Growth in plants

Growth in plants

Middle School

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Learning Objectives

• Describe how special tissues called meristems help plants grow.

• Explain the difference between a plant growing taller and growing wider.

• Identify the locations and functions of the meristems at the tips of plants.

• Explain how certain tissues help woody plants get thicker and form bark.

Key Vocabulary

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Meristem

Plant tissue with cells that divide to create new, specialized cells for growth and repair.

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Apical Meristem

Meristem at the tips of roots and stems, helping the plant to grow longer or taller.

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Primary Growth

The growth that occurs in a plant's length or height, managed by the apical meristems.

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Secondary Growth

The growth that increases the diameter or width in woody plants, managed by cambium tissues.

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Vascular Cambium

A secondary meristem producing new xylem and phloem, making stems and roots thicker over time.

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Cork Cambium

A secondary meristem that produces bark, which replaces the epidermis and protects the plant.

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How Plants Grow

• Plants grow using two main processes: cell growth and cell division (mitosis).

• During cellular differentiation, cells specialize to do different jobs, like in leaves or roots.

• Meristem is special tissue made of undifferentiated cells that have no specific job.

• These cells constantly divide and can become any type of cell the plant needs.

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Multiple Choice

What is the primary role of meristem tissue in plants?

• To store water and nutrients for the plant.

• To transport water from the roots to the leaves.

• To perform photosynthesis and produce food.

• To provide a continuous supply of new, undifferentiated cells for growth.

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Primary Growth: Growing in Length

• Primary growth is how plants get taller and their roots grow longer.

• ​This growth is directed by special tissues called apical meristems.

• Apical meristems are located at the very tips of roots and buds.

• They form the protoderm, ground meristem, and procambium tissues.

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Multiple Choice

Where would you find the apical meristem responsible for a tree growing taller?

• Deep inside the woody part of the stem.

• In the bark around the trunk.

• At the base of the leaves.

• At the tip of the highest shoot or bud.

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Secondary Growth: Growing Wider

• Secondary growth increases the width of stems and roots in woody plants.

• This growth is managed by the vascular cambium and the cork cambium.

• Vascular cambium produces secondary xylem (wood) and secondary phloem.

• The cork cambium creates a tough, protective outer layer called bark.

Multiple Choice

Which tissue is responsible for producing the wood that makes a tree trunk thicker?

• Cork Cambium

• Vascular Cambium

• Apical Meristem

• Protoderm

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Common Misconceptions About Plant Growth

Misconception	Correction
Plants only grow from their tips.	Growth occurs at tips, stems, roots, and at the base of some leaves.
All plants grow wider every year.	Only woody plants grow wider. Soft-stemmed herbaceous plants do not.
Any plant cell can divide and grow.	Only special cells in meristem tissues can divide for growth.

Multiple Choice

How does meristem tissue enable a plant to grow and repair itself throughout its entire life?

• By performing photosynthesis to create energy for cell division.

• By consisting of undifferentiated cells that can continuously divide and specialize.

• By storing large amounts of food and water for energy.

• By having thick cell walls that provide permanent structural support.

Multiple Choice

Compare the primary result of growth from an apical meristem versus growth from the vascular cambium.

• Apical meristem increases plant length; vascular cambium increases plant width.

• Apical meristem increases plant width; vascular cambium increases plant length.

• Apical meristem creates flowers; vascular cambium creates roots.

• Apical meristem creates bark; vascular cambium creates leaves.

Multiple Choice

A large, old oak tree has a very thick, woody trunk covered in rough bark. Analyze which tissues are responsible for these features.

• Procambium created both the wood and the bark.

• Apical meristem created the wood and protoderm created the bark.

• Vascular cambium created the thick wood (xylem) and cork cambium created the bark.

• Ground meristem created the wood and procambium created the bark.

Multiple Choice

If the apical meristem of a young plant is damaged or removed, what is the most likely consequence?

• The plant will be unable to perform photosynthesis.

• The plant will start to increase significantly in girth (thickness).

• The plant will immediately die due to lack of water transport. 

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• The plant's roots and stem will stop increasing in length.

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Summary

• Plants grow through cell division and cell growth.

• Primary growth makes plants taller, while secondary growth makes them wider.

• Meristem tissues are responsible for all growth throughout a plant's life.

• Cambium tissues produce wood, inner bark, and the protective outer bark.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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