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Plants
 

Plants

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Plants Plants Presentation Transcript

  • Lecture 7:Plants and Fungi
  • FungiNot plants, not animalsMulticellular eukaryotesNot closely related to either animals orplants
  • FungusMade of hyphae, which are thin cellfilaments packed closely togetherMycelium is the main body of thefungus- it penetrates whatever thefungus is growing onThey can be HUGE in the soil and covergiant areas
  • MushroomsThe part we eat is a fruiting body- it isthe part that produces spores, one way inwhich fungi reproduce
  • Fungi in the EcosystemMost are decomposers that break downorganic waste in the soilCan also feed on live animals andplants (ringworm, for example)Fungi also occur in mutualisticrelationships: lichen, mycorrhizal fungi
  • Economic BenefitsMake cheese, beer, bread, wine, soy sauceUse to make medicinesOf course we also just eat themCan break down some pollutants withorganic sources
  • Fungal DiseasesCan damage crops- corn smutCandida- yeast infections, oral thrush Can damage heart and brain if untreatedTinea- ringworm, athlete’s footBatrachochytrium dendrobatidis- chytridfungus in frogsHistoplasma- from bird droppings
  • PlantsMulticellular, eukaryotic, photosyntheticChallenge: live on land, avoid drying outPlants evolved from algae ~500 mya5 main groups of plants Each associated with an evolutionary event
  • The 5 groupsMosses: No way to transport water, but canavoid drying out if in a moist areaLycophytes: Have a vascular system totransport waterFerns: Have large leaves, allows morephotosynthesisGymnosperms: Have seedsAngiosperms: Have flowers
  • Plant reproduction Alternation of Generations A plant has two forms: one is diploid and the other is haploid
  • Plant Reproduction Dominant generation: The one we recognize as the plant itself. In vascular plants, this is the sporophyte - only this generation evolved vascular tissue. The gametophytes are typically microscopic In nonvascular plants, this is the gametophyte
  • Nonvascular plantsAlso called bryophytesNo true roots, stems or leaves- thesewould require vascularityLiverworts and mosses
  • Vascular PlantsHave roots, stems, and leavesRoots absorb water from the soil, send itup the stem to the leavesLeaves covered by waxy cuticle to preventdehydration, except for stomata- poresthat allow for gas exchange
  • Vascular PlantsVascular tissue is a big advantage, plant can livefurther away from water, can get water out of thesoilVascular tissue has two parts: Xylem- brings water and minerals up from soil Phloem- brings organic nutrients form one part of plant to another Lignin- found in cell walls and makes them very strong
  • LycophytesAlso sometimes called club mossProbably the first plants to developvascular tissueLeaves are very small and each have asingle vein with xylem and phloemDo not produce seeds
  • FernsHave megaphylls- large leaves with branched veins These provide larger surface area for photosynthesisDo not produce seedsDuring the Carboniferous period, the ferns andlycophytes were the size of trees When they fell, they were covered by water and did not decompose completely- they were slowly compressed to form....COAL
  • Seed PlantsMost plentiful plants todaySeeds consist of embryo (sporophyte), seed coat,and stored food Coat allows seed to stay dormant until conditions are favorable to growth- some seeds can be dormant for decadesSeed plants produce male and femalegametophytes: pollen is male, ovule (seed origin)is female
  • GymnospermsOvules and seeds are exposed on a conescaleConifers (pines, cypress, firs, etc) are themost common gymnosperms todayWell adapted to dry conditions Needlelike leaves resist dessication Can live in very cold regions
  • AngiospermsFlowering plants240,000 living speciesThe flowers are really the sex organs ofthe plant
  • Flower AnatomyStamenContains pollen Stigma is sticky; accepts pollen grains
  • AngiospermsThe flower produces a seed; it is enclosedby fruitIn order to angiosperms to reproduce,they must spread pollen and then seedsaround Flowers help to do this
  • Adaptations of AngiospermsWind-pollenated flowers- small and dullInsect or bird pollenated- usually colorful andlargerBee-pollenated have ultraviolet colors to lead bees topollenNight- blooming flowers to attract nocturnalanimalsFruits enhance seed spread because eaten byanimals and thus dispersed
  • Importance of PlantsFood sourceWood productsPharmaceuticalsPlants produce O2Plants carry out carbon and water cyclesSome can absorb toxic chemicalsAesthetic value
  • Flowering Plant AnatomyShoot System: stem, leaves and flowersRoot System: the rootsTerminal Bud: at tip of main stem orroot where primary growth occurs Grow in both directions this way
  • Flowering Plant AnatomyLeaves Usually primary place for photosynthesis Require sunlight, CO2, and water Can be highly modified Cactus spines, tendrils, flytraps
  • Flowering Plant AnatomyStems Supports leaves, transport between roots and leaves, produces new tissue Some stems do other things: cactus, etc.
  • Flowering Plant AnatomyRoots: Supports and anchors the plant Absorbs water and minerals from the soil Different structures: root hairs, taproots, etc.
  • Monocots and EudicotsTwo types of flowering plantsNamed after number of cotyledons-embryonic leaves, in the seed. Monocots have one, eudicots have twoMany differences between the two types Monocots: grass, corn, lilies, palms, wheat Eudicots: dandelions, oak trees, potatos
  • Monocots Eudicots One cotyledon Two cotyledons Parallel leaf veins Net veined leaves Vasc. bundles in stems are Vasc. bundles in stems are in scattered a circle Flower parts in 3’s Flower parts in 4’s or 5’sSeed chambers in fruit in 3s Seed chambers in fruit in 4’s or 5’s Tap root system Fibrous root systsem
  • Plant Tissue3 Specialized tissues: Epidermal tissue- outer protective covering “skin” Ground tissue: Interior of a plant, carries out functions Vascular tissue: Transports water and nutrients, provides support
  • Plant TissuePlants continue to grow their entire livesbecause they have merisetm tissue:embryonic tissue that divides and canproduce any of the three specializedtypes
  • EpidermisThe outer layerOutside that is exposed to air is covered bywaxy cuticle- minimizes water lossProtects plant from pathogensIn leaves, contain stomata- openings for gasexchange to occurIn trees, cork replaces epidermis to help formbark
  • Ground TissueMost of the plant is ground tissue- 3 kinds ofcells: Parenchyma: least specialized cells, found everywhere Collenchyma: give flexible support to plant- strands in celery, for example Sclerenchyma: have cell walls that contain lignin, makes them strong- mostly dead cells like in nut shells, cotton and flax fibers
  • Vascular TissueTwo types, usually found together Xylem: water and minerals from roots to leaves Phloem: sugar, etc. from leaves to roots X up, P down!In the stem and roots, and the veins ofleaves
  • More About LeavesFlat part is blade, stem that attaches leafto rest of plant is the petioleSimple leaves- undividedCompound leaves- several leaflets makeup one leafMost of the time, the cells that carry outphotosynthesis are in the leaves
  • More About StemsNonwoody stems- Herbaceous plantsHave vascular bundles that containxylem and phloemMonocot stems are less organized thaneudicot stems- see book
  • More About StemsWoody stems, such as in trees, have secondarygrowth that increases the girth of the plantPhloem is in the bark, so removing the barkprevents transport of nutrientsWood is secondary xylem, that increases year byyear- the wood is what carries enough water to getall the way up to the leaves on the treeCan tell a tree’s age by looking at annual ringsin the trunk
  • More About RootsVery nice list of root structure andfunction in book on page 351, pleaserefer to that for next slide
  • Pericycle can start development ofnew root branches Endodermisregulates whatenters vascular tissue
  • Roots and NutrientsPlants (and therefore all animals too) relyon bacteria in the soil to fix N Have a symbiotic relationship- the bacteria take N from the soil, the plant provides food for the bacteriaPlants also rely on fungus: mycorrhizalassociation, to increase water uptake andbreak down nutrients for the plant
  • Water transport in plantsHow does water get from roots to leaveswithout a heart or other organ to push it?Cohesion-tension modelSee book; drawing on boardLOTS of water lost from plants throughtranspiration
  • TranspirationReduces floodingReturns water to the water cycle from thesoilWhy plants need more water as theygrow- they are losing it all the time
  • Movement in PhloemPressure-flow model1. Plants make sugar2. It is transported to phloem through active transport3. As it accumulates in phloem, water follows due toosmotic pressure4. Starts flow5. Tissues without sugar are a SINK- they take upsugar