Post on 31-Dec-2015
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