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Biological Systems > Chapter 25 Plant Nutrition and Transport > Flashcards

Chapter 25 Plant Nutrition and Transport Flashcards

1
Q

Where do plants get their nutrients from?

A

Carbon from CO2, H and O2 mostly from water
Nitrogen from bacteria and fungi
Phosphorus, sulfer and other mineral nutrients from soil

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2
Q

What are essential elements

A

Element that when absent severely disrupt plant growth and reproduction

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3
Q

What macronutrients do plants need?

A 
Nitrogen
Phosphorus
Potassium
Sulphur
Calcium
Magnesium
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4
Q

What micronutrients do plants need?

A 
Iron
Chlorine
Manganese
Zinc
Copper
Nickel
Boron
Molybdenum
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5
Q

How were the six macronutrients identified/

A

Hydroponically

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6
Q

Why is identifying micronutrients more difficult

A

A seed may contain enough to suply a plant through its lifetime and laboratories need to be controlled with special air filters

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7
Q

What does soil provide to a plant?

A

Anchorage
Nutrients and water
O2 for root respiration
Soil organisms

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8
Q

What are the living and nonliving componetns of soil?

A

Living - plant roots, bacteria, protists, animals and insects

Nonliving - rock fragments, dissolved mineral nutrients, air spaces and dead organic matter

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9
Q

What are the horizons of soil?

A 
horizontal layers
A Horizon (topsoil) - most of living an dead organic matter
B horizon (subsoil) - accumulates material from topsoil and parent rock
C Horizon (parent rock) from which soil arises
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10
Q

How is parent rock weathered?

A

mechanical - by wetting, drying and freezing

Chemical - oxidation, water and acids

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11
Q

What is soil fertility

A

ability to support plant growth

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12
Q

What is humus?

A

Dead organic matter in soil

  • used as food source for microbes
  • Improves soil texture - creates air spaces to increase O2 availability to plant roots
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13
Q

What i sloam?

A

soil with sand, silt and clay that holds sufficient air, water and nutrients for platns

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14
Q

What does clay do?

A

binds water - is covered with negatively charged chemical groups that bind cations of important minerals (prevents them being leached out but also makes them unavailabe for plant updtake)

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15
Q

Where do minerals need to be for them to be available to plants?

A

A horizon - topsoil

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16
Q

What is the process of ion exchange?

A

Cations are released into the soil solution, thus made available to plant roots

  • Root hairs pump protons (H+) out of the cell and cellular respiration releases CO2
  • CO2 dissolves in soil water to form carbonic acid which ionizes
  • H+ concentration around roots inccreases
  • Protons bind to clay stronger than mineral cations, so swap places
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17
Q

How are negatively charged prevented from leaching?

A

There is no process for them to be bound or released

They aren’t

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18
Q

What are the 3 ways to replenish depleted soil nutrients from crop harvesting?

A

1) Shifting agriculture - mote to another location and natural processes replenish soil
2) Organic fertilizers - humus
3) Chemical fertilizers

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19
Q

What are the Differences between chemical and organic fertilizeres?

A

Organic - organisms break down into simple molecules for plants to use
Chemical - supply minerals directly in forms that are easily used

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20
Q

What is the disadvantage of chemical fertilizers?

A

Require alot of energy to produce

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21
Q

Describe the formation of arbuscular mycorrhizae

A

Roots produce strigolactones that stimulate growth of fungal hyphae towards root

  • Fungi signal plant to form prepenetration apparatus (PPA) which guides the growth of fungal hyphae to root cortex
  • Arbuscules from inside root cortical cell where nutrient exchange occurs
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22
Q

Describe the formation of nitrogen fixing nodules

A

Legume plant roots release flavenoids that attract rhizobia bacteria and stimulate Nod factor prouction - causes root cortex cells to divide and form nodule
- Bacteria enter nodule cell and differentiate into bacteroids that can fix nitrogen

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23
Q

How abundant are mycorrhizae?

A

occur in 90% of terrestral plants

24
Q

What is the primary nutrient obtained by mycrohhizae?

A

Phosphorus

also gets carbohydrates from plant’s photosynthesis

25
Q

What are the 2 types of bacteria that can fix N for plant use?

A

Free-living (nonsymbiotic) organisms in soil and water

Symbiotic (e.g. rhizoba)

26
Q

How does N fixation occur?

A

Nitrogenase used
Reduction reaction
- Reducing agent adds 3 H to N2 to make NH3

27
Q

What is the role of leghemoglobin?

A

O2 carrier that regulates O2 level so that it does not get too high and inhibit nitrogenase action

28
Q

What are the 2 types of parasitic plants?

A

Hemiparasites

Holoparasites

29
Q

What are hemiparasites?

A

Can photoxynthesize, but get water and mineral nutrients from living plans (e.g. mistletoe)

30
Q

What are holoparasitic plants?

A

completely parasitic, no photosynthesis

e.g. witchweed

31
Q

What is water potential?

A

tendency of a solution to take up water from pure water across a solution

Water moves towards lower water potential

32
Q

What are the two components of water potential?

A

Solute potential - Solutes reduce concentration of water. More solutes = lower water potential
Pressure potential - Turgor pressure decreases tendency to take up water

33
Q

What is the equation for water potential?

A

Water potential = solute potential + pressure potential

34
Q

What is the solute potential of pure water?

A

Zero - no solutes

35
Q

When is pressure potential zero?

A

When water pressure is equal to atmospheric pressure

  • Less than atmospheric pressure is negative, more is positive
36
Q

When will water cease to enter plant cells by osmosis

A

When pressure potential balances solute potential

37
Q

What happens if pressure potential decreases?

A

Plant wilts because physical structure is maintained by turgor pressure

38
Q

What is the role of the proton pump?

A

uses ATP to move protons out of the cell against proton concentration gradient

  • Creates electrical gradient for cations to enter
  • Anions then enter cell with H+ that diffuses back in with the concetration gradient
39
Q

What are the two pathways that allow water and ions to move through roots to xylem

A

Apoplast (Fast)

Symplast (Slow)

40
Q

What is the apoplast pathway?

A

water and ions move through Cell walls and intracellular spaces by continuous meshwork, water and slutes never cross a membrane

41
Q

What is the symplast pathway?

A

Continuous cytoplasm of living cells connected by plasmodesmata
Plasma membranes control movement

42
Q

Where do ions travel in the apoplast pathway

A

Travel as far as the endodermis
Casparian strips force water and ions to enter cytoplasm of endodermal cells using suberin force where they stay until they reach parenchyma cells in pericycle or xylem

Minerals and ions then actively transported into stele - creating negative water potential -> osmosis

43
Q

How does xylem move water to the top of trees?

A

Transpiration-cohesion-tension theory

Transpiration - evaporation of water from cells in leaves
Cohesion - water in xylem sap cohesive due to H bonds
Tension - on xylem sap resulting from transpiration prompts upwards movement

44
Q

What is the role of transpiration

A

Cool leaves
Create negative water potential to draw water from xylem of the nearest vein into the apoplast surroundign mesophyll cells

45
Q

What are guard cells/

A

cells that respond to light and control the opening and closing of stomata - thus controlling water loss and gas exchange

46
Q

Describe the mechanism of stomata opening

A

Guard cell pigments absorb light - actiates proton pump out of cell -> electrochemical gradient that drives K+ and Cl- into cell -> water enters by osmosis -> increase turgor pressur and cell stretches and opens stomata

47
Q

How do stomata respond to water conditions?

A

If mesophyll becomes dehydrated the cells release the hormone abscisic acid -> causes stomata to close

48
Q

Define translocation

A

movement of solutes in the phloem from sources to sinks

49
Q

Define source and sink

A

Source - organ that produces and stores carbohydrates (leaves, storage roots)
Sink - organs that consume carbohydrates (roots, flowers, fruit and developing leaves)

50
Q

How can phloem contents be analyzed?

A

Using aphids

- pressure potential in sieve tube is higher than outside, so phloem is forced out through aphid’s digestive tract

51
Q

What observations have been made from aphid experiments?

A

Most of phloem is sucrose
Flow rate can be very high
Different sieve tubes conduct in different directions
Movement of phloem sap requires living cells

52
Q

Describe the pressure flow model

A

Model of Translocation
At source: sucrose enters companion cells -> flows through plasmodesmata to sieve tube elements -> water enters by osmosis -
> increase in turgor pressure which pushes sieve tube contents to sink

At Sieve: sucrose moves out of phloem and water moves back into xylem

53
Q

Define loading

A

transport of solutes from sources into sieve tubes

54
Q

Define unloading

A

transport of solutes from sieve tubes into sinks

55
Q

How do solutes move from mesophyll to phloem?

A

by apoplastic or symplastic pathways

56
Q

How do solute travel through symplastic pathways to phloem?

A

solute remains in symplast at all times, no membrane crossed

57
Q

How do solutes travel through apoplastic pathways to phloem?

A

Molecules are actively transported into phloem - meaning solutes can be regulated

Biological Systems (20 decks)

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