Question

Match the column - I with column - II and select the correct option from the codes given below. Column-I A. Auxin B. Cytokinins C. Abscisic acid D. Ethylene Column-Il (i) Fruit ripening (ii) Phototropism (iii) Antagonist to GAs (iv) Growth of lateral buds (a) \(A-(\mathrm{iv}), \mathrm{B}-(\mathrm{ii}), \mathrm{C}-(i i i), \mathrm{D}-(\mathrm{i})\) (b) \(A-(i i), B-(i v), C-(i i i), D-(i)\) (c) \(A \cdot(i i) ; B-(i i i), C-(i v), D-(i)\) (d) \(A-(i i i), B-(i v), C-(i i), D-(i)\)

Short answer

The correct match is: A-(ii), B-(iv), C-(iii), D-(i), which corresponds to option (b).

Step-by-step solution

Understand Plant Hormones

Recognize that Column-I lists different plant hormones (Auxin, Cytokinins, Abscisic acid, Ethylene), and Column-II lists processes or effects related to plant hormones. We must match each hormone to its correct process or effect.

Match Hormones to Processes

Use knowledge of plant hormones to make connections: A. Auxin is associated with phototropism, the growth of a plant in response to light direction (ii). B. Cytokinins promote the growth of lateral buds (iv). C. Abscisic acid acts as an antagonist to gibberellins (GAs) and is involved in stress responses (iii). D. Ethylene is a gas hormone involved in fruit ripening (i).

Evaluate the Given Options

Check each option against the known effects of the hormones: (a) does not match the known effects; (b) matches all known effects correctly; (c) does not match the known effects; (d) does not match the known effects. Therefore, the correct answer is (b).

Key concepts

Understanding Phototropism

Phototropism is a fascinating plant behavior that involves the growth of a plant towards or away from light. This directional growth is guided by plant hormones called auxins, which are distributed unevenly within a plant when it is exposed to light coming from one direction. The cells on the darker side of the plant contain more auxins, causing them to grow longer and faster than those on the light side. As a result, the plant bends towards the light source.

It's a bit like having on one side of the plant some tiny workers stretching out the walls of the cells, causing the plant to lean over towards the sun or a light bulb. This movement towards light allows the plant to maximize the energy it captures for photosynthesis, which is the process plants use to convert light into food.

Cytokinins and Growth of Lateral Buds

Cytokinins are a group of plant hormones that play a key role in promoting cell division, plant growth, and development. These hormones are particularly interesting because they encourage the growth of lateral buds—the small meristems located at the base of the leaves. Without cytokinins, the central stem of a plant, known as the apical dominance, would overly dominate, and the lateral buds would remain dormant.

Imagine a relay race where the central stem is the runner with the baton and cytokinins are the coaches that signal to the lateral bud runners to start racing. By encouraging these side buds to grow, cytokinins help give a plant its full and bushy shape, as they develop into branches.

Abscisic Acid vs. Gibberellins

Plants' Balancing Act

Abscisic acid (ABA) is often described as a 'stress hormone' within plants since it kicks into gear during stressful conditions such as drought. It works as an antagonist to gibberellins (GAs), another type of plant hormone. Gibberellins stimulate plant growth and germination, but when ABA levels increase, it signals the plant to slow down growth and conserve resources.

It's as if gibberellins are pressing the gas pedal for plant growth, and abscisic acid is the brake pedal when conditions are tough. The balance between these two hormones is crucial; they ensure the plant doesn't waste precious energy when the resources required for growth—like water—are scarce.

Ethylene and Fruit Ripening

Ethylene is a gaseous plant hormone that serves as a key player in the ripening of fruits. It acts as a signal that triggers the series of processes that convert fruits from hard, green, and often sour to soft, colored, and sweet. This is why bananas ripen quicker in a bag - they're bathing in their own ethylene.

Besides ripening, ethylene has other roles, such as influencing the shape of the plant, promoting leaf fall (senescence), and even providing cues to neighboring fruits to ripen. In commercial fruit production, ethylene is harnessed to manage and synchronize the ripening process, so that fruits are perfect for eating by the time they reach the consumer.