Plants IIPlants II

Plant organsPlant organs

Plant organsPlant organs

Root system – rootsRoot system – roots Shoot system – stem and leavesShoot system – stem and leaves

Vegetative organs – (allow to live and Vegetative organs – (allow to live and grow): roots, leaves, stemgrow): roots, leaves, stem

Reproduction: flowers, seeds and fruitsReproduction: flowers, seeds and fruits

RootsRoots

Underground, usually equal to shoot Underground, usually equal to shoot system in sizesystem in size

Anchors and gives supportAnchors and gives support Absorbs water and mineralsAbsorbs water and minerals Penetrates soil as it grows Penetrates soil as it grows Root hairs increase surface Root hairs increase surface area area Produce hormonesProduce hormones

stemsstems

Main axis of plantMain axis of plant Support leaves so that leaves are Support leaves so that leaves are

exposed to as much light as possibleexposed to as much light as possible NodeNode – where leaf is attached – where leaf is attached InternodeInternode – space between nodes – space between nodes Vascular tissue used in transportVascular tissue used in transport Can store nutrients and water and Can store nutrients and water and

conduct photosynthesisconduct photosynthesis

leavesleaves

PhotosynthesisPhotosynthesis Size, shape and texture vary and is used Size, shape and texture vary and is used

in identificationin identification Blade – wide portion of leafBlade – wide portion of leaf Petiole – stalk, attaches blade to stemPetiole – stalk, attaches blade to stem Axillary bud – where branch or flower Axillary bud – where branch or flower

may originatemay originate

Monocot vs Eudicot Monocot vs Eudicot fig 25.3fig 25.3

Compare seed leaf, root, stem, leaf and flowerCompare seed leaf, root, stem, leaf and flower MonocotMonocot – 1 seed leaf, xylem and phloem in a – 1 seed leaf, xylem and phloem in a

ring, vascular bundles scattered, leaf veins ring, vascular bundles scattered, leaf veins parallel, flower parts in 3’s and multiples of 3parallel, flower parts in 3’s and multiples of 3

EudicotEudicot – 2 seed leaves, phloem between – 2 seed leaves, phloem between arms of xylem, vascular bundles in ring, leaf arms of xylem, vascular bundles in ring, leaf veins in net pattern, flower parts in 4’s, 5’sveins in net pattern, flower parts in 4’s, 5’s

EudicotsEudicots make up larger group and include make up larger group and include most familiar flowering plantsmost familiar flowering plants

MonocotsMonocots include grasses and most of food include grasses and most of food sources, like rice, wheat and cornsources, like rice, wheat and corn

Plant tissuesPlant tissues

Meristematic tissue = embryonicMeristematic tissue = embryonic Apical meristem – located on tip of stem and Apical meristem – located on tip of stem and

roots, growthroots, growth produces 3 types of meristemproduces 3 types of meristem

Protoderm Protoderm epidermisepidermis Ground meristem Ground meristem ground tissue ground tissue Procambium Procambium vascular tissue vascular tissue

WoodyWoody (non herbaceous), (non herbaceous), non woodynon woody (herbaceous – perennial, dies back in winter)(herbaceous – perennial, dies back in winter)

Epidermal tissueEpidermal tissue

Forms outer protective covering of plantForms outer protective covering of plant Walls of epidermal cells exposed to air are covered Walls of epidermal cells exposed to air are covered

with a waxy cuticlewith a waxy cuticle Roots – form root hairsRoots – form root hairs Stems and leaves – Stems and leaves – trichomestrichomes – hairs that protect – hairs that protect

form too much sun and moisture reserveform too much sun and moisture reserve Leaves – guard cells, stomataLeaves – guard cells, stomata PeridermPeriderm – old woody plants, replaces epidermis – old woody plants, replaces epidermis

Cork cells – protectionCork cells – protection Cork cambium – new cork cells made fromCork cambium – new cork cells made from Lenticels – areas of overproduction of cork cells, gas exchangeLenticels – areas of overproduction of cork cells, gas exchange

Ground tissueGround tissue

Bulk of a plantBulk of a plant 3 types: 3 types:

1.1. Parenchyma cells – most abundant, found Parenchyma cells – most abundant, found in all organs of plant, least specializedin all organs of plant, least specialized

2.2. Collenchyma – thick primary walls, flexible Collenchyma – thick primary walls, flexible support to immature regions, celery strandsupport to immature regions, celery strand

3.3. Sclerenchyma – thick secondary walls that Sclerenchyma – thick secondary walls that contain lignin (make walls tough), support contain lignin (make walls tough), support mature region of plantmature region of plant

Vascular tissueVascular tissue

Xylem – water and minerals, roots to leavesXylem – water and minerals, roots to leaves Phloem – sucrose and organic molecules Phloem – sucrose and organic molecules

(hormones) form leaves to roots(hormones) form leaves to roots Complex tissues – contain 2 or more kinds of Complex tissues – contain 2 or more kinds of

cellscells Both extend from roots to leavesBoth extend from roots to leaves

Roots- located in vascular cylinder, stem – vascular Roots- located in vascular cylinder, stem – vascular bundles, leave – leaf veinsbundles, leave – leaf veins

XylemXylemfigure 25.6figure 25.6

2 types of conducting cells, hollow and 2 types of conducting cells, hollow and non-livingnon-living TracheidsTracheids – tapered ends, contain pits – tapered ends, contain pits

where secondary wall does not formwhere secondary wall does not form Vessel elementsVessel elements – larger, perforation plates – larger, perforation plates Parenchyma cells that store substancesParenchyma cells that store substances

Phloem – Phloem – fig 25.7fig 25.7

Sieve tube members – continuous sieve Sieve tube members – continuous sieve tube – no nucleustube – no nucleus Companion cells – have nucleusCompanion cells – have nucleus

Connected to sieve tube member by Connected to sieve tube member by plasmodesmata plasmodesmata

Root organizationRoot organization

Root cap – apical meristem, replaced Root cap – apical meristem, replaced oftenoften

ZonesZones Cell division – primary meristem, mitosisCell division – primary meristem, mitosis Elongation – cells lengthen and specializeElongation – cells lengthen and specialize Maturation – root hairs, fully differentiatedMaturation – root hairs, fully differentiated

Eudicot root tissueEudicot root tissue

Epidermis – single outer layer, root hairsEpidermis – single outer layer, root hairs Cortex – thin walled parenchyma, food storageCortex – thin walled parenchyma, food storage Endodermis – boundary between cortex and Endodermis – boundary between cortex and

vascular tissuevascular tissue Casparian stripCasparian strip – prevents water and mineral ions – prevents water and mineral ions

between cell wallsbetween cell walls Vascular tissue – xylem and phloemVascular tissue – xylem and phloem

Pericycle – first layer of cells Pericycle – first layer of cells Monocots similar, differ in arrangement of Monocots similar, differ in arrangement of

xylem and phloem in a ring, ground tissue is xylem and phloem in a ring, ground tissue is pithpith

Root diversityRoot diversity

TaprootTaproot – grows straight down, fleshy, stores – grows straight down, fleshy, stores food, carrot, beetfood, carrot, beet

Fibrous root systemFibrous root system – in monocots – seen in – in monocots – seen in grasses, strong anchoragegrasses, strong anchorage

Adventitious rootsAdventitious roots – develop from shoot – develop from shoot system instead of root system, seen in corn, system instead of root system, seen in corn, can come above soil linecan come above soil line

Root nodulesRoot nodules – beans, peas…, nitrogen – beans, peas…, nitrogen fixationfixation

MycorrhizaeMycorrhizae – plant roots and funugs – plant roots and funugs

Stem organizationStem organization

Terminal bud – shoot tip protected by bud scalesTerminal bud – shoot tip protected by bud scales Leaf and bundle scars – location of leaves that have Leaf and bundle scars – location of leaves that have

droppeddropped Axillary buds – give rise to branches or flowersAxillary buds – give rise to branches or flowers Bud scale scar – indicates age of stem, one for each Bud scale scar – indicates age of stem, one for each

year of growthyear of growth Primary meristem Primary meristem primary tissues primary tissues

Protoderm Protoderm epidermis epidermis Ground meristem Ground meristem pith (ground tissue) pith (ground tissue) Procambium Procambium cortex (vascular tissue) cortex (vascular tissue)

Herbaceous stemsHerbaceous stems

Non woody, die off in winter, perennialNon woody, die off in winter, perennial Only primary growthOnly primary growth Eudicot, vascular bundle in rings, cortex Eudicot, vascular bundle in rings, cortex

separate from pith separate from pith Monocot – vascular bindles scattered, no Monocot – vascular bindles scattered, no

well defined cortex or pithwell defined cortex or pith

Woody StemsWoody Stems

Primary (length) and secondary (girth of Primary (length) and secondary (girth of trunks) tissuestrunks) tissues

Secondary tissues form from lateral Secondary tissues form from lateral meristem: vascular cambium and cork meristem: vascular cambium and cork cambiumcambium Vascular cambium produces new xylem and Vascular cambium produces new xylem and

phloem each yearphloem each year

3 distinct areas: bark, wood and pith3 distinct areas: bark, wood and pith

Bark and WoodBark and Wood

Contains Contains peridermperiderm when stem becomes woody, replaces when stem becomes woody, replaces

epidermisepidermis Cork, cork cambium and phloemCork, cork cambium and phloem Removing bark and be fatal to treeRemoving bark and be fatal to tree

Wood is secondary xylem, girth Wood is secondary xylem, girth Vascular cambium is dormant in winterVascular cambium is dormant in winter Annual ring – sapwood, inner rings - Annual ring – sapwood, inner rings -

heartwoodheartwood

Stem diversityStem diversity

StolonsStolons – aboveground horizontal – aboveground horizontal stems, reproduce where nodes touch stems, reproduce where nodes touch ground, runners, strawberriesground, runners, strawberries

RhizomesRhizomes – underground, horizontal – underground, horizontal stems, some contain tubers (food stems, some contain tubers (food storage) like potatoesstorage) like potatoes

CormCorm – bulbous underground stems, – bulbous underground stems, gladiolusgladiolus

Leaf organization Leaf organization

Consist of blade and petioleConsist of blade and petiole Veins are netted in eudicots, parallel in Veins are netted in eudicots, parallel in

monocotmonocot

Cross section leafCross section leaf

Trichomes – protective hairsTrichomes – protective hairs Cuticle – prevent desiccation but prevent Cuticle – prevent desiccation but prevent

gas exchangegas exchange Stomata on undersideStomata on underside Mesophyll tissueMesophyll tissue

PalisadePalisade spongyspongy

Leaf diversityLeaf diversity

SimpleSimple CompoundCompound

Pinnately compoundPinnately compound Palmately compoundPalmately compound

ArrangementArrangement AlternateAlternate OppositeOpposite WhorledWhorled

Leaves based on adaptation to environmentLeaves based on adaptation to environment