Transcript Online Counseling Resource YCMOU ELearning Drive…

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
School of Science and Technology, Online Counseling Resource…
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]
[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
apical
meristems
and
Pattern
Formation
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School of Science and Technology, Online Counseling Resource…
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 have the impressive abilities to
reproduce asexually and regenerate damaged
parts.
 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,
some
plants
have
intercalary
meristem.
 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
Role
Auxins
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
Cytokinins
Affect cell division, delay senescence, activate dormant buds
Gibberellins
Initiate mobilization of storage materials in seeds during
germination, cause elongation of stems, stimulate
bolting in biennials, stimulate pollen tube growth
Abscisic Acid
Maintains dormancy in seeds and buds, stimulates the
closing of stomata
Ethylene
Causes ripening of climacteric fruits, promotes abscission,
causes formation of aerenchyma tissue in
submerged stems, determines sex in cucurbits
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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
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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 cells of the apical
meristem use positional cues such as hormones
and cell-cell interactions as guides during
differentiation.
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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
mechanism
of
differential
gene
expression (the activation and inactivation of
genes during differentiation and organ
development) is binding of plant hormones to
the developing cell’s surface.
 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
tissue is the source of the
regenerative potential of a plant, meristems
also play a pivotal role in normal plant
growth
 Plants develop new organs (stems, leaves,
flowers, roots) via cell division and cell
differentiation.
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School of Science and Technology, Online Counseling Resource…
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
apical
formation.
meristem
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and
pattern
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Hints For Critical Thinking Question
1. Define and describe growth, primary and
secondary growth.
2. Define and describe hormones Auxins,
cytokinins, gibberellins, abscisic acid and
their function.
 Meristematic tissue at their tips shoot and
root
called
apical
meristems
and
the
formation of new organs and in the correct
placement of those organs within the plant
body is called pattern formation.
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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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