- Created by: Former Member
- Created on: 05-03-15 19:26
Photosynthesis produces Glucose using sunlight
1) Photosynthesis is the process that produces 'food' in plants. The food is glucose. It happens in the leaves of all green plants. 2) It happens inside the chloroplasts which are found in leaf cells. Chloroplasts contain a pigment which absorbs sunlight and uses its energy to convert carbon dioxide and water into glucose. Oxygen is also produced. 3) It converts light energy to chemical energy which is stored in glucose. This chemical energy is released when glucose is broken down during respiration.
CARBON DIOXIDE + WATER = GLUCOSE + OXYGEN
6CO2 + 6H20 = C6H12O6 + 6O2
The devil equation
AdaptionPurpose Large surface area To absorb more light Thin Short distance for carbon dioxide to diffuse into leaf cells Chlorophyll Absorbs sunlight to transfer energy into chemicals Network of veins To support the leaf and transport water and carbohydrates Stomata Allow carbon dioxide to diffuse into the leaf
Rate of photosynthesis
Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.
A limiting factor is something which stops photosynthesis from happening any faster. It depends on the environmental conditions
Rate of photosynthesis 2
Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.
Rate of photosynthesis 3
If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot.If you plot the rate of photosynthesis against the levels of these three limiting factors, you get graphs like the ones above.In practice, any one of these factors could limit the rate of photosynthesis.
Minerals for healthy growth
Plants need three main mineral ions for growth
1) Plants need certain elements so they can produce important compounds. 2) They get these elements from minerals in the soil. 3) Iif there aren't enough of these mineral ions in the soil, plants suufer from deficiency symptoms.
1) NITRATES - Contains nitrogen for making amino acids and proteins. Tthese are needed for cell growth. If a plant can't get enough nitrates it will be stunted and will have yellow older leaves.
2) PHOSPHATES - Contain phosphorus for making DNA and cell membranes and they're needed for respiration and growth. Plants without enough phosphates will have poor root growth and purple older leaves.
3) POTASSIUM - To help the enzymes needed for photosynthesis and respiration. If there's not enough potassium
Transport in plants
Multicellular organisms need transport systems.
Plants have two mainntransport systems.
Xylem tubes - which carry water and mineral salts from the roots up the shoot to the leaves in the transpiration stream.
Phloem tubes - which transport food (sugars - sucrose and amino acids) from where they are made in the leaves to other parts in the plant. The movement of food substances around the plant is known as translocation.
Root hair cells take in water.
1) The cells on plant roots grow into long hairs which stick out into the soil,
2) Each branch of root will be covered in millions of microscopic hairs.
3) This gives the plant a bigger surface area for absorbing water from the soil.
Water is taken in by osmosis. There is usually a higher conc of water in soil than in plant
Transpiration is the loss of water from the plant.
1) Transpiration is caused by the evaporation and diffusion of water from a plant's surface. Most transpiration happens at the leaves. 2) This evaporation creates a slight shortage of water in the leaf, and so more water is drawn up through the plant by the xylem vessel. 3) This means there is a constant flow of water from the roots which is called a transpiration stream.
It is affected by four things.
1) Light intensity - The brighter the light the greater the transpiration rate. Stomata closes when it is dark. So when stomata is closed very little water can escape. 2) Temperature- The warmer it is the faster transpiration happens. When it is warm the water particles have more energy to evaporate and diffuse out of stomata. 3) Wind speed - the higher the wind speed the greater the transpiration rate. If it is low the water vapour surrounds the leaf meaning theres a higher conc of water particles, meaning diffusion doesnt happen as fast. 4) Humidity - the drier the air the faster transpiration happens