Phylogeny of Green Plants

Chlorop

hytes

Coleoc

haeta

lesCha

rales

Embryophytes(land plants)

“Green algae”

Ref.4

Embryo

Ref.5

Cuticle

Ref.6

Sporopollenin

Ref.7

Green plants

Pop Quiz

According to the phylogenetic tree shown in the previousslide, the group “green algae” is:

A. MonophyleticB. ParaphyleticC. PolyphyleticD. I have no idea

Liverw

orts

Mosses

Hornwort

s Tracheophytes(vascular plants)

“Bryophytes”

Phylogeny of Land Plants

Embryophytes (land plants)

Ref.8 Ref.9 Ref.10

stomata

Ref.11

tracheidsin vasculartissue

Ref.12

Lycop

hytes

Ferns

and f

ern al

lies

Ref.13

Ref.14

Phylogeny of Tracheophytes

Tracheophytes (vascular plants)

Seed plants(Gymnosperms+Angiosperms)

true leaves

seedsRef.15

pollen

Ref.16

Phylogeny of Seed Plants

Ref.17Ref.18

Angiosperms

Seed plants

Gymnosperms

reduced female gametophyte

Ref.19

bitegmic ovules

endosperm

carpel

Ref.20flowers

Homework

Integrate the information from the previous slides and draw a treeshowing the relationships of the major plant groups. Also, mark the synapomorphies defining those major monophyletic groups along the branches.

Life Cycle: Angiosperm (Flowering plants)

Ref.1

Some Key Concept in Angiosperm Life Cycle

NOTE: definitions used in lectures of this class are mainly following the textbook (Judd et al., 2008.Plant systematics: a phylogenetic approach, 3rd ed.)

Meiosis: two-stage nuclear division process that reduces the chromosome numberof a cell by half (from a diploid cell to 4 haploid daughter cells), followed byproduction of spores.Mitosis: nuclear division that maintains the parental chromosome numberfor daughter cells; the basis for growth in size and asexual reproduction in plants.Fertilization: fusion of the sperm nucleus and the egg nucleus.Zygote (2n): the cell formed by the fusion of the sperm (1n) and egg (1n) atfertilization, germinates to produce a multi-cellular sporophyte (2n) via mitosis.Spore (1n): the first cell of a gametophyte (1n), product of meiosis.Sporophyte (2n): diploid, spore-producing generation of the plant life cycle,produces spores via meiosis in a structure called sporangium (plural, sporangia).Gametophyte (1n): Haploid, gamete-producing generation of the plant life cycle;produces gametes via mitosis in specialized structures/sex organs—gametangia(male: antheridium, produce sperm; female: archegonium, produce eggs)

Some Key Concept in Angiosperm Life Cycle (cont.)

Embryo vs. Embryo sac

Embryo (2n): young sporophyte, from the first cell after fertilization (zygote)until germination of the seed (in seed plants) or emergence from protective gametophytic tissues (other land plants).

Embryo sac (1n): female gametophyte of the angiosperms (flowering plants).

Life Cycle: Fern and Fern Allies

Ref.2

Life Cycle: Bryophytes

Ref.3

The sporophyte generation is dependent on the photosynthetic gametophyte fornutrition

Generalized Life Cycle in Plants

Alternation of generations = cycle between haploid (1n) and diploid (2n) phase

Difference between plants and animalsAnimals: meiosis produces gametes directly.Plants: meiosis produces spores (to start gametophyte generation), and mitosis

produces gametes.

Variation of Life Cycle in Plants

“Bryophytes” (mosses, liverworts, hornworts) - Most of life is in 1n phase,therefore, gametophyte (green leafy base) dominant life cycle; sporophyte (brownstalked capsule/sporangium) dependent on gametophyte (grows out ofgametophyte and gets all nutrition from gametophyte).Sporophyte produces spores that land on ground & germinate into gametophytes.

Ferns and fern allies - sporophyte dominant; gametophyte free-living, but smalland short-lived.Leaves = sporophyte, free-living. Spores germinate from sporangia on underside of leaves (sori) and produce small, green, free-living heart-shaped gametophyte on ground.Gametophyte with separate structures that produce egg & sperm; lives ~1 year, reproduces, then dies.Sporophyte dominant life cycle: lives longer and larger and reproduces many years.

Seed plants (Angiosperms and Gymnosperms) - sporophyte dominant;gametophyte dependent on sporophyte and very reduced and short-lived.Microsporangia in pollen-bearing structures (pollen cones or anthers) that produce male gametophyte,

short-lived and inside the pollen grain, which consists of 2-3 cells, one cell becomes sperm.Megasporangia in ovules that produce female gametophyte in cone (“gymnosperms”) or ovary

(angiosperms) and produces the egg.Spores grow into pretty small gametophytes which are contained within the parent plant (inside cones or

flower).

Pollination vs. Fertilization

Distinction and Relationship of Pollination and FertilizationPollination: transference of pollen from the anther to the stigma.

Fertilization: fusion of the sperm nucleus and egg nucleus.

Pollination occurs only in seed plants; Fertilization occurs in all sexuallyReproducing organisms.

In plants, pollination must occur before fertilization! (Without pollination,fertilization can not take place. )

“Sexual Encounters of the Floral Kind”Handout to accompany film – Biology 117/317

Pollination syndromes

Wind Pollination:1) flowers appear before leaves are out2) large number of flowers (especially males), often in catkins3) individual flowers small and inconspicuous - without parts for attraction4) Big stamens produce lots of pollen5) Stigmas large and plumose or roughened (papillate) to catch pollen6) Ratio of pollen to ovules VERY HIGH (up to 6,000 to 1)

Many different kinds of insects function as pollinators; often these involve very differentfloral characteristics:

Bees, butterflies, etc.:1) flowers showy, with brightly colored petals2) flowers usually with some food reward, two common ones are:

pollen - protein rich rewardnectar - rich in nutrients (e.g., amino acids and sugars)

3) flowers often with strong favorable scent during the day4) flowers often with ultraviolet markings visible only to the insects (not to humans)

Pollination Syndromes

Pollination Syndromes (cont.)

Moths:1) flowers often white2) flowers open and scent released in the evening or at night3) nectar reward4) flowers often long and tubular to limit access only to long tongued moths

Carrion flies (Blowflies):1) flowers purple or brown or greenish-brown2) flowers often close to the ground3) scent strong and foul (like dead animal)

“Buzz” pollination by bees:1) no nectar reward (pollen sole reward)2) connivent anthers (anthers held together) at center of flower3) anthers opening by terminal pores; pollen shakes out when the bee buzzes the flower

Birds often pollinate flowers, too:Hummingbirds (found in North and South America only):1) flowers with long tubular corollas2) flowers usually red3) nectar reward in large quantity, rich in sugars (few other nutrients)4) flowers often dangle away from plant so that bird can reach it while hovering

In other parts of the world different birds, including Honeycreepers (Hawaii), Honeyeaters(Australia) and Sunbirds (S. Africa) act as pollinators. Flowers adapted to these birds differ fromthose adapted for hummingbirds by having a “landing platform” for the birds to perch on, becausethey cannot hover. The flowers still have long tubular corollas and lots of sugar-rich nectar.

Image Source

Ref.1 http://8e.devbio.com/image.php?id=525Ref.2 http://8e.devbio.com/image.php?id=524Ref.3 http://8e.devbio.com/image.php?id=523Ref.4 http://content.answers.com/main/content/wp/en-commons/thumb/c/c9/250px-Haeckel_Siphoneae.jpgRef.5 http://www.vcbio.science.ru.nl/images/stemgrowth/SGembryo-apicalmeristem.jpgRef.6 http://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/cut1a.jpgRef.7 http://en.wikivisual.com/images/a/a4/Misc_pollen.jpgRef.8 http://www.hiddenforest.co.nz/bryophytes/mosses/familys/racopilaceae/images/racop01bt.jpgRef.9 http://ux.brookdalecc.edu/fac/biology/lab/102/images/liverwort1.jpgRef.10http://www.cartage.org.lb/en/themes/Sciences/BotanicalSciences/ClassificationPlants/Cryptogamia/Bryophyta/Nonvascular/hornwort1.JPGRef.11 http://www.freewebs.com/jdingfel/Stomata.jpgRef.12 http://f030091.ffpri.affrc.go.jp/image/OM_code_E/60.Tracheids.gifRef.13 http://media-2.web.britannica.com/.../04/7604-004.jpgRef.14 http://static.howstuffworks.com/gif/define-ferns-1.jpgRef.15 http://home.pacbell.net/kenww/my_iris/other/I_foetidissima_seeds-web.jpgRef.16 http://www.bioquest.org/scope/projectfiles/PollenMixb.jpgRef.17 http://www.icbgpanama.org/website/gall_pictures/Gnetumfrutos.jpgRef.18 http://www.dickcontino.com/images/ginkgo.jpgRef.19 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/fertil1.gifRef.20 http://web.gccaz.edu/~lsola/Flower/capsella3.jpg