Mycorrhizae = symbiotic association between fungi and plant roots
● Fungi (hyphae) act as an extension of plant roots to increase surface area of root system
● To increase rate of uptake / absorption of water and inorganic ions
● In return, fungi receive organic compounds eg. carbohydrates
Give examples of biological molecules that contain nitrogen?
Amino acids / proteins or enzymes / urea / DNA or RNA / chlorophyll / ATP or ADP / NAD or NADP
Describe the role of bacteria in nitrogen fixation?
● Nitrogen gas (N2) converted into ammonia (NH3), which forms ammonium ions (NH4 + ) in soil
● By nitrogen-fixing bacteria (may be found in root nodules)
Describe the role of bacteria in ammonification?
● Nitrogen-containing compounds eg. proteins / urea from dead organisms / waste are broken down / decomposed
● Converted to ammonia, which forms ammonium ions in soil
● By saprobionts - secrete enzymes for extracellular digestion
Describe the role of bacteria in denitrification?
● Nitrates in soil converted into nitrogen gas (reduction)
● By denitrifying bacteria in anaerobic conditions (no oxygen, eg. waterlogged soil)
Describe the role of bacteria in nitrification ?
● Ammonium ions in soil converted into nitrites then nitrates, via a two-step oxidation reaction ○ For uptake by plant root hair cells by active transport
● By nitrifying bacteria in aerobic conditions (oxygen)
