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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
What are the 2 types of bacteria that can fix N for plant use?
Free-living (nonsymbiotic) organisms in soil and water | Symbiotic (e.g. rhizoba)
26
How does N fixation occur?
Nitrogenase used Reduction reaction - Reducing agent adds 3 H to N2 to make NH3
27
What is the role of leghemoglobin?
O2 carrier that regulates O2 level so that it does not get too high and inhibit nitrogenase action
28
What are the 2 types of parasitic plants?
Hemiparasites | Holoparasites
29
What are hemiparasites?
Can photoxynthesize, but get water and mineral nutrients from living plans (e.g. mistletoe)
30
What are holoparasitic plants?
completely parasitic, no photosynthesis e.g. witchweed
31
What is water potential?
tendency of a solution to take up water from pure water across a solution Water moves towards lower water potential
32
What are the two components of water potential?
Solute potential - Solutes reduce concentration of water. More solutes = lower water potential Pressure potential - Turgor pressure decreases tendency to take up water
33
What is the equation for water potential?
Water potential = solute potential + pressure potential
34
What is the solute potential of pure water?
Zero - no solutes
35
When is pressure potential zero?
When water pressure is equal to atmospheric pressure - Less than atmospheric pressure is negative, more is positive
36
When will water cease to enter plant cells by osmosis
When pressure potential balances solute potential
37
What happens if pressure potential decreases?
Plant wilts because physical structure is maintained by turgor pressure
38
What is the role of the proton pump?
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
What are the two pathways that allow water and ions to move through roots to xylem
Apoplast (Fast) | Symplast (Slow)
40
What is the apoplast pathway?
water and ions move through Cell walls and intracellular spaces by continuous meshwork, water and slutes never cross a membrane
41
What is the symplast pathway?
Continuous cytoplasm of living cells connected by plasmodesmata Plasma membranes control movement
42
Where do ions travel in the apoplast pathway
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
How does xylem move water to the top of trees?
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
What is the role of transpiration
Cool leaves Create negative water potential to draw water from xylem of the nearest vein into the apoplast surroundign mesophyll cells
45
What are guard cells/
cells that respond to light and control the opening and closing of stomata - thus controlling water loss and gas exchange
46
Describe the mechanism of stomata opening
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
How do stomata respond to water conditions?
If mesophyll becomes dehydrated the cells release the hormone abscisic acid -> causes stomata to close
48
Define translocation
movement of solutes in the phloem from sources to sinks
49
Define source and sink
Source - organ that produces and stores carbohydrates (leaves, storage roots) Sink - organs that consume carbohydrates (roots, flowers, fruit and developing leaves)
50
How can phloem contents be analyzed?
Using aphids | - pressure potential in sieve tube is higher than outside, so phloem is forced out through aphid's digestive tract
51
What observations have been made from aphid experiments?
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
Describe the pressure flow model
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
Define loading
transport of solutes from sources into sieve tubes
54
Define unloading
transport of solutes from sieve tubes into sinks
55
How do solutes move from mesophyll to phloem?
by apoplastic or symplastic pathways
56
How do solute travel through symplastic pathways to phloem?
solute remains in symplast at all times, no membrane crossed
57
How do solutes travel through apoplastic pathways to phloem?
Molecules are actively transported into phloem - meaning solutes can be regulated

Biological Systems (20 decks)

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