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Plants grow by using energy from sunlight and raw materials from water, air, and soil. Their roots absorb water and minerals, while their leaves capture light and take in carbon dioxide from the air. Inside the plant, these inputs are turned into food that supports growth, repair, and reproduction. Understanding this process helps explain how ecosystems work and why plants are essential for life on Earth.
The main process that powers plant growth is photosynthesis, which happens mostly in the leaves. Water moves upward from the roots through xylem tissue, and carbon dioxide enters through tiny leaf openings called stomata. Using light energy and chlorophyll, the plant makes glucose, which can be used immediately or stored for later. Minerals from the soil also help build proteins, cell walls, and other structures needed for healthy growth.
Key Facts
- Photosynthesis equation: 6CO2 + 6H2O + light -> C6H12O6 + 6O2
- Roots absorb water and dissolved minerals from the soil.
- Water moves upward through xylem from roots to stems and leaves.
- Leaves contain chlorophyll, which absorbs light energy for photosynthesis.
- Glucose made in photosynthesis can be used for respiration: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy
- Plant growth depends on sunlight, water, carbon dioxide, and essential mineral nutrients.
Vocabulary
- Photosynthesis
- The process by which plants use light energy to make glucose from carbon dioxide and water.
- Chlorophyll
- A green pigment in plant cells that absorbs light energy for photosynthesis.
- Xylem
- The vascular tissue that carries water and minerals upward from the roots.
- Stomata
- Tiny openings in leaves that allow carbon dioxide to enter and oxygen and water vapor to leave.
- Glucose
- A simple sugar made by plants that provides energy and building material for growth.
Common Mistakes to Avoid
- Thinking plants get most of their food from soil, which is wrong because plants make most of their food as glucose during photosynthesis. Soil mainly supplies water and minerals, not the main source of mass.
- Assuming sunlight is a material that becomes part of the plant, which is wrong because light provides energy rather than atoms. The atoms in plant sugars come mainly from carbon dioxide and water.
- Believing roots only anchor the plant, which is wrong because roots also absorb water and mineral ions needed for growth. Without root uptake, photosynthesis and cell function are limited.
- Confusing photosynthesis with respiration, which is wrong because photosynthesis stores energy in glucose while respiration releases energy from glucose. Plants do both processes, not just one.
Practice Questions
- 1 Write the balanced equation for photosynthesis and name the reactants and products.
- 2 A plant uses 12 molecules of carbon dioxide in photosynthesis. How many molecules of glucose and oxygen can it produce according to the balanced equation?
- 3 A plant is placed in sunlight but its stomata are closed for a long time. Explain how this would affect photosynthesis and growth.