The Importance of Plants: Feeding the World and Beyond, Slides of Botany and Agronomy

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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 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

• 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).

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.

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 Docsity.com

The Chloroplast

• Membranes contain chlophyll and it’s associated proteins - Site of photosynthesis
• Have inner & outer membranes
• 3 rd^ 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

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 chlorophylla, will instead be captured by chlorophyllb

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