Plant Tissues: Quick Revision

A brief note on Plant Tissues. Try each question at the end before you open its answer.

Meristems: where a plant grows

• Apical (tips of root and shoot): longer. Lateral, the cambium (sides): thicker. Intercalary (base of leaves): regrowth.
• Each division doubles the cells: $2^n$ after $n$ divisions. New cells then differentiate into permanent tissue.

Permanent tissues

Water climbs thin xylem vessels by capillary action, $h = \dfrac{2T}{\rho g r}$, but transpiration from the leaves is the main pull in a tall tree.

A worked example

A tree's bark is stripped all round, through the phloem but not the xylem.

1. What is cut. The phloem, which carries food down.
2. First. The leaves stay green, because the xylem still brings water up.
3. Later. The roots starve, stop taking in water, and the whole tree dies.

Practice with new numbers

A program to try

The program is a tiny key that names a tissue from two clues.

Mistakes to avoid

• Water in the phloem. Water goes up in the xylem; food goes in the phloem.
• Collenchyma is dead. It is alive; sclerenchyma is dead.
• Stomata in cork. Stomata are in the epidermis.
• Adding 2 cells a division. Cells double.

Check yourself

1. Which meristem lets bamboo grow back after its top is cut?

2. Which tissue is dead but carries water?

3. Water rises 1.2 m in a tube of radius 12 µm. How high in a tube of radius 4 µm?

4. What makes cork waterproof?