Download Why bother with plants?

Why, oh why, should I
bother with plants?
Indeed why?
• Hunger, starvation, and malnutrition are endemic in
many parts of the world today.
• Rapid increases in the world population have
intensified these problems!
• ALL of the food we eat comes either directly or
indirectly from plants.
• Can’t just grow more plants, land for cultivation has
geographic limits
– Also, can destroy ecosystems!
Indeed
Figure why?
9.1
The Earth is currently experiencing
the most population increase in
Human
history.
2.5 billion in 1955 to 6 billion in 1999
At current rate, will double within
30 years!
Fastest growing nations have growth
rates at or above 4% - this will
double the countries population
every 17 years
Indeed why?
• At the latest count there are between 250,000 and
400,000 plant species on the earth.
• But three - maize, wheat and rice - and a few close
runners-up, have become the crops that feed the
world. All produce starch, helping to provide energy
and nutrition, and all can be stored.
• Maize converts the sun’s energy into sugar faster,
and potentially produces more grains, than any of
the other major staples.
Plants to feed the world
• The term Green Revolution is
used to describe the
transformation of agriculture in
many developing nations that led
to significant increases in
agricultural production between
the 1940s and 1960s
• Scientists bred short plants that
converted the sun’s energy into
grain rather than stem, so
preventing the mass starvation in
the developing world predicted
before the 1960s, at a cost of
higher inputs from chemical
fertilizers and irrigation.
Plants to feed the world
• Disease-resistant wheat
varieties with high yield
potentials are now being
produced for a wide range of
global, environmental and
cultural conditions.
• The Green Revolution has had
major social and ecological
impacts, which have drawn
intense praise and equally
intense criticism.
Plants to feed the world
• The Green Revolution is
sometimes misinterpreted to
apply to present times.
• In fact, many regions of the
world peaked in food
production in the period 1980
to 1995, and are presently in
decline, since desertification
and critical water supplies
have become limiting factors
in a number of world regions.
What comes from plants
Popular stimulants like coffee, chocolate,
tobacco, and tea.
Simple derivatives of botanical natural products; for
example, aspirin is based on the pain killer salicylic
acid which originally came from the
bark of willow trees.
Most alcoholic beverages come from fermenting
plants such as barley (beer), rice (sake)
and grapes (wine).
What comes from plants
• Plants also provide us with many natural materials
– hemp, cotton, wood, paper, linen, vegetable oils, some types
of rope, and rubber.
• The production of silk would not be possible
without the cultivation of the mulberry plant.
• Sugarcane, rapeseed, soy and other plants with a
highly fermentable sugar or oil content have
recently been put to use as sources of biofuels,
which are important alternatives to fossil fuels
A few of the many medicinal plants
Environmental changes
• Plants can also help us understand changes in on our
environment in many ways.
– Understanding habitat destruction and species extinction is
dependent
on
an
accurate
and
complete
catalog of
plant systematics and taxonomy.
– Plant responses to ultraviolet radiation can help us monitor
problems like ozone depletion.
– Analyzing pollen deposited by plants thousands or millions of years
ago can help scientists to reconstruct past climates and predict
future ones, an essential part of climate change research.
– Recording and analyzing the timing of plant life cycles are
important parts of phenology used in climate-change research.
– Lichens, which are sensitive to atmospheric conditions, have been
extensively used as pollution indicators.
A typical Plant cell
The Chloroplast
• Contain their own DNA and
protein-synthesizing
machinery
– Ribosomes, transfer
RNAs, nucleotides.
– Thought to have evolved
from endosymbiotic
bacteria.
– Divide by fusion
– The DNA is in the form of
circular chromosomes, like
bacteria
– DNA replication is
independent from DNA
replication in the nucleus
The Chloroplast
• Membranes contain chlophyll
and it’s associated proteins
– Site of photosynthesis
• Have inner & outer
membranes
• 3rd membrane system
– Thylakoids
• Stack of Thylakoids = Granum
• Surrounded by Stroma
– Works like mitochondria
• During photosynthesis, ATP
from stroma provide the
energy for the production of
sugar molecules
Energy flow through an ecosystem
• Energy enters as sunlight
• Producers convert sunlight to
chemical energy.
• Consumers eat the plants (and each
other).
• Decomposer organisms breakdown
the organic molecules of producers
and consumers to be used by other
living things
• Heat is lost at every step – So Sun
must provide constant energy input
for the process to continue!
Photosynthesis
•Very little of the Sun’s
energy gets to the ground
gets absorbed by water
vapor in the atmosphere
•The absorbance spectra of
chlorophyll.
Absorbs strongly in the
blue and red portion of
the spectrum
Green light is reflected
and gives plants their
color.
•There are two pigments
•Chlorophyll A and B
Photosynthetic pigments
• Two types in plants:
• Chlorophyll- a
• Chlorophyll –b
• Structure almost identical,
– Differ in the composition of a
sidechain
– In a it is -CH3, in b it is CHO
• The different sidegroups 'tune' the
absorption spectrum to slightly
different wavelengths
– light that is not significantly
absorbed by chlorophyll a, will
instead be captured by chlorophyll b
The chemical reaction of
photosynthesis is driven by light
• The initial reaction of
photosynthesis is:
– CO2 +H2O
(CH2O) + O2
– Under optimal conditions
(red light at 680 nm), the
photochemical yield is almost
100 %
– However, the efficiency of
converting light energy to
chemical energy is about 27
%
• Very high for an energy
conversion system
Overview of the carbon reactions
• The Calvin cycle:
• The cycle runs six times:
– Each time incorporating a
new carbon . Those six
carbon dioxides are reduced
to glucose:
– Glucose can now serve as a
building block to make:
• polysaccharides
• other monosaccharides
• fats
• amino acids
• nucleotides
The Plant Golgi Network
The Plant Cell wall
• Cell walls are held
together by the middle
Lamella.
• Made up of:
• Cellulose
• Xyloglucan
• Pectin
• Proteins
• Ca ions
• Lignin
• other ions
• Water
The Plant Cell wall
• The plant cell wall is a layer
of structural material
external to the protoplast,
built from polysaccharides
and proteins.
• Contains components for
signaling and communication
• Is the organelle that
ultimately controls the shape
of plant cells and
consequently of organs and
whole organisms.
Example of cell wall growth
Tropisms: Positive or negative growth
responses of plants to external stimuli
that mainly come from one direction.
As tropisms effect the growth pattern
of plants, they greatly effect the plant
cell wall.
Best known:
Phototropism
Induces cells AWAY from light to
elongate. Cell wall expands in a
specific direction.
From: Biochemistry and Molecular Biology of plants
The Plant cell wall
• Critical to:
•
plant cell growth
•
plant growth and development
•
differentiation
•
response to biotic and abiotic stress
• Impact human activities in many ways:
•
wood
•
paper
•
textile
•
fuel
•
food
•
livestock feed
•
brewing
•
pharmaceuticals
Genetically modified crops
• All plant characteristics, such as size, texture, and
sweetness, are determined on the genetic level.
•
•
•
•
•
•
Also:
The hardiness of crop plants.
Their drought resistance.
Rate of growth under different soil conditions.
Dependence on fertilizers.
Resistance to various pests and diseases.
• Used to do this by selective breeding
Genetically modified crops
• Agrobacterium method
– Uses the natural infection mechanism of
a plant pathogen
– Agrobacterium tumefaciens naturally
infects the wound sites in
dicotyledonous plant causing the
formation of the crown gall tumors.
– Capable to transfer a particular DNA
segment (T-DNA) of the tumor-inducing
(Ti) plasmid into the nucleus of infected
cells where it is integrated fully into
the host genome and transcribed,
causing the crown gall disease.
• So the pathogen inserts the new DNA with
great success!!!
Genetically modified crops
• The vir region on the plasmid inserts DNA between
the T-region into plant nuclear genome
• Insert gene of interest and marker in the T-region
by restriction enzymes – the pathogen will then
“infect” the plant material
• Works fantastically well with all dicot plant species
– tomatoes, potatoes, cucumbers, etc
– Does not work as well with monocot plant species - corn
• As Agrobacterium tumefaciens do not naturally
infect monocots
Genetically modified crops
• Issues:
• Destroying ecosystems – tomatoes are now
growing in the artic tundra with fish antifreeze
in them!
• Destroying ecosystems – will the toxin now
being produced by pest-resistance stains kill
“friendly” insects such as butterflies.
• Altering nature – should we be swapping genes
between species?
Genetically modified crops
• Issues:
• Vegetarians – what about those tomatoes?
• Religious dietary laws – anything from a pig?
• Cross-pollination – producing a super-weed
• Human health – what of the antibiotic marker
gene?
The End.
Any Questions?