Skip to main content
Pearson+ LogoPearson+ Logo

Nitrogen Fixation quiz #3 Flashcards

Nitrogen Fixation quiz #3
Control buttons has been changed to "navigation" mode.
1/15
  • In what forms do plants primarily absorb nitrogen from the soil?
    Plants primarily absorb nitrogen as ammonium (NH4+) and nitrate (NO3-).
  • What is nitrogen fixation?
    Nitrogen fixation is the process by which certain bacteria and archaea convert atmospheric nitrogen (N2) into ammonia (NH3), a form usable by plants.
  • How much energy is required to convert one molecule of N2 into ammonia during nitrogen fixation?
    Converting one molecule of N2 into two molecules of ammonia requires 16 ATP molecules.
  • What are root nodules and what is their function in legumes?
    Root nodules are swollen structures on legume roots that house rhizobia bacteria, facilitating nitrogen fixation.
  • What are nod factors and what role do they play in nitrogen fixation?
    Nod factors are signaling molecules released by rhizobia that induce root hair changes, allowing bacteria to enter the plant root and form nodules.
  • How do mycorrhizae assist plants in nitrogen absorption?
    Mycorrhizae are symbiotic fungi that increase the surface area for nutrient absorption and help break down organic matter, making nitrogen more available to plants.
  • Besides bacteria, what other organisms contribute to nitrogen availability in soil?
    Fungi, especially mycorrhizae and decomposers, contribute to nitrogen availability by breaking down organic matter.
  • How do carnivorous plants obtain nitrogen?
    Carnivorous plants obtain nitrogen by digesting animals, supplementing their nitrogen intake beyond what is available from the soil.
  • What is the main benefit plants receive from their symbiotic relationship with rhizobia?
    Plants receive usable nitrogen compounds, such as ammonium, from rhizobia.
  • What is the significance of the nitrogen cycle in ecosystems?
    The nitrogen cycle ensures the continuous availability of nitrogen in forms usable by living organisms, supporting ecosystem productivity.
  • Why do some plants, like epiphytes, not rely on soil for nitrogen?
    Epiphytes absorb water and nutrients, including nitrogen, from the air, rain, and debris, rather than from soil.
  • How does leghemoglobin protect nitrogenase during nitrogen fixation?
    Leghemoglobin binds oxygen, reducing its concentration and preventing oxygen from inactivating nitrogenase.
  • How do arbuscular mycorrhizae differ from ectomycorrhizae in their interaction with plant roots?
    Arbuscular mycorrhizae penetrate plant root cells, while ectomycorrhizae only surround the root cells without entering them.
  • How do plants benefit from the breakdown of organic matter by fungi?
    Plants benefit because fungi release nitrogen and other nutrients from organic matter, making them available for plant uptake.
  • Why is the mutualistic relationship between legumes and rhizobia considered beneficial for both partners?
    Legumes gain usable nitrogen, while rhizobia receive carbohydrates and a protected environment from the plant.