Kingdom Plantae

Biology 391Chapters 12 and 11

Floweringplants

Cone-bearingplants

Ferns andtheir relatives

Mosses andtheir relatives

Green algaeancestor

Flowers; SeedsEnclosed in Fruit

Seeds

Water-Conducting(Vascular) Tissue

Phylogeny & Reproduction

Sections12.412.5

Plant Reproduction & Development

• Plant Phylogeny & Life Cycles– Bryophyta, Pterophyta, Gymnosperms, Angiosperms– Alternation of Generations

• Focus on Angiosperms– Germination of the Seed– Monocots vs. Dicots– Structure and Growth– Factors Affecting Growth

Cone-bearing plants760 species

Ferns andtheir relatives11,000 species

Mosses andtheir relatives15,600 species

Floweringplants235,000 species

Section 22-1

Remember…

• Mitosis

• Meiosis

• Fertilization

• n to n• n to 2n• 2n to n• 2n to 2n

• Haploid?• Diploid?• Triploid?

Reproductive & Dev’t ThemesPlants

• Early plants need moisture but not seed plants

• Alternation of Generation– Lifeforms can vary between

Haploid & Diploid

• Pollination then fertilization• Angiosperms have “double

fertilization”• Indeterminate adult growth

possible– Meristem can always produce

more leaves, etc.

Animals

• Fertilization requires water• Adult is diploid, gametes

are haploid• Determinate adult growth

Alternation of Generations

Antheridia – male gametophyte, produces sperm

Archegonia – female gametophyte, produces egg

Sporangium – produces spores

Moss Life Cycle

Requires moist environment for sperm to reach egg.

Short, simple – no vascular tissues

Gametophyte dominant

Fern Life Cycle

Ferns

• Still requires a moist environment for sperm Still requires a moist environment for sperm to reach the eggto reach the egg

• Small, almost unnoticeable gametophyteSmall, almost unnoticeable gametophyte• Sporophyte dominantSporophyte dominant

Fig. 30-6-4

Microsporangium (2n)

Microsporocytes(2n)

Pollengrains (n)

Pollencone

Microsporangia

MEIOSIS

Maturesporophyte(2n)

Haploid (n)Diploid (2n)

Key

MEIOSIS

Survivingmegaspore (n)

Pollengrain

Megasporocyte (2n)

Ovule

Integument

Ovulatecone

FERTILIZATION

Pollentube

Femalegametophyte

Spermnucleus (n)

Egg nucleus (n)

Archegonium

Seedling

Seeds

Seed coat(2n)

Foodreserves(n)

Embryo(2n)

Megasporangium(2n)

Gymnosperms• Plant is a large diploid structure• Vascular tissues present• Ova protected• Pollen grains water no longer necessary for

sperm to travel

Evolutionary Adaptations – Flowering Plants (AngiospermsAngiosperms)

• Dominant diploid stage – allows development of complex structures

• Evolution of pollen – transfer of sperm without water

• Evolution of seed – protection of embryo, internal food source, only grows under good conditions

• Adaptations that promote seed dispersal

Flower Structure • Carpels – modified

leaves, female structure– Ovary – carpels fuse to

form hollow structure– Ovules – small structure

in ovary where ova develops

• Stamen – male structure– Anther – produces pollen

Flowering Plants Overview

Gametophyte Dev’tPollenCells in sporangium undergo meiosis producing four microspores, each of which through mitosis will form a pollen grain.

Each pollen grain will have a tube nucleus and two sperm nuclei.

EggMegaspore undergoes meiosis forming 4 cells, but only one survives. Megaspore undergoes three mitotic divisions to form embryo sac.

Pollination & Fertilization• Anther sheds pollen• Lands on stigma• Pollen germinates and

forms a pollen tube• Tube grows down towards

ovule, carrying two sperm nuclei

• Double Fertilization– One sperm nucleus fuses with

egg– Other sperm nucleus fuses

with polar nuclei triploid cell that develops into endosperm

• Endosperm will provide nutrients to developing embryo

Seeds• Endosperm nourishes developing embryo• Eventually the entire ovule forms a seed• Seed spreading techniques

– Float, wind, burrs, fruits

Fig. 30-2

Reduced (usually microscopic), dependent on surroundingsporophyte tissue for nutrition

Reduced, independent(photosynthetic andfree-living)

Gametophyte

Sporophyte(2n)

Sporophyte(2n)

Gametophyte(n)

Sporophyte

Example

Gametophyte(n)

Dominant

Dominant DominantReduced, dependent ongametophyte for nutrition

Mosses and othernonvascular plants

Ferns and other seedlessvascular plants

Seed plants (gymnosperms and angiosperms)

PLANT GROUP

Gymnosperm Angiosperm

Microscopic femalegametophytes (n) insideovulate cone

Microscopic malegametophytes (n) inside pollencone

Sporophyte (2n) Sporophyte (2n)

Microscopic femalegametophytes (n) insidethese partsof flowers

Microscopic malegametophytes (n) insidethese partsof flowers

Recap

• Differentiate between gametophyte and sporophyte.

• In flowering plants, why is fertilization called double fertilization?

• How do insects help pollination?• What is meant by alternation of generations?

– Do all plants have this?

Plant Growth & DevelopmentPlant Growth & Development

Chapter 11Chapter 11Bio 391Bio 391

Plant Reproduction & Development

• Plant Phylogeny & Life Cycles– Bryophyta, Pterophyta, Gymnosperms, Angiosperms– Alternation of Generations

• Focus on Angiosperms– Germination of the Seed– Monocots vs. Dicots– Structure and Growth– Factors Affecting Growth

Development of the Seed• 1. Mitosis in zygote forms mass of cells

embryo• 2. Endosperm forms

– Transfers nutrients from mother plant to embryo– Some species – completely digested by embryo,

others… endosperm persists as nutrient source for young plant until photosynthesis begins

• 4. Elongation– Quick cell division elongates embryo– New cells differentiate into specialized structures

• Apical Meristem – forms zone of undifferentiated cells– At tip of roots and of shoots– Divides into new cells that specialize into certain tissues

• Cells between coytledons embryonic shoot• Embryonic root

• 5. Seed Coat– Maternal flower tissue encloses endosperm &

embryo– Embryo stops growing dormant

• No enzyme activity• No transcription or translation• Very slow, little cell respiration

• 6. Waits for optimal conditions to sprout

11.2 Seed Germination• Process:

1. Good water, oxygen temperature2. Embryo resumes metabolism, growth, development3. Enzymes made – digest food in endosperm &

cotyledons goes to growing areas of embryo4. Respiration ramps up5. Water restores turgor pressure to embryo cells6. Embryo cells swell & grow7. Seed coat ruptures8. Embryonic root emerges9. Shoot grows up through soil

MONOCOTS Vs DICOTS

Germination is an evolutionary adaptation

– Seeds only grow under optimal conditions, increasing survival

• EX: apple seeds don’t sprout in fall – too cold in winter

– Many seeds genetically programmed to wait for several weeks of cold followed by warmer temps (or another abiotic factor)

• EX: desert plants – many wait for enough rainfall• EX: some forest trees germinate only after intense fire

– ash full of nutrients & reduced competition• EX: Avocado – germinates only in complete dark, a

signal that enough soil is covering the seed

11.3 Primary & Secondary Growth

Cell Tissue Organ System Organism

include

includes includes includes

includes includes

Section 23-1

Plant Tissues

Dermaltissue

Meristematictissue

Vasculartissue

Groundtissue

Epidermalcells Xylem Phloem Parenchyma

cellsCollenchyma

cellsSchlerenchyma

cells

Tracheids Vesselelements

Sieve tubeelements

Companioncells

Primary Growth• Root & stem begin from meristem in embryo

– Apical meristem cell division lengthens plant along the root-shoot axis

– Node meristem tissue provides cells to stem growth

– Also point at which leaf emerges

– Starch & lipids in cotyledons/endosperm support growth until leaves emerge and photosynthesis begins

– Root penetrates soil anchors plant, absorbs water & nutrients

– Root Cap covers and protects apical meristem as root grows through soil

PLANT TISSUE SYSTEMS (4)A) MERISTEMATIC Source of new growth

for the entire life of the plant• Primary Growth plants grow taller and

deeper– Only in tips of roots & shoots– Apical meristem “the bud”

• Secondary Growth plants grow wider– Lateral Meristem tissue– (Also known as: vascular or cork cambium)

PLANT TISSUES cont.B) DERMAL TISSUE The outer covering of the

plant, “the skin”– May have waxy covering to prevent water loss

C) VASCULAR TISSUE transports fluids & nutrients throughout the plant, “the bloodstream”– Xylem transports water– Phloem transports food (sugars made)

D) GROUND TISSUE fills plant’s body, gives shape and internal support

-Becomes specialized mesophyll for photosynthesis, nutrient storage, etc.

• Two important factors in development are growth of the cell wall and orientation of cell division– Wall get thicker with maturity, and hardens– Mitosis produces small, thin walled cells that can

expand– Primary growth – cell divisions in stem & roots are

horizontal– Cellulose molecules wind around cells – they can’t

expand sideways BUT grow vertically– Lengthens stem and root

Secondary Growth• Growth in diameter

– Vascular Cambium – cylindrical layer of cells near outer surface of roots and stems

• Inner cells become xylem (water conducting)• Outer cells become phloem (sugar conducting)

– Cork Cambium (shoot)• Meristem that produces bark in trees & woody plants

– Pericycle (root)• Forms root branches/secondary roots• Meristem that surrounds xylem and phloem in root

Chimney Tree

The xylem cells at the center of the tree no longer carry water So even if the inner part is destroyed, a tree maintains normal growth and function

Recap

• What is the role of the endosperm for the developing plant embryo?

• What is the purpose of the cotyledons for the young plant?

Plant Growth Regulation

HORMONES• GROWTH PROMOTION• Auxins• Giberellins• Cytokinins• GROWTH INHIBITION• Abscisic acid• Ethylene

TROPISMS• Phototropism• Gravitropism

• Photoperiodism

Auxins, Gibberellins, Cytokinins• Promote cell division & stem elongation• Produced in apical meristem (shoots & roots)

– Auxins: Inhibits growth of lateral bud (pruning) but promote lateral roots

– Cytokinins: promotes lateral growth (buds & stems) but inhibits lateral roots

• Produced by seed to promote fruit dev’t– Spraying plants directly can cause fruits to grow– Seedless varieties produced this way

Cell Culture can be achieved at any plant stage by manipulating cytokinin and auxin levels

Abscisic Acid & Ethylene• Inhibit cellular activities & help plants survive

environmental threats• AA – made during drought

– Close stomata – Seeds & buds become dormant, storage proteins made– This is why some seeds need ample rain for germination – inhibitor

must be “washed out of seed”

• Ethylene – gas that promotes aging– Ripens fruits– Opposes auxins & cytokinins– Stimulates breakdown of proteins = dropping of leaves, flowers, fruits– Green Bags® have a mineral that absorbs ethylene

Tropisms• Growth toward or away from a stimulus• PHOTOTROPISM: Growth towards light

– Caused by auxin production, moving to shade

• GRAVITROPISM: growth w/ or against gravity– Auxins important, plastid “weight” in roots

• PHOTOPERIODISM: response to the relative length of light & darkness in 24hr– Long-day vs. short-day plants uninterrupted

darkness and the pigment phytochrome

http://trc.ucdavis.edu/biosci10v/bis10v/media/ch19/day_length.html

Recap…• How does putting a green tomato in a bag

promote ripening?• Name the tropism:

• What hormone has been removed to produce this plant?

Resources and Other Info

Teacher links, ok• http://www.youtube.com/watch?v=m1Adgz1h0ok• PBS, > 7min, ok…good burrs & interesting seed adaptations, velcro invented• http://www.youtube.com/watch?v=yMq_wp-jn-E&NR=1• >20min, boring but complete: out of the ocean through hormones• http://www.youtube.com/watch?v=XETgoSgEJmE• Supercute seseme street, <1min on intro to seed mobility• http://www.youtube.com/watch?v=3EBfmZbqBc8&feature=related• Supercute musical montage with clamation but gets weird at end• http://www.youtube.com/watch?v=_HqEJD5h68A&feature=related• Neat video showing elongation vs. replicating growth (rubberband demo)• http://www.youtube.com/watch?v=d2ys4UD6F3U&feature=related• 2 min, fast pictoral slideshow of plant diversity• http://www.youtube.com/watch?v=RuYrFwDuYn0&feature=related• 4 min, pollination by britannica. Good.

worthwhile• http://www.youtube.com/watch?v=bwCpQflmQG4&NR=1• Great – fruit formation, , 1min• http://www.youtube.com/watch?v=D9byVQxvMXs&NR=1• Conifer seed production, <2min, male and female• http://www.youtube.com/watch?v=jcWYAnmm-QE&NR=1• Moss reproduction• http://www.youtube.com/watch?v=jcWYAnmm-QE&NR=1• >3mn, plant reproduction• http://trc.ucdavis.edu/biosci10v/bis10v/media/ch19/day_length.html• Talking graph of photoperiodism. Day and Night experiments explained very well