Problem 95 - Objective Biology for NEET

Question

As a response to stimuli the coleoptiles caused (a) Bending (b) Flowering (c) Budding (d) All of these

Step-by-Step Solution

Answer

The correct answer is (a) Bending. Coleoptiles show a response to light stimuli by bending towards the source.

Step 1: Identify the Biological Attribute

Recognize that this question involves the biology of plants, specifically regarding the characteristic behaviors of coleoptiles. Coleoptiles are the protective sheaths covering the emerging shoot in monocotyledons.

Step 2: Recall the Phototropic Behavior

Remember that coleoptiles exhibit a unique trait known as phototropism. This means they have the ability to bend in accordance to the direction of light in order to maximize photosynthesis.

Step 3: Select the Correct Response

Given that coleoptiles do not perform flowering or budding, and are specifically known for their bending behavior in response to light stimuli, select the appropriate option that reflects this characteristic.

Key Concepts

Phototropism

Phototropism is a fascinating mechanism observed in plants. It refers to the movement or growth of a plant towards or away from a light source. This is an essential process for plants as it helps them maximize their ability to photosynthesize by ensuring that their leaves are oriented towards the light. Phototropism occurs because of differential growth in the plant, where one side of the plant grows faster than the other. This growth differential results in the plant bending towards the light.

There are a few important points to note about phototropism:

• It involves the hormone called auxin, which is responsible for promoting growth in plant tissues.
• When light strikes one side of the plant, auxin redistributes towards the shaded side, causing that side to grow more rapidly.
• This rapid growth on the shaded side results in the bending of the plant toward the light.

Understanding phototropism is crucial for understanding how plants respond dynamically to their environmental stimuli, particularly light.

Coleoptiles

Coleoptiles are structures found in monocotyledons, such as grasses and cereal crops. They serve the important function of providing protection to the young shoot as it emerges from the soil. These structures ensure that the delicate tip of the shoot is shielded from damage as it pushes through the ground.

Some key characteristics of coleoptiles include:

• Coleoptiles are tube-like in shape and form a sheath around the emerging shoot.
• They are pivotal in the phototropic response, as they can detect light and facilitate bending toward the light source.
• Once the shoot emerges above the soil surface, the coleoptile stops growing and eventually withers away, allowing the leaf to unfurl.

By protecting the young shoot and aiding in the orientation of growth, coleoptiles play a crucial role in the early stages of a plant's development.

Monocotyledons

Monocotyledons, often referred to as monocots, comprise one of the two major groups of flowering plants. They differ from dicotyledons, or dicots, in several distinct ways.

Monocots are characterized by the presence of a single cotyledon in the seed, which provides nutrients to the developing embryo. The following features are typical in monocot plants:

• Monocots have parallel leaf venation, meaning the veins run side by side along the length of the leaf.
• Their vascular bundles in stems are usually scattered, unlike those of dicots, which are arranged in a ring.
• Monocots typically produce flowers with parts in multiples of three, such as six petals or stamens.

Understanding monocotyledons is important for botanists and agriculturalists alike, as this group includes economically significant plants like wheat, rice, and corn.

Plant Responses

Plants exhibit a variety of responses to stimuli, which enable them to adapt and thrive in their environments. These responses can be triggered by a wide range of factors, such as light, gravity, water, and touch. One of the most observable responses is the movement towards or away from light, known as phototropism.

Key plant responses include:

• Gravitropism - the orientation of a plant or part either towards (positive) or away from (negative) the gravitational pull.
• Hydrotropism - where roots grow towards higher moisture levels to ensure adequate water supply.
• Thigmotropism - a plant's growth response to touch, which can be seen in climbing plants like vines wrapping around a support.

By understanding these responses, we can gain insights into how plants interact with their environments and harness these mechanisms to improve agricultural practices and plant care.