Lesson 52: How Plants Function

Key Ideas

• Roots take in water and minerals from the soil. They also help hold many plants in place.
• Plants lose water vapor through tiny openings, mostly in their leaves. This water loss is called transpiration.
• Stems connect a plant’s parts. Tiny tubes inside carry water, minerals, and sugars.
• As water leaves a plant’s leaves, it helps pull more water up from the roots.
• A plant’s parts work together. Roots supply water, leaves make sugars, and stems move these materials around the plant.

Vocabulary

• Absorption / Root Hairs: Absorption means taking something in. Tiny root hairs help roots take in water and minerals.
• Transpiration / Wilting: Transpiration is water vapor leaving a plant. Wilting happens when cells lose the water pressure that helps keep the plant firm.
• Transport / Xylem / Phloem: Transport means moving materials. Xylem carries water and minerals. Phloem carries sugars to parts of the plant that need or store them.
• Nutrients: Substances living things need to grow and stay healthy. Plants take in mineral nutrients through their roots.
• Guard Cells: Cells that open and close the tiny pores in a leaf.
• System: Parts that work together. A plant’s roots, stems, and leaves form a system.

Discussion Questions

1. Cut flowers in a vase last about a week and then wilt, even though they are standing in water. What has gone wrong, given what you now know about roots and stems?
2. Why can removing a complete ring of bark seriously harm a tree? Use phloem transport in your explanation.
3. After heavy rain, a bare dirt slope washes into the street but the grassy slope beside it does not. Explain it using the third job of roots.

Supplies

• Two clear plastic bags, two twist ties, a leafy houseplant or shrub, and a sunny spot
• A stalk of celery with leaves, a white carnation, food coloring, and two glasses of water

Slideshow

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