Dandelions, tomatoes, and rice are common examples.

Madison Wiscott

~Kelly Ugrin~

CONCEPT CHECK 22.3

1. Give an example of a circadian rhythm in a plant or animal.

2. Describe the difference between a short- and a long- day plant and give an example of each.

3. Explain how phytochromes are activated.

Jenna Voigt

CONCEPT CHECK ANSWERS22.3

1. When a plant’s functions change throughout a 24 hour period. An organism’s “biological clock” is set by daily signals from the environment, especially sunlight.

2. Certain plants, such as chrysanthemums and poinsettias, flower in fall or winter when the dark period exceeds a certain length called critical night length. Which is also the same thing as short-day plants. Long-day plants, such as spinach, lettuce, and irises, usually flower in late spring or early summer when dark periods shorten.

3. When phytochromes absorb the red light that is abundant at sunrise, they change shape to an active form that triggers a variety of plant responses. After sunset, the phytochromes gradually change back to their inactive form.

Jenna Voigt

Short-Day PlantShort-Day plants when plants flower in fall or winter when it stays dark out for a certain amount of time.Specific plants that bloom during this time are Chrysanthemums PoinsettiasThey flower during fall and winter. Another name for Short-Day plants would also be called critical night length.

Jenna Voigt

BLAYNE-SLIDE 2,3CHRISTIAN-SLIDE 2,5

COLLIN-(NOT IN CLASS)JACOB-SLIDE 4

JENNA-SLIDE1,9,10,11, 12, 13KELLY-SLIDE 8

MADISON-SLIDE 7TERESA-SLIDE 6

THE END!Group 3