Problem 23 - Biology E/M

Question

Questions \(17-23\) Choose from the terms below. (A) Auxins (B) Gibberellins (C) Abscisic acid (D) Ethylene (E) Cytokinins Promotes the ripening of fruit

Step-by-Step Solution

Answer

D) Ethylene promotes the ripening of fruit.

Step 1: Identify the Function

The question is asking for a hormone that promotes fruit ripening. We need to identify which plant hormone is associated with this function.

Step 2: Hormone Options

Review the provided hormone options: (A) Auxins (B) Gibberellins (C) Abscisic acid (D) Ethylene (E) Cytokinins.

Step 3: Key Association

Recall that ethylene (D) is the plant hormone responsible for promoting the ripening of fruit. It is a gaseous hormone that plays a significant role in the process of fruit maturation.

Step 4: Conclusion

Based on the function of promoting fruit ripening, the correct hormone is Ethylene.

Key Concepts

Ethylene

Ethylene is a unique gaseous plant hormone. This hormone is essential for various processes in the plant lifecycle. One of its primary roles is to promote the ripening of fruits. Unlike other hormones, ethylene can diffuse through the air, affecting distant parts of a plant or even nearby plants. It is often associated with a positive feedback mechanism.
During fruit ripening, ethylene production increases significantly. This surge initiates changes in texture, color, and flavor, making the fruit appealing and consumable. It also triggers the breakdown of cell walls, resulting in the softening of the fruit.

• Stimulates the production of enzymes that soften fruit.
• Promotes the conversion of starches to sugars, enhancing sweetness.
• Leads to the degradation of chlorophyll, causing color change.

Overall, ethylene is crucial in making fruits ready for consumption. Farmers sometimes use ethylene commercially to ripen fruits quickly, ensuring they reach markets in good condition.

Fruit Ripening

Fruit ripening is a transformative process. It involves a series of biochemical changes that make the fruit palatable. Changes in taste, color, and texture occur, influenced mainly by ethylene, as mentioned. These changes signify that the fruit is ready for seed dispersal.
Ripening ensures that seeds of the fruit are matured and ready to spread. Ethylene orchestrates this process by breaking down complex molecules into simpler ones.

• The starches convert into sugars, improving sweetness.
• Chlorophyll breaks down, altering the fruit's color.
• Pectinase enzymes soften the pulp, easing consumption.

Each stage of ripening is carefully regulated, and ethylene acts as the primary conductor of this remarkable transformation. This process provides nutritional, ecological, and evolutionary benefits.

Gibberellins

Gibberellins are a diverse group of plant hormones. They play a crucial role in promoting plant growth and development. Originally discovered in rice plants, these hormones have since been found in various plant species.
Gibberellins influence stem elongation, seed germination, and flowering. These hormones are crucial during the plant's growth phases, ensuring robust development.

• Stimulate cell elongation, leading to taller plants.
• Break seed dormancy, activating germination.
• Promote flowering, contributing to reproduction.

Although gibberellins are not directly involved in fruit ripening, they are vital in other key plant processes. Their ability to promote growth makes them invaluable for agriculture.

Abscisic Acid

Abscisic acid (ABA) is often referred to as the "stress hormone" of plants. It plays a protective role, especially during stressful conditions like drought.
ABA is vital in regulating plant responses to environmental stress. It helps control several physiological processes to ensure plant survival.

• Induces stomatal closure to reduce water loss.
• Promotes seed dormancy for protection in unfavorable conditions.
• Regulates plant's resistance to cold or drought.

Though not involved in ripening like ethylene, abscisic acid maintains plant health under stress, ensuring resilience and survival.

Auxins

Auxins are a group of hormones central to plant growth and behavior. They are commonly associated with the elongation of plant cells and organ development.
These hormones help plants respond to environmental stimuli, such as light and gravity.

• Encourage cell elongation, enabling stem bending toward light (phototropism).
• Facilitate root development, enhancing nutrient absorption.
• Play a role in plant organ formation and expansion.

Auxins are foundational to a plant's growth regulation but do not directly cause fruit ripening, as ethylene does. They, however, promote the plant's health and structural integrity, allowing it to support fruitful development.

Cytokinins

Cytokinins are plant hormones that work synergistically with other hormones. They are instrumental in promoting cell division and growth.
These hormones ensure that plants maintain optimal growth conditions throughout their lifecycle.

• Stimulate cell division in plant roots and shoots.
• Delays leaf senescence, keeping plants green longer.
• Influence nutrient mobilization, crucial for plant health.

While cytokinins play various roles, their primary involvement is in cell growth and differentiation. Although they are not directly linked to the process of fruit ripening, they are essential for sustaining the overall growth and health of a plant.