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Leaf anatomy. Leaves start as outgrowths from apical meristem: leaf primordia

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Text of Leaf anatomy. Leaves start as outgrowths from apical meristem: leaf primordia

  • Leaf anatomy

  • Leaf anatomyLeaves start as outgrowths from apical meristem: leaf primordia.

  • Leaf anatomy3 primary meristemsprotoderm: becomes __________procambium: becomes ___________ground meristem: becomes ____________.

  • Leaf anatomyEpidermis: note cuticle, stomataVeins with vascular tissues (____________________)Supply water & nutrients, remove sugars for transport elsewhere.

  • Leaf anatomyMesophyll Parenchyma tissue layers (palisade and spongy: do ____________.

  • Monocot vs dicot anatomyStem: Dicot with bundles __________. Pith and cortex present. Monocot: scattered vascular bundles. No _______________.

  • Monocot vs dicot anatomyRoot: Dicot, < 6 phloem patches, no pith

  • Monocot vs dicot anatomyRoot: Monocot, many _____________, pith present

  • Monocot vs dicot summaryNote root system type: dicot often with single major root axis (taproot system), monocot lacking this (fibrous root system)

  • Plant Growth PhenomenaHormones: molecules produced in small amounts that change __________________________Can inhibit or stimulate processes to occur5 major types: auxinscytokininsgibberellinsethyleneabscisic acid

  • AuxinsPromote stem elongation and growthExample, ___________. Bending of stem toward light

  • AuxinsAlso involved in ______________: suppression of lateral meristems by apical meristem

  • AuxinsCan stimulate production of ______________ roots (roots produced on stem or leaf)Useful in rooting cuttings (asexual plant reproduction)

  • CytokininsStimulate cell division where auxin is also presentActs as ____________ hormone (keeps detached leaves green).

  • GibberellinsPromote stem elongationMutant plants with low amounts are _________ (internode lengths short)

  • EthylenePromotes fruit ripeningStimulates ____________ (dropping) of leaves, flowers

  • Abscisic acidInduces formation of winter buds (bud scales, dormant meristem)Involved in opening and closing of _____________Can cause seed dormancy

  • Other plant growth phenomenaGravitropism: response of stem/root to gravityStems bend away from gravity (___________ gravitropism)Roots bend toward gravity (_________ gravitropism)

  • Other plant growth phenomenaMechanism unclear. May involve ________ ________ called statoliths (in root cap of root, in parenchyma cells of stem)

  • Other plant growth phenomenaThigmotropism: response of plant to __________Examples: Many tendrils grow toward stimulus and wrap around object

  • Turgor movementNot growth: involves loss of water pressure (turgor pressure) in some cellsCan be reversedMay involve rapid movement (electrical signal)Ex, sensitive plant

  • FloweringSome plants use daylength as flowering cueCan measure length of night (photoperiod) by pigment called ______________

  • FloweringLong day plants: flower when night is ________ than some critical time Short day plants: flower when night is _______ than some critical timeDay neutral plants: dont use photoperiod as flowering cue

  • FloweringUse: Can make some plants bloom when we want themEx, poinsettia. A short-day plant that growers make flower for Christmas holidays.

  • Plant transportPhloem: sugars and water (often from leaf to root)Xylem: water and minerals from root to shootMovement driven by _____________: measure of tendency of water to move from one place to another

  • Plant transportWater potential is affected by:solutes (high solutes = ______ tendency to move)pressure (high pressure = ______ tendency to move)tension (pull: high tension = ______ tendency to move).

  • Water transportXylem: water and minerals from root to shootHow much of water remains in plant?
  • Water transportTranspiration: evaporation of water from leavesDriven by _______ from leaves. Water under tension. Water potential high in soil and low in air.

  • Water transportDriven by pull from leaves. Water under tension. Water potential high in soil and low in air.

  • Water transportTranspiration greatly controlled by stomataStomata open in ________ but can close if plant lacks sufficient water.Stomata!

  • Sugar transportPhloem: sugars and water Flow from ______ to _____Pressure flow mechanism

  • Sugar transportSource: lots of sugar dissolved in water. Generates pressure as water flows in to _______ sugarSink: little sugar dissolved in water. Low pressure as water flows outCreates ___________ gradient that moves fluid thru sieve tubes.

  • Sugar transportResult: sugar flows to wherever demand is high

  • Secondary Growth

  • Secondary GrowthTwo types of growthPrimary growth: up and down. Generated by apical meristems. Form _________ tissuesSecondary growth: growth in girth. Generated by lateral (secondary meristems). Form __________ tissues.All plants do primary growthWoody plants do __________ growth

  • Secondary GrowthLateral meristems1) ______________: makes new phloem and xylemCalled ________ phloem and xylem tissues (vs. primary phloem and xylem made directly from procambium)Function: xylem takes water + minerals to leaves, phloem takes sugars to roots

  • Secondary GrowthLateral meristems2) ___________: makes new cell type, cork cell. Cork cells with primary wall impregnated with waxy material (_______). Dead at maturity. Forms waterproof layer on outside of body to replace epidermis._________: Tissue composed of cork cells and made by cork cambium. Also is a secondary tissue.

  • Secondary GrowthStem cross section

  • Secondary GrowthVascular bundles contain __________________Located between primary xylem and phloemMeristematic: can still do _______________

  • Secondary GrowthResidual procambium cells start to divideProduce new cells ______________

  • Secondary GrowthParenchyma cells between bundles also start to divideTogether form solid ring of cells, all dividing laterallyThis is __________________

  • Secondary GrowthVascular cambium makes secondary xylem on __________, secondary phloem on __________Note how cambium moves outward over time

  • Secondary GrowthNote arrangement of primary phloem and secondary phloem, primary xylem and secondary xylem

  • Secondary GrowthSecondary xylem may contain:1) Vessel elements2) Tracheids3) ____________4) FibersSecondary phloem may contain:1) Sieve tube elements2) Companion cells3) Parenchyma4) ___________

  • Secondary GrowthTwo

  • Secondary GrowthLater secondary growth

  • Secondary GrowthFirst cork cambium: Forms under ___________

  • Secondary GrowthCork cambium: Makes files of cork cells to outside. Forms first __________. Epidermis cut off from rest of stem and dies.

  • Secondary GrowthProblem: cork cells are dead at maturity. Cork layer cannot _________ as vascular cambium continues to grow.Solution: form new ______ ______ in cortex under old oneAfter time, several __________ build up (yellow lines). Newest (inner) one cuts off water to layers beyond it and they _______.

  • Secondary GrowthPeriderm replaces epidermis. How get _______ into stem?

  • Secondary GrowthLenticels: Loosely packed __________. Allow oxygen to diffuse into stem to support living cells there.

  • Secondary GrowthNote ____ made by vascular cambium: Form ________ transport system (often parenchyma cells)In phloem: phloem rayIn xylem: xylem ray (wood ray)

  • Secondary GrowthIn temperate zone, cambium activity varies between _____ and ______ in growing seasonSpring: big cells (_______ wood). Summer: small cells (_______ wood).Form growth ring (tree ring): one seasons growthEx, pine (mostly tracheids)

  • Secondary GrowthEx, oak (note vessels, thick-walled _________)

  • Secondary GrowthYoung tree section: Note rays here (phloem and xylem)Also note growth rings: early and late woodHow old was this stem when cut?

  • Secondary GrowthIn older tree: wood is secondary xylemHeartwood: old non-functional xylem________: younger often functional xylem

  • Secondary GrowthBark: From vascular cambium outward___________: From current cork cambium outward (all is dead)__________: From vascular cambium to current cork cambium. Contains functional secondary phloem

  • Secondary GrowthRemoving inner bark is deadly: girdling tree often will kill itWhy? Roots ______Why? No ________ from leaves.

  • Secondary GrowthFlow chart, showing how primary and secondary tissues develop in stem

  • Secondary GrowthNote that roots of woody plants also do secondary growthVascular cambium forms from __________First cork cambium forms in _____________.

  • Secondary GrowthSo outer cortex and epidermis are sloughed off and lost

  • Uses of Growth Rings1) Fire frequencyBreak in bark (_________) allows fire to burn through vascular cambium into woodLeaves burned layerIf tree survives, can have record of fires in wood.Ponderosa pine, WY

  • Uses of Growth Rings1) Fire frequencyHelpful information when trying to determine natural frequency of fires for managing forests.

  • Uses of Growth Rings2) Climate patterns (___________________)Width of rings can indicate growth conditions for tree (rainfall, etc.)Can reconstruct climate informationOldest reconstructions go back 8,000 yr B.C.

  • Uses of Growth Rings2) Climate patternsOldest reconstructions from bristlecone pine wood go back as far as ________ yr B.C.

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