All living organisms including plants require certain nutrients to sustain their growth. Plants get most of their nutrients from the soil that anchors them. However, some of these nutrients like nitrogen are found in a fixed state and needs to be converted to usable forms. Nitrogen is a key component of living cells as it is used to build certain structures e.g protein, DNA etc. in the cell.
Certain groups of bacteria called NITRIFYING BACTERIA which are capable of using energy from chemical compounds to form organic molecules. They are important aerobic microbes that play a significant role in Agriculture, as in the process of them obtaining nutrients, they help convert ammonium in the soil into nitrites (fixed nitrogen). Groups of nitrifying bacteria that perform this initial task include: Nitrosomonas, Nitrosococcus etc. Other nitrifying bacteria from another genus-Nitrobacter, converts the nitrite into the most usable form by plants (nitrates).
Because each subject in an experiment has to have equal conditions to ensure the most accurate results. And water temperature is known to impact plant growth. An experiment using different water temperatures is a terribly inaccurate experiment.
