How Plants Tell Time

Plants can move without muscles or nervous systems through processes like nyctinasty and heliotropism. Nyctinasty involves leaf movements in response to non-directional stimuli, influenced by temperature and chemical reactions. Phytochrome, a light-absorbing molecule, plays a key role in these movements by cycling between forms Pr and Pfr. Turgor pressure in pulvini helps flex leaves. Heliotropism, a directional movement, allows plants to track the sun, with sunflowers using auxin to grow towards light. These processes show plants' sophisticated responses to their environment.

What is a dramatic example of plant movement mentioned in the video?

• Flower opening

• Venus flytrap

• Sunflower turning

• Leaf drooping

What is the term for the process where plants tuck their leaves at night?

• Nyctinasty

• Phototropism

• Thigmotropism

• Heliotropism

Which molecule is involved in the reversible chemical reaction that helps plants respond to light?

• Chlorophyll

• Auxin

• Gibberellin

• Phytochrome

What is the function of pulvini in plant movements?

• Store water

• Absorb sunlight

• Produce seeds

• Act as flexible joints

What is the main difference between nastic movements and tropisms?

• Nastic movements are non-directional

• Tropisms do not involve light

• Nastic movements are directional

• Tropisms are non-directional

How do young sunflowers track the sun?

• By altering root direction

• By changing leaf orientation

• By growing their stem on one side

• By opening and closing petals

What hormone is responsible for the growth response in sunflowers?

• Ethylene

• Auxin

• Cytokinin

• Abscisic acid