The roles of plants in the environment. The Biosphere Depends on Plants. Cellulose: a large and complex carbohydrate We cannot digest it but can use it in different ways Examples: grass for cattle, Cottons, fabrics, paper, cardboard. 2. Plants as a Food Source.
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The roles of plants in the environment
The Biosphere Depends on Plants
Plants as a Food Source
Canola: 12, 642
Barley: 11, 781
Grain corn: 10, 592
Top Crops in Canada
Production (thousands of tons)
One type of plant is grown in place of the natural ecosystem
What are some pros and cons of this approach?
increase crop yield, ease of caring
nutrient depletion in soil, vulnerable to pests, require synthetic fertilizers
25% of prescription medicines contain plant extracts
Rosy periwinkle (vincristine and vinblastine) – childhood leukemia and Hodgkin’s. Survival rates have gone from 20% to 90% with these 2 compounds
Ginseng – immune system function
Plants as a Source of Biochemicals
Coals –decomposed plants buried deep underground
Biofuels: fuels that are produced from renewable biological sources
Most biofuels come from corn (ethanol).
1 L of fossil fuel to produce 1.25L of corn ethanol
The paradox of farming: farmers need good soil to farm, yet farming destroys good soil.
About 1/3 of the country's topsoil has been lost due to urbanization and soil erosion.
Soil erosion can be reduced by covering the area with plants
Movement mechanism of substances in plants
The theory is based on the 3 properties of water:
Plasmolysed after being placed in a concentrated solution of sucrose.
Root hairs absorb ions and minerals. Water follows by osmosis.Water will make its way to the xylem cells.As pressure builds, water goes up the xylem.Root pressure is not enough to carry water up to the leaves.
1) Sun causes water to evaporate and exit the leaves through stomata.
2) As the water exits the leaves, it pulls on water molecules below dragging them up from the roots to the leaves.
3) Cohesion (attachment of water molecules to each other) allows for water molecules to come up together.
4) Adhesion (attachment of water to xylem walls) prevents water molecules from going back down to roots.
This is TRANSPIRATION
Plant Growth and Development
Plant Growth Regulators (PGRs)
Produced in plants at the apical meristem (stems and roots)
Regulate cell expansion in plant responses to light and gravity
Auxins promote elongation of cells, stimulate growth and ripening of fruit, and also inhibit the dropping of fruit and leaves.
Synthetic auxins can be used to stimulate growth of fruit from unpollinated plants, resulting in, for example, seedless tomatoes.
Lettuce bolting after it has been treated with gibberellins.
4. Abscisic Acid
Maple tree seeds. Some seeds can remain dormant for years and still be viable in newfound hospitable conditions.
Ethylene is a gas produced in many of the plant’s tissues.
External Factors that Regulate Plant Development
the stem is trying to grow back upwards and fight gravity.
Anatomy of a flower