Transport In Plants Water Potential • The physical property predicting the direction in which water will flow Solute Concentration – ____________________ – 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 Guttation • _____________: accumulation of water Transport of Xylem Sap Xylem • Pulling ______________ – Transpiration • evaporative loss of H2O from a plant through the stomata Transport of Xylem Sap The Control of Transpiration Guard Cells • ______________ – 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 Sugar source leaves, tuber or bulbs • ____________– • Sugar sink – growing roots, shoots, fruits Pressure Flow and Translocation A A) Pressure is high B) Pressure is low C) Xylem recycles water D) Allows Phloem sap to flow from source to sink C B Plant Nutrition Uptake of Nutrients Hydroponic _______________ 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 Loams – 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 CO2 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 Black Blizzards • 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 Nitrogen-fixing • _____________ 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 • • • • Acid Growth ___________ 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 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 Canavanine _________ (an amino acid similar to arginine) • Recruitment of predatory animals Why plants are important? • Food! • Humans have domesticated plants for 13,000 years. 80% 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 25% of all US •_____ Prescription Drugs contain one or more active ingredients from plants. 50% 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 quinine __________ • 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. trees • From Willow _____________ 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