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13.4.3.3 - Cytokinins

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Introduction to Cytokinins

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Teacher
Teacher

Today, we're focusing on cytokinins, a crucial group of plant hormones. Can anyone tell me what they know about them?

Student 1
Student 1

I think they help plants grow. Like, they support cell division?

Teacher
Teacher

Exactly, Student_1! Cytokinins are very much involved in promoting cytokinesis or cell division. They were discovered in herring sperm. Kinetin is one of the early examples, found from purified DNA.

Student 2
Student 2

So, where exactly are cytokinins made in the plant?

Teacher
Teacher

Great question, Student_2! Cytokinins are primarily synthesized in areas of active growth, such as the root apices and young fruits. This allows them to play a critical role in growth regulation.

Teacher
Teacher

To help remember this, think of 'C' for Cytokinesis and 'C' for Cell growth! Can you all come up with another point about cytokinins?

Student 3
Student 3

Uh, do they help with the growth of shoots too?

Teacher
Teacher

Yes! Cytokinins promote lateral shoot growth as well, which often helps overcome apical dominance by encouraging side shoot development. Remember the acronym 'LAD' for Lateral shoot and Apical dominance.

Teacher
Teacher

Key points here: cytokinins support cell division, are synthesized in growing tissues, and encourage lateral growth!

Functions of Cytokinins

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Teacher
Teacher

Let’s delve into the physiological functions of cytokinins. They help delay leaf senescence, but how does that work?

Student 4
Student 4

Is it related to how they help with nutrient mobilization?

Teacher
Teacher

Exactly right, Student_4! Cytokinins promote nutrient mobilization from other parts of the plant to the leaves, delaying aging. Can anyone think of why delaying senescence might be beneficial?

Student 1
Student 1

It could help the plant gather more sunlight or energy before it starts dying?

Teacher
Teacher

Exactly! Longer-lasting leaves mean more photosynthesis and better growth potential. Now, let’s summarize the effects of cytokinins: they promote cell division, lateral shoot growth, and delay leaf senescence.

Application of Cytokinins in Agriculture

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Teacher
Teacher

Next, let’s talk about the practical applications of cytokinins in agriculture. How might farmers use cytokinins?

Student 2
Student 2

Maybe to increase the yield of certain crops?

Teacher
Teacher

Correct again, Student_2! Farmers can use cytokinins to boost crop yields by promoting healthier, stronger plants. This includes enhancing flowering, fruit set, and even extending the harvesting period.

Student 3
Student 3

What about when it comes to plant tissue culture?

Teacher
Teacher

Excellent point, Student_3! Cytokinins are essential in plant tissue culture as they stimulate cell division and help in the development of new plants from cells. To help you remember, think of 'CTC'—Cytokinins in Tissue Culture!

Teacher
Teacher

So in summary: cytokinins are key in agriculture for yield improvement and are vital in plant propagation technology.

Introduction & Overview

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Quick Overview

Cytokinins are plant growth regulators that play a crucial role in promoting cell division and influencing various growth and developmental processes in plants.

Standard

Cytokinins, first discovered in herring sperm DNA, are essential for stimulating cytokinesis, promoting lateral shoot growth, and delaying leaf senescence. They are synthesized in rapidly dividing tissues and can help in overcoming apical dominance, playing a vital role in plant development and growth regulation.

Detailed

Detailed Summary of Cytokinins

Cytokinins are a class of plant growth regulators primarily known for their ability to promote cell division (cytokinesis). They were first identified from kinetin derived from herring sperm DNA and later, zeatin was discovered in corn and coconut milk. These hormones are synthesized in areas of active growth, such as root apices and developing shoots. Cytokinins play several critical roles in plants, including:

  • Promotion of Cell Division: They stimulate the division of plant cells, making them crucial during the development of new tissues and organs.
  • Influencing Shoot Growth: Cytokinins promote the growth of lateral shoots, effectively overcoming apical dominance where the main shoot inhibits the growth of side shoots.
  • Delaying Senescence: By promoting nutrient mobilization, cytokinins help delay leaf senescence, thus prolonging the life of leaves and improving overall plant vitality.

Their significance extends to agricultural applications, where they are used to enhance crop yield and manage plant growth more effectively. A deeper understanding of their mechanisms can provide ways to optimize plant growth and health.

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Audio Book

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Discovery of Cytokinins

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Cytokinins have specific effects on cytokinesis, and were discovered as kinetin (a modified form of adenine, a purine) from the autoclaved herring sperm DNA. Kinetin does not occur naturally in plants. Search for natural substances with cytokinin-like activities led to the isolation of zeatin from corn-kernels and coconut milk.

Detailed Explanation

Cytokinins are a type of plant growth regulator that play a vital role in cell division (cytokinesis). The discovery of these compounds began with kinetin, which is a synthetic version derived from DNA of herring sperm. Although kinetin is not naturally found in plants, researchers sought natural equivalents and found zeatin, which is present in corn kernels and coconut milk. This highlights the journey of scientific exploration in plant biology.

Examples & Analogies

Imagine discovering a new type of nutrient for plants similar to finding an alternative energy drink that boosts energy in athletes. Just as athletes seek out the best supplements based on research, scientists sought natural compounds in plants that enhance growth and vitality.

Functions of Cytokinins

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Since the discovery of zeatin, several naturally occurring cytokinins, and some synthetic compounds with cell division promoting activity, have been identified. Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits etc.

Detailed Explanation

Cytokinins are produced in areas of the plant that are actively growing, such as the tips of roots and shoots, and in young fruits. This production supports the plant's ability to develop new tissues. When cytokinins are present, they stimulate the formation of new leaves and help in the growth of shoots. They are essentially growth boosters for developing plant tissues.

Examples & Analogies

Think of cytokinins as plant fertilizers that are specifically designed to promote new growth. Just as gardeners add fertilizer to boost flower blooms or vegetable growth, cytokinins enhance the plant's ability to create new structures and sustain life.

Role in Overcoming Apical Dominance

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Cytokinins help overcome the apical dominance. They promote nutrient mobilisation which helps in the delay of leaf senescence.

Detailed Explanation

Apical dominance is the phenomenon where the main bud of a plant suppresses the growth of lateral buds. Cytokinins counteract this effect, allowing lateral buds to grow, which leads to a more bushy and fuller plant appearance. They also assist in moving nutrients within the plant, which not only supports growth but also helps keep leaves alive longer before they fall off.

Examples & Analogies

This situation can be compared to a family where the oldest sibling tends to take charge, controlling the younger siblings' activities. If support (cytokinins) is provided to the younger siblings, they can flourish and show their potential just as the lower buds on a plant can grow when apical dominance is reduced.

Definitions & Key Concepts

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Key Concepts

  • Cytokinins: Plant hormones that primarily promote cell division.

  • Kinetin: The first identified cytokinin.

  • Zeatin: A naturally occurring cytokinin in corn.

  • Apical Dominance: The suppression of side shoots by the main shoot.

  • Nutrient Mobilization: How cytokinins help in moving nutrients to delay leaf senescence.

Examples & Real-Life Applications

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Examples

  • Use of cytokinins in tissue culture to develop new plant tissues.

  • Application of cytokinins in agriculture to increase crop yields by promoting lateral growth.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Cytokinins grow stems and leaves, helping plants achieve their heaves.

📖 Fascinating Stories

  • Imagine a garden where little green sprouts come to life as cytokinins work their magic, giving energy and strength to those tiny shoots reaching towards the sun.

🧠 Other Memory Gems

  • Remember 'C.A.L.S.' for Cytokinins, Apical dominance, Lateral growth, and Senescence delay.

🎯 Super Acronyms

Cytokinins = 'C' for Cell division, 'Y' for Young tissues, 'T' for Tissue culture applications.

Flash Cards

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Glossary of Terms

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  • Term: Cytokinins

    Definition:

    A group of plant hormones that promote cell division and affect growth and development.

  • Term: Cytokinesis

    Definition:

    The process of cell division, resulting in the formation of two daughter cells.

  • Term: Apical Dominance

    Definition:

    The phenomenon where the main shoot suppresses the growth of lateral shoots.

  • Term: Senescence

    Definition:

    The process of aging in plants, leading to the eventual death of tissues.

  • Term: Kinetin

    Definition:

    The first cytokinin discovered, derived from herring sperm DNA.

  • Term: Zeatin

    Definition:

    A naturally occurring cytokinin found in corn and coconut milk.