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Dead Week Notes

by: Sarah Martin

Dead Week Notes BIOL 201

Sarah Martin

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These notes cover plant hormones, growth, and changes in our environment.
Organismic Biology
Dr. Ari Jumpponen
Class Notes
botany, Bio, 201, plants
25 ?




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This 10 page Class Notes was uploaded by Sarah Martin on Friday May 6, 2016. The Class Notes belongs to BIOL 201 at Kansas State University taught by Dr. Ari Jumpponen in Spring 2016. Since its upload, it has received 83 views. For similar materials see Organismic Biology in Biology at Kansas State University.


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Date Created: 05/06/16
BIO 201 Notes 5/2 Plant Hormones ?) Plant hormones can be produced… yes (transport) A in one part of a plant and have an effect in another yes B by one plant and have an effect in another plant yes C by one plant species and have an effect on another yes D by a non-plant and have an effect on a plant therefore this is the correct answer E All of the above Growth: Irreversible increase in mass by division and enlargement of cells (divide and enlarge) Determinate growth = Plant grows, stops growing and dies in one season Indeterminate growth = Plant or parts of plant grow and continue to be active for several years Differentiation = Cells develop different forms adapted to specific functions Development = Coordination of growth and differentiation of a single cell into tissues and organs Nutrients = Substances that furnish elements and energy to produce organic molecules (obtained from air and soil) Vitamins = Organic molecules of varied structure that participate in catalyzed reactions, mostly by functioning as electron acceptor or donor; Synthesized in cell membranes and cytoplasm; Required in small amounts for normal growth and development Hormones = Production dictated by genes; Mostly produced in actively growing regions; Produced and active in smaller amounts than vitamins and enzymes Some effects of vitamins similar to those of hormones, thus they are sometimes difficult to distinguish. Growth regulators = Compounds that affect plant development similar to those of naturally produced hormones and vitamins Hormones can have multiple effects Hormones act by chemically binding to specific receptors: Hormone- receptor association initiates effect; triggers series of biochemical events, including turning genes on and off (biochemical events = Signal transduction) Major types of hormones: auxins, gibberellins, cytokinins, abscisic acid, ethylene – and maybe more… All hormones: Are organic compounds; Are made in one part of the plant and transported to another where effect is manifested; Regulate growth and/or development via either growth stimulation or inhibition 2 components of plant hormone function: 1) chemical: stimulus or inhibition of plant function - alternatively, interaction with inorganic compounds and other plant hormones; 2) regulation of gene expression: Hormones activate the genes to be transcribed and expressed as proteins/enzymes Groups of hormones (6): 1) Auxin - cell elongation and differentiation Growth control is not a function of the tip, but rather something transported from the tip; Auxins transported through the parenchyma cells in cortex, pith or vascular tissue; Polar movement in both roots (towards the tip) and stems (towards the base); Polar movement: Possibly by carrier proteins in the cell membranes and consumes energy - ATP ?) Growth stimulated by IAA involves… no A Accelerated cell divisions no B Breaking of the cell wall or its chemical structure seems legit C Filling of the vacuoles D A and C THIS ONE! E B and C Auxin cont: Auxin is mainly involved in cell elongation, not cell division. Acid growth hypothesis: Auxin stimulates acquisition of H+ into the cell (H+ pumps in the cell membrane pump H+ against the gradient into the cell); Lower pH (higher H+ concentration) activates enzymes that break bonds among the cellulose fibers. This results in increased plasticity; After breaking the bonds mere turgor pressure stretches the cell Acid growth hypothesis may only explain some (early stages) of the cell elongation In addition to simple chemical control of the cell structure and function, auxin likely induces gene expression for protein(s) necessary for cell growth Apical dominance: Apical meristem inhibits the growth and development of axillary buds; High auxin levels may stimulate ethylene (another hormone) production. Ethylene then puts a lid on axillary bud growth - a marvelous example of hormone interaction Leaf abscission: Auxin inhibits senescence and abscission; Environmental stimuli in the fall decrease auxin production; This allows the abscission to begin Vascular cambium - activation and differentiation: Activated in the spring by auxin from the apical meristems and young leaves; Sucrose concentration regulates differentiation to phloem and xylem 2) Gibberellin - cell division and flowering Gibberella fujikuroi: Silly rice disease in Japan caused abnormal growth of rice; The causal agent was Gibberella fujikuroi, a root pathogen; Gibberella is better known by its conidial (asexual) state - Fusarium; In rice, the disease symptoms were also induced by fungal extract or the filtered culture media; Conclusion, Gibberella fujikuroi produced and secreted a water-soluble compound that controlled rice growth - gibberellin Not polar like auxin. Likely as solute - moves in all directions in xylem and phloem Growth stimulant: Internodal elongation in mature regions of plants; Cell elongation and division (auxin only in elongation). The mechanism does not involve cell wall acidification or H+ pumps Seed germination: Imbibition releases gibberellin from the embryo; Gibberellins launch the transcription of the genes coding for hydrolytic enzymes - amylases; Amylases catalyze starch conversion to sugar; energy and stimulant for the growing embryo 3) Cytokinins - cell division and organ formation Cell division: Accelerates cell cycle - effect depends on auxin concentration Stimulation of cell expansion and division in cotyledons: Does not involve wall acidification like proposed for auxin Tissue differentiation and organ formation: The ratio of auxin/cytokinin determines which organs produced Like auxin, inhibits senescence 4) Ethylene - fruit ripening, senescence This is our first gaseous plant hormone; Known since Egyptian times Large amounts produced in roots, shoot apical meristems, ripening fruit, and senescing flowers Fruit ripening: Several components in the process: Pigment degradation; Enzymatic cell wall degradation; Enzymatic conversion of starch to sugars Flowering: Usually inhibitory effect but mango and pineapple flowering is stimulated 5/4 5) Abscissic acid - stress hormone, e.g., stomatal closure abscissic acid has nothing to do with the leaf abscission; Known as the stress hormone. Counteracts the stimulatory effects of auxin, gibberellins, and cytokinins; One extremely important function - stomatal closure ?) Which of the following is most true? no A One hormone; one function maybe, maybe not B One hormone; chemical control of function YES C One hormone; hormonal control of function [6) Brassinosteroids – development, growth, stress, etc.] Trophisms: ?) Phototropism is a result of… YES A Faster growth rate on the shade side of the plant no B Faster growth rate on the sunny side of the plant YES C A result of a hormone’s sensitivity to light A and C (growth elongation on the shade side) B and C Brassinosteroids: Brassinosteroids (BRs) are a family of > 50 structurally related compounds that contribute to: Growth; Cell division, elongation, and differentiation; Defense against pathogens; Stress tolerance; Reproductive development BL is not very abundant in plant tissues; Brassinolide and castasterone are steroids like some animal hormones; essential (as shown in det2 and cpd) ?) Brassinosteroid deficient mutant Arabidopsis… no A Is stunted by brassinosteroid addition YES B Is similar to wildtype with brassinosteroid addition no C Is unresponsive to brassinosteroid addition D A and B E All of the above Plant tropisms: term referring to plant responses to external stimuli. Obscure examples include hydro-, chemo-, thermo-, traumo-, electro-, and aerotropism Four kinds: Phototropism; Gravitropism; Thigmotropism; Heliotropism Usually, hormonally controlled Phototropism: Light causes auxin (IAA) to accumulate on the shaded side of the stem; Result, increased rate of cell elongation on the shaded side - curvature towards light Gravitropism: Amyloplast deposition - old school idea about gravitropisms; We know better now… lack amyloplasts and the root still goes towards the center of the earth because of hormones A fine example of hormone-inorganic compound interaction: Ca2+ accumulation triggers IAA accumulation which in roots inhibits elongation; Similar mechanism possibly involved in shoots: IAA accumulates in the lower side of the horizontally oriented stem Thigmotrpoism: Plant response to contact with solid objects; Examples include tendrils of peas and many climbing vines; This coiling is similar to the phototropism – i.e. the coiling occurs as a result of the unequal elongation of the cells – the cells opposite to the stimulus expand faster; Sometimes turgor movements, which are not thigmotropisms per se, are included under this category of responses Turgor movements: include barberry anther responses to pollinators and the bush monkey flower stigma folding to retain pollen Thigtropism cont: A curious and cool example is also the sensitive plant (Mimosa pudica) response to touch; The response is a K+ ion migration induced rapid movement of water; K+ ions rush from one side to another changing the osmotic potential – water follows and loss of turgor on the flaccid side folds the leaf and leaflets; Similarly to the sensitive plant, the venus flytrap closure is a result of sudden expansion of the outer epidermal cells; Cells in an outer epidermis are compressed. This creates tension in the plant tissue that holds the trap open; Mechanical stimulus of the trigger hairs initiates ATP-driven water pressure changes; The cells expand by the increasing water pressure, and the trap closes as the tension relaxes ?) Plant responses to external stimuli... yeah A Facilitate pollination yeah B May be selected for because they are advantageous probs not C Lack evolutionary significance YES D A and B E None of the above Seasonal responses: Photoperiodism: Controls flowering, senescence, and dormancy (plants change colors cause saving resources for winter); Shortening days launch a chain reaction that results in non-replacement of chlorophyll, making the yellow and red pigments (carotenoids and anthocyanins) visible; Shortening of days results ultimately in dormancy - period of decreased metabolism Four different kinds of plants that are photoperiodism: Neutral - day length has no effect Short-day - flower when days shorter than critical length Long-day - flower when days longer than critical length Intermediates Short-day and long-day plants require uninterrupted period of darkness longer or shorter than the critical length If interrupted by a brief flash - flowering as if the day length would have been uninterrupted. How is this possible? Answer is phytochrome Pr (red) Pfr (far-red) reversible reaction: Pr absorbs red light (proportionally more red than far-red light in sunlight) and is converted to Pfr; Pfr absorbs far-red and is converted to Pr in absence of light Pr is inactive; Pfr promotes flowering in long-day plants and inhibits it in short-day plants Presence of phytochrome is likely to explain how plants measure light Cont: In brief, the longer the day, the more active phytochrome (Pfr) present in plant tissues. Little memory aid: Pr – Phytochrome; PFr – Flowering phytochrome ?) Flowering... no A is induced by moon light yeah B is controlled by the decay of the active form at night yeah C is controlled by accumulation of the active form during the day YES D B and C E All of the above 5/6 Global Change The main anthropogenic mechanism that drives human alteration of global systems is… A) private automobiles, B) fossil fuel mining, C) land transformation, D) human population size Pattern of human population growth: 1st billion after 1800; 2nd billion 1930; 3rd billion 1960; Today, past 7 billion; 2030, expected >9 billion Present age distribution suggests continuing growth Conclusion: humans comprise a large population that is likely to increase Do the places where people live also change? yeah, they have to expand outward Population size is increasing Most of the increase in the less developed countries that are likely to increase their resource use Cumulative effect of human enterprises increases through 1) land transformation, 2) impacts on global biochemistry, and 3) biotic additions (invasions) or losses (extinction) These parameters interact with each other; they are not separate from each other No land is pristine and beyond human impact - humans impact biochemical cycles affecting all the global ecosystems; However, the land transformation means usually one of the following: Clearing land for agriculture, Deforestation because of silviculture and failure to reforest 10-15% of all Earth’s land surface is occupied by row crops or industrial areas industrial areas and crop lands are biological deserts in terms of biodiversity 6-8% of all Earth’s land surface is pasture - these neither include native grasslands (pampas, Australia, American prairies) that are used for grazing, nor forested areas in active or intensive silviculture Land transformation also impacts climate: 20% of the anthropogenic CO2 emissions result from land transformation. The burning of organic materials contributes by release of greenhouse gases and pollutants: CH4 and NOx (CH4 is more potent greenhouse gas than CO2, NOx contributes to acid rain). Humans dominate the terrestrial environments. How about the marine ecosystems? 60% of the population lives within 60 miles from the coast The coastal areas are the most productive in the marine environment 50% of the coastal mangrove forests have been cleared by human activity Humans use only c. 8% of the NPP of the marine ecosystems, but 25-35% in the temperate upswelling and shelf areas. Commercial fishing is predicted to collapse by 2050. End of the line? Human alteration of the biogeochemical cycles: Humans have a substantial impact on the carbon, hydrological, and nitrogen cycles; We’ll get more familiar with these cycles and talk about the human impact on those. Human effects on C cycle include: A) CO2 emissions B) modifications of C sequestration C) desertification D) ocean acidification E) all of the above Human alteration of the carbon cycle: C6H12O6+6O2<=>CO2+6H2O Four major pools: Ocean, Soils, Atmosphere, Vegetation Plants take up CO2 All organisms respire Large quantities diffuse in and out of the oceans Combustion: Mainly fossil fuels, stowed away during the carboniferous (286- 360mya) or prior; Increase in the atmospheric CO2 concentration Land transformation: Decreasing size of the vegetative C pool; Decreasing photosynthesizing pool ?) CO2 enrichment A) makes plants grow faster B) makes animals grow slower C) bleaches coral reefs YES D) all of the above E) none of the above cont. Effects of increasing CO2 concentration on vegetation: CO2 fertilization - likely improves plant growth; Decreased food quality for herbivores - C/N ratios; Slower rate of decomposition - C/N ratio ?) Ground water mining means A) insertion of mines in the water table B) removal of historic water reserves for current use C) using wells for irrigation D) A and B YES E) B and C Four major pools: Ocean, Ice and icecaps, Groundwater, Atmosphere Evaporation and transpiration supply the atmospheric pool Precipitation returns H20 to the other pools Fresh water constitutes about 3% of the total supply Globally, about 50% of the total fresh water supply is used by humans 70% of this fresh water is used for agriculture Examples of our water use: In US only 2% of the rivers run unimpeded; Colorado, The Nile and Ganges rivers are almost completely used prior to their reaching the ocean; Aral-sea was substantially reduced by irrigation: Decimation of endemic and native flora and fauna, Altered local climate, Exposed and airborne salt-rich sediments cause respiratory problems, miscarriages and increase cancer; In arid regions within US, groundwater mining exceeds recharge endangering sustainable supply of fresh water ?) N in the air A) is not available for plants B) is less abundant than O C) can be made plant available by humans and microbes YES D) A and C E) B and C N is one of the major nutrients in all living organisms - CHNOPS Atmosphere is 78% N2 - not available to plants How do plants get their N: Atmospheric N is fixed by bacteria and then maintained in the biotic pool through decomposition; Atmospheric N is fixed by humans and incorporated into the terrestrial and aquatic pools (dead zones) and volatilized into the atmosphere Let’s look at the totals: Global bacterial fixation c. 170 million tons; Human input as fertilizer 90-130 million tons; Cultivation of crops with symbiotic N fixation (alfa-alfa) may add another 40 million tons; Combustion of fossil fuels will contribute c. 20 million tons; Land transformation may release another 50 million tons - WHY? Consequences of the N cycle alteration: Added N increases productivity in the “non-target” ecosystems resulting in greater CO2 storage; Unfortunately, only some species are very responsive to N fertilization - potential loss of local biodiversity; The added N may leaching - N enters the ground water and in aquatic environments. This Eutrophication can increase algal blooms and oxygen demand in water. ?) Human population A) is small enough not to have global consequences B) is consuming less resources than are sustainably available C) is the likely cause of the on-going mass extinction YES D) all of the above


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