LSM 3261LSM 3261Life Form and Function

This module explores the complex and diverse forms and functions of plants and animals. Each living group shares a common basicplants and animals. Each living group shares a common basic structural plan, but contains many members that deviate from the basic design in response to selection pressure of the environment. Knowledge of organismal biology is enhanced through selected topics

C di t d L t

Knowledge of organismal biology is enhanced through selected topics in morpho-anatomical designs and functional adaptations.

Coordinator and LecturerAssociate Professor Hugh T.W. Tan

(Lectures 1 to 7)

LecturerMr. N. Sivasothi(Lectures 8 to 13)

Hugh Tan’s Topics for 7 Lectures

1. Introduction to LSM 3261; diversity of life; form and function; plant growth andform and function; plant growth and differentiation

2. Leaf structure and function3 Stems and plant transport3. Stems and plant transport4. Roots and mineral nutrition5. Reproduction in plants6 Growth responses and regulation of growth6. Growth responses and regulation of growth7. Review and revision

Lecture 1 Topics• Brief details of module

R f• Reference• Diversity of life• Form and function• Plant variation• Plant variation• The organization of plants• Plant tissue and cellular

organization• Mechanisms of plant growth

Module Details

• Visit the IVLE website for the details

• Only the key points will be• Only the key points will be covered in this lecture

Brief Details of Module

• Teachers• References• AimsAims• Teaching modes• Assessment• Websites for learning resourcesWebsites for learning resources

Teachers

• Coordinator and teacher: Assoc. Prof. Hugh T.W. Tan

• Co-teacher: Mr. N. SivasothiCo teacher: Mr. N. Sivasothi• Chief TA: Ms Xu Weiting

Assoc. Prof. Hugh TAN Tiang WahAssoc. Prof. Hugh TAN Tiang Wah• Research

–Conservation biology, restoration ecology, plant systematicsgy, gy, p y–Consultant on environmental projects to government, quasi-

government and private institutionsT hi• Teaching– SSS 1207 The Natural Heritage of Singapore– LSM 3256 Tropical HorticultureLSM 3256 Tropical Horticulture– LSM 3261 Life Form and Function– BL5230 Invasion Biology(New Module)

Assoc. Prof. Hugh TAN Tiang Wah•Service–Deputy Director Raffles Museum of Biodiversity Research

Assoc. Prof. Hugh TAN Tiang Wah

Deputy Director, Raffles Museum of Biodiversity Research–Editor, Nature in Singapore

http://rmbr.nus.edu.sg/nis/bulletin2011.html–Editor, Raffles Museum Books

http://rmbr.nus.edu.sg/raffles_museum_pub/raffles_museum_books.htmlAdvisor for Greening of NUS Campuses and Facilities– Advisor for Greening of NUS Campuses and Facilities

•Contact detailsdb tt @ d–dbsttw@nus.edu.sg

–6516-2717R S2 02 03 Pl t S t ti L b t t Blk S2–Room S2-02-03 ― Plant Systematics Laboratory at Blk S2 Level 2 (middle of floor)

Mr. N. Sivasothi• Research

– Otter, mammal ecologyMangrove ecology– Mangrove ecology

– Freshwater crab ecology• Teaching

LSM 1103 Bi di it– LSM 1103 Biodiversity– LSM 1303 Animal Behaviour– LSM 2251 Ecology and Environment

LSM 3261 Lif F d F ti– LSM 3261 Life Form and Function– LSM 4262 Tropical Conservation

BiologyS i• Service– Conservationist– Internet resources– Habitatnews– International Coastal Cleanup

• Contact detailsContact details– sivasothi@nus.edu.sg – 6516-8869

Ms Xu Weiting• Research

– Palm civet ecology– Palm civet ecology• Teaching

LSM1103 Biodiversity– LSM1103 Biodiversity– LSM3254 Ecology of Aquatic

EnvironmentsEnvironments– LSM3261 Life Form and

FunctionFunction• Contact details

iti @ d– xuweiting@nus.edu.sg – 6516-8869

References• Main Text

– Solomon E P L R Berg and D WSolomon, E.P., L.R. Berg and D.W. Martin. 2011. Biology. 9th ed. (Main text)

• Supplementary TextsSupplementary Texts– Hickman, C.P., L.S. Roberts, A. Larson, H.

l’Anson and D.J. Eisenhour. 2006.l Anson and D.J. Eisenhour. 2006. Integrated Principles of Zoology. 13th ed.

– Pough, F.H., C.M. Janis and J.B. Heiser. g , ,2005. Vertebrate Life. 7th ed.

– Ruppert, E.E., R.S. Fox and R.D. Barnes. 2004. Invertebrate Zoology. 7th ed.

– Campbell, N.A. and J.B. Reece. 2005. hBiology. 7th ed. (More detailed)

General Aims of the Module• Overall aim: Understand the basic relationships

between form (anatomy morphology) andbetween form (anatomy, morphology) and functionS ifi i• Specific aims– Content mastery

• Definitions• Apply terminology• Apply analyse and synthesise knowledge• Apply, analyse and synthesise knowledge

– Skills• Application of scientific skillsApplication of scientific skills• Learn independently• Communicate: essays, online discussion• Think critically• Think creatively

Teaching Modes

Type Hours No. of Total per Session

Sessions No. of Hours

Lecture 2 13 26Laboratory practical 4 3 12Laboratory practical 4 3 12Field trip practical 2 3 6Tutorial 1 6 6

Total 50

Practicals• Laboratory practicals

LS L b 7 (Bl k S2 L l 3)– LS Lab 7 (Block S2, Level 3)– Starts promptly at 2.00 pm with detailed briefing– Finishes at 4.45 pm– 15 minute break before Tutorial

• Field trip practicalsB i G d d Si Z– Botanic Gardens and Singapore Zoo

– Buses leave for site promptly at 3.00 pm for Botanic Gardens

– Buses return to campus by 5.30 pmp y p– Tutorial before field trip

Assessment• All assessments are open book• Mark allocation

– Continual assessment (40%)– Continual assessment (40%) – Semestral examination (60%)

Continual Assessment

• Hugh Tan’s assignments (20%)– Tutorial 1: Personal particulars form-filling and

questionnaire on how you learn (3%); tutorial on Practical 1– Tutorial 2: Structure to function experiment (5%)– Tutorial 3:Essay writing (12%)

• N. Sivasothi’s assignments (20%)A th d di ti (2 5%)– Arthropod dissection (2.5%)

– Setting thinking questions (2.5%)P ti l t t (15%)– Practical test (15%)

Semestral Examination

• Short or multiple choice questions (Tan 30%)• Short questions (Sivasothi 20%)

E ti (Si thi 10%)• Essay question (Sivasothi 10%)• All questions compulsoryq p y• Choice within questions for the essay question

Web Resources• For tips on becoming a better learner: Successful Learning website

of the Centre for the Development of Teaching and Learning of NUS: http://www cdtl nus edu sg/success/http://www.cdtl.nus.edu.sg/success/

• For tips on improving your English and writing: Useful Links for English Language Learning of the Centre for English Language and Communication: http://www.nus.edu.sg/celc/resources/index.htm

• For one useful method to organize the large amountof informationyou are going to be taught: Mind mapping by H.T.W. Tan:you are going to be taught: Mind mapping by H.T.W. Tan: http://www.cdtl.nus.edu.sg/success/sl9.htm

• To learn scientific names, since this module will employ many i tifi f th i ill b t d i f th fscientific names of the organisms you will be studying for the form

and function of: Understanding and learning the scientific names of species by H.T.W. Tan and K.-x. Tan: http://www.cdtl.nus.edu.sg/success/sl43.htm

A Warning!• A deceptively simple module

S fi i l f ili it ith t k• Superficial familiarity with some concepts makes one complacent (leaf, stem, root, tissues, etc.)

• Must have deep understanding of the topics taught to be able to apply, analyse, synthesisetaught to be able to apply, analyse, synthesise and evaluate (open book examination questions)L t f t i l id bl• Lots of terminology ― unavoidable, so no whining please!

• Students do fail this module• This is NOT a soft option module!• This is NOT a soft option module!

Some Questions Answered in this Moduleh i h l d h i i• What is the real reward that awaits martyrs in

the Islamic heaven?• Why can’t trees grow taller than they have

been recorded? (about 130 m)been recorded? (about 130 m)• Can you enlarge your brain by simple actions

that anyone can do?• Is a leaf more efficient than a photovoltaic s e o e e c e p o ovo c

cell at capturing solar energy?What is the largest seed in the orld?• What is the largest seed in the world?

• What is the largest fruit in the world?• What is the secret to happiness?

Reference

• Solomon, E.P., L.R. , ,Berg and D.W. Martin. 2011 Biology 9th2011. Biology. 9Edition. Thomson-B k /C l USABrookes/Cole, USA– Skim Chapters 28, 30– Read Chapter 33

Diversity of Life• Domain Bacteria

Kingdom Bacteria– Kingdom Bacteria• Domain Archaea

– Kingdom Archaea• Domain Eukaryay

– “Supergroups” formerly under Kingdom Protista Revision ofg

– Kingdom Fungi– Kingdom Plantae = Plants

Revision of LSM 1103 BiodiversityKingdom Plantae Plants

– Kingdom Animalia = Animals

Life Form and Function is a very big topic!

• Time extremely limited for module• Only examples from 2 kingdoms will be

considered– For plants, emphasis on angiosperms– For animals, emphasis on chordatesFor animals, emphasis on chordates

• If interested in other taxonomic groups, read the other chapters of the main andread the other chapters of the main and supplementary textbooks, or see me for extra referencesextra references

Kingdom Plantae• Non vascular plants

– Phylum Hepatophyta (liverworts)Phylum Bryophyta (mosses)– Phylum Bryophyta (mosses)

– Phylum Anthocerophyta (hornworts)• Vascular plantsp

– Seedless plants– Phylum Lycopodiophyta (club and spike mosses)– Phylum Pteridophyta (ferns fern allies whisk ferns horsetails)Phylum Pteridophyta (ferns, fern allies, whisk ferns, horsetails)

– Seed plants• Gymnosperms

Ph l C if h ( if ) Revision of– Phylum Coniferophyta (conifers)– Phylum Cyacadophyta (cycads)– Phylum Ginkgophyta (ginkgo)

Ph l G t h t ( t h t )

Revision of LSM 1103 Biodiversity

– Phylum Gnetophyta (gnetophytes)• Angiosperms

– Phylum Anthophyta (angiosperms)

Kingdom Animalia• Choanoflagellates• Parazoa

– Porifera (sponges)Porifera (sponges)• Eumetazoa

– Radiata– CnidariaCnidaria– Ctenophora

– Bilateria• Protostomia

Pl t h l i th– Platyhelminthes– Nemertea– Nematoda– Rotifera

di dRevision of LSM 1103– Tardigrada

– Onychophora– Arthropoda– Annelida

LSM 1103 Biodiversity

– Molusca• Deuterostomia

– Echinodermata– Hemichordatae c o data– Chordata

Learning Objectives– Learn the meaning of the words: form, morphology, function,

adaptionDiscuss how function is not always easy to perceive for any– Discuss how function is not always easy to perceive for any structure

– Describe the various functions of the plant body and its constituent parts: organ system, organ, tissue system, tissue, cell

– Distinguish between herbaceous and woody, plant habits, life history strategyhistory strategy

– Describe structure and function of• Ground tissues and their cell types• Vascular tissues and their cell types• Vascular tissues and their cell types• Dermal tissues and their cell types

– Distinguish between primary and secondary growthDistinguish between apical and lateral meristems– Distinguish between apical and lateral meristems

– To appreciate these concepts• Continuum• Artificial (arbitrary) classification• Artificial (arbitrary) classification• Comparison tables

Form• Form = Structure =

Manner of building or constructionManner of building or construction• Morphology (narrow sense) =

E t l f f i– External form of an organism• Morphology (broad sense) =p gy ( )

– External form and internal structure (anatomy) of an organism(anatomy) of an organism

• Function =N l d i l i f fNormal and special action of any part of a living organism

Adaptationd p o• Definition (in Glossary of main textbook) =

An evolutionary modification that improves an organism’s chances of survival and reproductiveorganism s chances of survival and reproductivesuccess

• Note conditions of definition

Functions of Structures• Mutations may be

– Harmful– Neutral– Beneficial

St t h• Structures may have– No apparent function

o Not yet perceivedo Not yet perceivedo Neutralo Vestigial

Function (depending on– Function (depending on environment and other factors)

Sli h l b fi i lo Slightly beneficialo Moderately beneficialo Greatly beneficial

Plants Vary in WoodinessWoodiness

• HerbaceousL k h l– Lacks tough structural (woody) parts

– E.g., most leafyE.g., most leafy vegetables

• Woody y– Have structural

components made of li ifi d ll l i lllignified cellulosic cell walls

– E.g., treesg ,• Half-

herbaceous/woodyy– Intermediate– E.g., papaya

Digression: Concept of the ContinuumOften, man-made categories are nodal points

g p

Partially Totally herbaceous

g palong a gradient, e.g.,

Totally woodyy

woody (no woody tissues)

Gradient of woodiness

OR

Gradient of herbaceousnessGradient of herbaceousness

Plants Vary in HabitHabit

• Habit = General form of a plant

• Types of habitb b (– Herb = Herbaceous (non-

woody) plant; erect, single or multiple-trunked; usually small-sized

– Tree = Woody plant; erect, singled-trunked; usually largeg y g

– Shrub = Woody plant; erect, multiple-trunked; usually intermediate sizedintermediate sized

– Climber or trailer = Herbaceous or woody plant; climbing or trailing stem; canclimbing or trailing stem; can be very large

What kind of mechanical property does woodiness confer p p yto stems?

Plants Vary in Life History Strategy• Annuals are herbaceous

– Die in one year or less– E.g., cock’s comb (Celosia cristata)

• BiennialsTake two years to complete life– Take two years to complete life cycles

– E.g., Chinese radish (Raphanus sativus ‘‘Longipinnatus’)sativus Longipinnatus )

• Perennials– Can be herbaceous or woodyy– Have capacity to live more than two

years– Emergent growth may die back but

The Changi Tree was 76 2– Emergent growth may die back but

roots, other underground growth remains alive but usually dormant(i e in a low state of metabolic

76.2 m tall!

(i.e., in a low state of metabolic activity)

– E.g., rain tree (Samanea saman)

This is the thale cress (Arabidopsis thaliana), a member of the mustard family (Cruciferae y (= Brassicaceae), an important model research organism. Its genome was decoded in 2000 to reveal about 125 million nucleotide base pairs (compare with soya bean, with a genome hundreds of times larger!). This plant has been called an ideal ‘laboratory mouse’ for the plant world.

Besides a small genome andBesides a small genome, and short life cycle explain why Arabidopsis thaliana was selected as the model plant for plant genetics research (based

h t h j t l t)?on what you have just learnt)?

(Hint: Amount of space matters i h l b )in research labs.)

If you want to sell as many plants as y y ppossible every Lunar New Year, which would you choose: annuals biennials orwould you choose: annuals, biennials, or perennials?

Tan, H.T.W. and X. Giam, 2008. Plant Magic: Auspicious and Inauspicious Plants from A d th W ldAround the World. Marshall Cavendish, Singapore. 216 pp.

Flowering Plant OrganizationOrganism (e.g., plant)

• Organ system (e.g., root/shoot system)O ( l f )– Organ (e.g., leaf, root, stem)• Tissue system (e g dermal vascular ground)Tissue system (e.g., dermal, vascular, ground)

– Tissue (e.g., meristematic, epidermis, periderm, collenchyma parenchyma sclerenchyma phloemcollenchyma, parenchyma, sclerenchyma, phloem, xylem)

C ll ( i t ti id l h» Cell (e.g., meristematic, epidermal, parenchyma, fiber, etc.)

Flowering Plant Organization• Shoot system

– StemStem• Axillary bud

– Vegetative branchg– Reproductive branch

» Flower» Inflorescence

– Leaf• Root system

Root– Root• Tap• Branch/lateral roots• Branch/lateral roots

Plant Organs• Plant organs are

functional units that contain all three mature tissue systems (dermal, y ( ,vascular, ground)

• Roots stems leaves• Roots, stems, leaves, flower components and fruit are all organsfruit are all organs

• They are continuous; ll l ie.g., all vascular tissues

are continuous in a plant —they are connected

Can leaves, internodes, nodes,internodes, nodes, roots be considered

th d l ?growth modules?

Lego blocks

Tutorial Assignment 1Tutorial Assignment 1• Personal particulars of yourself• Download soft copy from LSM 3251 IVLE

website workbin CA Assignment folderwebsite workbin, CA Assignment folder• 3% of the module’s marks ― A gift from me!• Useful to find out about your own motivation• Hand in hard copy by 1800 hrs of the day of• Hand in hard copy by 1800 hrs of the day of

the next lecture, Thursday, 18 Aug 2011(each d l i 1% l !)day late is a 1% penalty!)

• Upload data of your learning style to this p y g ywebsite: http://tinyurl.com/lsm3261-learningstyle

Singapore Biodiversity Encyclopaediay p

• Useful for many of your modules

• Buy this now while the special offer is availablep

• Excellent value ($52) for 552-page book in552 page book in COLOUR

Plant Tissues• Tissues are groups of cells that

form a structural andform a structural and functional unit and share a common origincommon origin

Credit: © Brad Mogen/Visuals Unlimited

Plant Tissue Classification• Tissues classified• Tissues classified

according to cell typestypes– Simple tissues have 1

cell typecell type• Meristematic• ParenchymaParenchyma• Collenchyma• Sclerenchyma

– Complex tissues have ≥2 cell types

Credit: © Carolina Biological/Visuals Unlimited

Credit: © Brad Mogen/Visuals Unlimited• Phloem

• Xylem• Epidermis

Unlimited

• Epidermis• Periderm

Digression: Artificial Classification• Continuum in various biological

h t i ti

g

characteristics• Man-made categories are considered artificial g

or arbitrary, e.g., 1 cell type = simple tissue; 2 = complex tissue– 1 cell type = simple tissue; 2 = complex tissue

– Why not 3, 4, etc.?– Arbitrary designation of simple and complex

tissues because• Some tissues are variable, and do not fit neatly only in

one of the categories all the time• The categories apply most of the time, but not always

The Tissue Systems of a Plant• Dermal tissue system (covering)

• Epidermis (primary growth)

• Periderm (secondary growth)

• Vascular tissue system (transport)

Phl (f d)• Phloem (food)

• Xylem (water and mineral nutrients)

• Ground tissue system (‘filler’)

• Parenchyma tissue (multi purpose)• Parenchyma tissue (multi-purpose)

• Collenchyma tissue (flexible support)

• Sclerenchyma tissue (rigid support)

The Tissue Systems of a Plant

Dermal tissue system

Vascular tissue system

Ground tissue systemLeaf

Dermal tissue system

Vascular tissue system

Ground tissue system

Stem

Dermal tissue system

Vascular tissue system

Ground tissue system

R tRoot

Cell Walls• Cell wall organization

– Growing plant cells produce a g p pprimary cell wall, which stretches as the cell grows

– A secondary cell wall may then be produced, inside the primary wall

• Strong, thick

– Secondary cell walls set limits to cell growth

A porous exoskeleton

Cell Walls• Cell walls are:

– Involved in growth (expandability of primary– Involved in growth (expandability of primary wall allows increase in size) 1st li f d f i t i di th– 1st line of defense against invading pathogens

– Provide signal transduction pathways for cells (carbohydrate and protein molecules in the plant cell walls communicate with other molecules i id d id h ll)inside and outside the cell)

Cell Wall Chemistry• Cell walls containCell walls contain

cellulose, hemicellulose, pectin and ligninpectin and lignin

• Cellulose is the major componentcomponent – Most abundant polymer in

the worldthe world– ~40-60% of dry weight of

cell wallcell wall– Form strong strands of

parallel chains called p e c s c edcellulose microfibrils

– Cellulose strands are cemented together by hemicellulose and pectins

Hemicellulose, Pectin and Lignin• Hemicellulose varies in• Hemicellulose varies in

composition– Some are polymers of -1-4 glucoses

i h id h i f h 5 Cwith side-chains of the 5-C sugar xylose

– Lie flat against the cellulose fibrils• Pectins are polymers of -

galacturonic acidA id ti l l l– Acid pectins are long molecules

– Neutral pectins act as linking molecules between acid pectins,

l t i d h i ll lglycoproteins and hemicellulose polymers

– Act as embedding ‘glue’• Lignin is very hard, tough

– Chemistry is not fully elucidatedP l f l i id– Polymer of complex, amino-acid derived monomers

– Creates strong, durable cell walls

Ground Tissues

• ParenchymaC ll h• Collenchyma

• SclerenchymaSclerenchyma

ParenchymaI ti li i ti• Is an active, living tissue

• Simple tissue (1 cell type)• Parenchyma cells have thin cell• Parenchyma cells have thin cell

walls• Is evident as softer parts of a plant;Is evident as softer parts of a plant;

the pith of a herbaceous plant; the edible part of fruit such as apples or a tuber such as a potato

• Multiple functions of parenchyma ll (lik S i k if )cells (like Swiss army knife)

– Some are photosynthetic– Storage for important biologicalStorage for important biological

molecules ― starch, oil droplets, water– Storage for plant hormones, resin,

enzymesenzymes– Can differentiate into other cell types ―

such as during wound healingPotato tuber cells

SclerenchymaAt t it ll ft d d• At maturity, cells are often dead

• Simple tissue (1 cell type)C ll h b h i d S l id• Cells have both primary and secondary cell walls (thick walls) hence not very flexible

Credit: © Carolina Biological/Visuals

Sclereids

walls) hence not very flexible• Hard parts of stems (e.g.,

bamboo) roots and leaves

Unlimited

TSbamboo), roots and leaves, fruits, seeds

• Functions of sclerenchyma cells

TS

Functions of sclerenchyma cells (rigid support; like granite chips or steel rods in concrete) LS

– Sclereids: hard cells found in nuts, fruits, leaves F b l d ll h– Fibers: long tapered cells that occur in patches or clumps

Collenchyma• Living cells at maturity• Simple tissue (1 cell type)• Primary walls are unevenly

thickened, very thick in corners – not uniformly distributednot uniformly distributed, usually appear as strands

• Provides support in nonwoody TS

pp yplant organs (flexible support)

• Found in petioles of celery LS

(Apium graveolens)

TS celery collenchymaCredit: © Arnold Karpoff/Visuals Unlimited

Cell Walls of the Ground Tissues

• Distinguished by their chemicalDistinguished by their chemical composition

P h ll ll– Parenchyma cell walls• Mainly composed of cellulose

S ll f i d h i ll l• Small amounts of pectin and hemicellulose

– Collenchyma cell walls• Much more pectin, esp. in thickened regions

– Sclerenchyma cell wallsy• Contain relatively large quantities of lignin, in

addition to pectin, hemicellulose and cellulose

Digression: Comparison Tablesg p

What’s a good way to learn aboutWhat s a good way to learn about somewhat similar entities like the three tissues collenchyma, parenchyma and sclerenchyma?parenchyma and sclerenchyma?

Vascular Tissues

• Xylem• Phloem• Phloem

Phloem Xylem

Functions include:• Conducts water and

Functions include:• Conducts water and nutrients

photosynthates from the leaves to the rest of the plant

from roots to the rest of the plant• Support for the stem

Continuous throughout the plant body

Continuous throughout the plant body

Phloem XylemComplex tissue (≥2 cell types) Complex tissue (≥2 cell types)

Cell types include: Cell types include:• Sieve tube

member/element/cell• Tracheids• Vessel member/element/cell

• Companion cell• Fiber

• Fiber• Parenchyma

• Parenchymay

Phloem Cell TypesSieve tube element

Companion cell

Fiber Parenchyma cellelement cell cell

For conduction of water and

Controls sieve tube element and

For structural

For mostly lateral conduction ofwater and

photosynthatestube element and assists in moving photosynthates in

structural support

conduction of water and photosynthatesp y

and out of sieve tube element

p y

Phloem Cell TypesSieve tube element

Companion cell

Fiber Parenchyma cellelement cell cell

Combines with other sieve tube

Not applicable Not applicable

Combines with other parenchymaother sieve tube

elements to form the sieve tube

applicable other parenchyma cells to form rays

Phloem Cell TypesSieve tube element

Companion cell

Fiber Parenchyma cell

Alive at maturity

Alive at maturity Dead at maturity

Alive at maturityy y y

At maturity lacks nucleus

At maturity has nucleus and

At maturity, only has

At maturity has cytoplasm and

and other organelles but h t l i

cytoplasmic connections ( l d t )

primary and secondary cell

ll l ki

nucleus

has cytoplasmic connection with other sieve tube

(plasmodesmata) with sieve tube element

walls, lacking cytoplasm and nucleusother sieve tube

elements and companion

element nucleus

cells

Phloem Cell TypesSi b C i Fib P hSieve tube element

Companion cell

Fiber Parenchyma cell

End walls are sieve plates

Not applicable Not applicable Not applicable

Phloem fiber cap

Primary phloem

Secondary phloem

Xylem Cell TypesTracheid Vessel

elementFiber Parenchyma

cellFor conduction of water and

For conduction of water and

For structural support

For mostly lateral

mineral nutrients and

l

mineral nutrients and

l

ppconduction of water and

i lstructural support

structural support

mineral nutrients and storagestorage

Xylem Cell TypesTracheid Vessel

elementFiber Parenchyma

cellNot applicable Combines with

other vessel Not applicable Combines with

other elements to form the vessel

parenchyma cells to form

i lrays or vertical (axial) parenchymaparenchyma strands

Xylem Cell TypesT h id V l Fib P hTracheid Vessel

elementFiber Parenchyma

cellDead at maturity Dead at maturity Dead at maturity Alive at maturity

At maturity, only has primary and secondary

At maturity, only has primary and secondary

At maturity, only has primary and secondary

At maturity has cytoplasm and nucleusprimary and secondary

cell walls, lacking cytoplasm and nucleus. No secondary wall at

primary and secondary cell walls, lacking cytoplasm and nucleus. No secondary wall at

primary and secondary cell walls, lacking cytoplasm and nucleus

cytoplasm and nucleus.

pits. pits.

Xylem Cell TypesT h id V l Fib P hTracheid Vessel

elementFiber Parenchyma

cellNot applicable

End walls are perforated or

Not applicable Not applicable

absent at maturity

Secondary xylem

Primary xylem

Dermal Tissues

• EpidermisP id• Periderm (covered later )( )

Epidermal Cells

• Ground epidermal cellscells

• Guard cells• Trichomes

Ground Epidermal Cells• Unspecialized live cells• UsuallyUsually

nonphotosynthetic; clear ― covered with a waxy covered with a waxy cuticle

• Cells tightly connected• Cells tightly connected (right); prevents water loss or entryloss or entry

Guard Cells– A stoma (plural, stomata) is a type of pore– Guard cells are found on either side, open usually during , p y g

day; close at night and during droughtOpening/closing mechanism covered in

Closed Open

Opening/closing mechanism covered in lecture 2

Closed Open

Guard cell Guard cellCredit: © Carolina Biological/Visuals Unlimited

Trichomes • Trichomes =• Trichomes

Outgrowths –‘hairs’

• Vary considerably in size

• Functions include:Functions include:– Stinging hairs– Some leaf trichomes

used to discourage

Credit: © RMF/Visuals Unlimited

Trichomes on an Arabidopsisthaliana leaf.

used to discourage herbivory

– Some used to eliminate salteliminate salt

– Some thought to increase reflection to reduce stem/leafreduce stem/leaf temperature

– Root hairs are a type of trichome, ,increase surface area to increase uptake of nutrients

Meristems• Plant growth involves

– Cell division C ll l ti– Cell elongation

– Cell differentiation• Occurs locally unlike in• Occurs locally, unlike in

animals– Places of growth called meristemsg– Meristems made of cells that form

new cells by mitosisi l i• Apical meristems

– Elongation of the stem or rootL t l i t• Lateral meristems– Increase in girth

Only seen in gymnosperms and– Only seen in gymnosperms and woody dicots

– Periderm, woody stem or root

Mechanisms of Growth

• Primary growth (apical growth)– Elongation of the stem or root– All plants show this kind of growth– All plants show this kind of growth

• Secondary growth (lateral growth)– Increase in girth– Only seen in gymnosperms andOnly seen in gymnosperms and

woody dicots and rarely, some large, woody monocotswoody monocots

Primary Growth:Root

• Elongation of the plant• Elongation of the plant occurs at apical meristems, which are located at thewhich are located at the tips of roots and shoots and within buds of stemsand within buds of stems

Credit: © Biodisc/Visuals Unlimited

Primary Growth: Shoot Apex• Shoot apexes (also, apices) have apical meristematic tissue• Inside the shoot apex dome of apical meristemInside the shoot apex, dome of apical meristem• Bud primordia, which can grow into buds, have

meristematic tissuemeristematic tissue

Explain how cultivated trees may get their branches shortened or removed? How about the case for wild trees growing in forests?the case for wild trees growing in forests?

Secondary Growth• Secondary growth, the increase

in girth, occurs at lateral meristemsmeristems

• Extends along the length of the stem except at tips

Vascular cambium– Vascular cambium• Thin continuous cylinder within

stem/root• Between bark and wood• Cells divide, adding more cells to

the wood– Cork cambium

• Thin cylinder of meristematic cells• Thin cylinder of meristematic cells located in outer bark

• Divide to form cork cells on the outside, 1 or more layers of cork

h ll h i idparenchyma cells on the inside• Bark

– All tissues located outside of the l bivascular cambium

– Made of cork cells, cork cambium and cork parenchyma