Plant Reproduction I

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Plant Reproduction I

• Unless a tree has borne blossoms in spring, you
  will vainly look for fruit on it in autumn.
• - Sir Walter Scott

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Plant Reproduction

• Asexual reproduction (cloning),

• well suited genotypes can reproduce rapidly,
• cloned offspring often have greater resources
  than embryos.

• Sexual reproduction,

• diversity, especially important
• when coping with environmental
• change,
• control of timing, number,
• dispersal, and others factors...

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Today

• Angiosperms,
• Flowers,
• Flower Development,
• Flowering,
• Graphic images of sex.

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Angiosperms Evolutionary Perspective

• Reproductive Challenges,
• dry land and swimming sperm are not very
  compatible,
• sessile habit requires some means of sperm,
  spore, and/or seed dispersal.

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Plant Reproduction (Terrestrial)

• nonvascular gt vascular,
• haploid dominant gt diploid dominant,
• homosporous gt heterosporous,
• motile gametes gt nonmotile gametes,
• seedless gt seeds,
• water gt wind and animals
• gamete, spore and seed disbursement.

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Transition to Land
aquatic plants
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Alteration of Generations
Plants
Humans

• Gametophyte,
• muticellular haploid phase,
• produce gametes by mitosis, after meiosis
• Sporophyte,
• formed by the fusion of two gametophytes (male
  and female) to yield a multicellular
  diploid/triploid,
• produce haploid spores by meiosis,
• mitosis produces gametophytes.

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Haploid Dominant gt Diploid Dominant
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Reproductive Bodies

• Spore (haploid) the reproductive organ in
  cryptogams which, in function, corresponds to a
  seed but possesses no embryo,
• cryptogam a general name for plants that lack
  flowers, including ferns , mosses, and algae,

• seed a plant embryo with nutritive tissue to
  fuel its early growth, and surrounded by an
  outer, matenal, protective layer (seed coat),
• embryo immature plant (more later).

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Homospory vs. Heterospory

• The principal difference between homospory and
  heterospory is the separation of sexes at
  different points in the life cycle,

• heterospory promotes out crossing among plants,
  since male gametophytes may travel farther from
  the sporophyte than spermatids (moss sperm).
  And, allows the female gametophyte to adapt
  dispersal mechanisms.

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Mosses

• nonvascular (mostly)
• haploid dominant
• homosporous
• motile gametes
• seedless
• water dependent

Simple, unbranched sporophyte dependent on
gametophyte.
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Angiosperms

• vascular
• diploid dominant
• heterosporous
• nonmotile gametes
• seeds w/ 3n endosperm
• not water dependent

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Angiosperm Advantages

• improved vasculature,
• extreme heterospory,
• pollen in anthers,
• ovules are reduced in form and are completely
  surrounded by integuments,
• results in the potential for diverse
  dissemination of pollen,
• results in the potential for diverse
  disbursement of seeds.

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Pollen Dissemination
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Seed Dispersal
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Which is Domesticated?
Maize
Wheat
Rice
Wild
Domestic
Wild
Domestic
Wild
Domestic
North America
Europe
Asia
Sunflower
Soybeans
Africa
Barley
South America
Millet
Australia
Potato
Humans - or - Plants
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Angiospermssmall
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Angiospermslarge
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Amorphophallus titanumTitan Arum, Corpse flower,
Bunga Bangkai
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Amorphophallus titanumTitan Arum, Corpse flower,
Bunga Bangkai
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Flowersexual

• Androecium (male),
• all stamens,
• filament stalk,
• anther pollen bearing compartment,
• Gynoecium (female),
• all carpels,
• stigma receptive surface for pollen grains,
• style column of tissue through which pollen
  grows,
• ovary enlarged basal portion of the carpel,
  holds ovules.

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Megaporophyll to Carpel

• .hypothesis for the origin of the carpel from a
  reproductive leaf sporophyll,

• .pea fruit carpels form the pod, peas are the
  ovules,
• remember, integument (sporophyll tissue)
  surrounds the megasporangium.

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Microsporophyll to Stamen

• Extant species showing intermediate morphologies.

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Flowerother

• Perianth,
• corolla (petals collectively),
• petal modified leaf, usually conspicuously
  colored,
• calyx (sepals collectively),
• sepal modified leaf, usually green.
• usually the outermost layer of the flower,
• often encloses the flower bud before blooming,
• Recepticle,
• the part of the floral stalk that holds the
  floral organs.

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Variations
Trillium
Incomplete (lacking one or more floral
organs) unisexual monoecious male and female
flowers are on the same plant.

Complete bisexual
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Monoecious
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Dioecious
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More Variations
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Arabidopsis flower

• Wild-type,
• perianth,
• calyx (4 sepals),
• corolla (4 petals),
• androecium,
• 6 stamens,
• gynoecium,
• 2 carpels.

Model Flower System
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Phase Changes
Developmental Life Cycle
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Phase Change Studies

• Genetic and molecular genetic approaches,
• isolate mutants that fail in some way to change
  phase properly,
• study genes, gene products and associated
  molecules, and resulting structures.

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Assignmentsread pp. 475 - 478

• Homeotic Genes,
• genes that control the overall body plan through
  DNA transcription control,
• transcription factors,
• associate with promoter regions of genes,
  influencing transcription.

Study Associated Figures
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Floral Homeotic GenesABC Hypothesis
Study Fig. 23.12
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Floral Homeotic GenesABC Hypothesis
Study Fig. 23.13
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More Homeotic Mutants
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Phase Change Studies
Vegetative apical meristem produces leaves, and
very short internodes,
Floral meristem produces indeterminant
inflorescence, with determinant floral organs.
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Floral Meristem Identity
day length temperature water status nutrient
status hormones etc.
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Floral Transition Mutants
Inhibitory Conditions

• Circadian clock mutants,
• Photoreceptor mutants,
• Hormone mutants,
• Homeotic mutants,
• Others.

wild type
mutant
Inducing Conditions
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Today

• Spore formation,
• Gamete formation,
• Pollination,
• Germination.

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Now

• pp. 901 - 912,
• Questions!!!