Chapters 32: Plant Nutrition and Transport

Chapters 32: Plant Nutrition and Transport
I. Nutrients from soil and air A. Plants need to make everything (organic) from scratch (inorganic) B. 95% of a plant’s dry weight is organic (built mainly from CO2) - plant’s are predominantly built from the air C. Sugar - carbon and oxygen from CO2 - hydrogen from water - Two fates - cellular respiration or biosynthesis (Some) Fig. 32.1A

I. Nutrients from soil and air D. Nitrogen, phosphorus, Mg++, etc… from soil i. nitrogen - used in combination with glucose to make hormones, ATP, coenzymes (chlorophyll), nucleotides, amino acids, etc… ii. Magnesium (Mg++) - part of chlorophyll iii. phosphorus - ATP, nucleic acids, phospholipids, etc… (Some) Fig. 32.1A

II. PM of roots control solute uptake A. Root hairs provide high surface area B. Must be dissolved in solution to enter C. Epidermis --> cortex --> endodermis --> xylem - Intracellular route vs. Extracellular route - Casparian strip - waxy belt through walls of endoderm - stops solution from entering xylem via cell walls D. Endodermal membrane is highly selective (gatekeeper -> can’t get into xylem without being aloud through) Fig. 32.2

III. Getting xylem sap up to the shoot system A. Water/minerals (xylem sap) must somehow get up xylem vessel B. How does it do this against gravity??? i. Root pressure - minor push from roots actively pumping ions into xylem (water follows by osmosis) - works over a few meters - not enough for taller trees, and many trees (i.e. giant sequoia) produce NO root pressure

III. Getting xylem sap up to the shoot system A. Water/minerals (xylem sap) must somehow get up xylem vessel B. How does it do this against gravity??? ii. Transpiration - loss of water from leaves (stomata) pull xylem sap upward - Two properties of water that make this possible: a. cohesion (water hydrogen-bonding to other waters): makes the xylem sap like a continuous string b. Adhesion (water sticking to other molecules): sticks to cellulose walls of xylem Fig. 32.3

III. Getting xylem sap up to the shoot system A. Water/minerals (xylem sap) must somehow get up xylem vessel B. How does it do this against gravity??? ii. Transpiration - water molecule at end of chain in leaf is heated by solar energy - This molecule diffuses out of the stomata and evaporates - As it does this, it pulls on the neighboring waters (cohesion), the neighbors pull on their neighbors and so on all the way to the roots (Without the suns KE, the water in the leaf would remain stuck to its neighbors - no pulling force, no transpiration) Fig. 32.3

III. Getting xylem sap up to the shoot system A. Water/minerals (xylem sap) must somehow get up xylem vessel B. How does it do this against gravity??? ii. Transpiration - What about adhesion? - adhesion counters downward pull of gravity by “grabbing” walls of xylem - holds water in xylem when transpiration is not occurring (at night) Fig. 32.3

IV. Guard cells control transpiration A. Transpiration works for and against plants i. Water loss - plant needs to lose water in order to get minerals - average maple tree loses 200L per hour during summer - not a problem only if there is enough water in soil A wilting plant caused by water loss under dry conditions

IV. Guard cells control transpiration B Stomata i. Each has a pair of guard cells - change shape to control opening - open during day when photosynthesis rates are high (need CO2) - closed at night to save water Guard cells of stomata

IV. Guard cells control transpiration B Stomata ii. How do guard cells change shape to regulate open/closed state? 1. opening stomata - guard cells ACTIVELY take up K+ - water follows by osmosis - causes swelling and high turgor pressure (pressure of cells contents against cell wall) - causes cells to bend away from each other due to arrangement of cellulose fibers: Fig. 32.4

IV. Guard cells control transpiration B Stomata ii. How do guard cells change shape to regulate open/closed state? 1. opening stomata - What stimulates guard cells to take up K+? a. sunlight, low CO2, circadian rhythm (biological clock) Fig. 32.4

IV. Guard cells control transpiration B Stomata ii. How do guard cells change shape to regulate open/closed state? 2. Closed stomata - actively pump out K+ - water follows passively (osmosis) - cells sag and stomata close: Fig. 32.4

IV. Guard cells control transpiration B Stomata ii. How do guard cells change shape to regulate open/closed state? 2. Closed stomata - stimulation to pump out K+ a. Too much water loss during day - result in decline of CO2 uptake (sugar production declines), which is why crop yields decline in droughts 3. Opening and closing balanced b/w need to save water and need to make sugar Fig. 32.4

V. Phloem transport (sugar/organic compounds) A. Phloem sap i. Sugary solution moving through seive-tube members ii. Main solute = sucrose iii. Hormones, inorganic ions, amino acids iv. Moves in ALL directions v. All phloems have a source and sink - sugar source: where sugar is made (in leaves by photosynthesis or generated by breaking down from starch) - sugar sink: where sugar is consumed or stored (growing roots, shoot tips, fruits, non-photosynthetic stems, etc…) -storage sites can be both sources and sinks depending on environment (tubers, taproots, bulbs, etc…) a. sinks during summer (maximum photosynthetic activity) b. source during spring (growth)

V. Phloem transport (sugar/organic compounds) A. Phloem sap vi. How does phloem sap move from source to sink? - pressure-flow mechanism a. Sugar enters phloem at source by active transport b. Water follows by osmosis - makes water pressure high at source c. Sugar actively transported out of phloem at sink d. Water follows by osmosis - water pressure low at sink e. Hydrostatic pressure gradient causes water to flow from source to sink NO MATTER WHERE THEY ARE LOCATED (sugar goes along for the ride) Fig. 32.5

V. Phloem transport (sugar/organic compounds) A. Phloem sap vii. How can one test the pressure-flow mechanism? i. Using Aphids a. Aphids feed by inserting their stylus into phloem of plant b. Releases honeydew (phloem sap minus nutrients absorbed by aphid) from anus c. Sever aphid from stylet d. Closer stylet to source, quicker it drips: Fig. 32.5

VI. The essential nutrient of plants A. Hydroponics i. Can be used to determine essential nutrients ii. Grow plants in a solution (NO soil) of minerals with known concentration iii. Air bubbled into solution so roots get enough oxygen for cellular respiration iv. Remove minerals(s) or change concentration of mineral(s) and compare to control plant Fig. 32.6

VII. Essential nutrients of plants A. macronutrients i. 9 out of 17 ii. Need in large (macro) amounts iii. C, N, O, H, S, P (The big six of course) iv. Ca, K, Mg - Calcium (Ca++) - formation of cell walls, combines with proteins to form “glue” of middle lamina, regulate selective permeability - Potassium (K+) - cofactor (non-protein chemical compound bound to an enzyme and required for catalysis) of many enzymes, opening and closing stomata (main solute for osmotic regulation) - Magnesium (Mg++) - component of chlorophyll, cofactor of many enzymes

VII. Essential nutrients of plants B. micronutrients i. The other 8 ii. Need in small (micro) amounts iii. Fe, Cl, Cu, Mn, Zn, Mo, B, Ni - cofactors of enzymes a. ex. Fe (iron) is a cofactor of many ETC proteins as it accepts and donates electrons - Recycled over and over again (need very little) a. ex. There is one molybdenum (Mo) for every 16,000,000 hydrogens

VIII. Quality of nutrients in soil determines quality of your own nutrition Corn growth in nitrogen rich (left) vs. nitrogen poor (right) soil Fig. 32.6

IX. Root hairs take up cations using cation exchange A. Cation i. Positively charged ion (K+, Mg++, Ca++) B. Clay tends to me negatively charges C. Cations stick to clay - keeps them from draining away D. Roots secrete H+ (acid) in exchange for another cation - this is why acid rain is not good for soil, it strips away the cation nutrients E. Anions are easier for roots to absorb (NO3- (nitrate) vs. NH4+ (ammonium) - anions drain out of soil easily - unfertile soil, eutrophication Fig. 32.8

X. Parasitic plants A. Dodder Dodder i. yellow-orange threads ii. No photosynthesis iii. Gets organic nutrients from other plants iv. Uses specialized root to tap into vascular tissue B. mistletoe i. CAN do photosynthesis ii. Supplements diet by siphoning sap from vascular tissue of host Mistletoe Both dodder and mistletoe may kill host by blocking too much light or taking too much food Fig

Sundew video XI. Carnivorous plants A. Sundew and venus flytrap i. Get nitrogen by digesting flies ii. Sundew uses sticky sugar substance to attract and trap insects iii. Venus flytrap has touch sensory hairs that close when touched twice in a row iv. Both secrete digestive enzymes onto their prey Fig

XII. Most plants depend on bacteria to supply nitrogen A. Recall the nitrogen cycle i. Plants can’t use N2 (N N) ii. Nitrogen cycle: Fig iii. Ammonium is a cation (gets stuck to clay and therefore hard to absorb) iv. Plants prefer Nitrates (anion) Fig

XII. Most plants depend on bacteria to supply nitrogen A. Recall the nitrogen cycle v. Plants will convert nitrates back to ammonium for amino acid biosynthesis Fig

XIII. Legumes house nitrogen-fixing bacteria A. Legumes (plants that produce pods) i. Have nodules on roots filled with Rhizobium ii. Rhizobium - genus of most nitrogen-fixing bacteria in roots of legumes - convert N2 directly to ammonium, which can be used by plant directly (it’s already inside) - excess leaks into soil making it more fertile a. This is why farmers tend to rotate their crops: one year legume, one year non-legume iii. Plants give organic molecules to Rhizobium (mutualistic) Fig

XIV. Genetic engineering plants A. Gene gun i. Used to “shoot” foreign genes into plant cell (or animal cell) ii. DNA integrates into genome iii. Cells now make new protein Fig

XIV. Genetic engineering plants A. Gene gun iv. Many new organisms have been made this way: - virus resistant cotton plants - potato plants that produce their own insecticide - slow spoil tomatoes - Can we get plants to synthesize medicine? Make grain with all eight essential amino acids? Put genes for nitrogen fixation into non-leguminous plants? Insect resistant corn

Chapters 33: Control systems in plants
AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones A. Phototropism (video) i. Growth of a shoot towards light ii. mechanism - cell on dark side elongate faster iii. What causes different growth rate? Fig. 33.1

AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones B. Experiment done by Darwin and his son Francis i. Observation - grass seedlings grow toward light only if shoot tips were present: Fig. 33.1

AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones B. Experiment done by Darwin and his son Francis i. Observation - grass seedlings grow toward light only if shoot tips were present: ii. Conclusion - tip responsible for sensing light - chemical signal must be sent from tip Fig. 33.1

AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones C. Follow-up experiments done by Peter Boysen-Jensen i. Experiment: put permeable gelatin block b/w tip and bottom of shoot or impermeable mica ii. Result - phototropism occurred with permeable gelatin iii. Conclusion - chemical signal diffusing through gelatin from tip Fig. 33.1

AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones D. Frits Went extracted the chemical messenger (1926) i. Experiment: - put tip on agar (permeable) block to get chemical signal (hormone) into block - place block on different parts of cut shoot: Fig. 33.1

AIM: How are hormones used by plants in regulation? I. Experiments on phototropism led to the discover of plant hormones D. Frits Went extracted the chemical messenger (1926) ii. Conclusion: - blade bends away from side with chemical - chemical stimulates cell to elongate - called the chemical “auxin” (Greek, auxein, to increase) Aside: Not all plants work this way Fig. 33.1

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development A. Affect growth/development by affecting division, elongation and differentiation B. Trigger signal transduction pathways (just like in animals) i. Turn genes ON/OFF ii. Inhibit or activate enzymes iii. Changes in membrane properties C. Produced in growing parts of plants (apical meristem; young, growing leaves and developing seeds) Pg. 662

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxins - class of molecules that affects plant growth patterns a. IAA = indolacetic acid - the major auxin of plants b. Phototropism IAA - Side receiving sunlight has reduced auxin concentration - auxin causes shaded side to grow more quickly - IAA is associated with phototropism

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxin - class of molecules that affects plant growth patterns c. Geotropism (gravitropism) (video) - growth of plant towards or away from gravity - negative geotropism: shoots grow upward, away from gravity - gravity causes auxins to be more concentrated on lower side of horizontal plant and less concentrated on upper side. - cells on lower side elongate (grow) quicker than on upper side…plant bends upward

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxin - class of molecules that affects plant growth patterns c. Geotropism (gravitropism) - positive geotropism: roots grow toward pull of gravity - auxins have opposite effect in roots - they still concentrate on lower side of a sideways root, but this INHIBITS elongation. - Result: root bends downward Fig. 33.3

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxin - class of molecules that affects plant growth patterns c. Auxin made in apical meristem of terminal bud - inhibits development of lateral (axillary) buds - mechanism of apical dominance - also made in root apical meristem… inhibit formation of lateral roots Taller seedlings received auxin (Fig. 33.3A)

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxin - class of molecules that affects plant growth patterns d. How do auxins cause elongation? - hypothesis: they weaken cell walls - stimulate proteins to pump protons (H+) into cell wall - activate enzymes to break H-bonds b/w cellulose fibers - cells swell as more water can now fit within due to cell wall stretching Fig. 33.3

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types i. Auxin - class of molecules that affects plant growth patterns e. Other effects of auxins - induces division in vascular cambium (promotes growth in diameter) - produced by developing embryo - promotes fruit growth - some plants develop fruit w/o fertilization if you spray them with auxin

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types ii. Cytokinins (kinins) a. Class of growth regulators that promote cell division (cytokinesis) b. Produced mainly in roots c. Effects of kinins are influenced by concentrations of auxins - auxins from terminal bud inhibit axillary bud growth - cut off terminal bud - cytokinins from roots can now activate axillary buds (auxins overpower cytokinins) d. Auxins and cytokinins are antagonistic hormones Fig. 33.4

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types ii. Cytokinins (kinins) e. Other effects of cytokinins - affect root growth and differentiation - delay aging (florists sometimes spray cytokinins onto flowers) - breaking seed dormancy (germination)

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types iii. Gibberellins a. History of discovery - Fungus of genus Gibberella - infects rice seedlings, causes them to grow very tall - rice topples over and dies before flowering Foolish seedling diseased plants - Japanese called it “foolish seedling disease” - Japanese scientist discovered chemical released by the fungus that caused disease - named it Gibberellin - it was later discovered to exist naturally in plants Control plants Fig. 33.5

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types iii. Gibberellins b. More than 100 known c. Produced in roots and young leaves d. Stimulates stem elongation and cell division in stems - enhances auxins e. Enhance fruit development sprayed with gibberellins control

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types iii. Gibberellins f. Terminate seed and bud dormancy (activate them) - spray seeds with gibberellins and they germinate regardless of environmental requirements - naturally: when seed absorbs water, embryo triggered to release gibberellins g. Induce some biennial plants to flower during 1st year of growth

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types iv. Abscisic acid (ABA) a. Inhibits many plant processes - Ex. inhibits germination Fig. 33.6 - must inactivate ABA for germination to occur - inactivation triggered by cold temperature in some seed (winter inactivates for spring germination) - seeds activated by water: water flushes ABA out of seed - prominent in desert seeds after a hard rain: b. Ratio of gibberellins to ABA determines germination in many seeds (antagonistic hormones) c. ABA signals stomata to pump out K+ when plant wilts

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types v. Ethylene a. History - observed that fruit ripened in sheds with kerosene stoves - hypothesized that heat caused ripening - kerosene stoves were replaced with cleaner-burning stoves - fruit did not ripen as quickly - need to modify hypothesis - ethylene is a gaseous byproduct of burning kerosene

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types v. Ethylene b. Plants produce ethylene c. Ethylene triggers fruit ripening and other aging processes (e.g. apoptosis)

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types v. Ethylene d. Fruit ripening - ethylene diffuses from fruit to fruit through air (it’s a gas!) (one bad apple does spoil the lot) Fig. 33.7 - triggers enzymatic breakdown of cell walls (softens fruit) 3 bananas put in plastic bag. One with an orange, one with ethylene glycol and one alone - triggers conversion of starch to sugar (sweetens fruit) - new scent and color attracts animals (operant conditioning) to eat and disperse seeds - what would happen if you put fruit in a plastic bag and sealed it? - many fruits are picked green, placed in large tanks, and ethylene is pumped over them for ripening - CO2 inhibits action of ethylene (slows ripening): pick apples in AUTUMN, pump CO2 over them to inhibit ripening, and sell the following summer

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development C. The five major types v. Ethylene e. Falling leaves - color change - leaves lose chlorophyll unmasking other pigments - new pigments made as well - leaves stripped of essential elements before falling off - petiole separates from stem Fig. 33.7 1. Abscission layer - region of separation (parenchyma cells with thin walls, weakened by enzymes) - triggered by increasing levels of ethylene and decreasing level of auxin (antagonistic hormones) 2. Triggered by shortening days

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development D. Hormones used extensively in agriculture i. Ex. Low dose of auxins to prevent fruit from falling off before being picked Fig. 33.8

AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development E. Growth responses and biological rhythms in plants i. Tropisms a. Orient plant growth toward or away from environmental stimuli b. Types 1. Phototropism 2. Gravitropism (geotropism) Fig. 33.9

Fig. 33.9 AIM: How are hormones used by plants in regulation? II. Five major types of plant hormones regulate growth and development E. Growth responses and biological rhythms in plants i. Tropisms a. Orient plant growth toward or away from environmental stimuli b. Types 1. Thigmotropism - growth or movement in response to touch (Greek, Thigma, touch) - Ex. Tendril of pea plant i. Grows straight until it touches something ii. Contact causes cell to grow at different rates on opposite sides of tendril (just like phototropism and gravitropism) - slower growth in area of contact - result: plant coils around branch - great for support while heading for sun (phototropism)

AIM: How are hormones used by plants in regulation? III. Lichen is not to be confused with plants A. Lichens i. Associations of millions of algae or cyanobacteria held in a network of fungal hyphae a. Mutualism is so tight that lichens are named as a single species b. Photoautotrophs supply fungus with food, and fungus gives photoautotrophs a suitable environment to live c. Can live where little or no soil (recall primary succession) Fig. 17.8

AIM: How are hormones used by plants in regulation? IV. Kingdom Fungus A. Fungus a. Greek, mycos, fungi (mycelium, mycorrhizae, etc…) b. Fungi are heterotrophs that absorb food after digesting with enzymes outside their body c. Often saprophytes d. Cells have cell wall made of chitin e. Mushroom, mold and yeast f. Most reproduce sexually (fertilization) and asexually (spores or fragmentation) hyphae - spend most of life in haploid form g. Mushroom is spore-bearing fruiting body of a fungus Fig

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