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

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

Transport of Xylem Sap

• ______________ – Transpiration

• evaporative loss of H2O from a plant through the stomata

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

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

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

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

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)

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.

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 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

•  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 • ____________

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

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.

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!

Cinchona tree

• Bark contains __________ • Grows in the

Andes in peru • Used since the

early 1600’s to treat malaria

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