Describe aerobic and anaerobic respiration and the factors that affect them.

State the equations for aerobic and anaerobic respiration in words:

RESPIRATION

Aerobic: sugars, oxygen, water, carbon dioxide, high yield of energy.

AEROBIC with oxygen

AEROBIC RESPIRATION Carbohydrate (glucose) + oxygen = high yield of energy + carbon dioxide + water.

Anaerobic: sugars, ethanol, carbon dioxide, low yield of energy.

ANAEROBIC without oxygen

ANAEROBIC RESPIRATION Carbohydrate (glucose) > ethanol + energy (very little energy compared to what went in).

ETHANOL alcohol, produced in anaerobic respiration

YEAST

FERMENTATION

List the factors that affect the rate of respiration: oxygen and temperature.

RESPIRATION RATE Oxygen: % in the air.

Temperature: Low/high.

Describe how these factors affect the rate of aerobic respiration.

Oxygen: If the % of oxygen is reduced, the rate of respiration drops; If the process is aerobic it needs the normal air % of oxygen. This is normally supplied by such things as having a good air change rate in greenhouses/good air filled porosity ratio of potting compost/well drained soils/soils not compacted; Under conditions where oxygen is missing the respiration becomes anaerobic. This can happen in capped compost heaps resulting in smelly, slimy compost and in water logged conditions of the soil. If this is prolonged, roots can be damaged/areas of lawns or crops go yellow (due to root damage by the chemicals building up in the soil to toxic levels/alcohols).

Temperature: As the temperature raises the rate of cell metabolism, so the rate of respiration increases. But if the plant gets too hot the process of respiration shuts down (hot air temperature as well as internal plant temperature); 5ºC minimum – below which respiration is very slow; 30ºC optimum; 40ºC maximum – above which respiration ceases; Depending on the plant species.

Describe how these factors affect the rate of aerobic respiration.

CELL METABOLISM

WATERLOGGED If prolonged, roots can be damaged/areas of lawns or crops go yellow (due to root damage by the chemicals building up in the soil to toxic levels/alcohols) and death of the grass or plant can occur. Use of drainage/cultivations/not puddling wet soils/spiking/aeration of lawns are all gardening activities used to avoid or correct the likelihood of water logging

Describe the significance of anaerobic and aerobic respiration in horticultural situations: waterlogging, propagation, produce storage, seed storage.

PROPAGATING CUTTINGS

Quick rooting of cuttings is helped if supplied with oxygen for respiration to give energy for cell division/ water for maintaining turgidity/ heat for increased rate of cell metabolism and increased rate of respiration.
The oxygen and water are supplied by the compost being “water retentive but draining”?, (often a peat/grit mixture). Heat from the use of a propagation case or soil warming mat/cable

STORAGE (PRODUCE)

Storage of produce is affected by respiration: Controlled atmosphere storage for apples. In special stores the conditions can be controlled.

Oxygen and Carbon Dioxide Levels: Between 0.5 and 2.5% depending on the cultivar (O2 taken down CO2 taken up and controlled by passing the air though scrubbers).

Relative Humidity: To 95% reduces transpiration and the fruit losing moisture.

Temperature: Down to 1ºC. To slow respiration rate.

All very closely monitored.

You in the Home: Place undamaged apples in a polythene bag with a small hole pierced in it. (O2 taken down, CO2 taken up by the natural respiration) and place in fridge; Seed storage – foil packet seed (Suttons) are sealed with a low humidity atmosphere; the seeds stay viable for a longer time if unopened than the same seeds in a paper packet; In the home seeds will store longer if the rate of respiration is lowered. Store dry seeds in paper packets by placing in: An air tight container (natural respiration will lower the O2 and raise the CO2); Place a silica pouch in to lower the relative humidity; Place in the bottom of the fridge for low temperature, do not freeze.