Plant Structures for Plant Structures for DefenseDefense

Plants have special Plants have special structures that function structures that function for defense, survival, and for defense, survival, and reproduction.reproduction.

Structures for defense Structures for defense protect plants from protect plants from threats. They might die threats. They might die without these defenses.without these defenses.

ThornsThorns

Are sharp outgrowths on the Are sharp outgrowths on the stems of plantsstems of plants

Defend the plant from being Defend the plant from being eaten by some animalseaten by some animals

CactusCactus

PoisonsPoisons

Some plants have chemical substances Some plants have chemical substances designed to discourage animals from designed to discourage animals from eating them.eating them.

Some taste bad; some sicken or kill Some taste bad; some sicken or kill the predator.the predator.

Some have high poison levels only Some have high poison levels only until the fruit matures, then it until the fruit matures, then it decreases so the fruit can be eaten decreases so the fruit can be eaten and seeds dispersed.and seeds dispersed.

Ex. Poison ivy, poison oak, sumacEx. Poison ivy, poison oak, sumac

Poison IvyPoison Ivy

Other DefenseOther Defense

The ability to close its leaves The ability to close its leaves when touched is called when touched is called ((thigmotropismthigmotropism).).