Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Growth is a permanent and irreversible increase in the size and mass of a living organism. In plants, growth occurs primarily at the tips of roots and stems and continues throughout their lifespan.
Unlike animals, most plants are fixed to the soil and do not show locomotion (moving from one place to another). However, they exhibit movement through the bending or growth of specific parts.
Phototropism: This is the movement of plant parts towards light. For example, a plant kept near a window will bend its stem towards the sunlight. This movement is represented as a response to the stimulus of light.
Geotropism: This is the movement of plant parts in response to gravity. Roots show positive geotropism by growing downwards into the soil, while stems show negative geotropism by growing upwards against gravity.
Hydrotropism: The growth movement of plant roots towards a source of water, ensuring the plant can absorb necessary moisture for survival.
Nastic Movements: These are non-directional responses to stimuli. A classic example is the 'Touch-me-not' plant (), where leaves fold up almost instantly when touched. This is a rapid movement compared to growth-related movements.
📐Formulae
💡Examples
Problem 1:
A sapling was measured to be tall on Monday. By the following Monday, it measured . Calculate the total growth in one week.
Solution:
Explanation:
Growth is calculated by subtracting the initial height from the final height. The plant grew by over the course of the week.
Problem 2:
Identify the type of movement when a potted plant is placed horizontally on the ground and its stem starts curving upwards after a few days.
Solution:
This is an example of Negative Geotropism.
Explanation:
Even when the plant is horizontal, the stem responds to gravity by growing away from it (upwards), while the roots would show positive geotropism by growing downwards.