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Photosynthesis & Life Occurs in the chloroplasts Uses light energy to combine Water and Carbon dioxide into Starch and Oxygen 6H2O + 6CO2 + Sunlight = 6O2 + C^H12O6 Enzymes control the process which is a very complicated step by step process. Chlorophyll is what makes the leaves greenwhich absorbs blueand redlight from the sun. Total photosynthesis across the globe is about 200,000,000,000 tonnes of glucosea year this is turned into Cellulose
Light, temperature and availability of raw materials all affect the rate of photosynthesis Brighterlight increase the rate of photosynthesis. Therefore the rate of photosynthesis changes throughout the day. The rate of photosynthesis doubles with 10oC increase of temperature up to a temperature of 40oC. Lack of water will cause plants to wilt and stopphotosynthesising. The atmosphere is made of 0.03% CO2. If this changes the rate of photosynthesis also changes Rate of Photosynthesis
Adaptations to cope Because of all the environmental factors that affect photosynthesis plants are able to adapt to survive these. The most important of these is water Mesophytic plants like roses are very adapt at dealing with water shortages.
External Leaf adaptations Surface area Petiole and Veins Cuticle You fill in the blanks -
Gas exchange Stomata During the day CO2 defuses into the cell and H2O and O2 defuse out During the night and when respiration is happening CO2 defuses out and O2 defuses in. Guard cells If they absorb water they become turgid (swollen) and open the stoma.
Recall Transport Mechanism Passive vs. Active Plant Transport Tissues Xylem Phloem
Transport Mechanisms Passive transport Passive Diffusion Facilitated Diffusion Osmosis Active transport Bulk transport
Plant Transport Tissues Xylem Vessel elements Tracheids Phloem Sieve tube member Companion cells
Problem of Terrestrial Plants Ancestral plants: transport is through diffusion Modern plants: transport from roots to shoots Long distance transport Figure 36.1
Transport in Plants Three scales of plant transport Intracellular Epidermal cells Short distance: cell-to-cell At the levels of tissues and organs Long distance: xylem and phloem
4 3 2 1 Through stomata, leaves take in CO2 and expel O2. The CO2 provides carbon for photosynthesis. Some O2produced by photosynthesis is used in cellular respiration. Sugars are produced by photosynthesis in the leaves. Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 6 5 7 Water and minerals are transported upward from roots to shoots as xylem sap. Roots absorb water and dissolved minerals from the soil. Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars. A variety of physical processes Are involved in the different types of transport CO2 O2 Light H2O Sugar Sugars are transported as phloem sap to roots and other parts of the plant. O2 H2O CO2 Minerals Figure 36.2
Effects of Differences in Water Potential To survive Plants must balance water uptake and loss Osmosis Determines the net uptake or water loss by a cell Is affected by solute concentration and pressure
Water potential Is a measurement that combines the effects of solute concentration and pressure Determines the direction of movement of water Water Flows from regions of high water potential to regions of low water potential Both pressure and solute concentrations affect water potential
Plasmolyzed cell at osmotic equilibrium with its surroundings Water potential Affects uptake and loss of water by plant cells If a flaccid cell is placed in an environment with a higher solute concentration The cell will lose water and become plasmolyzed
Initial flaccid cell: Distilled water: Turgid cell at osmotic equilibrium with its surroundings Figure 36.6b If the same flaccid cell is placed in a solution with a lower solute concentration The cell will gain water and become turgid
Bulk Flow in Long-Distance Transport In bulk flow Movement of fluid in the xylem and phloem is driven by pressure differences at opposite ends of the xylem vessels and sieve tubes
The xylem sap and phloem sap Xylem sap Root pressure Transpiration-cohesion-tension mechanism Phloem sap Pressure Flow Theory Translocation
Turgor Pressure This is what happens when plants don’t have enough water Turgor pressure is when water presses on the cell wall – inflating the cell Soft plants have lots of soft tissue that needs a regular supply of water
The vascular system is made of three sections
Root pressure Root tip cells have a large number of tiny extensions called root hairs Root hairs provide a huge surface area in the soil. Water enters the root via osmosis ?? – What happens as the water pressure builds up?
Transpiration pull More than 90% of the water moving up a plant is lost through transpiration as water vapor through the stomata. As the water leaves the the plants the concentration of solutes increases within the cells, this draws more water into the cells from the xylem
Phloem transport Sugar and amino acids are transported from the leaves to pares of the plants requiring food through the phloem The pressures gradient that moves this is created via the concentration of sugars Dissolved food transport is called translocation