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Hiya,

Very good question!! Before getting into all the science lets use a quick abbreviation. Lets say I wanted to quench my hunger and get some food. If I had food in the fridge or ordered takeaway, I would maybe just heat it a little then gobble up. However, if all I had were plain ingredients/ parts that are not appetising on their own, I would have to invest time and effort to make this meal, yet the end result is the same... I would just eat it. For plants, photosynthesis is the cooking and respiration is taking in that delicious meal (glucose storage could be the leftovers)!

Putting photosynthesis and the pun aside, plants use aerobic respiration just the same way we do (except plants don't breath, obviously)! They use oxygen and glucose to make carbon dioxide and water. So remember during the night where there is insignificant photosynthesis, plants have to rely on excess glucose in stores from the day and available oxygen for energy. Luckily, they will have oxygen from photosynthesis earlier too and can get more through gaps in stoma (gates that let gases in or out). Plants can also get dissolved oxygen from the water in the roots. Now during morning/ a-lot of light, photosynthesis is the main process and during the night respiration is. However, during dim light, the plant tries to utilise both as much as possible. If the plant cannot get enough oxygen or lacks photosynthesis/ light for a long time though, it will use anaerobic respiration but differently then animals that produce lactic acid. Instead, anaerobic plant respiration is similar to microorganisms or yeast. Plants in this case break down glucose into ethanol and carbon dioxide to produce little energy in the form of two ATP molecules.

I was unaware of the level this question is studied at but hope it still helps!! 

Get at me for tutoring if you are interested at all

Thanks, Sal

As plants make their own food by photosynthesis but they use aerobic respiration to release energy, aerobic respiration occurs opposite direction as photosynthesis is building up sugars at the same time as respiration is using them up.

Aerobic respiration occurs in the mitochondria and requires oxygen. Plant cells do not have mitochondria and therefore cannot respire using aerobic respiration. 

Anaerobic respiration occurs in the cytoplasm, therefore plants do experience anaerobic respiration. They convert glucose into 3c (3 carbon) pyruvate through glycolysis. 3c pyruvate is then converted into ethanol + carbon dioxide through fermentation. 

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