LIFE 103 Week 7 Erik Arthun
LIFE 103 Week 7 Erik Arthun LIFE 103
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This 10 page Class Notes was uploaded by Lauren Caldwell on Friday March 4, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Erik Arthun, Tanya Dewey in Spring 2016. Since its upload, it has received 26 views. For similar materials see Macrobiology; Plants and Animals in Biology at Colorado State University.
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Date Created: 03/04/16
2/28 Chapter 37: Soil and Plant Nutrition Most water and minerals are absorbed from the upper layers of soil living organisms play an important role in these soil layers o Stratified into layers called soil horizons o Topsoil Mineral particles, living organisms, and humus (decaying organic material) This is called the A Horizon o B Horizon Less organic material o C Horizon Rock, essentially Pretty much none of the organic material found in the A horizon Cellular respiration occurs in roots o As such, the essentially best type of soil for a plant is one with half water, half oxygen That’s why overwatering the plant is such a bad thing Topsoil Composition Composition -> inorganic (minerals) and organic chemical components Inorganic components -> cations adhere to negatively charged soil particles o Cation - positively charged ions o Doesn’t get leeched out as easily from the soil o Minerals have to be absorbed into the soil solution Cannot simply be absorbed straight into the roots Cation exchange o Cations are displaced from soil particles by other cations o Generally H+ o Hydrogen ions released by the roots into the soil in tern attach to different minerals, which releasing cations The cations then are abosrbed into soil solution Roots absorb minerals then Negatively charged ions o Anions o Don’t bind to soil particles o Instead, during hard rain, since they aren't attached to anything, they are often simply leeched out and into deeper layers 3 This includes two key things that help the plant - PO - 4nd NO - 3 Humus builds a crumbly soil that retains water but keeps it porous o Also increases the soil's capacity to exchange cations and serves as a reservoir of mineral nutrients o Topsoil's bacteria, fungi, algae, protists, insects, worms, nematodes, and roots all help decompose organic material and mix the soil. Fertilization Naturally, a plant that does recycles all of the nutrients and minerals it needs into the soil for the next generation o Our society (agriculture) removes the dead stuff, so the material that’s needed isnt naturally recycled back in o Fertilization replaces mineral nutrients that have been lost from the soil High in nitrogen, phosphorus, and potassium Plant Life Cycle Soil, water, and air contribute to plant growth 80-90% of a plant's mass is water o 96% of what remains is carbon dioxide This contributes to making carbohydrates during photosynthesis Remaining 4% is inorganic substances (other minerals) Essential Elements o 50 elements are in plants 17 that are REQUIRED are called Essential Elements Without these 17, a plant cnanot complete their life cycle and reproduce 9 MACROnutrients -> needed in big amounts Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium Nitrogen Important for crop growth and plant yield Nucleic acids are made of nitrogenous bases Thus, without it, there's a struggle Potassium required for stomatas opening (it directly impacts the guard cells) MICROnutrients -> needed in very small amounts Enzyme cofactors - pushes forward chemical reactions Commonly non-protein components Plant Relationships When plants die, they provide the energy needed for the organisms in the soil This is a mutualistic relationship between plants and soil microbes o Microbes get sugars, carbohydates, amino acids, etc from plants o Microbes produce chemicals to help plants grow Also protects the plant from bacterial invaiders Also increases nutrient availability Nitrogen Cycle Nitrogen can be an important limiting nutrient for plant growth o Plants can absorb nitrogen in two forms: N03- (Nitrate) or NH4+ (Ammonium) Most nitrogen comes from soil bacteria fixating it for the plant The nitrogen cycle transforms nitrogen and nitrogen-containing compounds o Nitrogen in the air (with its triple bonds) is not usable by plants o Nitrogen fixation is the change from N2 to NH3 NH3 can be changed into the two usable forms ALL of the fixators are bacteria o Rhizombium Bacteria Legumes Feeds off the plant, but also provides for the plant Conversion to NH4+ o Microbes decompose dead things into amino acids Changes it into ammonia, which abosrbes H+ from the soil, and makes ammonium o Nitrogen-fixing bacteria take N2 and make it into NH3, Ammonia, which can be used in the step above Legume Nodules Legume (alfalfa and other plants) have swelled bulbs called nodules o Nodules Plant cells infected by nitrogen-fixing Rhizobium bacteria Plants get a constant supply of fixed nitrogen Bacteria gets sugar Creates more usable nitrogen than any artifical product for farmers Fungi o Mycorrhizae Mutualistic asssociations of fungi and roots Fungus benefits by getting sugar Host plant gains since the fungus increases the surface area absorption for water and mineral absorption Also gains growth factors Fungal hyphae Essentially the fungus roots Two types: Extomycorrhizae Will move into the extracellular space of roots, but will never break into cells This all increases surface area Arbuscular mycorrhizae Moves into the cell, doesn’t rupture it, but still increases surface area More common of the two Different Plants Nonmutualistic adaptations o Epiphytes Grows on other plants Doesn’t necessarily feed off other plants though o Parasitic plants Roots tap into other plants and feeds off them to get nutrients Some will not be capable of photosynthesis and will literally feed off other guys to the bitter end o Carnivorous plants Photosynthetic Obtains nitrogen by killing and digesting other things Usually insects canNOT use nitrogen gas 3/2 Chapter 38: Angiosperm Reproduction and Biotechnology How did early plants absorb water and minerals? They had mycorrhizae absorbing for them 3 key features of flower reproduction o Flowers The reproductive shoots of the angiosperm sporophyte Attaches to a part of the stem called the receptacle Four floral organs - carpels, stamens, petals, and sepals o Double fertilization o Fruit Anatomy review o Stamen - stalk (filament) sac at the tip called an anther Pollen is produced at the anther o Carpel - ovary at the base of the style Leads up to the sticky stigma Pollen is received at the sticky stigma o Specific pollenators are attracted to particular types of flowers Wind pollinated species Grass and many trees Release large amounts of pollen Bees Typically blue or yellow, but likes all bright colors Most have UV markings called "Nectar Guides" Likes sweet smells Flies Attracted to flowers that smell like rotten meat Ex: Carrion flower Will lay eggs on these flowers Moths, bats, butterflies Attracted to white/yellow flowers b/c they're out at night (nocternal) -> easier to see them then Birds Poor smell ability, so they go for anything that just tastes good Double fertilization Upon fertilization on the stigma, a pollen tube grows down the style o The tip of the pollen tube enters the microphyle (hole into it) and leaves 2 sperm in the embryo sac Fertilization (fusion of gametes) occurs after the two sperm reach the female gametophyte 1 sperm fertilizes the egg 1 sperm combines with the two polar nuclei This leads to the triploid food-storing endosperm (3n) The fleshy part of the fruit The seed A mature seed dehydrates o This allows it to enter a state of dormancy Little to no metabolism and no growth - this allows it to wait until conditions are prime for growth Triggered by specific environmental cues Ex: animal digestion, temperature, lighting changes, fire, water Most remain viable after a year or two of dormancy Some, however, last only days while others can last for centuries Cotyledons o Below the cotyledons, the embryonic axis (the HYPOCOTYL) terminates in the RADICLE (embryonic root) Aka, the hypocotle is the baby plant's first stem. Its name comes from the fact that it is below ("hypo") the leaves ("cotyl") The radicle is the root, essentially Imbibition - uptake of water by dry seeds o Germination depends on imbibition Imbibition is triggered through enzymes being activated through water uptake o The radicle emerges first So the plant can root self to ground as well as absorb water o Shoot tip breaks through the soil surface next o Ex: for a coconut, the liquid is endosperm liquid. The coconut meat is also endosperm o Most monocots have thin cotyledons o In most eudicots, the cotyledons are thick b/c partly the fact that nutrients are stored in it Sexual v asexual Fragmentation o Separation of a parent plant into parts that develop into whole plants A type of ASEXUAL reproduction Asexual -> results in genetically identical clones to the parent Adventitious shoots o Shoots are sent out from the roots o They can all rise to form new plants Aspen trees can do this - each little emerging shoot can develop into a new tree Ex: 47,000 clones of one.original.aspen.tree make up one forest Advantages and disadvntages Asexual Sexual Benefits Successful plant in a stable Genetic variation; not all will die at environment that does not once change a whole lot allows the plant to thrive disadvanta IF the environment changes (a Less seedlings survive; the plant ges new viral disease, a fire, etc), must use a LOT of energy in order EVERY clone will likely die to produce and regulate all of the reproductive tools Some flowers can self-fertilize o Thus, every ovule will fertilize Better than relying on a bee (for example; any pollenator) to pollenate everything o Evenso, many plants have evolved to avoid self-fertilization Dioecious A plant cannot fertilize itself Staminate flower -> ONLY has stamens (male flower; produces pollen) Carpellate flower -> ONLY has carpels (female flower: has ovaries) Ex: Ginkos Biotechnology and genetic engineering People have been using plants for thousands of years Hybridization o Different organisms (not same species) can produce a hybrid Ex: wheat - a natural hybrid of wild grass species Ex: corn Maize is way different than it originally was Transgenic organism o Expressed genes from other species (aka, foreign genes are inserted in them) o Increases quality and quantity of food worldwide Ex: we can make food bigger, resist insects, or resist specific diseases Ex: golden rice Adds vitamin A to help the poor who don’t have what they realy need Ex: transgenic cassava Increased iron and beta-carotene The debate o Allergies may arise o Cross-pollenation of what we've created over what is natural may lead to something else SUPERWEEDS - resistant to weed killers Chapter 39: Plant Responses to Internal and External signals Reception Internal and/or external signals are detected by receptors o Receptors - proteins that change in response to specific stimuli o Example stimuli: light (a phytochrome), hormones, etc o Occurs in the cell membrane, generally Transduction Relay proteins and secondary messengers that transfer and amplify the original signal received o Response Signal transduction pathway leads to regulation of one or more cellular activities o Generally results in an increased activity of enzymes Hormones Chemical signals that modify or control one or more specific physiological processes within a plant o Produced in very, very low concentrations, but has a lot of impact on growth and development Transported to other loations within a plant Binds to a specific receptor and triggers specific responses in target cells Example hormone effects: o Alter gene expression, alter enzyme activity, change membrane properties Type Definition Application Auxin Stimulates cell elongation in Can be used to stimulate root young shoots development from literally any Produced in shoot tips plant piece (ie: add it to a leaf, and is transported down and shazam, it will create roots) the stem An overdose can be used Low pH leads to as an herbicide to kill expansin -> leads to eudicot species weakened cell walls o Weakened cell wall allows elongation by water entering the cell Cytokinins Stimulates plant cell Removing apical buds causes division; promotes lateral the plant to grow outward bud growth (causes This is caused by cytokinesis) cytokinins Giggerellins Stem elongation; helps o Can cause stems seeds break dormancy to grow or fruits, resulting in (germination) lager plants and or fruits, all Begins when water is in all imbibed Alpha amylase begins to digest the part of the seed that is stored food, causing germination to begin Ethylene Meditates/regulates fruit Causes senescence ripening (programmed/designed death), Takes away the leaf abscission (losing leaves), green or triple response A gas, results from drought, Triple response leads to: flooding, mechanical slowing stem elongation, pressure, injury, infection, thickening of the stem, etc and horizontal growth Ripening triggers more o Makes a normal ethylene release looking plant look really funny as it tries to strengthen itself and survive Fruit is softened and sweetened Hormone regulation is based on the enviornment o For light, plants detect presence, direction, intensity, and wavelength (aka color) o 2 major classes of light receptors 1. Blue-light photoreceptors 2. Phytochromes Pigments that regulate plant reponses to light throughout its life Tends to seed germination and shake avoidance o Shade avoidance 1. Shaded plants that don’t have access to the first light to hit the earth absorb a different spectrum of color Ex: far-red light is absorbed by shorter plants in rainforests; canopies absorb red light
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