Transport In Plants

Water Potential

• The physical property predicting the direction in which water will flow – ____________________ – Pressure

• water moves from high water potential to low water potential

Solute Concentration

Water Potential (a)

•  Left Side – Pure Water = 0

Water Potential •  Right Side

– Negative Water Potential •  0 pressure •  - solute (has solutes)

•  Water moves to the right

Water Potential (b) •  Left Side

– Pure Water = 0 Water Potential

•  Right Side – 0 Water Potential

• + pressure equal to solute conc.

•  - solute (has solutes)

•  Water is at equilibrium

Water Potential (c) •  Left Side

– Pure Water = 0 Water Potential

•  Right Side – Positive Water

Potential • + pressure more

than solute conc. •  - solute (has

solutes)

•  Water moves to the left

Water Potential (d)

•  Left Side – Pure Water and

Negative Tension •  Right Side

– Negative Water Potential •  0 pressure •  - solute (has

solutes)

•  Water moves to the left

Transport of Xylem Sap

•  Pushing Xylem – Root Pressure

•  caused by active pumping of minerals into xylem

•  _____________: accumulation of water

Guttation

Transport of Xylem Sap

• ______________ – Transpiration

• evaporative loss of H2O from a plant through the stomata

Pulling Xylem

Transport of Xylem Sap

The Control of Transpiration

• ______________ – turgid - open – flaccid - closed

• Potassium Ions – active transport of H+ out of

cell causes K+ to move in

Guard Cells

Stomata

• Open during the day / Closed at night – first light (blue light receptor) – depletion of Carbon Dioxide – internal clock (circadian rhythms)

Reducing Transpiration

•  Small, thick leaves

•  Thick cuticle •  Stomata are

recessed •  Lose their leaves •  C4 or CAM plants

Translocation of Phloem Sap

Translocation of Phloem

• Phloem Sap – 30% sucrose, minerals, amino acids,

hormones – Transported in sieve-tube members

• ____________– leaves, tuber or bulbs • Sugar sink – growing roots, shoots,

fruits

Sugar source

Pressure Flow and

Translocation A)  Pressure is high

B)  Pressure is low

C)  Xylem recycles water

D)  Allows Phloem sap to flow from source to sink

A

B

C

Plant Nutrition

Uptake of Nutrients

_______________ cultures used to determine which chemical elements are essential.

17 essential elements needed by all plants

Hydroponic

Soil • Develops from weathered

rocks – Anchors plants – Provides water – Provides dissolved minerals

Soil Texture • Pertains to sizes of soil

particles – includes the following:

• sands (0.02 - 2 mm) • silt (0.002 - 0.02 mm) • clay (less than 0.002 mm)

Soil Composition • Made up of sand, silt,

clay, rocks, humus, microorganisms (bacteria, fungi, algae, protists, insects, worms, roots)

• Soil contains a mixture of different sized particles – _______ – roughly equal

amounts of sand, silt, and clay – most fertile

Loams

The availability of soil water and minerals

The availability of soil water and minerals

•  Plant takes up water not tied to hydrophilic soil particles

•  Positively charged ions attach to soil •  H+ help displace minerals attached to

soil •  Roots add H+ to the soil directly and

through the release of ____

•  (reacts with water to form carbonic acid)

CO2

The availability of soil water and minerals

Soil Conservation • Fertilizers

– (Nitrogen, Phosphorus, Potassium)

The Nation that Destroys Its Soil Destroys Itself – Franklin D. Roosevelt 1937

Loss of Topsoil • 1930’s “_____________” • Due to inappropriate farming in

late 1800’s and early 1900’s • Wheat and cattle farming • Droughts • Steinbeck’s Grapes of Wrath • 30% of world’s farmlands have

reduced production due to poor soil conditions.

Black Blizzards

Nitrogen Fixation

Nitrogen Fixation • Plants absorb nitrogen in the

form of nitrate • _____________ and

ammonifying bacteria produce ammonium

• Ammonium is shifted to nitrate by nitrifying bacteria

• Plants shift nitrate back to ammonium for use

Nitrogen-fixing

Nitrogen Fixation

Unusual Nutritional Adaptations in Plants - Epiphytes

Unusual Nutritional Adaptations in Plants - Mistletoe

Unusual Nutritional Adaptations in Plants – Venus Fly Traps

Unusual Nutritional Adaptations in Plants – Pitcher Plants

Unusual Nutritional Adaptations in Plants - Sundews

Control Systems in Plants

Plant Hormones

• Coordinates growth • Coordinates development • Coordinates responses to

environmental stimuli

Plant Hormones

• Auxin (IAA) • Cytokinins • Gibberllins • Abscisic Acid • Ethylene • Oligogaccharins • Brassinosteroids

Auxins •  Stimulates stem elongation •  Stimulates root growth •  Stimulates differentiation and

branching •  Stimulates development of

fruit •  Stimulates apical dominance •  Stimulates phototropism and

gravitropism

Auxin Control •  Auxin stimulates

growth •  Auxin block on

right causes cells to elongate and the plant bends left

•  Auxin block on left causes cells to elongate the the plant bends right

___________ Hypothesis •  Proton pump stimulated by auxin lower pH of wall •  H+ activates Enzyme •  Enzyme breaks hydrogen bonds in cellulose •  Wall takes up water and elongates

Acid Growth

Auxin Others • Promotes secondary

growth by stimulating vascular cambium and secondary xylem

• Promotes adventitious root at the base of a cut stem

• Promotes fruit growth without pollination (seedless tomatoes)

Cytokinins • Stimulates root growth • Stimulates cell division and

differentiation (with auxins) – more cytokinin - shoot buds

develop – more auxin - roots develop

• Stimulates germination • Delays Senescence

Gibberellins • Promotes seed and bud

germination • Promotes stem elongation • Promotes leaf growth • Stimulates flowering and

fruits – (with auxin)

Abscisic Acid • Slows growth • Closes stomata under water

stress • Permits seed dormancy

Ethylene • Promotes fruit ripening • Controls Abscission (causes

leaf loss)

Plant Movements

• Phototropism • Gravitropism • ____________ Thigmotrophism

Plant Movement • Rapid Leaf

Movement (39.27) – drop in turgor

pressure within pulvini

– sent by action potentials

Plant Movement • Sleep Movements (39.21)

– cells on opposite sides of pulvinus control the movement

Daily and Seasonal Responses

• Circadian Rhythm • Photoperiodism

– controls flowering (short-day vs. long-day)

– critical night length

Photoperiodic Control

Flowering Hormones •  Experiment

indicates the presence of some type of flowering hormone

Phytochromes •  Function as photoreceptors / red (660nm) to

far red (730nm) •  Activates kinases (regulatory proteins)

Red vs. Far Red Response

Plant Responses to Environmental Stress

• Water Deficit • Oxygen Deprivation • Salt Stress • Heat Stress • Cold Stress • Herbivores

Responses to Herbivores •  Produce

_________ (an amino acid similar to arginine)

•  Recruitment of predatory animals

Canavanine

Why plants are important? • Food!

• Humans have domesticated plants for 13,000 years.

• ____ of all the calories consumed by humans come from six crops: Wheat, Rice, Maize, Potatoes, Cassava, and Sweet Potatoes.

• Also, we use plants to feed cattle, 5-7kg to produce 1 kg of beef.

80%

Pyramid of Net Productivity

Plants remove CO2

• _____ of all US Prescription Drugs contain one or more active ingredients from plants.

• ____ earth’s species will become extinct within the next 100 years (larger than the Permian or Cretaceous)

• Only 5,000 of 290,000 species have been studied.

• 3-4 species per hour,

27,000 per year!

25%

50%

Cinchona tree

• Bark contains __________ • Grows in the

Andes in peru • Used since the

early 1600’s to treat malaria

quinine

Aspirin •  Acetylsalicylic acid or ASA •  Dates back to 3000 B.C. •  Greek Physician Hippocrates

prescribed it. •  From _____________ and

other Salicylate-rich plants (leaves and bark)

•  Scientists at Bayer began investigating acetylsalicylic acid as a less-irritating replacement for standard common salicylate medicines. By 1899, Bayer named it this Aspirin

Willow trees