Presentation on theme: "Plant Structures Roots, Stems, and Leaves"— Presentation transcript:
1 Plant Structures Roots, Stems, and Leaves Chapter 23
2 23-1 Specialized Tissues in Plants Plants are as successful if not more successful than animalsSeed plants have three main structures:RootsStemsLeavesLinked together by various means
3 23-1 Specialized Tissues in Plants RootsAbsorbs water and nutrientsAnchor plant to the groundHold soil in place and prevent erosionProtect from soil bacteriaTransport water and nutrientsProvide upright support
4 23-1 Specialized Tissues in Plants StemsSupport for the plant bodyCarries nutrients throughout plantDefense system to protect against predators and infectionFew millimeters to 100 meters
5 23-1 Specialized Tissues in Plants LeavesMain photosynthetic systemsSuseptable to extreme dryingSight of oxygen/carbon dioxide intake and release
6 23-1 Specialized Tissues in Plants Plant tissue systemsExist within the root, stems, and leavesDermal tissueVascular tissueGround tissue
7 23-1 Specialized Tissues in Plants Dermal TissueOuter coveringSingle layer of cellsCuticle – waxy coatingTrichomes – Spiny projections on the leafRoots have dermal tissueRoot hairsGuard Cells
8 23-1 Specialized Tissues in Plants Vascular TissueTransport SystemSubsystemsXylemPhloemSubsystems are used to carry fluids throughout plant
9 23-1 Specialized Tissues in Plants XylemTwo typesSeed plantsAngiospermsTracheid – long narrow cellsWalls are connected to neighboring cellsWill eventually dieVessel Element – wider that tracheids
10 23-1 Specialized Tissues in Plants PhloemSieve Tube ElementsCells arranged end to endPump sugars and other foodsCompanion CellsSurround sieve tube elementsSupport phloem cells
11 23-1 Specialized Tissues in Plants Ground TissueCells between dermal and vascular tissueParenchymaThin cell walls, large vacuoulesCollenchymaStrong, flexible cell wallsSclerenchymaExtremely thick, rigid cell walls
12 23-1 Specialized Tissues in Plants Plant GrowthMeristems – tissues responsible for growthUndifferentiated cellsApical MeristemProduce growth increased lengthDifferentiationCells will assume roles in the plantFlower DevelopmentStarts in the meristem
13 23-2 Roots Types of Roots Taproots Fibrous roots Found in dicots Long, thick rootHickory and oak treesFibrous rootsFound in monocotsNo single root larger than any otherMany thin rootsHelp prevent erosion
14 Root Structure and Growth Outside layer = epidermisCentral cylinder = vascular tissueBetween these two = ground tissueRoots important in water and mineral transport14
15 23-2 Roots Root Structure Epidermis – outside layer Root hairsCortex – spongy layer of ground tissue inside epidermisEndodermis – layer inside cortexVascular cylinder – central vascular systemRoot Cap – the tip, cellular production
16 Root Growth Roots grow by producing new cells near the tip! Root lubricates its pathNew cells are added at the root capBehind the meristematic tissue, cells grow longerThese cells specialize and take on different functions (process of differentiation)
17 Root Functions Anchor a plant in the ground Absorb water and dissolved nutrients from the soilWater and nutrients do not just soak into the root from the soilThe plant requires energy to absorb water17
18 23-2 Roots Plant Nutrient Uptake Plant requirements Soil includes sand, silt, clay, air, bits of decaying organic matterSoil type determines plant type!Plant requirements- Oxygen, CO2- Nitrogen - Magnesium- Phosphorus - Calcium- Postassium - Trace elements
19 Types of soilSandy soil is made up of mostly grains of sand. Water passes through this type of soil quickly.Clay soil is mostly made of fine clay particles. Water poured on clay soil sinks slowly.Loamy soil contains decaying plant and animal matter along with clay and sand.
20 Essential NutrientsNitrogen is important for leaf growth and color. A plant that lacks nitrogen will have yellow leaves.Phosphorous is needed for roots, stems and flower growth as well as seeds. A plant lacking phosphorous will have stunted growth and few flowers.
21 Potassium is important in root, stem and flower development as well Potassium is important in root, stem and flower development as well. It helps the plants live in the cold and fight disease. Plants with too little potassium have stunted roots. Potassium is sometimes called potash.Calcium is needed for cell growth and for strong cell walls.Magnesium is needed to make chlorophyll. Plants will die without chlorophyll.
22 Plants also need very small amounts of what are called trace elements Plants also need very small amounts of what are called trace elements. The plant will not grow well if these trace elements are not present, but if there is too much of the trace elements in the soil they are poisonous to the plant.
23 23-2 Roots Active Transport in Plants Vascular Cylinder Root hairs use ATPPump minerals fromsoilCauses water moleculesto follow by osmosisVascular CylinderCasparian Strip – waterproof strip surrounding endodermal cells: H20 retention
24 Osmosis and Root Pressure Water moves into the vascular cylinder by osmosis (diffusion through semipermeable membrane)Water and minerals can’t pass through the Casparian strip, so they’re trapped once inside the vascular cylinder!Root PressureOne-way movement creates pressureForces water up into the plantIf pressure didn’t build up, roots would swell up!
25 23-3 Stems Stem Structure Essential part of transport system Produce leaves, branches, and flowersHold leaves up to sunlightTransport substance between roots and leavesEssential part of transport systemFunction in storage and photosynthesisLike other plant parts, stems have vascular, dermal, and ground tissue!
26 23-3 Stems Xylem and phloem – major tubule systems Transport water and nutrientsComposed of 3 tissue layersContain nodes – attachment for leavesInternodes – regions between the nodesBuds – undeveloped tissue
27 23-3 Stem Types Monocot – vascular bundles are scattered throughout - Distinct epidermisDicot – vascular tissue arranged in a cylinder- Pith – parenchyma cells inside the ring (ground tissue with thin cell wall, large vacuole)Monocot – vascular bundles are scattered throughoutDistinct epidermisDicot – vascular tissue arranged in a cylinderPith – parenchyma cells inside the ring (ground tissue with thin cell wall, large vacuole)
28 23-3 Stem GrowthPrimary growth – new cells produced at the root tips and shootsIncreases the lengthSecondary growth – increase in stem widthVascular cambium – meristematic tissue that produces vascular tissue and increases thicknessCork cambium – produces outer covering of stems
29 23-3 Stems Formation of Vascular Cambium Xylem and phloem bundles present in a ringSecondary growth initiates production of a thin layerThe vascular cambium dividesProduces new xylem and phloem
30 23-3 Stems Formation of wood Wood – layers of xylem Produced year after yearResults from the older xylem not conducting water – heartwoodBecomes darker with ageSapwood – surroundsheartwood
31 Annual RingsIn spring, growth happens quickly, producing light-colored xylem cells with thin cell wallsAt the end of the season, the cells become darker with thicker cell walls (late wood)Each season, a ring with light and dark is producedBy counting rings in a tree, you can estimate age!
32 23-3 Roots Formation of Bark All the tissues outside the vascular cambiumConsists of outermost layers of dead corkWater proof
33 23-4 Leaves Main site of photosynthesis Consist of: Blade – thin flattened sectionPetiole – stalk that attaches stem to bladeCovered by epidermis and cuticle (waxy covering)Create water proof barrier
34 23-4 Leaves Leaf Functions Photosynthesis – occurs in the mesophyll (specialized ground tissue in leaf)Palisade mesophyll – absorb lightSpongy mesophyll – beneath palisade level
35 Stomata Stomata – pores in the underside of the leaf Singular: stoma Guard Cells – epidermal cells surrounding the stomata, specialized to open and close
36 23-4 Leaves Transpiration Loss of water through its leaves Replaced by water drawn into the leaf through xylem
37 Gas Exchange Take in CO2 and release O2 Can do the opposite – when using food, take in oxygen and release CO2Gas exchange takes place at the stomataNot open all the timeStomata is controlled by water pressure in guard cells
38 Gas Exchange & Homeostasis Plants keep stomata open just enough to allow photosynthesis to occur, but not to lose too much water!When water pressure is high, guard cells pulled away and stoma opens!When water pressure is low, inner walls pull together and stoma closes!Usually: stomata open in daytime, closed at night… why?
39 23-5 Transport in Plants Water Transport Active transport and root pressureCause water to move from soil to rootsCapillary actionCombined with active transport and root pressure, moves materials throughout the plant
40 23-5 Transport in Plants Capillary Transport Capillary transport results from both cohesive and adhesive forcesWater molecules attracted to one anotherWater is also attracted to the xylem tubes in the plantCauses water to move from roots to the stem and upward
41 23-5 Transport in Plants Transpiration Evaporation is the major moving forceAs water is lost, osmotic pressure moves water out of vascular tissueThis pulls water up from the stem to the leavesAffected by heat, humidity, and wind
42 23-5 Transport in Plants Controlling Transpiration Open the stomata – increase water lossClose the stomata – decrease water loss
43 23-5 Transport in Plants Transpiration and Wilting Osmotic pressure – keeps plants semi-rigidWilting is a result of high transpiration ratesLoss of water causes a drop in osmotic pressureLoss of rigidityConserves water
44 23-5 Transport in Plants Nutrient Transport Source to Sink Most nutrients are pushed through plantNutrient movement takes place in phloemSource to SinkSource – any cell that produces sugarsSink – any cell where sugars are usedPressure-flow Hypothesis