How Plants Grow

In the last unit, students explored how living things are found in different habitats around the planet and depend on both living and nonliving parts of their environment for survival. In this unit, students focus on plants. They begin with an experiment that investigates the science phenomena of how light and water help plants grow from a seed into an adult plant, and then focus on the function of flowers, which produce seeds. This page showcases the key components of the first lesson in this unit.

Science Background for Teachers:

The science background section provides teachers with more in-depth information of the science phenomena being studied in this unit about plants.

Greenhouses can range in size from a small shed to an industrial-sized building. Regardless of their size, all greenhouses are structures with walls and a roof made of transparent materials so that sunlight and heat can enter inside. This is important because plants use sunlight to make their own food, so they cannot grow without light.

Plants need sunlight to carry out photosynthesis. Plants collect sunlight with their leaves. Leaves have chloroplasts in their cells, which have high concentrations of chlorophyll. Chlorophyll absorbs the sun’s energy, beginning the process of photosynthesis to turn light energy from the sun, along with carbon dioxide and water, into glucose, a sugar molecule that stores the energy plants need to grow.

Leaves also have pores called stomata that take in carbon dioxide from the environment and release oxygen. This exchange of gasses in plants is called respiration. Stomata store food and water as well. As the plant respires, some water is released from the stomata back into the environment.

In addition to sunlight, water is also essential for plant growth. Plants collect water from the soil with their roots, which grow underground and have two primary functions. The first is to hold plants in the ground against the forces of wind and water and to prevent plants from becoming unbalanced and toppling over as they grow upward. The second function is to gather water and nutrients from the soil for transport to the rest of the plant. Gardeners stay busy in a greenhouse because rain cannot enter, so they need to water all of the plants inside.

Supports Grade 2

Science Lesson: Discovering How Plants Grow

In this lesson, students build on their understanding of living things by focusing on plants. They discuss what plants need to survive and how plants grow from a seed to an adult plant. Students dissect a seed to explore how seeds can turn into plants and then compare the growth of seeds in different conditions.  

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Science Big Ideas

  • Plants are living things because they need food, air, and water, and they have different parts that help them get what they need to survive. 
  • Many plants begin as a seed, which is a young plant inside a protective coat.

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Science Essential Questions

  • Why do plants need food? How do plants get food?
  • What part of the plant collects sunlight?
  • How do plants get the air they need to survive?
  • Why do plants need water? How do plants get water?
  • How does food get from the leaves to the rest of the plant, and how do water and minerals get from the roots to the rest of the plant?
  • How can the seed begin to grow underground, even though there is no light there?  
  • What do seeds need to grow?

Common Science Misconceptions

Misconception: Plants are not alive because they don’t move.
Fact: Plants are alive, and they need air, water, and sunlight to survive.
Misconception: Plants need sunlight to stay warm.
Fact: Unlike animals, plants need sunlight because they make their own food from sunlight through photosynthesis.
Misconception: Plants get water from their leaves.
Fact: Plants take in water through their roots.

Science Vocabulary

Flower:  the part of the plant that makes seeds

Leaf: the part of the plant that takes in sunlight and makes food

Pollen: a fine powder that flowers make

Pollination: the way some plants make new seeds

Roots: the parts of a plant that grow under the ground; hold the plant in place; take in nutrients and water from the soil

Seed:  a young plant inside a protective coat

Stem: the part of a plant that holds the leaves and flowers in place; water and nutrients travel through the stem to the rest of the plant

Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

Plants and the Sun

Greenhouses are transparent so the sun can shine through. Plants need sunlight. Leaves are parts of plants that take in sunlight and make food.

Food gives plants energy. This helps them grow. Plants also need air to grow. Plants take in carbon dioxide from the air with their leaves. They release oxygen back into the air.

 
 

Plants and Water

Plants also need water to grow. Becky waters her plants in the greenhouse. Plants take in water with their roots. Roots grow under the soil. Roots also take in minerals from the soil. Plants use minerals to build their body.

 
 

How a Plant Grows

Most plants begin as a seed. A seed is a young plant inside a coat. The coat protects the seed. The seed stores food. The seed needs air and water.

Plants need a certain temperature to grow. It cannot be too hot or too cold. With the right temperature, air, and water, the seed will begin to grow.

 
 

Hands-on Science Activity

In this lesson, students will conduct an experiment and an investigation. In the experiment, students test whether plants need both water and light to grow by collecting and analyzing data on the height each of the plants grows over 10-15 days. Students then create a scientific diagram of their experiment-in-progress. In the investigation, students dissect a seed. Students use their observations from the seed dissection to help them construct an explanation about how plants change as they grow.

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Science Assessments

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Science Standards

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Standards citation: NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.

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