Mills AP Bio 2003/2013 Chapter 24 Plant Structure (Primarily Flowering Plants) Read Ch 24 in...

Mills AP Bio 2003/2013

Chapter 24Plant Structure

(Primarily Flowering Plants)

Read Ch 24 in TextbookRead pg 199-207 in Cliffs AP Book


Ch 24 Plant StructureOverview

• 24.1 Plant Organs• 24.2 Plant Tissues• 24.3 Root

Organization• 24.4 Stem

Organization• 24.5 Leaf

Organization

– 80% of all plants are flowering plants (angiosperms)

– Plants are essential for life on earth.

• Oxygen• Help regulate water

cycle and carbon dioxide cycle of the earth


Ch 24 Plant Structure 24.1 Organs of Flowering Plants

• Flowering Plant Organs– Roots

– Stems

– Leaves

• Anchors plant• Absorbs water and minerals• Stores products of photosynthesis (perennial

plants)• Produce hormones• Interact with soil fungi and microorganisms

• Supports leaves• Conducts materials to and from leaves and roots• Helps store plant products

• Take in carbon dioxide, release oxygen• Photosynthesis



• Flowering plants are divided into two groups based on structural differences– Monocots

• One cotyledon (seed leaf)• Smaller group• Crop plants and others (grasses, lilies, orchids,

rice, wheat, corn)

– Dicots• Two cotyledons• Larger group• Many familiar flowering plants and trees



One cotyledon in seed

Two cotyledons in seed

Root xylem and phloem in a ring

Root phloem between arms of xylem

Vascular bundles scattered in stem

Vascular bundles in a distinct ring

Leaf veins form a parallel pattern

Leaf veins form a net pattern

Flower parts in threes and multiples of three

Flower parts in fours or fives and their multiples

Usually have fibrous roots

Usually have tap roots

Also called Eudicots


• Plant Tissues– Plants can grow their entire lives because

they have embryonic tissue called meristem located in their stems and roots.

– Three types of meristem produce three different specialized tissues.

• Protoderm Epidermal tissue• Ground meristem Ground tissue• Procambium Vascular tissue (xylem and

phloem)

Ch 24 Plant Structure 24.2 Tissues of Flowering Plants



• Plant tissue– Epidermal tissue (from Protoderm)

• Forms the outer protective covering of a plant (epidermis)

• Different plant organs have different modifications– Epidermal cells exposed to air are covered with a

cuticle– Roots – root hairs– Leaves – guard cells and stomata and trichomes– Woody stems – epidermis (called periderm) is replace

by dead cork cells (produced by a meristematic tissue called cork cambium)– becomes outer covering of the bark

– Some epidermal cells secrete protective substances

Root Hairs SEM



• Plant tissue– Ground tissue (From Ground Meristem)

• Forms the bulk of the plant• Made up of

– Parenchyma

– Collenchyma

– Schlerenchyma

Least specialized and found in all organs of the plantMay contain chloroplasts or plastidsCan give rise to more specialized cellsThis is the “typical“ plant cell

Like parenchyma cells , but have thicker wallsAdd support and flexibilityStrand of celery stalks made of mostly collenchymaVery thick wallsUsusally non livingPrimary function is support of mature plant


• Plant tissue– Vascular tissue (From Procambium)

• Extends from roots to leaves– In roots – located in vascular cylinder– In stems – located in vascular bundle– In leaves – located in leaf veins

• Two types– Xylem

» Transports water and minerals» Have two cell walls – primary and secondary» Two types of cells: tracheids and vessel elements

(members)» Most are non living cells at maturity

– Phloem» Transports organic nutrients» Composed of sieve tube elements (members) and

companion cells» Are living cells at maturity (lack nuclei and

ribosomes)



Vessel elements – shorter and wider, water passes freely from one to the next through a perforation (area with no cell walls). Water movement faster than in tracheids.

Tracheids – narrower with tapered ends. Water passes through pits in tapered parts.


Sieve tube elements – have sieve plates at their ends – area with pores where cytoplasm of the cells connects.

Companion cells – parenchymal cells adjacent to sieve tube elements. Cytoplasm communicates through plasmodesmata. Physiologically support the nuclei free sieve tube elements.

Vascular Tissue Animation Link


• Root Organization– Root tip has three zones

• Zone of cell division (apical meristem)

– Continually dividing cells– Protected by root cap,

which is destroyed and replaced as root pushes through soil

• Zone of elongation– Cells elongate and

become more specialized

• Zone of maturation (has root hairs)

– Mature, differentiated cells

Ch 24 Plant Structure 24.3 Organization and Diversity of Roots



• Root Organization– Tissues of a dicot root

• Epidermis– Single layer of thin walled cells. – In zone of maturation, contain root hairs

• Cortex– Thin walled, irregularly shaped, loosely packed parenchymal

cells– Water and minerals can pass between cells.

• Endodermis– Single layer, tightly fit, rectangular cells– Casparian strip surrounded on four sides so that the only entry

into the vascular system is through the endodermal cells – can regulate what enters.

• Vascular tissue– Pericycle – can still grow- forms branches and lateral roots– Star shaped xylem– Phloem found between arms of xylem

Monocot root similar, but xylem and phloem arranged in a circle with pith in the center.

Pith Botany. The soft, spongelike, central cylinder of the stems of most flowering plants, composed mainly of parenchyma.


View looking down onto root – see arrow

Water and minerals cannot pass between the endodermal cells, has to go through them.


Can you identify these root cross sections?

Can you name the parts?

Dicot Monocot

1. Epidermis

2. Cortex

3. EndodermisMcGraw Hill Tutorial w micro slides

http://www.mhhe.com/biosci/pae/botany/histology/html/rootov.htm




• Root Organization– Root diversity

• Many adaptations– Associate with fungus – mutualistic - Mycorrhizae– Associate with nitrogen fixing bacteria – mutualistic – root

nodules– Parasitic roots – dodder plant sends roots into vascular

tissue of host plant

• Dicots usually have primary root/taproot– Carrots, sweet potatoes, beets, turnips

• Monocots usually have fibrous roots – Actually arise from the shoot tissue so called Adventitious

roots» prop roots, rhizomes, “holdfast” ivy roots

– Grasses, onions, corn



Many types of roots

Nodules on pea rootsMycorrhiza on grass roots


Aerial roots on Virginia creeper


Root Nodule Animation



• Stem Organization– Primary growth from shoot

apical meristem, which is protected by the terminal bud

– Leaves are produced by apical meristem at nodes

– Space between nodes = internode, which get longer as plant grows

– Three types of primary meristem develop

• Protoderm epidermis• Ground meristem pith and

cortex (parenchymal cells)• Procambium xylem and

phloem– Herbaceous (nonwoody)

plants have only primary growth

McGraw Hill Tutorial w micro slides.http://www.mhhe.com/biosci/pae/botany/histology/html/

apicbmic.htm

Ch 24 Plant Structure 24.4 Organization and Diversity of Stems



Herbaceous monocot stem cross section

(corn)

Herbaceous dicot stem cross section (buttercup)

http://www.umanitoba.ca/Biology/lab9/biolab9_4.html#Structure



• Stem Organization– Woody stems

• Have primary and secondary growth

• Secondary growth due to vascular cambium, which produces new xylem and phloem each year – increases girth of tree

• Cork cambium produces new cork cells as needed – increases girth of tree

• Epidermis replaced by cork• Bark contains cork, cork

cambium and phloem• Wood contains annual rings

of xylem• Woody Dicot animation link



• Stem Organization– Woody stems

• Trees with growing seasons have spring wood and summer wood.

• These two together make an annual rings (mostly xylem)

Mills AP Bio 2003/2013http://fig.cox.miami.edu/Faculty/Dana/stemanatomy.jpg

http://botit.botany.wisc.edu/images/130/Secondary_Growth/Woody_Stems/Tilia_Stem/Secondary_Growth/1-2-3-year_old_stems_MC_.php?highres=true

How old are we?

1 year 2 year 3 year


• Tree girdling– A way to kill a tree on purpose (without chemicals)

takes a few years– Can happen accidentally due to dog chains, vines

etc

www.umext.maine.edu/onlinepubs/htmpubs/7126.htm

www.plantphys.net/printer.php?ch=10&id=130



• Stem Organization– Stem diversity

• Stolens – above ground horizontal stems – strawberry, grape vine

• Rhizomes – underground horizontal stems-some with enlarged portions called tuber - potatoes

• Corms – underground modified stems (gladiolus)

Baobab tree stores water in stem and can live over 100 years!


• What am I?

Ch 24 Plant Structure 24.5 Organization and Diversity of Leaves



• Leaf Organization– Place where

photosynthesis occurs– Veins contain vascular

tissue– Epidermal cells

covered by cuticle and contain stomates on the lower surface (mostly)

– Body of leaf contains mesopyhll (palisade and spongy parenchymal cells)-this is area where photosynthesis occurs


• Venus flytrap link



Do you know what this is?

Upper surface of a coleus leaf with thrichomes (epidermal outgrowths)


• BBC Secret life of Plants clip


DISTINGUISHING CHARACTERISTICS OF MONOCOTS, DICOTS AND GYMNOSPERMS

Division Spermatophyta - seed bearing plants

SubdivisionAngiosperms

(Angiospermae) (flowering plants with seeds enclosed)

Gymnosperms (Gymnospermae) (cones with naked seeds)

ClassMonocots

(Monocotyledoneae) (means 1 cotyledon)

Dicots (Dicotyledoneae)

(means 2 cotyledons)

Seeds1 cotyledon; endosperm often present

2 cotyledons; endosperm often lacking

1 to many cotyledons; no endosperm; female gametophyte tissue present

Flowers Flower parts in multiples of 3 Flower parts in multiples of 4 or 5 No true flowers

LeavesLinear; leaf base or petiole (if present) sheathing; parallel venation

Broad; petiole present; net venation Needle-like or scale-like

Vascular System of Stem

Scattered vascular bundles; no cambium or secondary growth

Ring of vascular bundles in primary growth; cambium present; may have woody secondary growth

Ring of vascular bundles in primary growth; cambium present; may have woody secondary growth

Growth HabitHerbaceous to wood-like (ex. palm), but no true wood (secondary xylem)

Herbaceous or woody Herbaceous or woody

General Appearance


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Mills AP Bio 2003/2013 Chapter 24 Plant Structure (Primarily Flowering Plants) Read Ch 24 in...

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