What Is a Plant Made Of?: teacher key

How Plants Grow, grade 9 edition, written for 9th grade. From a 1600s willow experiment to plant hormones and underground fungi: the evidence behind how a seed becomes a plant.

Read the book. Print this page for the key.

Questions and answers

1. What did van Helmont fail to consider?
   • That gases in the air might be involved (answer)
   • That willows need water
   • That soil can be moist
2. What did Ingen-Housz show about oxygen?
   • Roots gave off the most
   • Only the green parts of plants gave it off (answer)
   • Seeds gave it off in the dark
3. Why would Darwin's finding about the tip matter for a seedling in a dim room?
   • Roots would stop growing
   • Its tip would sense the light and the plant would bend toward it (answer)
   • The seed coat would harden
4. What is typically the force that moves water up in a plant?
   • Root pressure
   • Pollen
   • Transpiration (answer)
5. In the fungus trade, what do trees give?
   • Sugars from photosynthesis (answer)
   • Nitrogen and phosphorus
   • Water vapor

Words

• auxin: plant growth signal
• endosperm: seed food store
• transpiration: plant water loss
• phytoplankton: tiny ocean plants