Domain EukaryaKingdom Plantae

What makes a plant a plant?

• Cell wall primarily of cellulose

• Starch as primary photosynthetic storage product

• Multicellular with complex specialized tissue development

• Chl a, Chl b, xanthophylls, carotenoids

Plant evolution simplified

Radiates from simple to more complex – in both form and environments

• Seedless non-vascular

• Seedless vascular

• Seed producing, vascular

• Seed producing, vascular, fruits/flowers

Semi-aquatic to more terrestrial

• Ancestral “plants”

transitions to primitive plants– Requirements met from aquatic environment

• Gas, water, light, buoyancy support

• Complex plants– Adapt to two environments

• Shoot system

• Root system

Plants: categorized by structures and lifecycles…

Alternation of Generations

Moss sporophytes and gametophytes

gametophytes

sporophytes

Moss antheridia

Sperm

Moss antheridia w/sperm

Moss archegonia

ovum

Moss archegonia 2

ova

Moss archegonia 3

Moss sporophytes

Moss capsule (sporophyte)

Operculum

Spores

Liverwort

Liverwort antheridiophore

Liverwort antheridiophore 2

Liverwort antheridia

Antheridiophoresperm

Liverwort antheridia w/sperm

Liverwort archegoniophore

Liverwort archegonia w/ova

Archegoniophore

Archegonium

ovum

Liverwort sporophyte

Archegoniophore

Liverwort sporophyte 2

spores

Liverwort gemmae cups(cupules)

Gemmae cups (cupules)

Gemma cup (cupule)

gemma

Hornwort

sporophytes

gametophyte

Hornwort 2

“Horn –like” Sporophyte

gametophyte

Tracheophytes ancestral e.g. Rhyniophyta

• Ferns and “fern allies”

• Seedless

• Vascular plants– Xylem composed of

Tracheids – tapered porous cells

• capillary action moderately efficient

• Sporophyte dominant

Psilophyta

Psilophyta gametophyte

Lycophytastrobila

leaves

Lycophyta strobilus

megaspores

microspores

sporophylls

Lycophyta strobilus 2

megsporangium

Microspores

Megaspores

Lycophyta gametophyte

Sphenophyta

strobilus

Sphenophyta strobilus

Sphenophyta gametophyte

Pterophyta sporophyte

Pterophyta sporophyte2

Fern frond w/ sori

Sori on fern leaflets

Sorus

Fern sporangia

Sporangium

Annulus

Spores

Fern sporangia and spores

Fern gametophyte

Fern gametophyte

Gametophyte w/antheridia

Gametophyte

(prothallus)

Antheridia sperm

Antheridia w/sperm

Antheridium

sperm

Gametophyte w/archegonia

Archegonia

Gametophyte w/archegonia 2

Archegonia

Archegonia on surface of prothallus

Fern sporangium and prothallus

Sporophyte

Gametophyte

(prothallus)

Fern Life Cycle

Seed producing plants Gymnosperms

• Sporophyte dominant

• Conifers & relatives

• Heterosporous– Mega- and micro-

– Small gametophye matures in protected cones

• Female in ovulate cones• Male in staminate cones

– Wind blown-pollen

• Seeds protected in ovulate cone– Dispersed by wind, animal,

water sometimes

Angiosperms

• Sporophyte dominant

• Flowering plants

• Heterosporous– Mega- and micro-

– Small gametophye matures in protected flowers

• Female in flower ovary

• Male in flower anthers– Animal pollination and

some wind-blown

• Seeds protected in fruit– Dispersed by animal mostly

Seed? Ovule to seed• Ovule: sporophyte tissue surrounding sporangia

• Seed coat: protective diploid tissue

• Embryo: diploid zygote develops to sporophyte

• Endosperm: nutritive tissue surrounding embryo to feed it until it can photosynthesize on its own

Evolutionary importance of Seeds

• These plants produce pollen– Pollen produces sperm nuclei (no water requrd)

• Expand over drier habitats– Very protective over seasons (dormancy)

• Endosperm (embryonic food) – headstart

• Seed dispersal not dependent on water– Collected and distributed further

• Flowering plants…even further in fruits

Pine lifecycle a

Pine lifecycle b

Pinus staminate cones

Pinus Ovulate cone (mature)

Staminate cone with pollen

Pollen grains (microspores or micorgametophytes)

Pinus microgametophytes (mature pollen grains)

Generative nucleus

Tube nucleus

“Wing”

Pinus ovulate conemegasporophyll

ovule

Pinus megasporophyll

Megasporophyll

Megaspore mother cell

Ovule w/megaspore mother cell

Megaspore mother cell

Ovule

Pinus Mega-gametophyte

Ovule

Ovum

Pollen tubes

Pollen tube 2

Ovule (megagametophyte)

Pinus seed

Haploid endosperm (gametophyte tissue)

Cycadophyta (male)

Cycadophyta

Cycadophyta ovulate cones

Ginkgophyta

Ginkgophyta leaves

Ginkgo ovules/seeds

(naked) ovules

(naked) seeds

Ginkgo staminate cones

Gnetophyta

Welwitschia mirabilis • found in Angolan desert

• “desert onion”

Gnetophyta/Ephedra

Angiosperms /Anthophyta

• Flowering Plants (anth = flower)

• Seeds in a fruit (angio = container)

• Double fertilization (see life cycle)

• Like other pollen producers, is not dependent on water for fertilization

What is a flower?

Flower structure

(carpel)

(corolla)

(calyx)

Plants:• Monecious

– Has both sexes

• Dioecious– Separate sexed plants

Flowers:• Perfect

• Imperfect

• Complete

• Incomplete

• Regular

• Irregular

• Inflorescences

Inflorescences

Anther1

Anther 2

Dehiscing anther

Pollen grains

Angiosperm lifecycle

Mature pollen grains

Lilium ovary (immature)

Lilium ovule

ovule

Megagametophyte (embryo sac)

funiculus

Dicot Seed

E

A= plumule

B= hypocotyl

C = cotyledon

D = testa

E = radicle

Dicot seed germination

Radicle

Monocot seed

Plumule RadicleCotyledon

Endosperm

Embryo

Testa

Monocot seed germination

Vascular tissue

• Transport water, nutrients and food between roots and shoots

• System of xylem and phloem cells

• Varied organization in roots & shoots

Xylem cells – mature cells that become lignified (thickened 2o cellulose), dies, and perforates from lysosomes

• Tracheids– Primitive vascular plants

– Tapered, pits on ends, less capillary action vs. vessel elements

• Vessel elements– Less primitive vascular plants

– Pits on sides, open ends

– Stacked to form long tubes

– Advanced capillary action

• Transpiration– Roots → shoots → leaves → out– Via: root pressure and diffusion,

capillary pressure, negative pressure of evaporation and cohesion

Phloem cells – living cells that transport sugars (sap)

• Sieve tubes– no nucleus nor organelles– Open sieve plates

• Companion cells– Nucleated– Adjoined to sieve tubes via

plasmodesmata– Controls sieve tubes; regulates

movement• Translocation

– Movement of sugars; sources to sinks

leaves → roots, fruits, &/or meristems

Plant Structure• Apical meristem

– Mitotic division– Stem & root tips– Primary growth (length)

• Ground meristem– Mitotic division– Ground tissues:

• Parenchyma – large; storage• Collenchyma – smaller;

flexible support• Schlerenchyma – lignified;

rigid support; woody• Cambium

– Mitotic secondary growth– e.g. Vascular cambium– e.g. Cork cambium

Leaf bud

Ground meristem

Leaf bud 2

Provascular tissue

Ground meristem

Apical meristem

Monocot root Dicot root

• Vascular bundles centered in roots

• Cortex = outer layer• Pith = center tissue• Stele = pith + vascular tissue

Monocot root 2

Parenchyma

Pith (Parenchyma)

Monocot root 3Endodermis

Dicot root 2

Parenchyma

Dicot root 3Endodermis and casparian strip

Pericycle

Phloem

Xylem

Vascular cambium

• Vascular bundles– Xylem, phloem, and

cambium in between

– Scattered throughout monocot stems

– Organized around periphery of dicots

• Cambium– Mitotic secondary

growth

– e.g. Vascular cambium

– e.g. Cork cambium

Monocot stem

Monocot stem 2Sclerenchyma

Phloem

Sieve element

Companion cell

Xylem vessel

Air space

Inside

Outside

Dicot stem

Dicot stem 2

sclerenchyma

Vascular cambium

phloem

Woody stem

Summerwood

Springwood

Woody stem 2

Vascular cambium

Phloem

Phloem ray

Xylem

Cork

Woody stem 3

Cork (collenchyma tissue)

Vascular cambium

Fruit – ripened ovary that protects the seeds

• Ripened?• Layers of the ovary = Pericarp

– Exocarp• Outer layer /ovarian wall

– Mesocarp• Middle layer

– Endocarp• Inner/adjacent to ovules

Fleshy fruits

• One or more ovarian layer is fleshy– Drupe

• Endocarp is hardened; pit or stone• Peaches, nectarines, apricots, etc

– Berry• All or most pericarp is fleshy• Grape, tomato, etc

– Pepo• Berry with hard thick rind• Melons, pumpkins, etc

– Hesperidium• Berry with leathery rind• Citrus

– Pome• Swollen receptacle around ovary or

core• Apple, pear

Dry fruits

• Lacks fleshy tissue– Dehiscent fruits

• Split along a seam to disperse seeds

• Legumes – two seams• Capsules – multiple

seams• Bean, pea pods,

peanuts, etc

– Indehiscent• Do not split on a seam• Achenes, grains, nuts• Corn, wheat, etc

• Simple fruits– Single ovary of one

flower

• Aggregate fruits– Many ovaries of

one flower

• Multiple fruits– Many ovaries of

many clustered flowers (inflorescence)

• Accessory fruits– Tissue other than

ovary ripens (swollen)

What is a coconut? Fleshy? Dry? Other?

Drupe: a single fleshy fruit with a hard stone which contains the single seed

Plant Hormones (Ch. 39)

chemical communication and regulation

• Auxins– Cell elongation

– Apical dominance

– Abscission suppression• Slows the shedding of

leaves, flowers, fruits

– Fruit maturation

– Geotropism• Phototropism

• Gravitropism

A. The tips have been removed. No auxin is produced and the shoots do not grow longer.

B. The tips have been covered so light cannot reach them. Auxin is in the same concentration on both sides of the shoots, so they grow longer evenly on both sides.

C. One side of the tips are in more light than the other side. Auxin is in a greater concentration on the shaded side, causing the cells there to grow longer than the cells on the light side.

Plant Hormones (Ch. 39)

chemical communication and regulation

• Giberellins– GA or Giberellic acid

– Growth• Release some buds and

seeds from dormancy

• Dwarf plants lack GA– Spray on grapes =

bigger grapes

• Stem elongation– Spray on dwarf plants

= taller plants

• Related to flowering in some plants

Sold as common bio-fertilizer

Plant Hormones (Ch. 39)

chemical communication and regulation

• Cytokinins– Cell division

– Stimulate bud growth

– Stimulates fruit & embryo development

– Prevents leaf senescence

• Slows aging to decay With & without

Plant Hormones (Ch. 39)

chemical communication and regulation

• Abscisic Acid– General growth

inhibitor

– Induces dormancy• Wintering of buds

and leaves

– Closure of stomata

• Ethylene– Gaseous hormone

– Plays role in fruit ripening

– Fruit abscission• (shedding)

– One of the reasons why ripe bananas will “ripen” other fruits