Week 8 Lecture Notes/Chapter 26/27
Week 8 Lecture Notes/Chapter 26/27 BIOL 1306/1106
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This 21 page Class Notes was uploaded by Hayley Lecker on Thursday October 15, 2015. The Class Notes belongs to BIOL 1306/1106 at University of Texas at El Paso taught by Anthony Darrouzet-Nardi in Fall 2015. Since its upload, it has received 63 views. For similar materials see Organismal Biology in Biology at University of Texas at El Paso.
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Date Created: 10/15/15
Biology Week 8 Important Information Professor s Email aidarrouzetnardiutepedu or anthonvdnutepedu All vocabulary will be defined at the end of the notes Chapter 26 261 Plants Develop in Response to the Environment Plant development is regulated by environmental cues receptors hormones and the plant s genome Seed dormancy which has adaptive advantages is maintained by a variety of mechanisms When dormancy ends the seed germinates and develops into a seedling A Monocot corn 8 Eudicot bean A coleoptile a cylindrical sheath of The shoot apex of most eudicots When the shoot cells protects the is protected by the cotyledons as elongates the first early shoot as it the upper part of the plant is foliage leaves grows to the soil pulled above the soil surface emerge surface First foliage leaf Primary root covered by After the shoot emerges coleorhiza from the soil it continues to elongate and the Ieaves emerge root roots PRINCIPLES OF LIFE Figure 261 n 2012 Sinauer Associates Inc Hormones and photoreceptors act through signal transduction pathways to regulate plant growth and development Genetic screens using the model organism Arabidopsis thaliana have contributed greatly to our understanding of signal transduction pathways in plants 262 Gibberellins and Auxin Have Diverse Effects but a Similar Mechanism of Action Gibberellins stimulate growth of stems and fruits as well as mobilization of seed reserves in cereal crops The embryo The embryo secretes gibberellins The digestive enzymes from the aleurone 4 The enzymes digest the proteins imbibes H20 that diffuse into the aleurone layer layer move into the endospenn and starch in theendospenn and swells where they trigger the synthesis of releasing monomers from which digestive enzymes the embryo synthesizes new cells PRINCIPLES OF LIFE Figure 264 2012 Sinauer Associates Inc Auxin is made in cells at the shoot apex and moves down to the growing region in a polar manner leeCtlon Of transport 1 V Auxin enters the cell J by passive diffusion as a nonionized acid HA 1 Proton pumps in the plasma membrane maintain 39the cell wall at an acidic pH and set up a chemiosmotic 39 gradient to drive the H transport of HA A predominates in the cytosol which has a neutral pH Ionized auxin 39 exits the cell via auxin anion efflux carriers that are concentrated at the basal and of each cell llll 33 1 i l quot NJ 5 In the cell wall the 39 39 lower pH causes Aquot to become HA which diffuses into the next cell y l i minimIFruiuuniimiiuuuuminnit ATP llllllll quoturanium PRINCIPLES OF LIFE Figure 265 2012 Sinauer Associates Inc Lateral movement of auxin mediated by auxin efflux carriers is responsible for phototropism and gravitropism A Phototropism A higher auxin concentration causes more rapid growth Auxin moves to the The redistributed by cell elongation on the shaded side within auxin moves down shaded side The tip the tip the coleoptile curves toward the light Coleoptiie 2 A higher auxin concentration causes more rapid growth on the lower side The tip curves upward 1 Auxin moves downward in response to gravity PRINCIPLES OF LIFE Figure 266 2012 Sinauer Associates Inc Auxin plays roles in lateral root formation leaf abscission and apical dominance The acid growth hypothesis explains how auxin promotes cell expansion by increasing proton pumps in the cell membrane which loosens the cell wall Auxin acts with another protein to stabilize the proton pump and direct insertion of the pump into the plasma membrane Plasma membrane Cell wall The pH of the cell wall is reduced acidi ed ll ll llii Auxin enters the cell H 0 AT pump gene W 0 Hi mRNA NVW ll l ll li l ill l39ll l I lll il l 39Ml ili39l ill i l lli lill and stimulates expression of the proton pump gene llllil H illll l lll Expansin Nucleus Cytoplasm 1quot ii lllll illquot lllll lll l lllll illl39k Cellulose microfibrils Crosslinking polymers 6 The cell wall is loosened to allow cell expansion 5 Reduced pH activates expansins which disrupt interactions between cell wall polymers PRINCIPLES OF LIFE Figure 267 2012 Sinauer Associates Inc Both auxin and gibberellins act by binding to their respective receptors which then bind to a transcriptional repressor leading to the repressor s breakdown in the proteasome Gibbereliin or auxin Cytoplasm Receptor Nuclear 553 Hormone binds to a receptorw Q protein and the complex 7 enters the nucleus Nucleus The hormone receptor complex binds to the repressor In the absence of Ubiqumn hormone a repressor inhibits transcription of 4 Ci Binding stimulates growthstimulating genes the addition of Vi ubiquitin to the re ressor Transcriptionfactor RGDFS SSOr p D7ooooom J I o The repressor is L broken down in the r m proteasome Growth 3 stimulating genes are I now transcribed Proteasome mwWmmmmm PRINCIPLES OF LIFE Figure 268 0 2012 Sinauer Associates Inc 263 Other Plant Hormones Have Diverse Effects on Plant Development Cytokinins most of which are adenine derivatives often interact with auxin They promote plant cell division promote seed germination in some species and inhibit stem elongation along other activities Cytokinins act on plant cells through twocomponent signal transduction pathway The ratio of auxin to ethylene controls leaf abscission Ethylene promotes senescence and fruit ripening It causes the stems of eudicot seedlings to form a protective apical hook n stems it inhibits elongation promotes lateral swelling and decreases sensitivity to gravitropism stimulation Brassinosteroids promote cell expansion pollen tube elongation and vascular tissue differentiation but inhibit root elongation Unlike animal steroids these hormones act at a cell membrane receptor Abscisic acid inhibits seed germination promotes dormancy and stimulates stomatal closing in response to dry conditions in the environment 264 Photoreceptors Initiate Developmental Responses to Light Phototropin is a bluelight receptor protein involved in phototropism Zeaxanthin acts in a conjunction with phototropin to mediate the lightinduced opening of stomata Cryptochromes are bluelight receptors that affect seedling development and flowering and inhibit cell expansion A 436 nm 10 08 06 04 Absorbance 02 400 450 500 550 600 650 700 Wavelength nm Light 0 minutes l H I quot Time 90minutes PRINCIPLES OF LIFE Figure 2610 2012 Sinauer Associates Inc B Phytochrome is a photoreceptor that exists in cytosol in two interconvertible isoforms Pr and Pfr The relative amounts of these two isoforms are a function of the retio of red to farred light Phytochrome plays a number of roles in photomorhogenesis Renght 39 4frquotquotquot zrr sethhrtgn cg AT A 1H WQJTWQJ r Pfr 7quot quot 39 V Sheet i dehwgmhedt Far red light The isoform Pr absorbs red light and The isoform Pfr absorbs farred is converted into Pfr light and is converted into Pr PRINCIPLES OF LIFE lnText Art Ch 26 p 553 2012 Sinauer Associates Inc The phytochrome signal transduction pathway affects transcription in two ways the Pfr isoform interacts directly with some transcription factions and influences indirectly by phosphorylating other proteins Changes in the conformation of the ohromophore induce changes in the shape of the phytochrome protein exposing a nuclear localization signal sequence and a protein kinase domain iNuclear localization signal sequence NLS El E1 Protein kinase domain lDfr 3 Pfr moves to the nucleus minimummmmuummm39umm Wu gammm lmmlmuumm39mm absorbs red light Chromophore Red light W W Farred light Pr Mum Wmmummmm W E The phytochrome ohromophore K WWI 93mm W Nucleus Other proteins Some Pfr interacts directly I with transcription factors to Transcription tr change transcription l factor 1 Changes in Some Pfr acts as a I transcription protein kinase DNA phosphorylating other Changes In proteins that in turn transcr39pt39on affect transcription PRINCIPLES OF LIFE Figure 2612 2012 Sinauer Associates Inc Circadian rhythms are changes that occur on a daily cycle Light can entrain circadian rhythms through photoreceptors such as phytochrome Chapter 27 271 Most Angiosperms Reproduce Sexually Sexual reproduction promotes genetic diversity in a population The flower is an angiosperm s structure for sexual reproduction Flowering plants have microscopic gametophytes The megagametophyte is the embryo sac which typically contains 8 nuclei in 7 cells The macrogametophyte is the two or three celled pollen grain Microspores Pollen grains n n microgametophytes Anther 9 amp microsporangla Meiosis o er rm Microsporocyte 2n Tube cell sporophyte I Petal Generative nucleus Stigma cell Style Anther Pollen Carpel tube ovary Stamen Ovule Filament I Sepal I nteguments Survuvmg Antipodal megaspore cells Receptacle Three mitoses Meiosis Tube cell Sperm 2 nucleus Megasporangia quotquot39 Polar nuclei Megasporocyte2n Megaspores n Degenerated Synergids 599 Ge megaspores PRINCIPLES OF LIFE Figure 272 2012 Sinauer Associates Inc Following pollination the pollen grain delivers sperm cells to the embryo sac by means of a pollen tube Angiosperms exhibit double fertilization forming a diploid zygote that becomes the embryo and a triploid endosperm that stores reserves Three antipodal cells cell Tube cell nucleus nuclei Synergids PRINCIPLES OF LIFE Figure 274 2012 Sinauer Associates Inc 272 Hormones and Signaling Determine the Transition from the Vegetative to the Reproductive State In annuals and biennials flowering and seed formation are followed by the death of the rest of the plant Perennials live longer and reproduce repeatedly For a vegetativer growing plant to flower a shoot apical meristem must become an inflorescence meristem which in turn must give rise to one or more floral meristems These events are determined by specific genes Vegetative shoot A apical meristem Floral or inflorescence meristem Inflorescence B megtstem Meristem identity genes gt gt fil lingrure 276 Par l 551311 276 Part 2 C Ca r pe A Stamen Fl 0 ra I meristem Petal Floral organ Sepal identity genes PRINCIPLES OF LIFE Figure 276 Part 3 3933 2012 Sinauer Associates Inc Some plants flower in response to photoperiod Shortday plants flower when nights are longer than a critical length specific to each species Long day plants flower when nights are shorter than a critical length 14 hours 14 hours Light f Dark Light l Dark Maryland Mammoth tobacco shortday plant Henbane longday plant r Long days Short days Long days Short clays plant does plant flowers plant flowers plant does not flower not flower PRINCIPLES OF LIFE Figure 277 2012 Sinauer Associates Inc The mechanism of photoperiodic control of flowering involves phytochromes and a diffusible protein Photoperiodic stimulus signal florigen which is formed in the lead and is translocated to the shoot apical meristem w WWWA DNA gt Flowering l Transcription Shoot apical 39 meristem Com anion cell quot Ii l l Sieve tube 397 element CONSTANS protein G FLOWERING Locus T protein florigen FLOWERING LOCUS 0 protein APETALA1 protein APETALA1 protein PRINCIPLES OF LIFE Figure 2710 Part 1 539 ND SIIUUL I Assouatcs Incl CONSTANS protein E1 FLOWERING LOCUST protein florigen FLOWERING LOCUS D protein PRINCIPLES OF LIFE Figure 2710 Pan 2 20 Silxml 59Udlt395 In In some angiosperms exposure to cold called vernalization is required for flowering In others internal signals such as gibberellin induce flowering All of these stimuli converge on the meristem identity genes 273 Angiosperms Can Reproduce Asexually Asexual reproduction allows rapid multiplication of organisms that are well suited to their environment Vegetative reproduction involves the modification of a vegetable organ for reproduction Some plant species produce seeds asexually by apopmixis PRINCIPLES OF UFE Figure 2713 2012 Sinauer Assocates Inc Woodly plants can be propagated asexually by grafting Scion Stock PRINCIPLES OF LIFE Figure 2714 390 2012 Sinauer Associates Inc Lecture Notes A Twentytwo days after being sprayed with a dilute gibberellin solution this plant reached the size of a nondwarf plant This untreated mutant 1 plant remained a dwarf PRINCIPLES OF LIFE 2e Figure 263 2014 Sinaucr Assooatcs Inc Supplying auxin to this mutant plant made it grow This untreated mutant plant does not make auxin The image above illustrates how gibberellin stimulated fruit production and auxin promoted stock growth Sorry for the wide spacing the image are big and if they are made smaller you cannot read them The teacher points these table so its good to memorize these hormones and their function Plant Growth Hormones Part 1 Hormone Common Structure Abscrsrc acrd C CH3 CH3 3 OH 0 CH3 COOH Auxin indole 3acetic acid Brassinosteroids H O HO I Illln O PRINCIPLES OF LIFE 2e Table 262 Part 1 0 2014 Sinauer Associates ln Typical activities Maintains seed dormancy closes stomata Promotes stem elongation adventitious root initiation and fruit development inhibits axillary bud outgrowth leaf abscission and root elongation Promote stem and pollen tube elongation promote vascular tissue differentiation Plant Growth Hormones Part2 Hormone Common Structure Typical activities Cytokinins H OH OH Inhibit leaf senescence promote 2 00 cell diViSion and aXIllary bud out HN CHZ CH3 growth affect root growth N N Ethylene H H Promotes fruit ripening and leaf gtCclt abscission inhibits stem elonga H H tion and gravitropism Gibberellins 0 Promote seed germination stem growth and ovule and fruit devel w CH2 opment break winter dormancy mobilize nutrient reserves in grass 002H seeds PRINCIPLES OF LIFE 2e Table 262 Part 2 39 2 2014 Sinauer Associates Inc Plant Defense Secondary Metabolites Used in Plant Defense Part 1 Class Type Role Example Nitrogencontaining Alkaloids Neurotoxin Nicotine in tobacco OH Glycosides Inhibit electron Dhurrin in sorghum l H transport CH3 Nonprotein amino Disrupt protein Canavanine in jack acids structure bean CH3 Ephedrine an alkaloid Nitrogen and sulfurcontaining Glucosinolates Inhibit respiration Methylglucosinolate in cabbage S glucose HsC C N o sos Methylglucosinolate PRINCIPLES OF LIFE 2e Table 281 Part 1 2014 Sinauer Associates Inc Secondary Metabolites Used in Plant Defense Part 2 Class Type Role Example Phenolics Coumarins Block cell division Umbelliferone in carrots Flavonoids Phytoalexins Capsaicin in peppers Tannins Inhibit enzymes Gallotannin in oak trees HO o O Umbelliferone Terpenes Monoterpenes Neurotoxins Pyrethrin in Chrysan H C themums 3 Diterpenes Disrupt reproduction Gossypol in cotton o and muscle function R 1 O Triterpenes Inhibit ion transport Digitalis in foxglove o Sterols Block animal Spinasterol in spinach 39 hormones Pyrethr39n Polyterpenes Deter feeding Latex in Euphorbia PRINCIPLES OF LIFE 2e Table 281 Part 2 What plants need Macro and Micronutrients Macronutrients are nutrients they need in large amounts Nitrogen is the most limiting plant nutrient Nitrogen is needed by plants in large quantities to make enzymes such as RuBisCO and other proteins because of this nitrogen is the most limiting nutrient to plant growth this is very true in temperate ecosystems The next most limiting nutrients are Phosphorus and Potassium E39emei t Functions COH Major components of organic compounds ll Proteins nucleic acids P Nucleic acids ATP phospholipids 8 Proteins amp coenzymes K Enzyme activation water balance eg opening of stomata Ca Membrane structure amp permeability regulatory Mlg Part of chlorophyll activates enzymes Micronutrients are nutrients they need in smaller amounts These enzymes Fe Enzyme activation Cytochromes er carriers Cl Water balance photosynthesis waterrlsplitting 0 Enzyme cotactor M n Enzym e activation photosynthesis waterSpl ittinrg le39l Enzyme activation on formation Mo Nlitrate reduction B Garb transport Ni Enzyme activation Nutrients CG Minerals 139 A ostly needed for helping The Table below goes over the percentage of an element in a plant Nitrogen is only 2 but very important Soils are broken up into layers called horizons The top layer is usually browner it is filled with organic material Soil is usually 3 layers so below the organic layer the B layer can have many different colors and times The bottom layer quotparent material is usually broken up rock Most of the nitrogen plants get is from the topsoil Organic layers can take decades to centuries for it to build up back up this is important to the ecosystem so erosion is a problem A horizon Topsoil f B horizon lt Subsoil C horizon Weathering parent rock lt bedrock x 393 quot PRINCIPLES OF LIFE 2e Figure 253 2014 Sinauer Associates Inc Nutrients in soil are typically released from decaying organic matter the plant can uptake this In many ecosystems fungi are the primary decomposers i Carbon I Nitrogen photosynthesis CO Arespim Plantupmke nd fu ngi Htterf fidecomposition This is how a plant uptakes the nutrients Fungi and Bacteria help break down nutrients for plant In the second picture it shows the plant releasing H which acidifies the soil to help quotpopquot off the nutrients out of the soil matrix The main thing that nutrients stick to in the soil is not clay but really organic matter Mineral Worms Dead Bacteria particle or ganic Root Fungi iesand Clay matter particle a A clay particle which is negatively charged binds mineral cations I 7 V 8 The protons bind i39 z to the clay particle which releases the cations into the soil solution 002 H20 HZCOS b HCOS lie V K B Protons are pumped from the roots or la freed by the ionization of carbonic acid quot PRINCIPLES OF UFEZE Figure 254 mm Simmer Assotmte 4 Some plants are nitrogen fixers They contain symbiotic bacteria called Rhizobia within nodules in their root systems producing nitrogen compounds that help the plant to grow and compete with other plants When the plant dies the fixed nitrogen is released making it available to other plants and this helps to fertilize the soil These are plants with a pod pea plants In the roots of the plants they have nodules or lumps that have bacteria that take nitrogen directly out of the atmosphere 78 of the atmosphere is nitrogen and turn it into something the plant can use The nitrogen in the atmosphere is in a form that plants can t use and must be converted nitroge a c N2 ant 35 lit i TP ENEt H2 l ADP l P Mycorrhizae are fungi that occur natural in the soil for the past 450 million years They form a close symbiotic relationship with plant roots Mycorrhizal fungi colonize a plant s root system and create a network that increases the plant s capacity to absorb water and nutrients such as phosphorus copper and zinc This process in turn enhances growth and favors rapid development of roots and plants Plantwater relationships covered more in Week 7 notes As water evaporates via the stomata on the leaves it creates a force to pull water out of the soil Water is a polar molecule so it likes to stick to itself this is cohesion and it sticky to other things is adhesion and because water has cohesion it can stay together when being pulled up through the plant Pure water is 0 but water wants to go to a negative water potential air is 585 so it is pulled strongly to the air and through the plant to get there 3 Tension pulls water from the veins into the apoplast surrounding the mesophyll cells which in turn pulls water in the veins of the leaves upward l and outward I Water evaporates 39 from mesophyll I 39 cell walls quot 39 which in turn pulls the Mesophyquot water column in the xylem cell o o of the shoot and root upward 7 39 Q I During transpiration Lquot 0 water vapor diffuses out of the leaf through pores called stomata Cohesion between water molecules forms a continuous water column from the roots to the leaves Water enters the root from the soil by osmosis PRINCIPLES OF LIFE 2e Figure 2512 2014 Sinauer Associates Inc Here are a few measurements there are the pressure it takes to move the water out The more negative the more pressure it takes to push the water out REGION l11MPa Soil water 03 Xylem of root 06 Xylem of trunk 12 inside of leaf 20 Outside air 585 mxo uf M M x galtp l V r t If the plant cannot retain enough of its water it will wilt So not enough water the cell decrease in size The water potential of cells of this plant is zero because the negative solute potential is balanced by an equally positive pressure potential The plant is upright because its cells are turgid The cells in this plant have low turgor pressure and the plant is wilted PRINCIPLES OFLIFE 20 Figure 259 39 20 4 alnauer a Goat25 nlt Plant Resource Allocation IMPORTANT when plants are growing they have adapted to take up nutrients they have to allocate the nutrients and elements and energy This means they must decide what to do with it Plants can direct their photosynthesized sugars and nutrients towards growth reproductions maintenance storage defense or uptake of additional resources So if a plant needs to grow their roots longer they can choose to provide energy to that for more resource uptake Energy costs for different tissue are similar but nutrients can vary a lot Leaves need more nitrogen Litter Recycled 7 Growth and 39 materiaia maintenance ta ta 1 Acquisition b efenee Litter l l 391 liesewage me Li lite r Hilfunma timan 4 49 L Litterquot Hormone Signaling molecules that regulate and control physiology growth or behavior Secondary metabolites Organic compounds that are not directly involved in the normal growth development or reproduction of an organism Often they contribute to a secondary function such as defense against herbivory Allelopathy The chemical inhibition of one species by another The inhibitory chemical is released into the environment where it affects the development and growth of neighboring plants Soil The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants Pigment A compound that has a distinctive color due to selective color absorption Chlorophyll photosynthesis Accessory pigments Carotenoids xanthophylls photoprotection Anthocyanins Production during senescence often color owers and fruits Seed Bank Natural storage of seeds often dormant within the soil of most ecosystems In 2012 Russian scientists were able to germinated an Arctic plant from a 32000 year old seed this shows how long a seed can be dormant before being germinated Fun Fact There is a global seed vault in Svalbard Endosperm A specialized triploid seed tissue found only in angiosperms contains stored nutrients for the developing embryo Semelparity and Iteroparity Semelparity and iteroparity refer to the reproductive strategy of an organism A species is considered semelparous if it ischaracterized by a single reproductive episode before death and iteroparous if it characterized by multiple reproductive cycles over the source of its lifetime Semelparous put all their energy into making seeds so they end up dying Annuals Biennials twoyear life cycle First year they grow and collect resources and second year ower and die Perennials ower every year so they are iteroparous Photosynthesis 6C02 6H20 light energy gt C5H1205 602 Important equation to know Microbe A microscopic living organism often single celled though microscopic multicellular organisms are included Microbes include all the bacteria and archaea and almost all the protozoa They also include some fungi algae and certain animals such as rotifers Same as quotmicroorganismquot There can be up to 10000 species in a handful of soil and 1010 cells per gram Nitrogen Fixers Some plants are nitrogen fixers They contain symbiotic bacteria called Rhizobia within nodules in their root systems producing nitrogen compounds that help the plant to grow and compete with other plants When the plant dies the fixed nitrogen is released making it available to other plants and this helps to fertilize the soil nitrogch N2 l 8H 8amp2 l l ATP 7 ENE l H2 l ADP 16F Soil Organic Matter Organic carbon based material typically brown in color that builds up in the upper layers of soil as a result of long term decomposition of living tissues by soil microbes Water Potential The tendency of water to move from one area to another clue to osmosis gravity mechanical pressure or matrix effects such as capillary action which is caused by surface tension Water moves toward more negative water potentials