Life103, Exam 2 Study Guide
Life103, Exam 2 Study Guide Life 103
Popular in Biology of organisms-animals and plants
verified elite notetaker
Popular in Biology
This 27 page Study Guide was uploaded by Addy Carroll on Friday March 4, 2016. The Study Guide belongs to Life 103 at Colorado State University taught by Dr. Dale Lockwood and Dr. Tanya Dewey in Winter 2016. Since its upload, it has received 113 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
Reviews for Life103, Exam 2 Study Guide
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 03/04/16
Life 103 Exam 2 Study Guide Gymnosperms • Gymnosperm -Means “naked seed” • Seeds -A seed consists of an embryo and nutrients surrounded by a protective coat -Seeds changed the course of plant evolution, enabling their bearers to become the dominant producers in most terrestrial ecosystems ~In other words, land plants no longer had to live close to the water in order to reproduce -Foundational for modern ecosystems -One important key to civilization • Seed Plants -In addition to having seeds, the following are common to all seed plants ~Reduced gametophytes ~Heterospory (see heterospory section below) ~Ovules (female gametophyte) ~Pollen (male gametophyte) -The gametophytes of seed plants develop within the walls of spores that are retained within tissues of the parent sporophyte • Heterospory -The ancestors of seed plants were likely homosporous (homo=same), while seed plants are heterosporous (hetero=different) -Megasporangia produce megaspores that give rise to female gametophytes -Microsporangia produce microspores that give rise to male gametophytes • Ovules and Production of Eggs -An ovule consists of a megasporangium, megaspore, and one or more protective integuments (outside coating that is made up of sporophyte tissue) -Gymnosperm megaspores have one integument -Angiosperm megaspores usually have two integuments • Gymnosperm Female Anatomy -Megasporangium: diploid tissue where haploid microspores are formed (meiosis) -Megaspore: haploid cell that grows into the female gametophyte, including the egg nucleus • Gymnosperm Male Anatomy -Microsporangium: diploid tissue where haploid microspores are formed (meiosis) -Microspores: develop into male gametophyte -Pollen: contains the male gametophyte within the tough pollen wall ~Pollen grains have few cells, so they need protection from the environment by the pollen wall • Gymnosperm Fertilization (see textbook figure 30.3a) -The pollen is released into the air and it spreads for miles -The pollen grain reaches ovule and germinates -The pollen tube grows from the pollen grains and begins digesting through the Megasporangium -After digging its way through the megasporangium, the pollen tube reaches the egg nucleus, discharges sperm nucleus into the egg nucleus of female gametophyte • Pollen and Production of Sperm (see textbook figure 30.3b) -Microspores develop into pollen grains, which contain the male gametophytes -Pollination is the transfer of pollen to the part of a seed plant containing the ovules -Pollen eliminates the need for a film of water and can be dispersed great distances by air or animals -If a pollen grain germinates, it gives rise to a pollen tube that discharges two sperm into the female gametophyte within the ovule • The Evolutionary Advantage of Seeds (30.3c) -A seed develops from the whole ovule -A seed is a sporophyte embryo, along with its food supply, packaged in a protective coat -Seeds provide some evolutionary advantages over spores ~They may remain dormant for days to years, until conditions are favorable for germination ~They may be transported long distances by wind or animals • The gymnosperms have “naked” seeds not enclosed by ovaries (fleshy fruit) and consist of four phyla: -Cycadophyta (cycads) -Gingkophyta (one living species: Ginkgo biloba) -Gnetophyta (three genera: Gnetum, Ephedra, Welwischia) -Coniferophyta (conifers, such as pine, fir, and redwood) • Phylum Cycadophyta -Individuals have large cones and palmlike leaves -These thrived during the Mesozoic, but relatively few species exist today -About 300 species alive today -Rare plant collectors are willing to steal these plants • Phylum Ginkgophyta -This phylum consists of a single living species, Ginkgo biloba -It has a high tolerance to air pollution and is a popular ornamental tree -Leaves remain little changed for 270 million years -Ginko biloba- Miracle cure? ~Used as culinary ingredient ~Many medicinal claims ~Recent large study -No benefit for memory ~In Alzheimer’s ~In Dementia • Phylum Gnetophyta -This phylum comprises three genera (see week 4 notes for different genera) -Species vary in appearance, and some are tropical whereas others live in deserts • Phylum Coniferophyta (see textbook figure 30.4 for life cycle of a pine) -This phylum is by far the larges of the gymnosperm phyla -Most conifers are evergreens and can carry out photosynthesis year round Angiosperms • Angiosperms (see textbook figure 30.12 for life cycle) -Single phylum ~Note, gymnosperms have multiple phyla, however, angiosperms make up the majority of plants on the earth ~Anthophyta ~The root “Antho” comes from Greek for flower -Seed Plants -Flowers -Fruits • Flowers (see textbook figure 30.8) -Specialized structure for sexual reproduction -Pollination by animals (insects, mammals, birds) and wind ~Pollinator has a large effect on the adaptations of the flower -Color -Shape -Scent ~Gymnosperms are primarily wind pollinated because they don’t have much to attract a pollinator -Huge diversity in flower color and form -Diversity linked to pollination methods • Amorphophallus titanium -Titan arum -Largest unbranched inflorescence ~Grows about 5-6 feet tall -Corpse flower ~Smells like rotting flesh when blooms -Flies serve as the pollinator -Only blooms for a couple days, making it very popular to watch during that time -Only found on Sumatra • Rafflesia schadenbegiana -Largest flower ~1 meter diameter -Bloom lasts 5-6 days -Corpse flower (see reasoning and pollinator in section above) -Indonesia and Malaysia • Wolffia arrhizia -Smallest flower • The Carpel -A carpel consists of an ovary at the base and a style leading up to a stigma, where pollen is received ~Note, the pollen tube that grows from the pollen, contrary to gymnosperms, has to travel a long way, all the way down the style to the ovary -Sometimes carpel is referred to as pistil ~Much confusion regarding these terms ~Pistil can be multiple fused carpels ~If there is one carpel, then it is also a pistil -The female gametophyte, or embryo sac, develops within an ovule contained within an ovary at the base of a stigma • The Stamen -Modified microsporophyll -Male part of flower -Anther ~Microsporangium-pollen sacs • Floral Structure -Complete Flower ~Has all four modified leaves (sepals, petals, carpels, stamens) ~Incomplete is missing one or more -Perfect flowers ~Have both male and female parts ~Imperfect flowers are missing one or both -Note, all perfect flowers aren’t complete flowers but all complete flowers are perfect flowers • Selfing Plants -Perfect flowers can theoretically self pollinate ~Some plants have a very high frequency of selfing -Plants can have mechanisms to prevent selfing; (inbreeding; there may be more reproductive success, but potentially less fitness) ~Gametophytic Self Incompatibility -Proteins prevent tube from growing ~Heterostyly -Stamens and Carpels are of different lengths ~Sporophytic Self Incompatibility • Pollen -Male gametophyte -Pollen structure influenced by dispersal methods -Exterior composed largely of Sporopollenin • The Life of a Pollen -A pollen grain that has landed on a stigma germinates and the pollen tube of the male gametophyte grows down to the ovary -The ovule is entered by a pore called the micropyle -Double fertilization occurs when the pollen tube discharges two sperm into the female gametophyte within an ovule -One sperm fertilizes the egg, while the other combines with two nuclei in the central cell of the female gametophyte and initiates development of food-storing endosperm -The endosperm nourishes the developing embryo • Cotyledons -Within a seed, the embryo consists of a root and one or two seed leaves called cotyledons ~The first leaves that emerge from a seed ~Gymnosperms have 2-24 cotyledons -Hypogeal cotyledons stay below ground and do not photosynthesize ~Often used for storage -Epigeal cotyledons expand on germination and push off seed shell, photosynthesizing above ground -Cotyledons often bear little resemblance to the other leaves on the plant • Fruit -A fruit typically consists of a mature ovary but can also include other flower parts -Fruits protect seed and aid in their dispersal ~Serve to attract animals to eat them and then disperse their seeds through digestion -Mature fruits can be either flashy or dry • Types of Fruits -Simple Fruits ~Ripened single or compound ovary within a single carpel -Dry fruits ~Achene: dandelions, strawberries ~Legume: pea, peanut, bean ~Samara: maple, ash, elm ~Nut: acorn, beech, hazelnut ~Fibrous Drupe: coconut, walnut -Simple fleshy fruits ~Berries: grapes, tomatoes, oranges ~Drupes: stone fruits, olives, mangoes -Aggregate fruits ~Single flower with multiple carpels ~Blackberries, raspberries -Multiple fruits ~Pineapple, breadfruit • Achene -Small, hard, dry fruit -Fruit is on the outside ~Ex.) Strawberry • Legume -Simple, dry fruit -Splits open when mature • Nut -Simple, dried fruit -The outside of the ovary becomes a hard shell -Doesn’t split open when mature (opposite of legume) • Drupe -Contains a fleshy exocarp and mesocarp -Hard endocarp ~Fleshy on outside, hard on inside -Stone fruits, coconuts, mangoes, olives • Berries -Fleshy fruit from a single ovary -Pepo: special berry with hard rind on outside ~Ex.) Watermelon, squash • Multiple fruits -Inflorescence ~Cluster of flowers ~Each flower becomes a fruit ~All fruits merge into one mass • Angiosperm Diversity (see textbook figure 30.16) -The two main groups of angiosperms are monocots (one cotyledon; see notes above) and eudicots (“true” dicots) -The clade eudicot includes some groups formerly assigned to the paraphyletic dicot (two cotyledons) group ~All eudicots share the same ancestor; not all “dicots” do -Basal angiosperms are less derived and include the flowering plants belonging to the oldest lineages -Magnoliids share some traits with basal angiosperms, but are more closely related to monocots and eudicots • Basal Angiosperms -Three small lineages constitute the basal angiosperms -These include Amborella trichopoda, water lilies, and star anise • Magnoliids -Magnoliids include magnolias, laurels, and black pepper plants -Magnoliids are more closely related to monocots and eudicots than basal angiosperms • Monocots -More than one-quarter of angiosperm species are monocots ~60,000 species ~Flower parts come in multiples of 3 -Ex.) 6, 9 ~Often have parallel leaf veins • Palms -Monocot -Evolved at the end of the Cretaceous -2,600 species -Tropical, subtropical, and warm climates -Example ~Talipot Palm ~Leaves up to 5 meters in diameter ~Largest inflorescence of any plant • Grasses -Monocot -Family Poaceae -9-10,000 species -Ex.) Bamboo, wheat, sugar cane, rye, maize • Orchids -Monocots -Not only considered the largest single family of monocots, but the largest single family of angiosperms (Asteraceae is comparable) - Approximately 22,000 species -Bilaterally symmetric -One pollinator • Eudicots -More than two-thirds of angiosperm species are eudicots -Very diverse species • Evolutionary Links Between Angiosperms and Animals -Pollination of flowers and transport of seeds by animals are two important relationships in terrestrial ecosystems -Clades with bilaterally symmetrical flowers have more species than those with radially symmetrical flowers -This is likely because bilateral symmetry affects the movement of pollinators and reduces gene flow in diverging populations • Plants and Humans -No group of plants is more important to human survival than seed plants -Plants are key sources of food, fuel, wood products, and medicine -Our reliance on seed plants makes preservation of plant diversity critical • Products from Seed Plants -Most of our food comes from angiosperms -Six crops (wheat, rice, maize, potatoes, cassava, and sweet potatoes) yield 80% of the calories consumed by humans -Modern crops are products of relatively recent genetic change resulting form artificial selection -Many seed plants provide wood -Secondary compounds of seed plants are used in medicines • Threats to Plant Diversity -Destruction of habitat is causing extinction of many plant species -Loss of plant habitat is often accompanied by loss of the animal species that plants support -At the current rate of habitat loss, 50% of Earth’s species will become extinct within the next 100-200 years Plant Structure • Plant Anatomy (see textbook figure 35.2) -Plants, like animals, are composed of organs made up of tissues, which are composed of cells -Three main organs include roots, leaves, and stems -Roots supply water and minerals to the plant -Leaves supply sugars to the plant -Stems supply support structure and transport systems • Roots -Roots are multicellular organs with important functions ~Anchoring the plant ~Absorbing minerals and water ~Storing organic nutrients -In most plants, absorption of water and minerals occurs near the root hairs (see textbook figure 35.3), where vast numbers of tiny root hairs increase the surface area • Types of Roots -Taproot system ~One main vertical root ~Lateral roots, or branch roots -Adventitious roots ~Can arise from stems or leaves -Fibrous Roots ~Seedless vascular plants and monocots ~Thin lateral roots with no main root • Modified Roots (see textbook figure 35.4) -Prop roots ~Aerial roots ~Add structural support -Strangling roots ~Grow around objects supporting the plant -Strangler Figs ~Epiphytes ~Roots grow down and around tree ~Stem grows up to sunlight -Pneumatophores ~Roots that rise up in the air ~Pores allow gas exchange ~Mangroves -Buttress roots ~Support large trees -Storage root ~Tap root ~Lateral root -Haustorial roots ~Parasitic pants -Examples: mistletoe, dodder, snow plants ~Absorb water and nutrients from other plants -Climbing root ~Adventitious root ~Supports climbing plants ~Negatively phototropic -Grows away from light ~Examples: Ivies • Stems -A stem is an organ consisting of ~An alternating system of nodes, the points at which leaves are attached ~Internodes, the stem segments between nodes -Axillary bud ~Can form a lateral shoot, or branch (in other words, where growth sideways occurs) -Apical bud, or terminal bud ~Located near the shoot tip and causes elongation of a young shoot (in other words, where growth upward occurs) -Apical dominance ~Dormancy in most nonapical buds • Modified Stems (see textbook figure 35.5) -Corm ~Short underground storage stem ~Examples: Taro, gladiolus, saffron -Rhizome ~Horizontal stem ~Usually underground ~Sends out roots, shoots (adventitious roots) ~Examples: Ginger, poison oak, Bermuda grass -Stolon ~Horizontal stem ~At the ground surface or just underground ~Adventitious roots ~Produces clone at the end of the stem ~Examples: Strawberry, many grasses -Bulbs ~Underground stems ~Have modified leaves -Storage when dormant ~Examples: Garlic, onion • Leaves (see textbook figure 35.6) -The main photosynthetic organ of most vascular plants -Generally consist of a flattened blade and a stalk called the petiole, which joins the leaf to a node of the stem • Modified Leaves (see textbook figure 35.7) -Bracts ~Associated with the reproductive structure ~Often brightly colored ~Examples: Bougainvillea, poinsettia -Tendrils ~Used for attaching for climbing ~Can photosynthesize ~Can be thigmotropic -Grows toward touch ~Example: Pea plant -Spines ~Used for defense ~Common in xerophytes ~Thorns and prickles are not the same as spines because they aren’t modified leaves -Thorns ~Modified stems -Prickles ~Modified epidermis ~Example: Roses -Storage Leaves ~Can store water, nutrients, and toxins ~Succulents have these storage leaves -Examples: Cacti, ice plants, agave • Plant Tissues (see textbook figure 35.8) -Three types of tissues ~Dermal ~Ground ~Vascular • Dermal Tissue System -Epidermis ~In non-woody plants -Cuticle ~Waxy coating ~Helps prevent water loss from the epidermis -Pericardium ~In woody plants ~Protective tissues ~Replaces the epidermis in older regions of stems and roots -Trichomes are outgrowths of the shoot epidermis and can help with insect defense • Vascular Tissue System -Carries out long-distance transport of materials between roots and shoots -Two vascular tissues -Xylem conveys water and dissolved minerals upward from roots into the shoots -Phloem transports organic nutrients from where they are made to where they are needed • Vascular Tissue -The vascular tissue of a stem or root is collectively called the stele -In angiosperms, the stele of the rot is a solid central vascular cylinder -The stele of stems and leaves is divided into vascular bundles, strands of xylem and phloem • Ground Tissue System -Tissues that are neither dermal nor vascular -Pith ~Ground tissue internal to the vascular tissue -Cortex ~Ground tissue external to the vascular tissue -Ground tissue includes cells specialized for storage, photosynthesis, and support Cellular Structure in Plants • Cells (see textbook figure 35.10) -Plants have a diversity of cells that perform a variety of functions ~Consider 5 general types -Parenchyma -Collenchyma -Sclerenchyma -Water conducting cells of the xylem -Sugar-conducting cells of the phloem • Ground Tissue -Composed of ~Parenchyma ~Collenchyma ~Sclerenchyma • Ground Tissue Cells -Mature parenchyma cells ~Have thin and flexible primary walls ~Large central vacuole ~Lack secondary walls ~Are the least specialized ~Perform the most metabolic functions -Store nutrients -Photosynthesize ~Retain the ability to divide and differentiate -Key for cloning -Collenchyma cells ~Grouped in strands and help support young parts of the plant shoot ~They have thicker and uneven cell walls ~They lack secondary walls ~These cells provide flexible support without restraining growth ~Example: strings in a celery stalk are bundles of collenchyma cells -Sclerenchyma cells ~Rigid because of thick secondary walls strengthened with lignin ~Dead at functional maturity ~Have very thick cell walls relative to the cell inside the walls ~Example: pears are grainy when bitten into due to bundles of sclerenchyma cells ~There are two types -Sclereids are short and irregular in shape and have thick lignified secondary walls ~Source of hardness in nutshells and seed coats -Fibers are long and slender and arranged in threads ~Source of linen (flax fibers) and rope (hemp fibers) -Linen is made from extracting fiber cells from the plant • Vascular Tissue Cells -Xylem cells ~Cells are dead at functionality because it’s not easy to move water through living cells because of the thick cytoplasm, while it’s easy to move water through dead, hollow cells ~Each cell has to be connected to allow water to move all the way through the plant ~Tracheids -Found in all vascular plants -Tubular, elongated and dead -Water transfers via pits in the tracheids ~Vessel Elements -Larger diameter and shorter -Aligned end-to-end to form vessels -End walls have perforation plates -Phloem Cells ~Sieve-tube elements -Alive at functional maturity ~Active transport is always required for sugar to get into a cell, which can only be performed by a living cell -They lack organelles, including nucleus -Allows sugars to flow more easily ~Sieve plates -The porous end walls that allow fluid to flow between cells along the sieve tube ~Companion cell -One for each sieve-tube element -Nucleus and ribosomes serve both cells ~Sends proteins etc. to sieve-tube elements to keep it alive and able to perform active transport while not having any organelles itself Cell growth • Growth -Indeterminate growth- growing throughout an organism’s life ~Example: roots and shoots -Determinate growth- some plant organs cease to grow at a certain size ~Example: leaves -Annuals complete their life cycle in a year or less -Biennials require two growing seasons and only bloom the second year -Perennials live for many years • Where growth occurs -Meristems ~Perpetually embryonic tissue ~Maintains indeterminate growth ~Functionally similar to animal stem cells -Apical Meristems ~Located at the tips of roots and shoots and at the axillary buds of shoots -Primary growth occurs when apical meristems elongate shoots and roots (see textbook figures 35.13, 35.14, and 35.15 for root growth) (see textbook figures 35.16 and 35.17 for stem growth) -Secondary growth (see textbook figure 35.11 for types of growth) (see textbook figure 35.19 for stem growth) ~Lateral meristems add thickness to woody plants, which is required for structural support -Two lateral meristems ~Vascular cambium -Adds layers of vascular tissue called secondary xylem (wood) and secondary phloem ~Cork cambium -Replaces the epidermis with periderm, which is thicker and tougher • Secondary Growth (see textbook figure 35.22 for tree trunk anatomy) -The vascular cambium is a cylinder of meristematic cells one cell layer thick ~”Rings” go all the way up the tree trunk, hence, cylinders -It develops from undifferentiated parenchyma cells -Secondary xylem accumulates as wood, and consists of tracheids, vessel elements (only in angiosperms), and fibers -Early wood, formed in the spring, has thin cell walls to maximize water delivery -Late wood, formed in late summer, has thick-walled cells and contributes more to stem support -In temperate regions, the vascular cambium of perennials is dormant through the winter ~Stops growing cells ~New growth is fragile and the thin-walled cells could burst due to cold -Tree rings are visible where late and early wood meet, and can be used to estimate a tree’s age -Dendrochronology is the analysis of tree ring growth patterns, and can be used to study past climate change ~If the rings are closer together, that indicates that it was colder, and if they are farther apart, that indicates that it was warmer -As a tree or woody shrub ages, the older layers of secondary xylem, the heartwood, no longer transport water and minerals ~Used for structural support -The outer layers, known as sapwood, still transport materials through the xylem ~In other words, only the more recent secondary growth is still functioning as xylem -Older secondary phloem sloughs off and does not accumulate Plant Anatomy • Morphogenesis in plants, as in other multicellular organisms, is often controlled by homeotic genes -Morphogenesis=a change in the structure in plants -Homeotic gene=influences where an organ is located on an organism • Gene Expression and Control of Cellular Differentiation -In cellular differentiation, ~Cells of a developing organism synthesize different proteins and diverge in structure and function even though they have a common genome -Homeotic genes -Positional Information ~Where a cell is positioned determines what they will grow into • Location and a Cell’s Developmental Fate -Positional information underlies all the processes of development: growth, morphogenesis, and differentiation -Cells are not dedicated early to forming specific tissues and organs -The cell’s final position determines what kind of cell it will become • Shifts in Development: Phase Changes -Plants pass through developmental phases, called phase changes, developing from a juvenile phase to an adult phase ~Juvenile phase=not sexually mature ~Adult phase=sexually mature -Phase changes occur within the shoot apical meristem ~In other words, plants grow from the top -The most obvious morphological changes typically occur in leaf size and shape • Phase Changes -Juvenile plants are not competent (not sexually mature) to flower -Some woody plants accumulate secondary compounds in juvenile phase -Regulation is controlled by plant hormones, similar to how hormones control development in mammals ~Giberellic Acid plays an important role • Genetic Control of Flowering -Flower formation involves a phase change from vegetative growth to reproductive growth -It is triggered by a combination of environmental cues and internal signals -Transition from vegetative growth to flowering is associated with the switching on of floral meristem identity genes -In some plants, this requires vernalization ~Vernalization is when a plant has to first go through a cold period to alter gene expression and then hit a warm period ~As the world gets warmer, vernalization may happen prematurely, but pollinators aren’t on the same schedule, so many flowers go unfertilized and there is less reproductive success -Plant biologists have identified several organ identity genes (plant homeotic genes) that regulate the development of floral pattern ~MADs box genes -A mutation in a plant organ identity gene can cause abnormal floral development • Analogous genes exist in animals (see textbook figure 35.31 for plant example) -Mutations in Hox genes result in misplaced structures • Flower Development (see textbook figures 35.34 and 35.35) -Researchers have identified three classes of floral organ identity genes -The ABC model of flower formation identifies how floral organ identity genes direct the formation of the four types of floral organs -An understanding of mutants of the organ identity genes depicts how this model accounts for floral phenotypes Water and Sugar (see textbook figure 36.2) • Evolutionary Notes -The algal ancestors of land plants absorbed water, minerals, and CO 2 directly from the surrounding water ~These plants always had access to everything they needed, but couldn’t grow too big -The evolution of xylem and phloem in land plants made possible the long- distance transport of water, minerals, and products of photosynthesis ~Plants gain ability to maximize access to light, increase dispersal distance, and occupy new habitats ~Have the ability to grow bigger because of vascular tissue -This comes at a cost involving the loss of H 2 • Light -Light absorption is affected by the leaf area index, the ratio of total upper leaf surface of a plant divided by the surface area of land on which it grows (see textbook figure 36.4) ~How much of the surface area of the ground the plant is growing on is covered by leaves ~Look at the plant from above and see how much of the ground can be seen inside the diameter of where the plant is growing ~Example: If you see no ground and just leaves, the index is 1 -Self-pruning ~When photosynthesis is reduced below basal respiration ~When the leaf doesn’t make enough sugars to survive without help from the rest of the plant, the plant gets rid of it ~Example: A tree cuts off lower branches as it grows and gets taller and just keeps the topmost ones with the best access to light -Leaf orientation affects light absorption • Leaf Orientation -Orientation affects sun angle ~Influences photosynthetic rate ~Influences water loss ~With more direct sunlight, the leaf gets hot and there is more evaporation/water loss, so the plant requires more uptake of water -Some plants control leaf orientation ~Many plants must strike a balance between minimizing water loss while maximizing light energy gained for photosynthesis ~Heliotropic- moving in relation to the sun -Diaheliotropism-following the sun -Paraheliotropism-avoiding the sun ~This is a water stress adaptation and often occurs to plants in an environment with limited access to water • From Roots to Shoots -Transport begins with the absorption of resources by plant cells -Selective permeability is the control of movement of substances into and out of cells ~Plants only want certain things from the soil because other things could harm them, so they have to be able to control what goes in and out of their cells -Diffusion ~Passive movement of particles across a membrane ~No energy is required for facilitating movement ~Moving from an area of high density and low density in an effort to reach equilibrium ~A type of diffusion is facilitated diffusion; it doesn’t require energy because its not going against a gradient, but it can’t get through the membrane without a transport protein -Active transport ~Pumping of solutes across a membrane ~Generally requires transport proteins embedded in the cell membrane ~Works against a gradient and against diffusion ~Sometimes the particles won’t fit through the membrane by themselves • Active transport (see textbook figure 36.6) -Proton pump ~Most important transport protein for active transport ~Create a hydrogen ion gradient that is a form of potential energy that can be harnessed to do work ~They contribute to a voltage known as a membrane potential -Plant cells use energy stored in the proton gradient and membrane potential to drive the transport of many different solutes -Cotransport ~A transport protein couples the diffusion of one solute to the active transport of another ~The “coat-tail” effect of cotransport is also responsible for the uptake of the sugar sucrose by plant cells • Diffusion of Water -Plants must uptake water to offset the loss of water ~Plants lose water out their leaves during photosynthesis because they open their stomata to uptake CO ,2simultaneously causing water loss -Osmosis ~Movement of water across a semi-permeable membrane down a water potential gradient ~Determines the net uptake or water loss by a cell and is affected by solute concentration and pressure -Water potential is a measurement that combines the effects of solute concentration and pressure ~Water potential determines the direction of movement of water across a membrane ~Water flows from regions of higher water potential to regions of lower water potential ~Water always wants to flow to a more negative region to reach equilibrium -Water potential is abbreviated as Ψ and measured in units of pressure called megapascals (MPa) - Ψ=0MPa for pure water at sea level and room temperature -The solute potential (Ψ )sof a solution is proportional to the number of dissolved molecules -Solute potential is also called osmotic potential -Pressure potential (Ψ ) Ps the physical pressure on a solution -Turgor pressure is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast - Ψ= Ψ +PΨ S ~water potential=pressure potential+solute potential -Plasmolysis-the cell membrane pulls away from the cell wall (see textbook figure 36.7a) -Turgid-cell membrane pushed against the cell wall (see textbook figure 36.7b) ~When plants are plasmolyzed instead of turgid, that means they aren’t getting enough water and, as the cell membrane pulls away from the cell wall, the cell starts to wither and shrink -Aka plant is dying because of lack of water ~Permanent wilting point-when a plant is so wilted that no amount of water can bring it back to life -Aquaporins are transport proteins in the cell membrane that allow the passage of water ~Restricts the flow of solutes, only allows water ~The rate of water movement is likely regulated by phosphorylation of aquaporin proteins ~Aquaporins exist in plants and animals • Transport Control -Transport is also regulated by the compartmental structure of plant cells -The plasma membrane directly controls the traffic of molecules into and out of the protoplast ~In other words, the plasma membrane blocks certain things but allows other things to diffuse -The plasma membrane is a barrier between two major compartments, the cell wall and cytosol -The third major compartment in most mature plants cells is the vacuole, a large organelle that occupies as much as 90% or more of the protoplast’s volume -The vacuolar membrane regulates transport between the cytosol and the vacuole • Cellular structures necessary for transportation -In most plant tissues, the cell wall and cytosol are continuous from cell to cell -The cytoplasmic continuum is called the symplast -The cytoplasm of neighboring cells is connected by channels called plasmodesmata ~Holes that go through the cell wall to connect cells to allow desirable substances to pass through from cell to cell -The apoplast is the continuum of cell walls and extracellular spaces • Water and minerals can travel through a plant by three routes -Symplastic route: via the continuum of cytosol -Apoplastic route: via the cell walls and extracellular spaces -Transmembrane route: out of one cell, across a cell wall, and into another cell • Bulk Flow in Long-Distance Transport -Efficient long distance transport of fluid requires bulk flow, the movement of a fluid driven by pressure -Water and solutes move together through tracheids and vessel elements of xylem, and sieve-tube elements of phloem -Efficient movement is possible because mature tracheids and vessel elements have no cytoplasm, and sieve-tube elements have few organelles in their cytoplasm • Absorption of Water and Minerals by Root Cells (see textbook figure 36.8) -Most water and mineral absorption occurs near root tips, where the epidermis is permeable to water and root hairs are located -Root hairs account for much of the surface area of roots -After soil solution enters the rots, the extensive surface area of cortical cell membranes enhances uptake of water and selected minerals • Transport of Water and Minerals into the Xylem (see textbook figure 36.10) -Water can cross the cortex via the symplast of apoplast -Endodermis ~The innermost layer of cells in the root cortex ~It surrounds the vascular cylinder and is the last checkpoint for selective passage of minerals from the cortex into the vascular tissue -The waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder • Bulk Flow Driven by Negative Pressure in the Xylem (see textbook figure 36.11) -Transpiration ~The evaporation of water from a plant’s surface -Xylem sap ~Bulk flow of water and minerals replacing water lost ~From the steles of roots to the stems and leaves -At night, when transpiration is very low, root cells continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential -This causes water flow in from the root cortex, generating root pressure -The root pressure is greater in the roots than the leaves -Root pressure sometimes results in guttation, the exudation of water droplets on tips or edges of leaves (see textbook figure 36.9) -Positive root pressure is relatively weak and is a minor mechanism of xylem bulk flow ~Therefore, there’s some push up from the roots, but mostly pull up by the leaves • Transpiration-Cohesion Theory -Transpiration produces negative pressure (tension) in the leaf, which exerts a pulling force on water in the xylem, pulling water into the leaf -Transpirational pull is facilitated by cohesion of water molecules to each other and adhesion of water molecules to cell walls • Stomata (see textbook figures 36.12 and 36.13) -Account for 95% of water loss -Three cues signal stomatal opening + ~Light simulates the uptake of K in guard cells ~Depletion of CO w2thin the leaf ~Internal clock -Circcadian rhythm -Plants kept in the dark continue to open stomata on a 24 cycle -Water stress is the major cue for closing during the day • Desert Adaptations (see textbook figure 36.14) -Xerophytes-plants adapted to low water conditions ~Reduced leaves ~Crassulacean Acid Metabolism (CAM) • CAM -Stomata open at night -CO s2ored as malate -Released during the day to the Calvin cycle allowing the stomata to be closed during the day -Ferns, gymnosperms, and monocots all have species that use CAM -Most of the CAM species are angiosperms • Movement of Sugar Sources to Sugar Sinks -Phloem sap is an aqueous solution that is high in sucrose -It travels from a sugar source to a sugar sink -A sugar source is an organ that is a net producer of sugar, such as mature leaves -A sugar sink is an organ that is a net consumer or storer of sugar, such as a tuber or bulb -A storage organ can be both a sugar sink in summer and a sugar source in winter -Sugar must be loaded into sieve-tube elements before being exposed to sinks -Depending on the species, sugar may move by symplastic or both symplastic and apoplastic pathways -Transfer cells are modified companion cells that enhance solute movement between the apoplast and symplast • Phloem (see textbook figure 36.15) -Some plants have a form of electrical signaling through the phloem -Moves macromolecules and some types of RNA via plasmodesmata ~Movement of proteins and RNA unique to plants Soil and Plant Nutrition • Dirt is the inorganic, nonliving part of underground, while soil is much more complex, as it involves everything, living and nonliving, belowground • Soil Ecosystems -Fragile Ecosystem ~There are many distinctly different layers of soil as you dig straight down ~Upper layers provide nutrients and water to plants ~Many organisms live in and create the structure of soil -Examples: Plants, bacteria, insects, fungi, nematodes • Soil Composition -Soil Stratification ~Layers known as horizons ~Upper layer is topsoil -Soil particles differentiated by size, smallest to largest: ~Clay-smallest particles; too close together and holds too much water ~Silt-more gaps in particles than clay; better for holding the right amount of water ~Sand-big spaces between particles; not good for retaining water -Topsoil consists of mineral particles, living organisms, and decaying organic material, humus • Soil Horizons (see textbook figure 37.2) -Loams are soils that support highly productive plant growth, composed of roughly equal parts sand, silt, and clay ~A horizon-Topsoil: broken rock of differing sizes and textures, living organisms and decaying organic matter ~B horizon-Less weathered rock and less organic material ~C horizon-Partially broken rock, parent material for upper layers • Inorganic Components -Cations (positive ions, for example, K , Ca , Mg ) adhere to negatively charged soil particles; this prevents them from leaching out of the soil as water flows through ~Leaching occurs when a substance is removed from soil due to liquid passing through ~Negatives don’t attract negatives, so the harmful anions are leached out of the soil so the plants can live ~Example: Acid rain is positively charged, and, when it enters the soil, it depletes it of all the necessary cations, which is why the plants die -During cation exchange, cations are displaced from soil particles by other cations (see textbook figure 37.3) -Displaced cations enter the soil solution and can be taken up by plant roots -Negatively charged ions do not bind with soil particles and can be lost from the soil by leaching from percolating groundwater • Soil Conservation -Agriculture impacts soil ~Depletes nutrients-when a plant is growing, it takes up nutrients from the soil that are then completely removed during harvest ~Increases erosion-the soil is disturbed during planting and harvesting, which causes erosion ~Taxes water resources ~Soil compaction- during planting, the soil is purposefully compacted somewhat, and the result of this is more water runoff because the compacted soil can’t hold as much water, and the runoff causes erosion • Agriculture and Water -Irrigation is a huge drain on water resources when used for farming in arid regions -Usable fresh water is either from surface water (lakes and streams) or ground water (aquifers) -The depleting of aquifers can result in subsidence, the settling or sinking of land -Irrigation can lead to salinization, the concentration of salts in soil as water evaporates ~The water evaporates, leaving the salt particles behind, as they don’t also evaporate ~When this happens, the soil is no longer useful ~This process is irreversible -Drip irrigation requires less water and reduces salinization ~Requires less water input, which consequently reduces salinization • Fertilization -Soils can become depleted of nutrients as plants and the nutrients they contain are harvested -Fertilization replaces mineral nutrients that have been lost from the soil -Commercial fertilizers are enriched in nitrogen, phosphorus, and potassium -Organic fertilizers are composed of manure, fishmeal, or compost -Crop rotations with legumes or other plants that have close associate with nitrogen fixers ~Legumes put necessary nutrients back in the soil because they produce more than they actually need, so crops planted in following years don’t require as much fertilizer -Letting fields go fallow for a season ~Not intentionally planting anything, but letting weeds and cover crops grow, and letting natural biological processes replenish the soil • Modern Agriculture and Soil -Large monoculture farms with high fertilizers have bacteria dominated soil food webs -Natural systems and organic farms have fungal based soil food webs • Controlling Erosion -Topsoil from thousands of acres of farmland is lost to water and wind erosion each year in the United States -Erosion of soil causes loss of nutrients -Erosion can be reduced by: ~Planting trees as windbreaks; it’s harder for the wind to disturb the soil ~Terracing hillside crops ~Cultivating in a contour pattern (see textbook figure 37.6) ~Practicing no-till agriculture; this is where you don’t disturb the soil as much by turning it over before planting, thereby decreasing erosion • Nutrients (see textbook table 37.1) -A chemical element is considered an essential element if it is required for a plant to complete its life cycle ~This is where the organism doesn’t make the nutrient itself, but have to ingest from an outside source ~Example in humans: vitamin C is essential because we can only get it through food, while vitamin D is nonessential because we make it ourselves when given access to sunlight -Nine of the essential elements are called macronutrients because plants require them in relatively large amounts ~The macronutrients are carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium -The remaining eight are called micronutrients because plants need them in very small amounts ~The micronutrients are chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum • Soil Bacteria and Plant Nutrition -Rhizosphere ~The layer of soil bound to the plant’s roots ~The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots -Rhizobacteria ~Free living -Not attached to or dependent on another organism ~Function in the rhizosphere ~Can enter roots • Rhizobacteria -Rhizobacteria can play several roles ~Produce hormones that stimulate plant growth ~Produce antibiotics that protect roots from disease ~Absorb toxic metals ~Make nutrients more available to roots -Inoculation of seeds with rhizobacteria can increase crop yields ~Because much of agricultural soil is composed of bacteria, adding yet more to seeds would consequently benefit growth • Bacteria in the Nitrogen Cycle (see textbook figure 37.10) -Nitrogen can be an important limiting nutrient for plant growth -The nitrogen cycle transforms nitrogen and nitrogen-containing compounds ~Without this transformation, nitrogen would be inert and not useful/not accessible to plants -Most soil nitrogen comes from actions of-soil bacteria + -Plants absorb nitrogen as either NO (ni3rate) or NH 4 (ammonium) -Bacteria break down organic compounds or use N to prod2ce NH 3 (ammonia), which is converted to NH + 4 - -Nitrification is carried out by bacteria that convert NH i3to NO 3 • Nitrogen-Fixing Bacteria -N 2s abundant in the atmosphere, but unavailable to plants -Nitrogen fixation is the conversion of nitrogen from N to 2H 3 -Symbiotic relationships with nitrogen-fixing bacteria provide some plant species with a built-in source of fixed nitrogen -Key symbioses occur between nitrogen-fixing bacteria and plants, including those in the legume family (peas, beans, and other similar plants) -Along a legume’s roots are swellings called nodules, composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria (see textbook figure 37.11 and 37.12) -Inside the root nodule, Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell -The bacteria of a root nodule obtain sugar from the plant and supply the plant with fixed nitrogen ~Mutualistic relationship Plant Reproduction and Biotechnology (see textbook figures 38.2, 38.4, 38.7) • Pollination (see textbook figures 38.5, 38.12) -In angiosperms, pollination is the transfer of pollen from an anther to a stigma -Pollination can be by wind, water, bee, moth, butterfly, cricket, beetle, wasp, ant, fly, bird, or bat • Plant sexuality -Many angiosperm species reproduce both asexually and sexually -Sexual reproduction results in offspring that are genetically different from their parents -Asexual reproduction can result in a clone of genetically identical organisms • Mechanisms of Asexual Reproduction -Fragmentation, separation of a parent plant into parts that develop into whole plants, is a very common type of asexual reproduction ~If you remove part of a parent plant and then just replant it, then it will grow into a whole new plant -In some species, a parent plant’s root system gives rise to adventitious shoots that become separate shoot systems -Apomixis is the asexual production of seeds from a diploid or haploid cell -Multiple forms of apomixis ~Nonrecurrent apomixis occurs when the haploid gametophyte gives rise to a haploid individual ~Recurrent apomixis occurs when meiosis is not completed ~Adventive embryony occurs when the embryo arises from the integument or other sporophyte cells ~Vegetative apomixis occurs when the flow is replaced by a bulbil ~Pollen apomixis is when the male pollen grains give rise to seeds without any female interaction • Advantages and Disadvantages of Asexual Versus Sexual Reproduction -Asexual reproduction is also called vegetative reproduction -Asexual reproduction can be beneficial to a successful plant in a stable environment -However, a clone of plants is vulnerable to local extinction if there is an environmental change Iclicker Questions • The sporophyte is always the dominant diploid generation of gymnosperms and angiosperms • Pollen grains contain the gametophyte • A carpal is composed of a style, stigma, and ovary • Corpse flowers are pollinated by flies attracted by the odor of rotting flesh • Fungal nutrition is heterotrophic • Double fertilization results in a diploid embryo and a triploid endosperm • The largest single family of angiosperms is the orchids • Apical dominance means axillary buds are dormant while apical buds continue to grow • Roots can function to provide nutrients and water to the plant, provide structural support, and provide storage • Which cell type performs most of the metabolic functions of the plant? Parenchyma • Which cell type carries water from roots to leaves? Vessel elements • The pith is located interior to the cortex • Which is true about mutations? Mutations are changes in the genetic code that can alter the function of genes and mutations can alter the morphology of the organism • Mitosis is the division of a diploid nucleus into two identical sets so that the cell can divide into two copies • Is sap mainly pushed up from the roots or pulled up by the leaves? Both, but they are not equal in their effects • At night, transpiration is lowest • Which are some of the effects of agriculture? Soil compaction and decreased soil nutrients • Bacteroids, ecologically are mutualists • Which adhere to soil particles? Cations Quiz Answers • Homework Quiz 3 -Mosses have gametophyte as the dominant generation, while pine trees have sporophyte as the dominant generation -In ferns, the dominant generation is sporophyte and diploid -In gymnosperms, the gametophyte generation is very small and dependent on the sporophyte -In a Lodgepole Pine tree, the fertilized seed contains the following layers: 2n embryo, 1n food supply, and seed coat -A plant species that is dioecious means that it has male plants and female plants -Gymnosperm seeds are found on modified leaves (sporophylls) -Do perfect flowers have to be complete flowers? No -Which of the following is true of anthers? Anthers are modified leaves that produce pollen -The relationship between a gametophyte and a sporophyte in a liverwort is like the relationship between a parent and a child -The phylum Gingkophyta is unique among gymnosperms because it contains only a single living species • Homework Quiz 4 -When comparing eudicots and monocots, which of the following is a trait unique to eudicots? Pollen grains with three openings -Which of the following is a fruit in the botanical sense? Tomato -Which of the following is a monocot? Palm -Which of the following roots does not provide structural support? Pneumatophore -Which of the following is not a modified leaf? Thorn -Since ground tissue is that tissue which is neither vascular, does that mean is provides no important function for the plant? No -The cells in ground tissue that perform photosynthesis are parenchyma -Which of the following cells are alive at functional maturity? Sieve-tube elements -Which of the following are the lateral meristems in a woody plant? Cork cambium and vascular cambium -You find a plant that has lost its leaves. You want to know if it is a monocot or eudicot. You cut through the stem. From what you see, you conclude it has a ring of vascular bundles, so it must be a eudicot • Homework Quiz 5 -Consider a container with a semipermeable membrane dividing the volume. If the volume on the right has a water potential of -0.7 MPa, which of the following water potential values in the left side will cause water to move to the left in the largest quantities? -0.20 -Water entering a root must travel by which route to enter the stele of the root? Symplastic -Cohesion in the xylem is function of hydrogen bonding -Guard cells open the stomata when the cells are turgid -Cations carry a positive charge -Acid rain negatively affects plants by leaching cations that the plant needs from the soil -Nitrogen from the atmosphere is converted to ammonia by which type of bacteria? Nitrogen fixing bacteria -Which of the following is a method of reproduction that plants cannot do to generate offspring? Binary fission -Which of the following is an adaptation for a plant in the desert? CAM photosynthesis -The movement of sugars into and out of cells is conducted by active transport
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'