NEET Practice Questions (MCQs) with Answers & Solutions

The correct sequence of growth phases in plants starts with cell formation (cell division), followed by cell elongation, and finally cell differentiation. This sequence ensures that new cells are produced, they grow to an appropriate size, and then they specialize to perform specific functions.

The optimal temperature range for the growth of most plants is between 20°C and 30°C. Within this range, the enzymatic activities necessary for growth processes are most efficient. Temperatures outside this range can slow down or inhibit plant growth.

Zeatin is a type of cytokinin, a class of plant hormones that promote cell division and growth. Cytokinins, including zeatin, play a crucial role in cell differentiation, shoot initiation, and delay of leaf senescence.

Gibberellic acid (GA) is known for promoting the growth in size of stem and root formation. It helps in the elongation of stems, breaking seed dormancy, and other growth-related processes in plants.

Ethylene gas is used to enhance the color of fruits and increase the juice content unnaturally. It is a natural plant hormone that regulates fruit ripening and other processes related to growth and development.

Auxin is a plant hormone that plays a key role in apical dominance, which is the phenomenon where the main, central stem of the plant is dominant over (i.e., grows more strongly than) other side stems. Auxins are produced in the apical meristem of the plant and inhibit the growth of lateral buds, ensuring that the plant grows taller rather than wider.

Phytochrome is a photoreceptor in plants that is sensitive to light in the red and far-red region of the electromagnetic spectrum. It is involved in the regulation of various plant processes, including photoperiodism, which is the physiological reaction of organisms to the length of day or night. Phytochrome helps plants detect the duration of light and dark periods, which is crucial for processes like flowering.

In the absence of light, plants tend to increase the elongation of internodes, a process known as etiolation. This is an adaptive response to grow taller and reach light sources. The elongation of internodes helps the plant to potentially find a light source more effectively when it is in a dark environment.

Abscission layer formation is associated with the decreased concentration of auxin. When the levels of auxin (a plant hormone) decrease, it triggers the formation of the abscission layer, leading to the shedding of leaves, flowers, or fruits.

Vernalization refers to the induction of a plant's flowering process by exposure to prolonged cold temperature. This process ensures that plants flower in the optimal season.