Plant Structure, Reproduction, and Development

Angiosperms

• Cotyledons – embryonic leaves• Monocot – one embryonic leaf• Dicot – two embryonic leaves• Differences between Monocots & Dicots

– Veins are parallel /branched– Vascular bundles complex /ring– Leaves arranged in multiples of 3 /multiples of 4 or 5– Fibrous roots /taproot

Figure 31.2

SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS

MONOCOTS

Onecotyledon

Main veins usually parallel

Vascular bundles incomplex arrangement

Floral parts usuallyin multiples of three

Fibrousroot system

Twocotyledons

Main veins usually branched

Vascular bundles arranged in ring

Floral parts usually in multiples of four or five

Taprootusually present

DICOTS

Angiosperms

• Most angiosperms are dicots

• This group includes shrubs, trees (except conifers), and many of our food crops

• Monocots include orchids, bamboos, palms, lilies, and grains and grasses.

Plant Body

• Root system – anchors the plant into the soil

– Roots have root hairs – outgrowth of epidermal cells

– Shoot system – part of plant above groundstems – support leaves and groundednodes – points where leaved are attachedleaves – main site of photosynthesisterminal bud – node at tip of plant; responsible for growth lengthwise; apical dominance (inhibits growth of axillary buds)axillary buds – located in angles formed by the leaf; usually dormant; causes the plant to become bushy

Figure 31.3

Terminal bud

Blade

PetioleAxillary bud

Leaf

Stem

Taproot

SHOOTSYSTEM

ROOTSYSTEM

Roothairs

Internode

Node

Flower

Modified Roots and Shoots

• Modified taproots – sweet potatoes, sugar beets, & carrots/ stores starch– Uses this stored sugar

source for active growth and producing flowers and fruit

• Modified Stems– runner – horizontal stem– rhizomes – horizontal stem

underground– tubers – white potatoes that

are at the end of rhizomes that store sugar

STRAWBERRYPLANT

POTATOPLANT

IRISPLANT

Runner

TuberTaproot

Rhizome

Rhizome

Root

Modified Roots and Shoots

• Modified leaves– Grasses have no petioles– Celery have enormous petioles that we eat– Tendrils have coiled tips which aid in climbing– Cactus have spines

Plant Tissue Systems

• Epidermis– Covers and protects– First line of defense– Cuticle is the waxy substance that helps

plants to retain water

• Vascular System– xylem/phloem – transports water and

nutrients– support

Plant Tissue System

• Ground Tissue System– Filling spaces, bulk– Parenchyma, collenchyma, sclerenchyma– Photosynthesis, storage, support

Plant Tissue System

• Roots– Epidermis

• Covers roots• Entrance for water and nutrients• May form root hairs• No cuticle

– Ground tissue• Cortex – parenchyma, store food• Endodermis – selective barrier, thin layer of cells decides what

passes between vascular tissue and cortex– Vascular Bundles

• xylem – spokes of wheel• phloem – fills in wedges between spokes

Figure 31.6B

Xylem

Phloem

Epidermis

VASCULARTISSUESYSTEM

GROUNDTISSUESYSTEM

Cortex

Endodermis

Plant Tissue System

• Leaf– Epidermis

• Covered by cuticle• Small pores called stomata• Surrounded by guard cells

– Ground Tissue• Mesophyll composed of parenchyma cells and chloroplast• Air located in spaces between cells

– Vascular System• Vein – composed of xylem and phloem surrounded by

parenchyma cells

Figure 31.6D

Plant Tissue System

• Stem– Epidermis

• Thin layer of cells• Covered by cuticle

– Ground Tissue• Dicot - 2 parts / Monocot – 1 part (ground tissue)

– Pith – food storage– Cortex – fills spaces

– Vascular Tissue• Occurs in vascular bundles

– Dicot – ring– Monocot - random

Figure 31.6C

Plant Cells

• Three main differences between animal cells and plants cells are – Cell wall– Central vacuole– chloroplasts

Figure 31.5A

Plant Cells

Five Major Types of Plant Cells 1. Parenchyma cells – most abundant type

• Remain alive at maturity• Primary cell wall (thin)• Function in food storage and photosynthesis• Multisided

2. Collenchyma cells

primary cell wall (thick)

alive at maturity

provide support in plants that are still growing

Figure 31.5B

Primarywall(thin)

Pit

Parenchyma Cells

Plant Cells

3. Sclerenchyma cells – Rigid secondary walls– Hardened with lignin– Found in regions that is not growing– Dead at maturity– Two types of sclerenchyma cells

• Fiber – long and slender and occurs in bundles; hemp fibers make rope

• Sclereid – stone cell; short, irregular shaped secondary wall; found in nutshells and sead-coats

Figure 31.5D

Pits

Primarywall

FIBER

Secondarywall

Fibercells

Sclerenchyma Cells

Sclereids (stone cells)

Figure 31.5D continued

Secondarywall

Sclereidcells

Primarywall

Pits

SCLEREID

Sclerenchyma Cells

Plant Cells

4. Water-Conducting cells – Rigid, lignin-containing

secondary cell walls– Cells are dead at maturity– Hollow in the middle– Functions in support

Two types of water-conducting cells

1. Tracheids – long cells with tapered

ends

2. Vessel Elements – wide, short cells

Pits

Vessel element

Tracheids

PitsOpeningsin end wall

Plant Cells

5. Food – Conducting cells (sieve tube members)

-arranged end to end

- thin primary walls with no secondary wall

-alive at maturity

-transports sugars and minerals

-sieve plates – located at the ends of the sieve tube members

Sieve plate

Companioncell

Cytoplasm

Primarywall

Sieve Tube Members

Primary Growth

• Indeterminate growth – continue to grow as long as they live– Annuals – wheat, corn, rice– Biennials – beets, carrots– Perennials – trees, shrubs, grasses

Primary Growth

• Apical meristem – lengthwise growth

• Root cap – protects apical meristem in roots

• Two functions of root apical meristem– Replaces cells of root cap– Produces cells for primary growth

Primary Growth

• Three regions of roots– Epidermis (outermost)– Cortex (bulk)– Vascular tissue

• Elongation – uptake of water– cellulose fibers extend (accordion)– forces roots into soil

• Differentiation – caused by master gene; causes unspecialized cells to specialize

Figure 31.7B

Vascularcylinder

Cortex

Epidermis

Root hair

Cellulosefibers

Apical meristemregion

Rootcap

DIF

FE

RE

NT

IAT

ION

EL

ON

GA

TIO

NC

EL

LD

IVIS

ION

Primary Growth

• Three Zones– Cell division– Elongation– Differentiation

• The angiosperm flower is a reproductive shoot consisting of– sepals– petals– stamen– carpels

Figure 31.9A

Stigma

Ovary

Carpel

Anther

Petal

Ovule Sepal

Stamen

Flower Reproduction

Fertilization of an Angiosperm

• Formation of a pollen grain– Cells that make pollen grains are located in

the anther– Meiosis- four haploid spores that eventually

form two haploid cells called a tube cell and a generative cell

– Wall forms around the two cells known as a pollen grain

– Animals, wind, and water transport pollen grain (male gametophyte)

Fertilization of an Angiosperm

• Formation of an Egg Cell– Megaspore mother cell – forms 4 haploid

megaspores and three degenerate– Surviving megaspore enlarges/ mitotic

division– End Result – One large cell with two haploid

nuclei and six smaller cells.– One of the six smaller cells is the haploid

egg.

Pollination

Sugar/enzymes on stigma causes tube cell to grow and form pollen tube

• Both cells (generative cell and tube cell) travel to embryo sac

• Generative cell forms two sperm cells• One sperm cell fertilizes the nucleus with the

polar nuclei (triploid nucleus/3n)

Pollination

• One sperm cell fertilizes egg cell (diploid nucleus/2n)

• Triploid forms endosperm/functions to nourish embryo (popcorn)

• Flowering plants (double fertilization)• Alternation of generations

– Haploid – female gametophytes (ovules/egg), male gametophytes (generative cell/sperm)

– Diploid – sporophyte (plant/flower); produces haploid spores by meiosis