What are the different types of tropisms in plants? Explain with examples.

Tropisms are growth movements of plants in response to external stimuli. They are classified into different types based on the nature of the stimulus. The main types of tropisms in plants are:

1. Phototropism

This is the growth movement of plants in response to light.

• Positive phototropism: Growth towards light (e.g., stems of sunflower and mustard plants bend towards sunlight).
• Negative phototropism: Growth away from light (e.g., roots grow away from light and downward into the soil).

2. Geotropism (Gravitropism)

This is the growth movement of plants in response to gravity.

• Positive geotropism: Growth towards gravity (e.g., roots grow downward into the soil).
• Negative geotropism: Growth against gravity (e.g., stems grow upward, away from the pull of gravity).

3. Hydrotropism

This is the growth movement of plants in response to water.

• Roots grow towards water sources, even in the absence of light or gravity (e.g., roots growing toward moist soil).

4. Thigmotropism

This is the growth movement of plants in response to touch.

• Plants respond to physical contact (e.g., tendrils of pea plants coiling around a support or wire).

5. Chemotropism

This is the growth movement of plants in response to chemicals.

• Pollen tubes grow toward the ovule due to chemical signals (e.g., in fertilization processes).

Each type of tropism helps plants adapt to their environment, ensuring survival and optimal growth. These movements are essential for processes like photosynthesis, nutrient absorption, and reproduction.