Lecture 5: Archaeplastida: Red Algae, Green Algae, Plants

Supergroup Archaeplastida (1: synapomorphies, characteristics, and clades)

• **chloroplasts with 1° endosymbiotic origin

• chloroplasts have 2 p.l bilayers

  • inner = plasma membrane

  • outer = lipid polysaccharide membrane

• clade (3)

  • Rhodophyta

  • Chlorophyta

  • Plantae

Archaeplastida: Rhodophyta (1: characteristics)

• red algae/ multicellular seaweeds

• body is the thallus (any multicellular alga)

• chloroplasts have 2 membranes

  • A and C

• stores food as a floridean starch

• due to phycoerythrin, can exist in deep water

Archaeplastida: Rhodophyta (1: synapomorphies)

• **(Phycobilisomes) phycoerythrin → absorbs the blue light (in cyanobacteria)

• ** loss of 9+2 microtubular structures

• ** chlorophyll c (ancient multicellular form

Archaeplastida: Viridiplantae (1: synapomorphies and characteristic

• all green algae + plants

• chlorophyll a and **b

• **storing food as starch in chloroplast

Archaeplastida: Viridiplantae: Chlorophyta (1: characteristics)

• green algae

• chlorophyll a and b

• cell walls of cellulose

• freshwater

  • unicellular biflagellates

  • colonial

  • filaments

  • multicellular

Archaeplastida: Viridiplantae: Plantae (1: plant evolution)

• plants appear 475 MYA

• plant evolution

  • multicellular

  • photoautotrophic

  • chlorophyll a and b

Archaeplastida: Viridiplantae: Plantae (2: general characteristics)

• cell walls of cellulose

• store food reserves as starch

• opening for gas exchange → stomata

• spores with cell walls of sporopollenin (a protective shell of plant spores and pollen grains)

Archaeplastida: Viridiplantae: Plantae (3: synapomorphies/fertilization)

• **waxy cuticle

• ** multicellular gametangia (produces sperm/eggs w. protective sterile cells

• after fertilization → zygote is retained and develops into embryo in female gametangium

Archaeplastida: Viridiplantae: Plantae: Bryophyta (1: characteristics

• system of non-vascular plants

• three phyla: moss, hornworts, liverworts

• no true roots (anchors) (rhizoids), stems (caulidium), leaves (phyllidium)

• needs moisture for reproduction

• gametophyte generation dominant

Archaeplastida: Viridiplantae: Plantae: Bryophyta

(2: gametangia)

• gametangia

  • antheridium (male)

  • archegonium (female)

Archaeplastida: Viridiplantae: Plantae: Bryophyta (3: moss: life cycle )

1. sporangium releases spores (n) from meiosis

2. germinating spore produces a protonema (initial filamental green photosynthetic stage)

3. bud can form a male or female gametophyte

4. sperm and egg forms in respective gametangium

5. fertilization → zygote remains in archegonium and develops to a sporophyte (2n)

Archaeplastida: Viridiplantae: Plantae: Tracheophyta (1: characteristics)

• vascular plants (phloem/xylem)

  • xylem = tracheids (in the xylem), which are dead cells in plants

  • thick cell wall = mechanical strength

• basal group = lycophytes (not discussed)

Archaeplastida: Viridiplantae: Plantae: Tracheophyta (2: synapomorphies)

• ** vascular tissues (xylem and phloem)

• ** branched sporangia

• **sporophyte generation dominant

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Monilophyta (1: characteristics)

• mainly ferns and horsetails

• apomorphies are technical

• monophyly

• roots - adventitious (developing from stem)

• leaves - fronds

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Monilophyta (2:ferns: lifecycle-sori)

• underside of leaf in sporophyte - sori (contains groups of sporangia)

• sporangia is covered and protected by the - indisium

• image

  • center = sterile sheath

  • darker spheres = sporangia

    

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Monilophyta (2.1:ferns: lifecycle-sporangium)

• the cell walls are not strong

• when lip cells rupture = spores are shed

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Monilophyta (2.2:ferns: full life cycle)

1. spores (n) develop in sporangia (2n) and released

2. spore → turns into gametophyte (1 cell layer thick)

3. in water the antheridium bursts and (biflagellate) sperm is released → going towards archegonium (antheridium & archegonium not matured at the same time)

4. fertilization → zygote (2n)

5. sporophyte still attached to gametophyte growth

   

fern sporophyll

leaf specialized for spore production; contains the sporangia

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Spermatophyta (1: characteristics)

• contains gymnospermae (seed plants) and angiospermae (flowering plants)

• gymnospermae → cycads, gingkos, conifers

  • when seed germinates food is being broken down for growth of sporophyte until photosynthetic properties are developed

Archaeplastida: Viridiplantae: Plantae: Tracheophyta: Spermatophyta (1: synapomorphies/adaptations)

• adaptations include

  • **reduction of gametophyte (retained in sporophyte)

  • ** pollination to deliver sperm to egg

  • **development of seed (embryo packed with food reserves) aiding in dispersal

Homosporous vs Heterosporous (life cycle)

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae (1: characteristic/organisms, synapomorphy)

• reproductive structures are **cones (sporophyte structure)

• sporophyte generation dominant

• includes ginkgo, cycads, conifers

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae (1: characteristic/organisms, synapomorphy)

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (1: characteristics, organisms, synapomorphies)

• pine, spruce, redwood, larch, fir, junipers, cedars - most are evergreen trees

• **needle-shaped leaves

• vascular → tracheids

  • H2O transport and mechanical strength

• Bristlecone pine → 4600 years (oldest living tree

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (2.1: Conifer life cycle: staminate cones)

• heterosporous cycles

• staminate cone → male cone that produces a sporangia that makes microspores

  • cone → modified leaves (scales)→ are microsporophyll

  • part of microsporophyll → microsporangium

• process

  • microsporocytes (2n) in the microsporangium → meiosis = 4 microspores (n)

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (2.2: Conifer life cycle: pollen)

• microspores germinate in cone produce 4-6 celled structure → pollen grain (male gametophytes)

• pollen grain has wings → aids in wind dispersal

• spores kept inside the sporangium until maturity

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (2.3: Conifer life cycle: pollen continued)

• mature pollen contains

  • tube cell

  • generative cell

• slit develops in microsporangium → releases pollen

• lots of pollen released but only some reach female cone

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (3.1: Ovulate cones structure)

• each scale has a bract and ovuliferous scale

• receives pollen

• ovule → proximal part of the scale, a single megasporocyte (2n)

  • each scale has two ovules (L/R)

• micropyle → thin area of the integument

  • facing central stem of cone

  • where archegonia is located

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (3.2: Ovulate cones - first summer)

• megasporocyte (2n) = megaspore mother cell → meiosis → 4 megaspores (n) (only 1 survives) → 2,000 cell structure = mature female gametophyte with 2/3 archegonia each with an egg

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (4: life cycle of a pine)

1. pollen cones and ovulate cones produces spores

2. in microsporangia of pollen cones → meiosis → microspores → pollen; ovulate cones = megaspores

3. pollination → pollen grain hits nar ovule on ovulate cone scale, penetrates through micropyle into 1 archegonia

4. pollen grain germinates → sterile tube and generative cell produced → generative cell makes 2 sperm nuclei

5. fertilization (2n) → 1 sperm nucleus makes an embryo → seeds

6. seed produced seedling → sporophyte

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (5: pollination and fertilization: tube and generative cells)

• pollen lands near micropyle of ovulate cone

• generative cell → divides and 1 cell is sperm nucleus

• tube cell grows a pollen tube (digesting path through thin integument at the micropyle)

  • reaches female gametophyte and sperm nucleus moves tube to archegonium = fertilization

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Gymnospermae: Coniferophyta (6: seed structure)

• zygote (2n sporophyte) → grows to embryo

  • contains radicle (future root)

  • 3-12 cotyledons (contain enzymes that breaks down food reserves for seed to grow

  • embedded in the tissue of female gametophyte (food) and food reserves from 1st gen. sporophyte

• seed = embryo + food + coat

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (1: characteristics)

• flowering plants

• adapted to dry conditions

• pollination using insects and other animals

• male gametophytes are reduced

• vascular tissues are more refined

  • tracheids and vessel elements

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (2: synapomorphies)

• **vessel elements - end to end cells forming tube

  • xylem; dead at maturity

  • evolved from tracheids

• **flowers (seeds enclosed in ovary)

• **fruit (matury ovary) - dispersal

  • embryo sporophyte with food reserves

• **double fertilization

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (3: life cycle: stamen & carpel )

• heterosporous

• flowers → sporophytes

• stamens - highly modified leaf that contains microsporangia (pollen sacs)

• carpel - female part of the flower that contains the megasporangium

• anther - pollen producing club-shaped tips of stamen

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (4: structure of a flower: perfect, imperfect, complete, incomplete )

• perfect → both stamens and carpels

• imperfect

  • staminate flower → stamen only

  • carpellate flower → carpels only

• complete

  • all four parts → sepals, petals, stamens, pistil

• incomplete

  • missing one part of the flower

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (5: microspore production)

• microsporocyte (2n) in anther → meiosis → microspores (in grps. of 4 and thick walled) (n) → mitosis (1 time) = 2 cells (tube and generative cell = pollen (male gametophyte)

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (6.1: pollination: pollen types )

• pollen shed through slit on anther

• brightly colored flowers (heavier pollen)

  • pollinators seeking nectar (at the base of the flower: nectuaries)

  • pick up pollen and carry to second flower

• inconspicuous small/green flowers (light pollen)

  • windblown pollen

  • hay fever & allergies

  • large quantities are released

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (6.2: pollination: cont.)

• pollen lands on stigma - tube cell thats growing

  • adds mass → female producing material for the tube cell

• tube nucleus starts growing pollen tube

• generative nucleus → divides and no flagellated sperm nuclei (2)

• male gametophyte reduced to 2 sperm nuclei and 1 tube nucleus

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (7.1: development of angiosperm gametophytes (pollen and embryo sacs)

1. flowering stem of mature sporophyte (2n)

2. meiosis → 4 megaspores and 3 undergoes mitotic division = 1 nuclei

3. cytokinesis produces a female gametophyte with 7 cells and one becomes an egg and the other (lage cell with 2 nuclei) forms endosperm

4. pollen released

5. pollination occurs → pollen grain develops to pollen tube (2 sperm) growing towards ovary

6. pollen tube enters ovule and one sperm will fertilize egg and one will fertilize binucleate endosperm = double fertilization

7. double fertilization = trinucleus cell = 3n endosperm → the seed

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (7.2: growth of pollen tube and 2x fertilization)

• pollen tube penetrates near egg

• 2 sperm nuclei

  • 1 with egg

  • 2 nuclei of polar cell = 3n structure (endosperm)

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (8: development of dicot plant embryo)

• dicot - characterized by seeds that produces cotyledons upon germination

  • cotyledons - as seed germinates it will break down food storage for growth of embryo

    • can have 1 or 2

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (9: Fruits: ovule, ovary )

• ovule → develops into seed

• ovary → develops into fruit

  • aids in dispersal

  • derived from tissues of first generation sporophyte

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (10.1:Classes: Monocotyledonae-synapomorphies, characteristics )

• ** veins in leaf that are parallel no minor veins

• **only one cotyledon in seed

• roots → fibrous

• e.g)grass, palm, lilly

Archaeplastida: Plantae: Tracheophyta: Spermatophyta: Angiospermae (10.2:Classes: Eudicotyledonae -synapomorphies, characteristics )

• **tricolpate pollen - three points in pollen grain

• roots → tap roots

• veins in leaf → netlike, branching