Problem 108 - Objective Biology for NEET

Question

Auxin was first isolated from (a) Frog's wine (b) Zeatin (c) Human wine (d) None of these

Step-by-Step Solution

Answer

The correct answer is choice d) None of these.

Step 1: Understand the choices

First, it is important to understand all of the options given. a) Frog's wine: This choice seems out of place in the context since the term 'wine' is often used in relation with fruits, not amphibians.ii. b) Zeatin: Zeatin is a cytokinin-type plant hormone. Therefore, it should not be associated with the origin of auxin. c) Human wine: This is also a strange term that seems out of context. Humans do not produce 'wine' naturally. d) None of these: If none of preceding options are correct, this would be the correct option.

Step 2: Recall the origin of Auxin

Auxin is primarily produced in the stem tip and diffuses down the stem causing cells in the stem to elongate. It is not associated with Frogs, humans or other plant hormones like Zeatin.

Step 3: Choose the correct option

Upon analyzing all the options and recalling where Auxin comes from, the best option would be d) None of these, since none of the other options represent the source of Auxin.

Key Concepts

Plant Hormones

Plant hormones, also known as phytohormones, are chemical substances produced by plants. They play crucial roles in controlling and regulating plant growth and development. Unlike animal hormones, they are not produced by specific tissues but can be synthesized in diverse regions of the plant.
Given their importance, they help the plant adapt to changing environments and aid in development.

Key features of plant hormones include:

• Regulation of growth processes such as cell division, elongation, and differentiation.
• Responses to environmental stimuli, like light and gravity.
• Coordination of various stages in life cycles, such as seed germination, flowering, and fruit ripening.

Plant hormones include several types, and Auxins and Cytokinins are two primary examples.
This leads us to a closer examination of Cytokinins.

Cytokinins

Cytokinins are a type of plant hormone essential for various developmental processes. They primarily promote cell division in plant roots and shoots.
These hormones work in collaboration with Auxins to control cell growth and differentiation.

Some important roles of Cytokinins include:

• Promotion of cell division, particularly in plant meristems (regions of active cell growth).
• Delay of leaf senescence, which is the natural process of aging in plants.
• Influencing the pathways to maintain nutrient mobilization and increase cell viability.

Cytokinins like Zeatin are naturally found in plants. Though related to Auxins, they function in different ways. While Auxin originates primarily in stem tips to aid in growth, Cytokinins ensure balanced cell proliferation.

Stem Elongation

Stem elongation is a vital process in plant growth and development, largely regulated by plant hormones, especially Auxin. When Auxin is produced at the stem tip, it diffuses downward, promoting cell elongation in the region. This results in the lengthening of the stem, allowing the plant to access more light and resources.

Highlights of stem elongation influenced by Auxin:

• Auxin's distribution in the plant promotes uneven growth, causing the stem to bend towards light, a phenomenon known as phototropism.
• The hormone's concentration aids in the opening and closing of stomata, small openings on leaves which regulate gas exchange and water loss.
• In addition to elongation, Auxin facilitates root initiation and branching, enhancing the plant's stability and nutrient absorption capabilities.

Through these actions, Auxin plays an indispensable role in ensuring plants grow adequately to survive and reproduce efficiently.