Botany MCQs for NEET — Practice Questions with Answers

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.

The initiative substance for Indole-3-acetic acid (IAA), which is a type of auxin, is Tryptophan. Tryptophan is an amino acid that serves as a precursor for the synthesis of IAA in plants.

Apical dominance is a phenomenon in which the presence of the apical bud inhibits the growth of lateral (side) buds. This ensures that the plant grows taller rather than wider. The apical bud produces auxins, which suppress the growth of lateral buds, thereby promoting vertical growth.

Abscisic acid (ABA) is known as the water stress hormone. It plays a crucial role in helping plants respond to drought and other stress conditions by closing stomata to reduce water loss and promoting root growth to access more water.

When the apical region of a stem is removed, the suppression of lateral buds is lifted due to the reduced production of auxins. This results in the emergence of lateral branches, as the plant shifts its growth focus from vertical to lateral direction.

2,4-D (2,4-Dichlorophenoxyacetic acid) is a synthetic auxin, a type of plant hormone. It is widely used as a herbicide to control broadleaf weeds.

2,4-D is a common herbicide known as a weedicide. It is primarily used to eliminate unwanted broadleaf weeds in agriculture and other areas.