Transcript PPT5 - Yashwantrao Chavan Maharashtra Open University
Online Counseling Resource
YCMOU ELearning Drive…
School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India
SBT/SBI/SGS011-CP3-05
Introduction
Programmes and Courses
SEP –SBT011 -U3-CP3
SEP –SBT011 -U3-CP3 SEP – SGS011-U3-CP3
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Credits
Academic Inputs by
Sonali Alkari
Faculty YCMOU Nagpur Centre, Faculty LAD college P.G. D of Biotechnology Research officer Ankur Seeds Pvt Ltd [email protected]
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How to Use This Resource
Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.
Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.
Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.
Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.
Appear several times, for all the Self-Tests, available for this course.
Student can use handouts for last minutes preparation just before end exam.
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Learning Objectives
After studying this module, you should be able to:
Describe growth Describe plant meristems Describe primary and secondary growth Describe hormones and their function Describe Formation apical meristems and Pattern © 2008, YCMOU. All Rights Reserved.
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Growth-1
Growth implies development, from the time of emergence or birth to the time of maturity and for many species, beyond maturity to eventual senescence or death.
Growth also implies increase in size resulting from cell multiplication and cell expansion, as well as maturation of tissues.
However, growth, while accentuating increased cell number and size, also necessitates programmed cell death, leading to the production of the final body form.
Thus, growth is an incredibly complex phenomenon, which involves changes in body form, metabolism, and body processes.
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Growth-2
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Growth-3
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Plant Meristem-1
Plants reproduce asexually and regenerate damaged parts.
have the impressive abilities to The secret to these abilities lies within a tissue type called meristem.
Meristematic cells are fully developed and functional at maturity but unlike other cells in the plant, they remain totipotent.
This means that when induced, they can develop into any specific plant tissue at any point during the life of the plant.
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Plant Meristem-2
Other cells in the plant are fully differentiated (meaning that they are specialized in both form and function) and do not divide.
Cells in the meristem, however, divide and produce all of the new cells in a plant.
While meristem tissue is the source of the regenerative potential of a plant, meristems also play a pivotal role in normal plant growth.
Plants have the unique ability to continue to grow and develop new organs while functioning as a mature, reproducing organism.
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Plant Growth-1
Plants grow larger via cell division and cell elongation.
Simple plant growth is facilitated by meristem tissue because it is the primary site of cell division (mitosis) in the plant.
Plants develop new organs (stems, leaves, flowers, roots) via cell division and cell differentiation.
Because the source of all new cells in a plant is the meristem, this tissue plays an important role in organ development as well.
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Plant Growth-2
While some of the cells of the apical meristem divide to generate new meristematic cells, most of the offspring cells differentiate into specialized cell types that stop dividing and function as a part of the organ in which they were generated.
Plants have meristematic tissue in several locations.
Both roots and shoots have meristematic tissue at their tips called apical meristems that are responsible for the lengthening of roots and shoots.
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Plant Growth-3
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Primary Growth
The shoot apical meristem is formed during embryonic development, but after germination gives rise to the stem, leaves, and flowers.
The root apical meristem is also formed during development, but during germination gives rise to the root system.
Cell division and cell elongation in the apical meristem is called primary growth and results in an increase in plant height and root length.
Increasing root length enables the plant to tap into the water and mineral resources of a new region or layer of soil.
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Secondary Growth-1
Increasing shoot length makes the plant taller, thus allowing it better access to sunlight for photosynthesis.
Many types of plants also increase the diameter of their roots and stems throughout their lifetime.
This type of growth is called secondary growth and is the product of lateral meristem.
Lateral meristem is called the vascular cambium in many of the plants in which it is found.
Secondary growth gives a plant added stability that allows for the plant to grow taller
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Secondary Growth-2
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Secondary Growth-3
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Regulation of Meristem
Lastly, meristem.
some plants have intercalary These are areas of plants that help in the regeneration of parts of the plant that have been damaged by predators or the environment.
Intercalary meristems produce growth at the base of grass blades, for instance.
Meristem tissue is not autonomous.
Throughout the life of the plant, the rate of cell division and cell elongation in the meristems is regulated by plant hormones.
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Hormones-1
Hormones are molecules released by a group of cells in the body that influence the behavior of another group of cells.
Plant hormones are chemical messengers that are produced in one part of the plant and have a physiological effect on target tissue that may be distant from the site of production.
When hormones reach the target tissue they can:
have a direct effect on the target tissue causing a rapid metabolic response;
involve the use of a second messenger within target cells; and/or affect transcription of nuclear deoxyribonucleic acid (DNA).
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Hormones-2
Plants have no specialized organs designed solely for hormone synthesis and secretion.
Leaves, stem tips, root tips, flowers, seeds, and fruits all produce hormones.
Most plant hormones are functional at very low concentrations.
Auxins, cytokinins, gibberellins, abscisic acid, and ethylene are the best known plant hormones.
All are in some way involved in regulating plant growth and development.
Some promote growth by stimulating cell division while others inhibit growth by inducing dormancy or promoting senescence.
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Plant Hormones: Roles Hormone
Auxins Cytokinins Gibberellins Abscisic Acid Ethylene
Role
Involved in differentiation of vascular tissue, control cellular elongation, prevention of abscission, involved in apical dominance and various tropisms, stimulate the release of ethylene, enhance fruit development Affect cell division, delay senescence, activate dormant buds Initiate mobilization of storage materials in seeds during germination, cause elongation of stems, stimulate bolting in biennials, stimulate pollen tube growth Maintains dormancy in seeds and buds, stimulates the closing of stomata Causes ripening of climacteric fruits, promotes abscission, causes formation of aerenchyma tissue in submerged stems, determines sex in cucurbits © 2008, YCMOU. All Rights Reserved.
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Apical Meristems and Pattern Formation:1
As the source for all new cells of the growing plant, the meristem plays an important role in the formation of new organs and in the correct placement of those organs within the plant body.
The process by which this organization happens is called pattern formation and, in plants, is directed by the meristem.
To accomplish this task, meristematic cells must be able to interpret their position in the plant and establish a certain fate.
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Apical Meristems and Pattern Formation:2
10x microscope image of root tip with meristem 1 – calyptrogen 2 - quiescent centre 3 – epidermis 4 – rootcap 5 - vascular cylinder © 2008, YCMOU. All Rights Reserved.
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Apical Meristems and Pattern Formation:3
During the development of a new leaf, the dividing cells of the meristem must differentiate into several different functional types of epidermal cells and parenchyma cells.
However, they do not need to differentiate into reproductive cells like those found in a flower.
How is it that meristematic cells “know” what to become?
The actively dividing differentiation.
cells of the apical meristem use positional cues such as hormones and cell-cell interactions as guides during
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Apical Meristems and Pattern Formation:4
Moreover, these positional cues result in the activation of certain genes and the inactivation of other genes in a set of cells, thus initiating their specific differentiation pattern based on their spatial location in the plant.
The specific genes that are initially activated in meristem cells during this process are called homeotic genes.
These genes encode a family of transcription factors that, once activated, will determine the fate of a cell by activating and inactivating a whole host of other genes.
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Apical Meristems and Pattern Formation:5
One genes mechanism during of differential expression (the activation and inactivation of differentiation the developing cell’s surface.
and gene organ development) is binding of plant hormones to Hormones such as cytokinins have been shown to affect ribonucleic acid (RNA) transcription and translation.
It is thought that the presence of both cytokinins and another class of hormones, called auxins, are important for proper root and shoot development.
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Apical Meristems and Pattern Formation:6
In the laboratory, if a set of undifferentiated meristem cells are grown in culture, they will not develop into a plant embryo unless they are stimulated with auxin and cytokinin.
A high cytokinin/auxin ratio will stimulate the meristematic cells to develop stems, leaves, and flower buds.
On the other hand, a high auxin/cytokinin ratio will stimulate the meristematic cells to develop roots.
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What You Learn-1…
You have learnt that…
Growth implies development, from the time of emergence or birth to the time of maturity
Growth is an incredibly complex phenomenon, which involves changes in body form, metabolism, and body processes.
Meristem growth tissue is the source of the regenerative potential of a plant, meristems also play a pivotal role in normal plant Plants develop new organs (stems, leaves, flowers, roots) via cell division and cell differentiation.
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What You Learn-2…
Source for all new cells of the growing plant, the meristem plays an important role in the formation of new organs and in the correct placement of those organs within the plant body.
Cell division and cell elongation in the apical meristem is called primary growth and results in an increase in plant height and root length.
Increase the diameter of their roots and stems is called secondary growth and is the product of lateral meristem.
Plant hormones are chemical messengers that are produced in one part of the plant and have a physiological effect on target tissue that may be distant from the site of production.
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Critical Thinking Questions
1.
Describe is details plant growth.
2.
Describe hormones and their function.
3.
Describe formation.
apical meristem and pattern
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Hints For Critical Thinking Question
1.
Define and describe growth, primary and secondary growth.
2.
Define and their function.
describe hormones Auxins, cytokinins, gibberellins, abscisic acid and
Meristematic root called tissue at their tips shoot and apical meristems body is called pattern formation.
and the formation of new organs and in the correct placement of those organs within the plant
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Study Tips
Book1
Title :The Living World Author : George Johnson Book2
Title : ABC Of Biology
Publisher : Holy Faith Book3
Title : Biological Science
Author : Taylor, Green & Stout
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Study Tips
www.en.wikipedia.org
Microsoft Encarta Encyclopedia http://en.wikipedia.org/wiki/ Wikipedia the free encyclopedia
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End of the Presentation
Thank You
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