Meristematic and Permanent Tissues of Plants: Quick Revision

A brief note on Meristematic and Permanent Tissues of Plants. Read it before a test. Try each question at the end before you open its answer.

The two big kinds of tissue

• Meristematic tissue: cells that keep dividing. Thin cellulose wall, large nucleus, dense cytoplasm, no big vacuole.
• Permanent tissue: cells that have stopped dividing and taken up a shape and a job. A simple tissue has one kind of cell. A complex tissue has more than one.

The meristems

• Apical and intercalary meristems are primary. The lateral ones, the vascular cambium and the cork cambium, are secondary.
• The vascular cambium makes xylem and phloem. The cork cambium makes cork.

The simple permanent tissues

• Parenchyma makes and stores food. Collenchyma gives flexible support. Sclerenchyma gives hard support.

• Parenchyma kinds: chlorenchyma (chloroplasts), aerenchyma (air spaces), storage parenchyma.
• Sclerenchyma kinds: fibres (long, pointed) and sclereids (short, in nutshells and pear grit).

The complex permanent tissues

• Xylem carries water and minerals. Tracheids, vessels and xylem fibres are dead. Xylem parenchyma is living.
• Phloem carries food. Sieve tube elements, companion cells and phloem parenchyma are living. Phloem fibres are dead.
• A sieve tube element has no nucleus. Its companion cell controls it.
• Protoxylem forms first. Stem: endarch, with protoxylem towards the centre. Root: exarch, with protoxylem towards the outside.

A worked example

A tissue has living cells with thin cellulose walls, and the cells hold chloroplasts. Name the tissue.

1. Thin cellulose walls and living cells: parenchyma.
2. Chloroplasts mean it makes food: chlorenchyma.

Practice with new numbers

A program to try

The program prints the permanent tissues in a table: simple or complex, living or dead, and the job.

Mistakes to avoid

• Saying that all plant cells divide. Only the meristems do.
• Calling collenchyma lignified. Lignin belongs to sclerenchyma.
• Saying that xylem is all dead. Xylem parenchyma is living.
• Giving a sieve tube element a nucleus. The companion cell has it.

Check yourself

1. Which meristems add length to a plant?

2. Which simple tissue is dead and has lignified walls?

3. Name the living cells of the xylem.

4. In which organ is the xylem exarch?