plant-microbial relationships

Question 1

what is a symbiosis relationship

Answer 1

a close and often long-term interaction between two different biological species

Question 2

what is the legume-rhizobia symbiosis

Answer 2

biological nitrogen fixation=conversion of atmospheric N2 to NH3, a form that can be used by plants

the most agronomically important one is the rhizobium bacteria that form a symbiotic relationship with legumes

the plant provides photosynthetically derived carbon to the bacteria in exchange for NH3

Question 3

describe the nodule formation in the legume-rhizobia relationship

Answer 3

nitrogen fixation by the rhizobium occur in specialized structures on the roots called nodules

legume roots release secondary metabolites called flavonoids under the N-starved conditions

the flavonoid induces nodulation genes in the rhizobia, which encodes the enzyme necessary to produce a chemical response called nod factor

nod factors initiate the development of nodules and their invasion by rhizobia bacteria

Question 4

what is nitrogen fixation

Answer 4

N2+8H+6e—->2NH3+H2

but all needed to remember is N2 is turned into NH3

Question 5

what enzyme helps break strong triple N2 bonds

Answer 5

nitrogenase

Question 6

what is leghemoglobin

Answer 6

chemical legumes have evolved to make that protect the enzyme by binding to excess O2

Question 7

How can nitrogenase be destroyed by

Answer 7

free-floating O2

Question 8

how can you tell if N fixation is active in a legume

Answer 8

nodules will have a pink color. if N fixation isn’t happening it’ll be pale in color

Question 9

how is nodule formation inhibited

Answer 9

too much nitrate and ammonium inhibits fixation

in other words, if the plant doesn’t need the N it won’t invest in the symbiotic relation required for N fixation

Question 10

how much total N can legumes fix from the air

Answer 10

anywhere between 40-80% of it required nitrogen from the air amounting to 25-190 kg N ha-1

Question 11

what is the mycorrhizal fungi symbiotic relationship

Answer 11

a symbiotic relationship with the plant roots.

the relationship is ubiquitous and non-selective meaning over 90% of plants associate with different species of mycorrhizal fungi.

Question 12

how long ago what the mycorrhizal fungi symbiotic relationship formed

Answer 12

it evolved 450 million years ago

Question 13

what species do mycorrhizal not form a relationship with

Answer 13

Brassica species ex. canola, mustard, cabbage, broccoli, etc

Question 14

what are the two types of mycorrhizae

Answer 14

arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi

Question 15

where are arbuscular mycorrhizal fungi (AMF) important

Answer 15

in agriculture systems

Question 16

where are ectomycorrhizal fungi important

Answer 16

in forests

Question 17

what is hyphae

Answer 17

microscopic hair-like structures grown by fungi

Question 18

what is the hyphal network and why is it important

Answer 18

a network of hair-like structures that extends outside of the root increases surface area and enables greater exploration of the soil.

important in the acquisition of water and immobile nutrients such as phosphorous

Question 19

in agriculture soils how much of the soil microbial biomass does the AMF make up

Answer 19

around 20-30%