Nitrogen Flashcards

1
Q

Why is it beneficial that N is less electronegative than oxygen?

A

The hydrogen bonds it participates in are weaker and easily separated (e.g., DNA)

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2
Q

What type of molecules is nitrogen found in?

A

All amino acids, all nucleotides, pigments (e.g., chlorophyll), plant hormones, secondary metabolites.

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3
Q

Why is nitrogen the most limiting nutrient?

A

Atmospheric N2 is extremely stable and cannot be broken by plants. -H and N_O bonds are more easily broken.

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4
Q

What are usable forms of nitrogen?

A

Ammonium, nitratte

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5
Q

How is N2 broken up for plants?

A

By bacteria

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6
Q

What is an issue with nitrate and nitrite?

A

Negatively charged, just like temperate soils. They are not retained well by soil and are often leached.

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7
Q

How is the triple bond in N2 broken down to be used by plants?

A

By the enzyme nitrogenase

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8
Q

What is an issue with nitrogenase?

A

O2 inhibits nitrogenase, thus requires anaerobic conditions

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9
Q

How many ATP molecules are required to fix one molecule of nitrogen?

A

16

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10
Q

How do plants attract free-living microbes to get N?

A

Deposit carbs from sloughed-off root cap cells and mucilage, which support bacterial growth. Produce N which is made available to plants by amoebae and fungi that feed on bacteria and organic matter.

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11
Q

How do plants maximize SA for N uptake?

A

Lateral root outgrowth responsive to nitrate or ammonium
Roots grow continuously
Thus, more growth where nitrogen signals are received

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12
Q

What specifically increases the SA for N uptake? How do they take in nitrogen?

A

Root hairs. Their cell membrane is covered in uptake transporters for nutrients such as nitrate.

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13
Q

What is a con for using root hairs to increase N uptake?

A

Increase in energy used for carriers and moving against concentration gradient

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14
Q

What are the benefits of mycorrhizae?

A

Fungi use extensive hypahe to scavenge nutrients over a much greater surface area/volume of soil than can be achieved by the root.

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15
Q

What are the different ways fungi can interact with roots?

A

Grow over surface = ecto
Enter root = endo
Enter cells = vam

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16
Q

What are nodules?

A

Complex structures with meristematic region and vascular connection

17
Q

How do legumes take in nitrogen?

A

Form symbiotic relationship with N-fixing bacteria. Nodule provides an anaerobic environment where bacteria can fix N.

18
Q

What does nodule formation require?

A

Coordinated exchange of signals between the plant and bacteria

19
Q

How do signals cause nodule formation?

A

Root hairs receive signals, they then curl around the bacteria, forming an infection thread, which bacteria then use to enter cells.

20
Q

What genes regulate the communication between legumes and bacteria?

A

NOD genes

21
Q

How does legum-rhizobium symbiosis benefit legumes?

A

Gets organic nitrogen

21
Q

How does legum-rhizobium symbiosis benefit legumes?

A

Gets organic nitrogen

22
Q

What is a cost of legume-rhizobium symbiosis to legumes?

A

Very costly in terms of energy. 16 ATP/N2. about 20% of photosynthate goes to this.

23
Q

How does legum-rhizobium symbiosis benefit bacteria?

A

Gets fixed carbon, energy from plants.

24
Q

What is a drawback of legume-rhizobium symbiosis for bacteria?

A

They die when the nodule does.

25
Q

What are endophytic bacteria?

A

Bacteria that live inside plants, not pathogenic

26
Q

How do carnivorous plants obtain N?

A

Trap and digest insects as sources of N.

27
Q

Where do carnivorous plants mainly live?

A

In low nitrogen environments.

28
Q

How can parasitic plants obtain N?

A

Tap into host’s N reserves either directly or indirectly.