Nitrogen cycle

Référence de la vidéo 11937589
Nitrogen cycle. Animation showing the stages by which nitrogen is fixed by bacteria from the atmosphere, used by plants, and ultimately released to the atmosphere again by other bacteria. The first step (white arrows) is the conversion of nitrogen gas (N2) to ammonium ions (NH4). This is followed by several oxidation stages (nitrification, red arrows) where bacteria like Nitrosomonas and Nitrosococcus convert the ammonium to nitrites (NO2). Further oxidation by Nitrobacter bacteria produces nitrates (NO3). The following stages (blue arrows) involve reduction as plants (tree at upper centre) convert the nitrates to nitrites. The final reduction from nitrite to nitrogenous substances (amino acids) takes place in the chloroplasts (one at lower centre) where photosynthesis occurs. Animals feed on plants to obtain this nitrogen content, and amino acids are used to construct proteins. The decay and oxidation of proteins produces ammonia and nitrates. The final step is the action of denitrifying bacteria that convert nitrogenous substances to nitrogen (N2) which returns to the atmosphere. For this animation without labels, see K004/3294.
Licence : Droits gérés
Crédit : Science Photo Library / Biocosmos / Francis Leroy & Sempot Amaury
Model Release : Non requis
Durée : 40 Secondes
Aspect ratio : 16/9
Restrictions : -

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