Nitrogen (Quiz 3)

Question 1

although most available nitrogen in soild comes from…

Answer 1

leaf litter, the. biggest pool of nitrogen is in the air (N2)

Question 2

N must be

Answer 2

fixed

(converted to usable form for production

Question 3

natural forms of N fixation (2)

Answer 3

lightning strikes

bacteria –> some bac are free-living heterotrophs & others associated w/ plants

Question 4

N fixation increases in

Answer 4

anaerobic conditions

Question 5

N fixation equation

& requires

Answer 5

N2 + 8H+ + 8e− → 2NH3 + H2

requires 16 ATP

Question 6

N usually is the

Answer 6

limiting nutrient for productivity in most ecosystems

Question 7

biggest nitrogen pool =

Answer 7

the atmosphere N2 –> NH3 = fixation

Question 8

N fixation in bac is

Answer 8

expedited

Question 9

root nodules formation: (4)

Answer 9

1. ) root hair signals with N fixing bacterium
2. ) root hair curls around bacterium & triggers “infection”
3. ) root nodule engulfs bacterium & triggers “mitosis”
4. ) development of the root nodule around bacterial colony w/in stele forming “nodule”

Question 10

legume bacterium (3)

Answer 10

1. ) rhizobium
2. ) bradyrhizobium
   - (root nodules)
3. ) leghaemoglobin
   - (binds O2)

Question 11

cycads form

Answer 11

corolloid roots (ring of cells w/ N-fixing cyanobac)

Question 12

many species of cyanobac can

Answer 12

fix N

Question 13

Most N in soil is available to plants as either

Answer 13

NO3- or NH4+

Question 14

nitrification =

Answer 14

conversion of ammonium (ammonia in ionic forms) to nitrate

Question 15

2 Steps of Nitrification & 3 Genera of Bac

Answer 15

drier soils have higher nitrate than ammonium

plants must reduce nitrate to ammonia using nitrate reductase for protein synth

Question 16

what can be absorbed by roots

Answer 16

NO3- or NH4+

Question 17

(aerobic nitrification) nitrate must be reduced to

Answer 17

ammonia in the plant