Tropism a growth response which a plant

makes with respect to a directional stimulus.

plant movement towards or away from a stimulus.

came from the Greek word “tropos” which means to turn.

TropismPositive Tropism

towards the stimulus

Negative Tropism

away from stimulus

Types of Tropism:1) Phototropism2) Geotropism3) Thigmotropism4) Hydrotropism

Phototropism movement towards or away from lighttropos = to

turnphoto = light

Importance: Increases the probability of stems and leaves intercepting light for photosynthesis

Roots obtain water and dissolved minerals that they need.

Phototropism

Geotropism movement towards or away from the earthtropos = to

turngeo = earth

Importance: Roots will be more likely to encounter water and minerals,

Stems and leaves will be better able to intercept light for photosynthesis.

Geotropism

Thigmotropism movement towards or away from touchtropos = to

turnthigma = touchImportance: Thigmotropism by tendrils allows plants to “climb” objects and thereby increases their chances of intercepting light for photosynthesis.

Thigmotropism

Positive Thigmotropism

Thigmotropism

Negative Thigmotropism

Hydrotropism movement towards or away from watertropos = to

turnhyrdro = water

Importance: This ability to bend and grow the root towards a moisture gradient is essential because plants need water to grow.

Hydrotropism