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Kingdom Plantae: Angiosperms Angiosperms (Phylum Anthophyta) Largest group of plants: 250,000 species! Still more to be discovered....... Finding New Species True New Discoveries: Bibb Glades, AL Limestone openings in forest Bibb County Finding New Species New Discoveries: Bibb Glades, AL

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angiosperms phylum anthophyta
Angiosperms (Phylum Anthophyta)
  • Largest group of plants: 250,000 species!
  • Still more to be discovered.......
finding new species
Finding New Species
  • True New Discoveries: Bibb Glades, AL
  • Limestone openings in forest

Bibb County

finding new species4
Finding New Species
  • New Discoveries: Bibb Glades, AL
  • Limestone openings in forest
  • Surveyed for plants in 1990’s
  • 8 new taxa discovered.

Cahaba paintbrush

Cahaba torch

Ketona tickseed

angiosperms phylum anthophyta5
Angiosperms (Phylum Anthophyta)
  • Are land plants, so make embryos, have multicellular gametangia with sterile jackets, etc.
angiosperms phylum anthophyta6
Angiosperms (Phylum Anthophyta)
  • Are vascular plants, so:
  • 1) Have vascular tissue (xylem, phloem)
  • 2) Make cuticle and stomata
  • 3) Make true stems, roots, leaves (megaphylls).
angiosperms phylum anthophyta7
Angiosperms (Phylum Anthophyta)
  • Are seed plants, so:
  • 1) Are heterosporous (make megaspores and microspores in specialized sporangia)
  • 2) Make pollen grains, ovules/seeds.
angiosperms
Angiosperms
  • Differ from gymnosperms by:
  • 1) Producing pollen and ovules/seeds in flower (new structure)
  • 2) Ovules/seeds made in fruit (new structure)
  • 3) Life cycle: Double fertilization occurs (two fertilization events when pollen tube reaches female gametophyte)
  • 4) Ovule has 2 integument layers, rather than 1.
the flower
The flower
  • Flower is short stem with modified leaves
the flower10
The flower
  • Additional flower terms:
    • Androecium: All of the stamens
    • Gynoecium: All of the pistils
    • Perianth: All of the petals and sepals (helpful when sepals and petals alike)
the flower11
The flower
  • Modified leaves:
    • easy to see for sepals (leaf-like)
the flower12
The flower
  • Modified leaves:
    • stamens? modified leaf bearing microsporangia (these now pollen sacs)
    • reduce leaf blade to leave microsporangia.
the flower13
The flower
  • Modified leaves:
    • pistil? modified leaf called carpel, bearing megasporangia in ovules
    • “ovule taco”
the flower14
The flower
  • Modified leaves:
    • pistils can be simple (1 carpel) or compound (> 1 fused carpels)
    • generally, number of chambers (locules) in ovary = number carpels.

1 locule=

1 carpel

(simple)

3 locules=

3 carpels

(compound)

the flower15
The flower
  • Modified leaves:
    • petals? modified stamens, that have lost sporangia and become flat and colored.
life cycle
Life Cycle
  • Overview:

Fig. 42.2

life cycle17
Life Cycle
  • Part 1: Making gametophytes (in anther and ovule)
  • Ovule: integumented megasporangium.
  • Notice 2 integument layers (gymnosperms had only 1)
  • Nucellus=megasporangium.
life cycle18
Life Cycle
  • Pollen grain: immature microgametophyte
  • Made by meiosis in sacs (microsporangia, or pollen sacs) in anther of stamen
  • When pollen released, typically has only 2 haploid cells in it.
life cycle19
Life Cycle
  • Embryo sac: mature megagametophyte
  • Very reduced: 7 cells and 8 nuclei.
  • Central cell has 2 haploid nuclei (polar nuclei)
  • One cell is egg. Note no archegonium made.
life cycle20
Life Cycle
  • Part 1: Making gametophytes (in anther and ovule)
  • Note: microsporocyte= microspore mother cell, megasporocyte= megaspore mother cell
life cycle21
Life Cycle
  • Pollen grain with only 2 cells (immature microgametophyte)
  • Arrives on stigma (instead of at ovule as in gymnosperms)
  • Pollen tube (contains 2 sperm cells: no flagella present, don’t swim) grows to ovule.
life cycle22
Life Cycle
  • Double fertilization
  • Creates zygote (2n): 1 sperm + egg
  • Creates endosperm (3n): 1 sperm + 2 polar nuclei.
life cycle23
Life Cycle
  • Zygote grows into embryo, endosperm also grows
  • Embryo uses endosperm for nourishment (eats sibling)
  • Seed: baby plant (embryo), in box (seed coat, made from integuments), with its lunch (endosperm).
life cycle24
Life Cycle
  • Seed or seeds develop inside of ovary to become fruit
  • Ovary wall in pistil becomes pericarp in fruit.
life cycle25
Life Cycle
  • Differences from gymnosperms:
  • 1) Pollen arrives at stigma rather than ovule
  • 2) Gametophytes reduced still further: pollen grain only 2 cells, megagametophye 7 cells/8 nuclei and no archegonium
  • 3) Double fertilization creates zygote and triploid endosperm
  • 4) Embryo digests endosperm
  • 5) Seed coat made from 2 integuments
  • 6) Seeds mature in ovary to make fruit.
floral variation and evolutionary trends
Floral variation and evolutionary trends
  • Earliest fossil flowers show:
    • many parts
    • parts spirally arranged rather than in whorls (rings)
    • parts separate, not fused to similar or different parts
    • ovary superior
    • radial symmetry.

Magnolia flower

floral variation
Floral variation
  • Some flowers have reduced numbers of parts
  • 4’s and 5’s: Class Dicotyledonae (dicots)
  • 3’s and multiples of 3: Class Monocotyledonae (monocots).

Magnolia flower

floral variation28
Floral variation
  • Quiz: To which Class does each species belong?

Malva flower

Sagittaria flowers

floral variation29
Floral variation
  • Parts may be fused
  • Example, petals fused to each other
  • Like parts fused: connation (ex., petals to petals)
  • Unlike parts fused: adnation (ex., stamens to petals)

Snapdragon flower

floral variation30
Floral variation
  • Fusing of petals can form floral tube (nectar made at bottom)
  • Only long-tongued pollinators can reach it.

Anisacanthus (Acanthaceae) flower

floral variation31
Floral variation
  • Flowers with stamens and pistils: perfect flowers
  • Some flowers imperfect. Either pistillate (have pistil) or staminate (have stamens).

Pistillate flowers of Sagittaria

Staminate flowers of Sagittaria

floral variation32
Floral variation
  • Note: some species make pistillate flowers and carpellate flowers on separate individuals
  • This termed dioecious
  • Monoecious is when both sexes on same individual.
floral variation33

Persimmon fruits

Floral variation
  • Example of dioecious species: Persimmon (Diospyros)

Pistillate

flower

Staminate

flower

floral variation34
Floral variation
  • Some flowers are missing one or more sets of basic parts: incomplete flowers
  • Note that all imperfect flowers are therefore incomplete!
floral variation35
Floral variation
  • Floral symmetry:
  • Radial: can be divided into similar halves by several planes
  • Bilateral: can be divided into mirror images by 1 plane.
floral variation36
Floral variation
  • Ovary position
  • Superior: other parts attach below ovary (hypogynous: “hypo-” =below, “gyn-” =female)
floral variation37
Floral variation
  • Example of superior ovary in a lily flower (ovary is E)
floral variation38
Floral variation
  • Ovary position
  • Perigynous: ovary superior, but cup formed of fused sepals, petals, stamens around it.
floral variation39
Floral variation
  • Ovary position
  • Inferior: other parts attach above ovary (epigynous: “epi-”=above, “gyn-”=female)
floral variation40
Floral variation
  • Example of inferior ovary: squash flower (this one is pistillate)

Ovary

floral variation41
Floral variation
  • Some flowers assembled into groups of flowers: inflorescence
  • Special inflorescence type: head
  • Example, sunflower and its relatives
  • Ray flowers have large fused petals (corollas fused), disk flowers small and crowded.

ray flowers

disk

flowers

floral variation42
Floral variation
  • Flowering dogwood (Cornus florida)
  • Inflorescence, white structures are modified leaves (bracts) that act like petals.

Closeup showing individual

greenish flowers

Inflorescence

pollination
Pollination
  • Why flowers so varied? Many form mutualism with animals to achieve pollination
  • Most gymnosperms are wind pollinated
  • Must make lots of pollen in hope some reaches ovule in female (seed) cone. Most pollen falls to ground within 100 m of plant.
pollination44
Pollination
  • Some flowering plants are wind pollinated too
  • Ex, most grasses (corn, wheat, etc.), many temperate zone flowering trees (oaks, willows, maples, hickories)
  • Flowers usually small, no petals, no nectar, make lots of pollen.

Small, greenish

grass flowers

pollination45
Pollination
  • Most flowering plants are pollinated by animals
  • This usually viewed as mutualism (where both species benefit)
    • Plant gets pollen transferred
    • Animal gets “reward”
    • Pollen: high in protein
    • Nectar: sugary fluid produced by nectar glands (nectaries) in flower
    • Oils/Resins: some used as construction materials, “cologne” (male bee uses oil as female attractant).
pollination46
Pollination
  • Benefits of animal pollination
    • 1) Directed dispersal of pollen. Animal can take pollen directly to where plant wants it to go (stigma of flower of same species). Less waste of pollen
pollination47
Pollination

Pollen grains

  • Benefits of animal pollination
    • 2) Style of flower as “selective racetrack”
    • Keep in mind that 1 pollen grain can fertilize 1 ovule
    • Suppose 5 pollen grains arrive on stigma
    • Start to make pollen tubes
    • How many can fertilize an ovule?
    • 2! First 2 to arrive!
    • Rest? LOSERS!

stigma

style

ovary

2 ovules

pollination48
Pollination

Pollen grains

  • Benefits of animal pollination
    • 2) Style of flower as “selective racetrack”
    • Pollen tubes are haploid (1n)
    • Haploid means only 1 allele (gene version) for every trait
    • If an allele is recessive, then it will be expressed (can’t be masked by another, dominant allele)
    • So, fittest (fastest) pollen grains mate
    • Inferior genes don’t get passed to offspring.

stigma

style

ovary

2 ovules

pollination49
Pollination
  • Style of flower as “selective racetrack”
  • Is there evidence that this works?
  • Example, Coyote melon
  • Gourd growing in desert
pollination50
Pollination
  • Style of flower as “selective racetrack”
  • Study done in 2000 showed that
    • 1) takes 900 pollen grains to fully pollinate flower
    • 2) 1 pollinator visit puts 650 grains/flower. By 2 hours, >4000 grains deposited on stigma
    • 3) Seeds produced from over-pollinated flowers produced more vigorous seedlings (compared to seeds from flowers with <900 pollen grains on stigma).
pollination51
Pollination
  • Style of flower as “selective racetrack”
  • Other studies with some crop plants have shown similar results.
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