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Plants
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Science
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Plants
What is Plant
Science?
Plant science
is more than photosynthetic energy capture!
Plants lie at
the base of nearly every food chain on our
planet. Directly or indirectly, they provide
us with all our dietary requirements, and
many of our raw materials for industry,
clothing and leisure. Many plants are crucially
important in biotechnology - providing,
for example, vaccines, pharmaceuticals and
even plastics.
The Plant Science
programme at The University of Manchester
examines the growth, development and productivity
of plants. To understand and exploit these
processes it is necessary to apply a wide
range of biological areas including genetics,
molecular biology, biochemistry and cell
biology.
Plant scientists,
by developing a more comprehensive knowledge,
have a realistic opportunity to directly
impact on the significance of plants, both
in global ecosystems and in our lives in
the 21st century.
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What is Plant Tissue Culture?
Plant cells can be grown in isolation
from intact plants in tissue culture systems.
The cells have the characteristics of callus cells,
rather than other plant cell types. These are
the cells that appear on cut surfaces when a plant
is wounded and which gradually cover and seal
the damaged area.
Pieces of plant tissue will slowly
divide and grow into a colourless mass of cells
if they are kept in special conditions. These
are:
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initiated from the most appropriate
plant tissue for the particular plant variety |
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presence of a high concentration of auxin
and cytokinin growth regulators in the growth
media |
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a growth medium containing organic and inorganic
compounds to sustain the cells |
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aseptic conditions during culture to exclude
competition from microorganisms |
The plant cells can
grow on a solid surface as friable, pale-brown
lumps (called callus), or as individual or small
clusters of cells in a liquid medium called a
suspension culture. These cells can be maintained
indefinitely provided they are sub-cultured regularly
into fresh growth medium.
Tissue culture cells
generally lack the distinctive features of most
plant cells. They have a small vacuole, lack chloroplasts
and photosynthetic pathways and the structural
or chemical features that distinguish so many
cell types within the intact plant are absent.
They are most similar to the undifferentiated
cells found in meristematic regions which become
fated to develop into each cell type as the plant
grows. Tissue cultured cells can also be induced
to re-differentiate into whole plants by alterations
to the growth media.
Plant tissue cultures
can be initiated from almost any part of a plant.
The physiological state of the plant does have
an influence on its response to attempts to initiate
tissue culture. The parent plant must be healthy
and free from obvious signs of disease or decay.
The source, termed explant, may be dictated by
the reason for carrying out the tissue culture.
Younger tissue contains a higher proportion of
actively dividing cells and is more responsive
to a callus initiation programme. The plants themselves
must be actively growing, and not about to enter
a period of dormancy.
The exact conditions
required to initiate and sustain plant cells in
culture, or to regenerate intact plants from cultured
cells, are different for each plant species. Each
variety of a species will often have a particular
set of cultural requirements. Despite all the
knowledge that has been obtained about plant tissue
culture during the twentieth century, these conditions
have to be identified for each variety through
experimentation. |
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| What
is Plant Pathology?
Plant Pathology
is the study of the diseases and disorders of
plants. Disease can be defined as a harmful
deviation from normal functioning of the physiological
processes caused by an infectious agent. In
the case of plant diseases, the causal agent
maybe a fungus, virus, bacterium or a parasitic
flowering plant. (A 'harmful deviation' caused
by a non-infectious agent, for example, herbicide
or nutrient deficiency, is a disorder.)
Much of the time
plant pathologists study diseases of crop plants.
These diseases have had a huge impact on crops
and subsequently on human history. One hundred
and fifty years ago the potato crops of much
of Europe including Ireland were devastated
by the potato blight fungus, Phytophthora infestans,
an introduced pathogen on a non-native crop.
The ravages of this disease lead to 1 million
deaths and 1,500,000 emigrations from Ireland
alone. One hundred years ago the coffee rust
fungus, Hemileia vastatrix, caused such devastation
in the coffee plantations of what is now Sri
Lanka that all coffee was dug up and replaced
with tea. Fifty years ago an epidemic of brown
spot on rice, caused by Cochliobolus miyabeanus,
in what is now Bangladesh led to many thousands
of deaths from starvation. On the 5th of May
this year, a headline in the British newspaper
proclaimed 'Meltdown for Chocoholics'. Further
reading revealed that the culprits for this
crisis were two diseases of cocoa, witches broom
and black pod.
Most plant pathologist
spend their time studying several of the thousands
of diseases of crop plants and working to limit
the damage caused by these infectious agents.
Eradication may be aimed at removing completely
the causal agent of a particular disease, or
under some circumstances, the eradication program
may be aimed at the alternate host of the pathogen
(the infectious agent frequently survives the
intercrop period on a totally unrelated host,
the alternate host). Eradication of this host
removes an essential part of the pathogen's
lifestyle. Examples of this include the removal
of Ribes spp. to control White Pine Blister
rust, or barberry to control black stem rust
of wheat. Grubbing up a diseased plant and burning
it is a very effective control method.
If this is the case do 'Conservation' and 'Biodiversity'
have anything to do with Plant Pathology? Or
are Plant Pathologists the only professionals
on earth paid to eradicate rare and endangered
species and not to be involved in conservation
or Biodiversity Action? While there are some
conservation initiatives for fungi (mainly aimed
at macro fungi and not plant pathogens) there
is virtually nothing that involves the conservation
of fungal plant pathogens, bacteria or viruses.
The World Health Organization rejoiced when
smallpox was eradicated as a disease, but some
samples of the causal agent have been 'conserved'
for future reference.
What should the
attitude of Plant Pathologists be towards conservation
and biodiversity initiatives? Read on and interact
with this site. |
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