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BIO 1030 > Topic 11 - Plant Nutrition > Flashcards

Topic 11 - Plant Nutrition Flashcards

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1
Q

Cellular Currency

A
  • Plants harvest solar energy
    • Photosynthesis
    • Produces sugars
      • Proteins, nucleic acids, lipids?
  • Plants cells still need
    • ATP
      • Cellular respiration
    • Inorganic minerals
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2
Q

Leaf Function

A
  • Requirements for photosynthesis
    • CO2
    • Water
  • Products of photosynthesis
    • Glucose
    • O2
  • Cellular respiration
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3
Q

The Necessities

A
  • Each cell needs:
    • A supply of each reactant
      • CO2
      • H2O
      • O2
      • Glucose
      • Minerals
    • A waste removal system
      • O2
      • Nitrogenous wastes?
  • A mechanism to connect these
    • The vascular systems
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4
Q

Short Distance Transport

A
  • Transport continuums
    • Symplast route
      • Through plasmodesmata
        not cell wall
    • Apoplast route
      • Through cell wall
  • Combination
    • Transmembrane route
      • From cell to cell
  • Where is the control of transport?
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5
Q

Solute Transport Across Membranes (Primary Active Transport)

A
  • Proton pumps
    • Membrane potential
    • pH gradients
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6
Q

Solute Transport Across Membranes (Secondary Active Transport)

A
  • Electrochemical gradient
  • Cotransport
    • Neutral solutes
    • Charged solutes
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7
Q

Solute Transport Across Membranes (Gated potassium channels)

A

Numerous functions

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8
Q

Water movement in the plant

A
  • To survive, plants must balance water uptake and loss
  • Osmosis is the diffusion of water into or out of a cell that is affected by
    solute concentration and pressure
  • Water potential is a measurement that combines the effects of solute
    concentration and pressure
    • Water potential determines the direction of movement of water
    • Potential refers to water’s capacity to perform work
  • If a flaccid cell is placed in a solution with a lower solute concentration,
    the cell will gain water and become turgid
  • Turgor loss in plants causes wilting, which can be reversed when the
    plant is watered
  • Water potential affects uptake and loss of water by plant cells
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9
Q

Water Potential – kinetic/potential energy (gradient)

A
  • Driving force of osmosis
  • Water potential (Ψ; MPa)
    • Tendency for osmosis
      • Pure water, Ψ = 0
      • As [solute] increases, Ψ decreases
    • Direction of osmosis
      • High to low Ψ
    • Solute potential (Ψ s) – always negative
      • Increased concentration
    • Pressure potential (Ψ p)
      • Physical pressure
      • Gravity
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10
Q

Mechanisms of Stomatal Opening and Closing

A
  • Changes in turgor pressure
    open and close stomata
    • When turgid, guard cells
      bow outward and the
      pore between them
      opens
    • When flaccid, guard cells
      become less bowed and
      the pore closes
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11
Q

Long-Distance Transport: The Role of Bulk Flow

A
  • Efficient long-distance transport of fluid requires bulk flow, movement of a fluid driven by pressure
  • Most water and mineral absorption occurs near root tips, where root hairs are located and epidermis is permeable to water
  • Water and solutes move together through tracheids and vessel elements of xylem, and sieve-tube elements of phloem
  • Efficient movement is possible because mature tracheids and vessel elements have no cytoplasm cytoplasm, and sieve-tube
    elements have few organelles
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12
Q

Water Transport in the Root

A
  • Apoplastic route
    • Hydrophilic cell walls
  • Symplastic route
    • Root hair membrane
      • Active mineral absorption
      • Osmosis
  • Control
    • Into the vascular cylinder
  • Endodermis
    • Caspian strips
    • Forces everything into the symplastic route
  • Xylem = apoplast
  • Water loss via transmembrane
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13
Q

Root Pressure

A
  • Nocturnal flow of xylem sap
    • Stomata are ______
    • Transpiration has ______
  • Endodermal active transport
    • Into the vascular cylinder
  • Water/minerals pushed
    • Positive pressure
  • Effective only in smaller herbaceous plants
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14
Q

Transport Within the Plant

A
  • The Vascular System
  • Xylem
    • Water & minerals
      • Xylem sap
    • Root to shoot
  • Phloem
    • Photosynthates
      • Phloem sap
    • Shoot to root
    • Root to shoot
  • Bulk flow
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15
Q

Transport of Water and Minerals into the Xylem

A
  • The endodermis is the innermost layer of cells in the root cortex
  • It surrounds the vascular cylinder, and is the last checkpoint for selective passage of minerals
    from the cortex into the vascular tissue
  • Water can cross cortex via the symplast or apoplast
  • The waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder
  • Water and minerals in the
    apoplast must cross the plasma membrane of an endodermal cell to enter the vascular cylinder
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16
Q

Transport of Water and Minerals into the Xylem (Part 2)

A
  • The endodermis regulates and transports needed minerals from the soil to the xylem
  • Water and minerals move from protoplasts of endodermal cells into their cell walls
  • Diffusion and active transport are involved in this movement from symplast to apoplast
  • Water and minerals now enter tracheids and vessel elements
17
Q

Xylem Sap Transport

A
  • Cohesion-Tension mechanism
    • Transpiration
      • Loss of water vapour
    • Cohesion
      • Hydrogen bonds between water molecules
    • Adhesion
      • Hydrogen bonds between water and cell wall
  • Negative pressure
  • Energy cost? Or… is ATP used?
18
Q

Xylem Sap Transport (Part 2)

A
  • Water potentials
    • Air y = –100 MPa
    • Air space y = –7.0 MPa
    • Leaf cell wall y = –1.0 MPa
    • Trunk xylem y = –0.8 MPa
    • Root xylem y = –0.6 MPa
    • Soil y = –0.3 MPa
19
Q

Control of Stomata Opening – Regulation of Water
movement

A
  • Guard cells
    • Microfibril orientation
    • Inner cell wall
    • Attachement to each other
      Opening
  • Proton pump
    • Electrochemical gradient
  • Potassium influx
    • Other ions (malate and chloride)
    • Cytoplasm/vacuoles → hypertonic
    • Water potential decreases
  • Aquaporins
20
Q

Sugars are transported from sources to sinks via the
phloem

A
  • The products of photosynthesis are transported through phloem by the process of translocation
  • Phloem sap is an aqueous solution that is high in sucrose
  • It travels from a sugar source to sugar sink
    • A sugar source
      • Where sugars are made – in the chloroplasts of leaves
      • Where sugars have been stored
      • WHERE THERE IS INITIALLY LOTS OF SUGAR
    • A sugar sink
      • Where sugars end up
      • WHERE THERE IS INITIALLY NOT A LOT OF SUGAR
21
Q

Phloem Sap Transport

A
  • Pressure-Flow Hypothesis
    • Source to sink
  • At source
    • Site of sugar production/liberation
    • Sugar → sieve tube
      • Active
    • Water potential decreases
      • Hydrostatic pressure
    • Bulk flow
  • At sink
    • Utilization site
    • Sugars transported out
      • Opposite effect
22
Q

Movement from Sugar Sources to Sugar Sinks

A
  • A storage organ can be both a sugar sink in summer and a sugar source in winter
  • Sugar must be loaded into
    sieve-tube elements before
    being exported to sinks
  • Depending on the species,
    sugar may move by symplastic or both symplastic and apoplastic pathways
23
Q

Adaptations for Water Conservation

A
  • Lose the leaves
  • Recess the Stomata
  • Reflect the sun
24
Q

Absorption

A
  • Young growing roots
    • Primary tissue region
  • Root hair zone
    • Epidermal trichomes
    • High turnover
  • Nutrient absorption
    • Cations
    • Anions
    • Water
    • Oxygen
25
Q

Information about Absorption

A
  • Soil, water, and air all contribute to plant growth
  • 80–90% of a plant’s fresh mass is water
  • 4% of a plant’s dry mass is inorganic substances from soil
  • 96% of plant’s dry mass is from CO2 assimilated into carbohydrates during photosynthesis
  • More than 50 chemical elements have been identified among the
    inorganic substances in plants
  • Not all of these are essential to plants
  • Only 17 essential elements, chemical elements required for a plant to complete its life cycle and reproduce
26
Q

Basic Plant Nutrition

A
  • Autotrophy
    • Carbon compounds
      • Generation of ATP
      • Generation of macromolecules
  • Essential minerals
    • Macro
      • Carbon, Oxygen, Nitrogen, Hydrogen, phosphorus, sulphur, potassium, calcium, and magnesium
    • Micro
      • Copper, nickel
27
Q

Source of Minerals

A
  • Good soil is a rich source
  • Soil particles are negatively charged
    • Cation retention
    • Anion leaching
      • PO4–
      • Nitrates
  • Ion absorption
    • Soil acidification
    • Cation absorption
28
Q

Mineral Deficiencies

A
  • Symptoms depend on nutrient’s function
  • Deficiency of a mobile nutrient usually affects older
    organs more than young ones
    • N, P, K, Mg, Cl, Zn, Mo
  • Deficiency of a less mobile nutrient usually affects
    younger organs more than older ones
    • Ca, S, Fe, B, Cu
  • Yellow midribs
    • Chlorophyll deficiency
    • Chlorosis
  • Yellow margins
    • Necrotic tips
  • Reddish margins
    • Anthocyanins
29
Q

Adaptations for Nutrient Acquisition

A
  • Epiphytes
    • Absorb water through leaves
  • Parasites
    • Tap host tissue to steal sap
  • Carnivores
    • Nitrogen-poor soils

BIO 1030 (12 decks)

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