EVST191 Fall 2015 Lecture2

EVST 191Trees: Environmental Biology & Global Significance

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Fundamental Differences Between Animals and Plants

Animals Heterotrophic No vacuole No cell wall Tight junctions Cytokinesis (w/ constriction) Cell migration critical Germ line sequestered Gametic meiosis typical Few totipotent cells Limited modularity Brief organogenesis Rigid development Limited biochemistry

Plants Phototrophic Vacuoles Rigid cell wall Plasmodesmata Cytokinesis (w/ phragmoplast) No cell migration No germ line Sporic meiosis typical Many totipotent cells Extreme modularity Continual organogenesis Plastic development Enormous biochemical diversity

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Figure 1.3 Schematic representation of the body of a typical eudicot (Part 1)

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Figure 4.4 Pathways for water uptake by the root

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Vacuole

Photos : Campbell and Reece

Vacuole• Contains vacuolar sap

(water, inorganic ions, sugars, organic acids, pigments)

• ~95% of total cell volume• Surrounded by tonoplast

(synthesized in ER)

Plastid Developmental Forms

Photos : plantphys.info

Consider transition in etiolated plants

Plastid Developmental Forms

Photos : plantphys.info

Consider transition in etiolated plants

Figure 16.2 Comparison of seedlings grown in the light versus the dark Comparison of plants grown in the dark vs. light

Chloroplasts

Chloroplasts• Double-membrane-enclosed plastid• Chloroplasts contain chlorophyll• Site of light reactions and dark reactions

Chloroplasts

Chromoplasts• Plastids with high conc. of carotenoid pigments• During fall, chloroplasts breakdown, and chromoplasts

become visible

Photos : commons.wikipedia.com

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Tissue Types

Dermal

• Epidermis and periderm

Ground

• Parenchyma, collenchyma, and sclerenchyma

Vascular

• Xylem

Photos : Campbell and Reece

Dermal Tissue Types

Epidermis • Unspecialized cells; guard cells and trichomes• Outermost layer of cells on primary plant• Mechanical protection; minimize water loss; gas exchange

Cuticle

Trichome

Stomata

Photos : Alison Roberts

Trichome

http://www.pnas.org/content/106/6.cover-expansion

Dermal Tissue Types

Periderm (yet another meristem)

• Comprises cork tissue, cork cambium, and phelloderm

• Beneath epidermis: eventually deeper in bark

• Protective tissue in roots and stems; gas exchange with lenticiles

bark cambium

www.apsnet.org

bark

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Ground Tissue Types

Parenchyma • Cell wall: primary or secondary; lignified, subarized, or

cutinized• Throughout plant body: from mesophyll to pith• Metabolic processes, storage and conduction, wound

healing

Palisades and spongy parenchyma Parenchyma with purple starch granules

Photos : Alison Roberts

Ground Tissue Types

Collenchyma • Elongated; non-lignified• On periphery in young stems; in cylinders; often along leaf

veins• Support in primary plant body

Photos: http://sydney.edu.au/

Ground Tissue Types

Sclerenchyma: Fibers • Very long; often lignified; often dead at maturity• Located in stems, often associated with xylem and phloem• Support and storage

Photos: http://sydney.edu.au/

Ground Tissue Types

Sclerenchyma: Sclereid • Shape is variable; shorter than fibers; generally lignified;

maybe dead at maturity• Throughout plant (example gritty texture of pears)• Mechanical; protective• Asterosclerids may help move water in some leaves

Asterosclerids in a conifer needle

Vascular Tissue Types

Xylem: Tracheid• Elongated and tapered;

lignified; dead at maturity• Located in the xylem• Water-conduction in

gymnosperms and angiosperms

Photos: Campbell and Reece

Ground Tissue Types

Xylem: Vessel elements• Elongated; not as long as

tracheids; several elements end-end equal vessel; dead at maturity

• Located in xylem• Water-conducting element

in angiosperms

Photos: Campbell and Reece

Vascular Tissue Types

Ground Tissue Types

Photos: Campbell and Reece

Phloem• Stacks of cells called sieve-

tube elements or sieve-tube cells; companion cells support metabolic function; alive at maturity; alive at maturity

• Located in phloem• Food-conducting element

Vascular Tissue Types

Bamboo is stronger than steel

www.archiexpo.com

Bamboo• Higher tensile strength than

steel (resistance to pulling apart)

• Fiber network is reinforced by lignin tissue

• Fibers are analogous to rebar and lignin the concrete in reinforced concrete

• Grows from equator to sub-arctic

• Grows very fast

Bamboo is stronger than steel

thetravellingtrini.comcalfeedesign.com

www.completebamboo.comwww.troutunderground.com

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Gambetta G A et al. Plant Physiol. 2013;163:1254-1265

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Primary and secondary cell walls and their relationship to the rest of the cell