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.
