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Photosynthesis/Respiration/transpiration/Nutrient Absorption, Mr P…
Photosynthesis/Respiration/transpiration/Nutrient Absorption
Which cells transport nutrients? (vascular bundles).
Xylem
cells transport water and minerals up the stem from the roots to the shoots and leaves. This transport occurs in one direction only.
Xylem cells are reinforced with lignin to strengthen their cell walls.
Phloem
cells transport sugars (food) (Glucose). produced in the leaves up and down the stem to growing and storage tissues.
Consists of:
phloem sieve tube cells
companion cells
Sugars can move up and down
Translocation
movement of sugars produced in the leaves (sources) to other regions of the plant for storage (sinks).
stored and used in the roots, flowers, fruits and stems.
Photosynthesis Plants making their own food
requires:
carbon dioxide,
water,
light energy,
chlorophyll.
Photosynthesis produces:
glucose
Glucose use within the Plant
Converted into starch and stored by the plant
Converted into cellulose provides strength and support to cell wall.
Broken Down in Aerobic Respiration in order to provide energy for the plant.
waste oxygen
Factors that affect the rate of Photosynthesis
Light Intensity
Carbon Dioxide Concentration
Temperature
Adaptations of a Leaf for Photosynthesis
Leaf - Flat Shape gives large surface area for maximum light absorption
Extremely thin which facilitates gas diffusion
Cuticle - Prevents Water Loss
Palisade Layer - Closely placed chloroplasts in a cell for the absorption of light.
Stomata -Gaseous Exchange
Spongy Mesophyll Layer -Rapid Diffusion of Gas through air space.
Respiration
release of energy from Glucose
Occurs in the Mitochondria
controlled by enzymes
energy is trapped in molecules called ATP (Adenine Tri-Phosphate)
Factors that affect the rate of Respiration
Temperature
Oxygen Available
Glucose Available
Water Available
C6H12O6 + 6O2 6CO2 + 6H2O + energy
Glucose + Oxygen Carbon dioxide + water + energy
Water uptake
Water enters the root hair cells by osmosis
water will move from low concentration to high concentration across a semi permeable membrane
Root Hairs
Thin walls
Large surface area
Piliferous layer
Water moves by Diffusion from the root hairs into the ground tissue and eventually reaches the xylem
Diffusion is the movement of anything from a region of higher concentration to a region of lower concentration.
The movement of water from roots up
Root pressure is caused by the continuous movement of water by osmosis from the soil into the root hairs.
Cohesion/Tension -
Water molecules tend to stick together causing a force known as cohesion.
Adhesion when different molecules stick together, water adheres walls of xylem
Transpiration
The loss of water by evaporation through the leaves
Factors affecting the rate of transpiration.
Temperature: At high temperature rate of transpiration increases
Light: the rate of transpiration is quite high in light.
Wind: The movement of the air increases the rate of transpiration
Availability of Water:
Humidity: transpiration is higher when the humidity is lower and lower when the humidity is higher.
Nutrient Absorption
requires energy so root hair cells have lots of mitochondria
Active transport is the movement of a substance from and area of low concentration to an area of high concentration against a concentration gradient. (Requires Energy)
Casparian strip is an important barrier that regulates the uptake of water and nutrients
Carrier molecules recognize and select specific nutrient ions
Mr P Reynolds