Question

Which among the following is not a function of cytokinins? (a) Essential for cytokinesis during cell division (b) Delays the senescence of leaves (c) Helps in fruit ripening (d) Helps to overcome apical dominance

Short answer

Option (c) 'Helps in fruit ripening' is not a function of cytokinins.

Step-by-step solution

Understanding the Concept of Cytokinins

Cytokinins are a class of plant hormones that promote cell division in plant roots and shoots, delay the aging of leaves (senescence), and help in the process of breaking apical dominance. Apical dominance is the phenomenon whereby the main central stem of the plant is dominant over other side stems.

Identifying the Functions of Cytokinins

Review the functions that are commonly associated with cytokinins: (a) they are essential for cytokinesis during cell division; (b) they delay the senescence of leaves, which means they keep the leaves green and functional for a longer time; (d) cytokinins help to overcome apical dominance, enabling the growth of lateral shoots.

Excluding the Known Functions

From the information we've gathered, we can determine that options (a), (b), and (d) are established functions of cytokinins. Therefore, we can exclude these options when looking for the answer to the exercise.

Determining the Incorrect Function

Since options (a), (b), and (d) are recognized functions of cytokinins, we can conclude that the remaining option (c) 'Helps in fruit ripening' is not a function traditionally attributed to cytokinins. Ethylene, another plant hormone, is primarily responsible for the ripening of fruits.

Key concepts

Plant Hormones

Plant hormones are chemical messengers that regulate various functions in plant growth and development. These hormones, including cytokinins, auxins, gibberellins, ethylene, and abscisic acid, work harmoniously to control processes such as cell division, flowering, fruit ripening, and response to environmental stimuli.
Cytokinins, in particular, play a critical role in promoting cell division and growth. They act by stimulating the plant cells to divide and differentiate, impacting root and shoot development. In addition to promoting cell division, cytokinins work in concert with other hormones to regulate plant processes, such as delaying leaf senescence and adjusting plant architecture through altering apical dominance.
Understanding the distinctive roles of these hormones is important for students studying plant biology, as it provides insight into how plants grow, adapt, and survive in their environments.

Cytokinesis in Cell Division

Cytokinesis is the process by which a single cell divides its cytoplasm to form two daughter cells after mitosis, the division of the cell's nucleus. Cytokinins are closely involved in this process by ensuring the cell's resources are allocated properly for the creation of new cells.
Without the action of cytokinins, this division could be disturbed, leading to issues in plant growth and development. For students studying cell biology, understanding cytokinesis is fundamental because it underscores how organisms grow and repair themselves. Cytokinins are significant in that they serve to maintain plant health, vitality, and productivity.

Apical Dominance

Apical dominance is a plant's tendency to concentrate growth in the main, central stem, known as the apical meristem, while inhibiting the growth of lateral buds. This phenomenon is regulated by a balance between cytokinins and another plant hormone called auxin.
While auxin, produced at the apex, promotes apical dominance, cytokinins, often originating in the roots, encourage the growth of lateral shoots by weakening the dominance of the apical meristem. This knowledge helps students understand the shaping of plant growth and how pruning can encourage bushier plants, a common practice in agriculture and horticulture.

Senescence in Plants

Senescence in plants refers to the aging process where cells break down and the plant gradually deteriorates until it dies. This biological process can be seen in leaves turning yellow as they age. Cytokinins play a vital role in delaying senescence, helping leaves maintain their green color and functional chlorophyll for photosynthesis longer.
Understanding plant senescence is important for students as it relates to the lifecycle of plants, agricultural productivity, and the ability to manage crop yields. It's an area of interest for those working towards increasing the longevity and health of plants, both for food and for ecological contributions.