Module 1 BIOL1050

Unit 1- Plant Reproduction

A binomial: scientific name by Carlos Linnaeus- Swedish botanist 1707

  • -  First part= genus

  • -  Second part= epithet (species)

  • -  Third part= authority (L.)

    Stamens- produce microspores that develop into pollen grains

  • -  Contains male gametophytes

  • -  Contain filament and anther

    Anther- develops 4 microsporangia (pollen sacs- where pollen is produced)

    Carpels- female gametophytes and produce megaspores

  • -  Some flowers many carpels, others only one

  • -  Tip of carpel is sticky, to collect pollen also called a stigma

    Style- leads stigma to the ovary of the flower
    Complete flowers: all four organs (sepals, petals, stamens, carpels)

    Incomplete: lacking one or more of the four above organs

    Fruits: fleshy or dry

  • -  Dry: ovary dries at maturity

  • -  Fleshy: ovary becomes thick, soft, sweet, coloured

    Angiosperm Life Cycle:

  • -  Flower of sporophyte produces microspores (forms male gametophytes) and megaspores (forms female gametophytes)

  • -  Male gametophytes are in the pollen grains within microsporangia in the anthers (anthers located in stamens

  • -  Male gametophytes- 2 haploid cells o Generative cell and tube cell

    •   GC divides into 2 sperm

    •   TC produces a pollen tube

  • -  Ovules in the ovary, contain female gametophytes (embryo sac)

  • -  Embryo sac contains the egg

  • -  Pollen released from anther to sticky stigma (tip of carpel)

    Some flowers self-pollinate- have mechanisms for cross-pollination
    Cross-pollination- anther from one flower to stigma of another flower of the SAME species

- Enhances genetic variability

DOUBLE FERTILIZATION

One sperm fertilizes the egg, forms a diploid zygote
Other sperm fuses with two nuclei in the FG forming a triploid cell

  • -  Unique to angiosperms

  • -  Triploid cell develops into endosperm (nourish the developing embryo)

  • -  Synchronizes with food development storage in the seed and development of the embryo

  • -  If the flower is not pollinated or the sperm cells are not discharged

    o Feralization does not occur, endosperm and embryo do not form Some double fertilization occurs in gymnosperms

- Two embryos than one embryo and endosperm

Angiosperms

The three F’s

- Flowers
- double Fertilization

- Fruits

Climate change may have significant effects on the development of pollen grains and fertility of many plant species

After DF, each ovule develops into a seed

  • -  Ovary develops into a fruit

  • -  When seed germinates, embryo develops into a new sporophyte

  • -  Mature sporophyte develops flowers and fruits

    Methods of pollination (from anther to stigma) - Animals

    - Wind

- Water (aquatic plants)

Endosperm stores nutrients that can be used by the seedling after germination Some dicots- food reserbves of the endosperm exported and stored in the cotyledons Seed dehydrates last stages of maturation- 5-15% of water is its weight

- Seed enter dormancy, embryo and food supply protected by seed coat

Cotyledons absorb nutrients from the endosperm and transfer them to the rest of the embryo when the seed germinates

Some seeds germinate when the environment conditions are suitable Others stay dormant until environmental cue breaks dormancy

Fruit: mature ovary of a flower

  • -  Fruit protects the enclosed seeds, when mature aids in their dispersal by wind or animals

  • -  If a flower is not pollinated, fruit does not develop

Parthenocarpy- fruit develops in absence of fertilization

Dioecious plants: imperfect flowers
- Male and female on separate plants

Monoecious Plants: imperfect flowers
Male and female flowers produced on the same plant

Asexual reproduction: one single parent without fusion of egg and sperm - Common in angiosperms

Fragmentation: the separation of a parent plant into parts that develop into whole plants - Common mode of asexual reproduction

Apomixis: seed is formed but the embryo is derived from an unreduced (2n) cell

  • -  Cell gives rise to embryo, ovules mature into seeds

  • -  Clone themselves by an asexual process

  • -  Have advantage of seed dispersal (associated with sexual repro)

  • -  Apomixis into hybrid crops is good

Grafting:

Twig or bud from one plant can be grafted onto a plant of a closely related species or diff variety of same species
Plant that provides the roots is called the stock
The twig grafted onto the stock- called the scion

A callus forms between adjoining cut ends of the scion and stock

Stolons: above ground
Rhizomes- below ground
Bulbs: storage organs with compressed stems and thick fleshy leaves Corms: compressed stem
Tubers: storage organ that can reproduce (formed on stolons or rhizomes)

Plant domestication- a process by which plants or animals are genetically modified over time by humans for traits that are more advantageous or desirable for humans

Breeding- creating new genetic variability
Cross pollinated plants- population improvement
Hybrids between populations- east lemming x bloody butcher
Heterosis: the tendency of a crossbred individual to show qualities superior to those of both parents

Grafting European grapes onto American Rootstock
Layering: like stem cutting but in reverse, root first, then cut stem Transgenics: insert foreign gene

- Biolistics : gene gun

- Agrobacterium
In vitro: tissue cultured in sterile environment

- Many applications

Tissue culture- meristem not connected to vascular system

  • -  Cells not yet infected

  • -  Regenerated plants can be virus free

    Applications of genetic transformation

  • -  Herbicide tolerance (glyphosate tolerance)

  • -  Insect resistance (bT corn)

  • -  Improved quality (fight malnutrition)

    Mutations- occur naturally
    -introduces new gene variants not found in crop or relatives

    Mutation breeding

  • -  Mutagens increase nature mutation rate o Chemicals, gamma, uv

  • -  Can alter ploidy

  • -  Erucic acid at high levels causes heart problems and is toxic

  • -  Canola: Canadian source of oleic acid

    Polyploidy: more than one genome copy

  • -  Common in nature : triploid, tetraploids, hexaploids, octaploids, megaploid

  • -  Evolutionarily important

  • -  Increased ploidy: larger leaves, larger fruit, larger stomates, altered chemistry and

    physiology

  • -  Unreduced gametes

    Climate is always changing- time frame is essential
    2015 winter was cold- England saw snow
    500 yrs ago winter was bad.. fur coats were in demand and the Thames river would freeze over Much worse 1000 yrs ago-warm period
    Many believe this fluctuation is related to solar cycles and volcanic activity
    Little ice age- shortened growing seasons, increased precipitation, famine population decline, composition of forests changed, glaciers began advancing

    Global warming- global average temperature have increase by 0.6 C since 1950

  • -  Rate of increase is about 0.1 C per decade

  • -  Warming will continue

  • -  CO2 levels are rising , more CO2 more pollen

  • -  More erratic weather patterns

  • -  Higher CO can increase yields but lower nutritional quality

  • -  Pest and disease pressure

  • -  Heat waves: effects crop production

  • -  USA consumes 37 million tonnes of meat/year

    Correlation is not causation

  • - Correlation indicates a relationship not cause and effect