Chapter 19: Kingdom Plantae

19.1 Land plants evolved from green algae

Multicellular

Usually photosynthetic

Mostly terrestrial

Plant: multicellular autotroph, embryo develops in female parent

Origins of Plants from Algae

Closest ancestors = multicellular green algae – Charophytes

Some shallows dried out – plants adapted

Challenges of Life on Land

4 challenges– 1. obtaining resources– 2. staying upright– 3. maintaining moisture– 4. reproducing

1. Resources

Air – light, carbon dioxide (photosynthesis)– Shoots, leaves

Soil – water, mineral nutrients– Roots

Vascular tissue– System of tube-shaped cells that branches

throughout the plant– Materials – roots/shoots

2. Staying Upright Water - buoyancy Air – rigid support tissue

– Lignin – hardens plants’ cell walls

3. Moisture Internal watery environment for cell

processes Adaptations:

– Waxy cuticle – retain water, slow exchange gases between air and leaves

– Stomata – pores in leaf’s surface Gas exchange Guard cells

4. Reproduction Gametes / offspring – moist

– Sperm – pollen grain– Egg – female tissues

Dispersal – Sperm – wind / animals

Embryo develops in female parents seeds

Overview of Plant Diversity

4 major periods plant evolution– 1. Bryophytes – mosses

No seeds, no lignin

– 2. Pteridophytes – ferns Lignin – vascular tissue

– 3. Gymnosperms – naked seeds, conifers– 4. Angiosperms – flowering plants

Fig. 19-5

                                                        

                                                             Figure 19-5Fossil evidence indicates that bryophytes are the oldest and angiosperms the youngest of the four major plant groups.

Alternation of Generations

Diploid (Sporophyte) / haploid (Gametophyte)

Multicellular Fig. 19-6

                                                                

                                                  Figure 19-6A plant's life cycle alternates between the gametophyte and sporophyte generations

Spores vs. Gametes

Spore Gamete

New organism without another cell

2 gametes fuse to form a zygote

Tough coat – harsh environments

Not adapted for harsh conditions

19.2 Mosses and Bryophytes

Damp habitats Lack rigid support tissues grow

close to ground

Bryophyte Adaptations Dominant generation = gametophyte

(1n) Nonvascular – no lignin Fig. 19-7 – overhead

Separate male/female gametophytes– Flagellated sperm swim to eggs– Fertilization – zygote grows from female

gametophyte into sporophyte– Sporophyte (2n) = stalklike, capsule at

top– Capsule produces/releases spores

new gametophytes

Diversity of Bryophytes

Hornworts – hornlike sporophytes

Mosses – Moss mat = many gametophytes in tight

pack– Stalks = sporophytes– Spongy – absorb / retain water

Liverworts – liver-shaped gametophytes

19.3 Pteridophytes: Ferns / other seedless vascular plants

Pteridophyte adaptations: Fig. 19-10 - overhead

– Vascular tissue – lignin – water, sugar– Carboniferous period – fossil fuel– Dominant generation = sporophyte– Underside of fronds – spore capsules

Haploid spores, gametophytes

– Underside of gametophyte Produce sperm / egg Sperm swim to egg zygote new

sporophyte

Diversity of Pteridophytes Ferns – most diverse Leaves = fronds Shady forests

Club “mosses” – little pine tree– Vascular tissue, no seeds, forest floors

Horsetails Marshy, sandy areas Outer layer = silica – gritty Scrub pots/pans “scouring rushes”

19.4 Pollen and Seeds Evolved in Gymnosperms

Gymnosperm adaptations Gymnosperms = plants that bear

seeds that are “naked” – Not enclosed in an ovary– Most common - conifers

3 more adaptations than ferns: 1. Smaller gametophyte

– Dominant generation = diploid sporophyte = pine tree

– Tiny gametophytes are in cones- protection 2. Pollen

– Reduced male gametophyte – Contain cells that become sperm – Wind – pollen from male to female- no water

needed 3. Seeds

– Plant embryo with a food supply in a protective coat

Life Cycle of Gymnosperms

Male pollen cone - spore sacs with haploid spores become pollen grains (male gametophyte)

Female gametophytes develop within ovules– On scale of cone – 2 ovules– Large spore cell – meiosis– 4 haploid cells – 1 survives female

gametophyte

Wind – blows pollen between trees Pollen lands in female cone Sperm matures and fertilizes egg in

female gametophyte 2 eggs fertilized often – still only 1

zygote into embryo (seed) = new sporophyte

Diversity of Gymnosperms

4 phyla today Gingkos

– Gingko biloba Fan-like leaves Shed in autumn Cities-

– Tolerates– pollution

Gnetophytes– Mormon tea, desert shrub

Cycads – large, palm-like leaves– Not true palms which are flowering plants

Conifers– Spruce, pine, fir, junipers, cedar, redwood– evergreen

19.5/20.1 Flowers and fruits evolved in

angiosperms Angiosperm Adaptations

– Gametophytes develop in flowers of sporophyte

– Flower = specialized type of plant shoot that functions in reproduction, only in angiosperms

Attract animal pollinators – variety Insects transfer pollen between flowers Grasses – wind pollinated – small flowers

Flower Anatomy

Flower – specialized shoot 4 rings modified leaves

– Sepals – protect flower bud– Petals – color – insects– Stamens – male, many– Carpels (pistils) – female,1+

Stamen – produces male gametophytes

Filament + anther Filament – supports anther Anther – pollen

– meiosis – spores – pollen grains = male haploid gametophytes

Each pollen grain – 2 cells with thick protective wall

Fig 20-2 in packet

Carpels – female gametophytes

stigma – style – ovary – Stigma – sticky – pollen– Style – supports stigma – pollen tube– Ovary - ovules

Angiosperm Life Cycle Pollen on stigma - pollination Pollen tube to ovule in ovary - style

– 2 sperm cells in pollen grain in tube– In ovules – diploid cell –

meiosis 4 haploid spores – ¾ die survivor enlarges – 3 cycles mitosis

embryo sac – 7 cells (1 egg cell + 1 large cell with 2 haploid nuclei)

Water lilies

Star Anise

– 1st sperm fertilizes 1 egg = zygote embryo

– 2nd sperm fuses with nucleus in larger center cell triploid cell = endosperm (nutrient storage)

– “double fertilization” – zygote and endosperm develop into seed

Many ovules, many seeds Seeds develop, ovary wall thickens

fruit Fruit = ripened ovary of a flower

– Protects, disperses seeds– Colorful, attract animals, eat, digest,

waste

Monocots – day lilies, orchids, irises, palms, grasses– Flower petals – multiples of 3

Dicots – poppies, roses, peas, sunflowers, oaks, maples– Flower petals – multiples of 4 or 5

Human Dependence on Angiosperms

Food – human, domestic animals– Corn, rice, wheat, fruit, vegetables

Furniture, medicines, perfumes, decorations, clothing fibers

Threat – tropical rain forest

20.1 Reproductive Adaptations contribute to angiosperm

success

Seed Development and Dispersal

Seed parts– Seed coat – outer layer – protects

embryo and endosperm– Mini root and shoot– Cotyledon – food storage

Monocot, dicot

Seed Dispersal Animals

– fur – burr– Eat, digest fruit, waste

Water – coconut Wind - dandelion

Seed Germination Plant embryo grows in favorable

conditions Soak up water Expands Seed coat splits

Adaptations to Germination

Dicot – hooked shoot tip Monocot – sheath around shoot tip Light – 1st leaves – photosynthesis =

seedling

Environment needed for Germination

Usually just warm, moist Others

– Heavy rainfall – soil– Long cold– Intense heat - clearing

Challenges to sexual reproduction

Pollination Damaged seeds Bad environment for germination Delicate seedlings – eaten, water

Asexual Reproduction in Plants

Vegetative Propagation – offspring identical to parent

Cacti- drop stems Strawberries - runners

Lifespan Annuals – one growing season Biennials – 2 years Perennials – multiple years

20.2 Plant Tissues / Organs

Roots– Anchor, support, absorb water, minerals

Monocots – – fibrous roots: many thin roots – grass

Dicots – – Taproot: 1 large vertical root with small root hairs– carrots, turnips, beets

Angiosperm shoots – stem, leaves, flower

Stems – Support leaves, flowers– Nodes – where leaves are attached– Internodes – between nodes– Transport – vascular tissue – leaves and

roots

Buds– Underdeveloped shoots– Terminal bud – tip of stem– Axillary buds – found in angles of leaf

and main stem – branches

Leaves– Photosynthesis – food– Blade – main leaf part– Petiole – connects leaf to stem– Veins – carry water, nutrients– Modified leaves

Grass – no petiole Celery – large petiole – eat Cactus spines

Main Tissue Systems: Dermal, Vascular, Ground

Vascular – transport roots / shoots– Support– 2 types:

Xylem: water, dissolved minerals up from roots to shoots

Phloem: food from leaves to roots, non food-making leaves, fruits

Locations: – Roots – center– Stems – vascular bundles

• Monocot – scattered• Dicot - ring

Dermal – outer covering– Epidermis – protects young plant parts

Ground – makes most young, nonwoody plants– Photosynthesis, storage, support– Root - cortex

Plant Cells: Parenchyma, Collenchyma, Sclerenchyma

Parenchyma– Food storage, photosynthesis, cellular

respiration– Fruits, phloem

Collenchyma– In strands, Celery strings– young parts

Sclerenchyma– Lignin-rich cell walls - ‘skeleton’ for mature plant– xylem

20.3 Primary Growth Meristematic tissue

– Meristems – create new tissue - always Mitosis, cell then differentiate

– Apical meristems Tip of roots, bud of shoots Lengthen, branch

– Primary growth Growth in plant length

Primary growth in Roots

Root cap = root tip – protects dividing cells of apical meristem

Root apical meristem– 1. Replaces root cap cells– 2. Produces cells for primary growth

Primary growth cells – 3 concentric circles– Out – dermal– Middle – bulk root tip – root’s cortex (ground)– In – vascular tissue

Primary growth depends on– Addition of new cells– Cells elongating – more water– Elongation – forces root tip through soil

Primary growth of shoots

Apical meristem – tip terminal bud Elongation – just below meristem –

push cells upward Some cells left behind

– Become axillary buds - branches 3 concentric circles – dermal, ground,

vascular

20.4 Secondary Growth Woody plants – vines, shrubs, trees Growth in plant width Cell division in 2 meristematic tissues:

vascular cambium and cork cambium

Vascular Cambium Between xylem and phloem Adds cells both sides

– Secondary xylem inside– Secondary phloem outside

Added to primary tissues during primary growth

Secondary xylem becomes wood each year during growing season– Dormant in winter– Stem / root thickens with each new xylem

Cork cambium cork Cork cells die – thick, waxy walls left –

water loss, helps protect internal tissues

Bark = everything outside vascular cambium = Phloem, cork cambium, cork

The Rings Age from annual growth rings Result of vascular cambium activity

each year

Environment Each ring

– Spring wood – large, thin-walled Cool temps, lots water

– Summer wood – narrow, thick-walled Hot, dry

21.2 Vascular Tissue Roots – absorb water, minerals Roots hairs –epidermal cells

– Grow between soil particles– Surface area

Root pressure– Pushes water up xylem – night– Root epidermal and ground tissue cells

use ATP to get minerals – into xylem– Endodermis – around vascular tissue,

waxy cell walls – doesn’t let water back out

– Water enters (osmosis) – pushes xylem sap upward

The Upward Movement of Xylem Sap

Transpiration – loss of water through leaves due to evaporation– “transpiration pull”

Cohesion – same kind molecules stick together (water)

Adhesion – attraction between unlike molecules (water sticks to cellulose in xylem walls)

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Regulating water loss Transpiration – lots water loss Evaporative cooling – keep good

temp. More transpiration than water delivery

= wilting

Adaptations for water loss

Leaf stomata – open / close – guard cells

Day – Stoma open – Carbon dioxide in– Sunlight and low carbon dioxide – more

potassium – water follows – Guard cells swell and open

Night– Stomata close– Potassium ions leave with water– Sag together

Flow of Phloem Sap Phloem Move sugar from source to sink

(storage or use) Different sinks, different seasons

– Summer – taproots, tubers – storage– Next Spring – become sugar source

Pressure – Flow Mechanism

Sugar produced Active transport to phloem tube Up sugar conc. at source end of

phloem – water follows = up water pressure at source

pressure low at sink Sink end = sugars leave phloem, water

follows, pressure drops = water flows high to low

21.3 Carnivorous Plants Some plants – N from animals Ex: sundews, Venus's flytraps, pitcher

plants Little organic N where they live

(wetlands, cold, acidic water, decay slow)

Still photosynthesize

22.1 Plant Hormones

Plant hormones – chemical messengers (only takes a little)

Control:– Germination– Growth– Flowering– Fruit production

Functions of 5 Major Hormones:

Balance of hormones acting together

Auxins Apical meristems – shoot tips Cell elongation

Auxin builds – shaded side Shaded cells lengthen more, more

water Uneven sides = bending

Secondary growth – vascular cambium Seeds – auxin – signal ovary to fruit Auxins - no pollination seedless

fruit

Cytokinins Cell division – made in roots Cytokinin with auxin

– Fewer / shorter branches near tip

Gibberellins Fruit – seedless, larger

Abscisic Acid (ABA) Limits cell division Stops growth Dormancy “stress hormone”

Ethylene Fruit ripening “leaf drop”

22.2 Plant Responses Rapid plant movements

– Touch– Rapidly reversible

Tropisms – slowly grow toward or away from a stimulus– Slow to reverse

Thigmotropism Touch Climbing plants – tendrils Seedling - obstacle

Phototropism Light Uneven auxins – light one side

Gravitropism Gravity Mature plant Seedling root / shoot

Stressful Environments Drought

– Water loss, wilting, drop photosynthesis– Succulents – water fleshy stems

Flooding – Clogs air spaces, less cellular respiration– Mangrove trees

Salt stress– Root cells drop water – osmosis– Halophytes – salt glands, pump out salt

Disease Viruses, bacteria, fungi Adaptations

– Epidermis– Chemicals – lignin– Resistant genes– Thorns, poisons