Photosynthesis, respiration etc. Flashcards
The equation of photosynthesis
Light
Carbon dioxide + water -»»»> Carbohyrates + oxygen
Chlorophyll
List the environmental factors that affect the rate of photosynthesis
- Temperature
- Light (intensity, quality/PAR and duration)
- Carbon dioxide
- Water
- Mineral nutrients
The law of limiting factors
The law of limiting factors states that the growth is controlled not by the total of resources but by the scarcest recourse of limiting factor. Whatever element is in the least supply controls the rate photosynthesis.
How does temperature affect the rate of photosynthesis
At what temperature the photosynthesis start and stop
Does the rate increase with temperature
At what temperature does photosynthesis generally start, and stop? 5C to 45C (Optimum is 25-35)
Does the rate increase with the temperature? Yes, as the temperature affects the rate of photosynthesis because chemical reactions are faster as temperature rises
How does light (intensity, quality/PAR, duration) affect photosynthesis
The intensity of the light varies during the year, as well as the duration; growers add artificial light to increase day length and to supplement natural light to give a higher intensity.
Light quality/PAR relates to the delivering the parts of the spectrum the plants can use (photosynthetically active) – supplementary lighting is chosen to give the most useful wavelengths.
How does carbon dioxide affect the rate of photosynthesis
If the plants are in a closed spaces (i.e. greenhouse with no vents open) and the CO2 can get depleted which would slow down the photosynthesis
How does water affect the rate of photosynthesis
Photosynthesis involves chemical reactions, and these need water to take place.
The stomata closes to limit evaporation which means that the CO2 cannot enter the plants
How does mineral nutrients affect the rate of photosynthesis
Nutrients are the chemical elements required for the plant to function efficiently
State the equations for aerobic and anaerobic respiration in words
Aerobic respirator (with oxygen) Sugars+Oxygen»_space;> CO2 + Water + High yields of energy
Anaerobic respiration (without oxygen) Sugars+zymase»>Carbon dioxide + ethanol + low yields of energy
List the factors that affect the rate of respiration
- Oxygen
* Temperature.
How does a lack of oxygen affect respiration?
Oxygen is needed for the plants to produce higher energy yields. Lack of oxygen forces anaerobic respiration which also produces ethanol which is toxic to plants.
What happens when the temperature falls?
When the temperature falls it slows downs respiration which in turn slows down growth and cell division
Describe the significance of anaerobic and aerobic respiration in horticultural situations: waterlogging propagation produce storage seed storage.
Waterlogging: Anaerobic respiration as there is not enough oxygen
Propagation: For cuttings to produce roots there needs to be an active cell division which requires a lot of energy so having higher amounts of oxygen and temperature helps the process
Produce storage: Low temperatures slow down respiration, therefore the produce stores longer
Seed storage: Seeds require warmth, moisture and oxygen to germinate, so to stop that they are kept in sealed containers
Definition of diffusion
The movement of molecules of substance from high concentration to a lower concentration
Definition of osmosis
the movement of water from high water concentration to a low water concentration across a semi-permeable membrane. This prevent too much minerals entering the cells
Examples of diffusion in plants
Transpiration – water evaporating through stomata
Gaseous exchange - when oxygen and carbon dioxide naturally flow from higher concentration to lower
Describe the pathway of water movement from the soil through the plant into the atmosphere.
- Soil water
- pathway across the root ( root hairs, osmosis across root cells, flow through root cell walls, endodermis)
- transport through xylem of stem (transpiration pull)
- pathway across leaf ( xylem in veins, osmosis across leaf cells, flow through leaf cell walls evaporation from leaf cell walls into mesophyll spaces)
- diffusion through stomata of leaf
Definition of transpiration
The evaporation of water from plants, generally from the leaves, while their stomata are open for the passage of CO2 and O2 during photosynthesis
List the factors that affect transpiration
- Relative humidity
- Temperature
- Wind Speed
How do plants slow down water loss
- Stomatal closure
* Leaf adaptions: hairs, thick cuticle, needle leaves
Describe the uptake and distribution of mineral nutrients in the plant
- nutrients from soil solution (active uptake against concentration gradient into root cells)
- transport through the plant in xylem
- distribution through phloem.
How is the leaf held and positioned to maximize photosynthesis?
The shape of a leaf blade and the arrangement of leaves allow light to reach the maximum amount number and maximise photosynthesis
How is water loss through transpiration controlled?
The stomata are on the underside of the leaf which is shadier side to reduce transpiration.