Plant Biology: EXAM 3, Tom Holder

hormones

-chemical messengers that regulate plant growth.

-most are transported in phloem tissues and ALL require an expenditure of energy on part of plant (ATP) for transport.

-they interact with external environmental factors to determine growth: soil moisture and temp. day length

hormones control

• growth

• seed germination

• flowering

• fruiting/seed production

• shedding of leaves

• color change of leaves

interact with environmental factors

hormones

-chemical messengers that regulate plant growth.

-most are transported in phloem tissues and ALL require an expenditure of energy on part of plant (ATP) for transport.

-they interact with external environmental factors to determine growth: soil moisture and temp. day length

hormones control

• growth

• seed germination

• flowering

• fruiting/seed production

• shedding of leaves

• color change of leaves

interact with environmental factors

color change of leaves is due to

the breakdown of photosynthetic pigments

hormones 2 broad characteristics

• growth inhibiting:

  • mostly fall/winter.

  • certain times of the year, growth is NOT good.

• growth promoting:

  • mostly spring/summer.

Auxins

• 1st group of plant hormones described

• growth promoting hormone

Auxins are produced in:

• shoot tips

• seeds

• fruits

• leaves

• stems

NOT:

• roots

Auxin Promotes

• cell elongation

• shoot elongation

• production of wood

• fruit development

Auxin Inhibits

• lateral bud development

  • its produce new later shoots

• abscission(dropping) of leaves, flowers, fruits

Cytokinins

• originally detected in coconut milk

• growth promoting hormone

Cytokinins produced in

• seeds

• fruits

• roots

Cytokinins promotes

• cell division

• lateral bud movement (opposite of auxin)

cytokinins inhibits

• leaf senescence

  • change of color due to breakdown of pigments (especially chlorophylls)

Gibberellins (gibberellic acids)

• biggest group

• growth promoting hormone

• found throughout plant, but concentrated in seeds*

Gibberellins promotes

• stem elongation by stimulating cell division(cytokinin) and elongation(auxin)

• *breakdown of food reserves in germinating seeds.

  • converting starch into glucose to be respired by cells to generate ATP for speed in growth.

Gibberellins embryo

• intake of water (adequate soil moisture) causes swelling and embryo hydration.

• embryo secretes gibberellins.

• gibberellins transported to cells of aleurone layer to secrete enzyme (alpha-amylase) for breakdown of endosperm (starchy stored food) to glucose.

• embryo will respire glucose to produce ATP.

• *embryo is the advantage of seed plants.

• *embryo is directing the timing of germination.

Abscisic Acid inhibits

• cell elongation

• alpha-amylase production

  • trying to curb early germination

Abscisic Acid promotes

• leaf senescence(loss of pigments).

• production of storage carbs in seeds.

  • keeps endosperm from breaking down.

Ethylene

• growth inhibiting hormone

  • actually chemical not hormone

• actually is a GAS produced by incomplete metabolism

  • not transported in phloem

Ethylene promotes

• fruit ripening

  • ex: bananas

• abscission of leaves, fruits, flowers.

• interacts with 3 growth promoting hormones to determine cell.

• promotes size and shape

  • cells can elongate too fast b/c of weak cell walls

Seed germination

• requires of dormancy—combination of internal and external factors

Seed germination: internal factors

• hormones

• stored food

• H2O absorption

• embryo swelling

seed germination: external factors

• sunlight

• temperature

  • air and soil

• longer day length

  • longer day: higher temps

• soil moisture

Generalize seed

• seed coat(s), embryo, stored food

• as seed coats crack:

  • radicle grows first down

  • shoot grows 2nd up

Seedling

• result of cellular respiration and increase in cell size

  • apical meristems

• internal development:

  • cells-tissues-organs-organism-plant

Plant Nutritional Requirements

-nutrients

-photosynthesis

-deficiency symptoms

nutrient

• any substance metabolized by or incorporated into an organism

Photosynthesis requires

• co2

• water

• elements

  • potassium

  • nitrogen

  • calcium

• all but co2 are taken up from soil (h2o and elements)

deficiency symptoms

• develop in plants that receive too little of a nutrient

Nutritional Resources

• essential elements

• macronutrients

• micronutrients or trace elements

• limiting factors

essential elements

• play many roles in plant metabolism, often functioning as enzyme cofactors

macronutrients

required in amounts of at least 1g/kg of plant dry mass

-amount >

micronutrients or trace elements

-required in amounts at or less than 0.1g/kg of plant dry mass

• amount -<

limiting factors

• resources that can limit growth

• light: photosynthesis

• co2: photosynthesis

• water: photosynthesis, all elongation, other factors

• other mineral nutrients

overview of essential elements

• 16 essential elements: C, H, O from co2 (air) and h2o (water)

• 13 soil nutrients(minerals)

  • absorbed and dissolved in H2O through roots from soil

• these 13 follow the same pathway through plant as h2o (xylem tissue)

Soil macronutrients

• 6

  • nitrogen (N)

  • potassium (K)

  • phosphorus (P)

  • Calcium (Ca)

  • Magnesium (Mg)

  • Sulfur (S)

Nitrogen (N)

component of proteins, nucleic acids, chlorophyll

potassium (K)

involved with osmosis and ion balance, opening/closing of leaf stomata (gas exchange)

phosphorus (P)

component of nucleic acids, ATP, phospholipids of plasma membrane(gatekeeper)

Calcium (Ca)

component of cell wall(support)

Magnesium (Mg)

component of chlorophyll and enzyme activator

Sulfur (S)

important for protein synthesis and enzyme function

Soil Micronutrients

• 7

  • Molybdenum (Mo)

  • Copper (Cu)

  • Zinc (Zn)

  • Manganese(Mn)

  • Chlorine(Cl)

  • Boron(B)

  • Iron(Fe)

Molybdenum (Mo)

enzyme cofactor

Copper (Cu)

enzyme cofactor

Zinc (Zn)

enzyme cofactor

Manganese (Mn)

• enzyme cofactor

• involved with chloroplast

• membrane and for oxygen release with photosynthesis

Chlorine (Cl)

• splitting of H2O in photosynthesis (generates electron energy)

• ion balance

Boron (B)

• enzyme cofactor

• cell wall component

• nucleic acid synthesis

Iron (Fe)

• enzyme cofacto

• component of cytochromes

  • photosynthesis and cellular respiration

• necessary for synthesis of chlorophyll

Overview of Flowering Plant Reproduction

• most flowering plants display sexual reproduction

  • 2 gametes fuse to produce offspring with unique combinations of genes

• they also undergo Alteration of Generations

What is Alteration of Generations?

• 2 multicellular life cycle stages

  • diploid and haploid

Diploid

• spore-producing sporophyte

• produces spores by meiosis

  • 2N to 1N

Haploid

• gamete-producing gametophyte

• produces spores by mitosis

  • 1N to 1N

Evolutionary Trends of Sporophyte and Gametophyte

S:

• has become larger and more complex

G:

• has become smaller and less complex

Evolutionary Trends of Moss

• Sporophytes small and dependent on gametophyte

Evolutionary Trends of a Flowering Plant

• Sporophyte is larger and independent. Also is more complex than gametophytes

• Dependent gametophytes are few-celled and contained within flowers

Flower and Sexual Cycle

• Flowers: ONLY in angiosperms; all sizes, shapes, colors, aromas

• essential processes of sexual reproduction occur within the flower

What are the essential processes of sexual reproduction that occur within a flower?

• meiosis/cytokinesis

  • reduces chromosome number

  • 2N to 1N

• syngamy

  • fertilization

  • restores chromosome number

  • 1N egg + 1N sperm = 2N zygote (fertilized egg)

“Ideal” Flower

• 4 sets of highly modified leaves arranged in whorls at the tip of a highly modified stem.

• A flower is a highly modified determinate (short term) shoot system

• shoot includes: stem and leaves

Part of the Flower and their functions:

Flower Diagram: important ideas

• Pedicel

  • flower stalk

• Receptacle

  • enlarged tip of pedicel

• 4 sets of highly modified leaves

  • ALL are 2N and attached to receptacle and part of the sporophyte generation

• Pollen (sperm) and egg (within embryo sec) are part of the 1N gametophyte generation

Sexual Cycle: MALE side occur site

• Pollen formation:

  • occurs within the anther of stamen.

• 2N microspore mother cells

• micro: male side/very small

Anther

• bilobed with 2 pollen chambers per lobe

Sexual Cycle: MALE pollination

• pollination

  • transfer of pollen from anther to a stigma of pistil

• self-pollination and cross-pollination

self-pollination

• transfer with same flower or between flowers on same plant.

• decreases genetic generation

• not the best :(

cross-pollination

• transfer between flowers of different plants

• increases genetic variation

• good! :)

Sexual Cycle: Pollinating Agents

• pollinating agents:

  • mechanisms utilized for transfer of pollen

  • 3 types: wind, water, animals

Pollinating Agent: Wind

small, light weight pollen

Pollinating Agent: Water

transfer with a few aquatic plants

Pollinating Agent: Animals

• MAJORITY of plants utilize a ‘trick and reward’ system

• trick and reward:

  • nectar, colors, aromas to attract animals

Sexual Cycle: FEMALE: Ovule Development

• female side:

  • ovule: future seed

  • enclosed within ovary of pistil(carpel)

  • one to many ovules per ovary

  • ovary: future fruit

  • ovule attached to central axis or to wall of a hollow ovary—ALWAYS enclosed(angiospermy)

Angiospermy

ALWAYS enclosed hollow ovary

within ovule is 1 large 2N cell is called?

• megaspore mother cell

  • mega: female, large

Sexual Cycle: FEMALE: ovary with enclosed ovules

Sexual Cycle: FEMALE: ovule enlarged

Sexual Cycle: FEMALE: megaspore transformation

Sexual Cycle: FEMALE: megaspore to embryo sac process

• 1N functional megaspore to start

  • 3 mitosis/cytokinesis divisions

    • unequal and incomplete

  • one cell with 1N nucleus become 8 (1N) nuclei, but only 7 cells

• Embryo sac created

  • making a female gametophyte

  • inside

Sexual Cycle: FEMALE: embryo structure

• Embryo sac

  • 8 nucleate, 7-celled structure=female gametophyte

  • 3 antipodal cells (1N) → opposite end from micropyle

  • 1 central cell with 2 large 1N nuclei (polar nuclei)

  • 2 synergid cells (1N) → micropyle end on outside

  • 1 egg (1N) → middle at micropyle end

Sexual Cycle: FEMALE: syngamy

• Syngamy:

  • 1N egg + 1N sperm = 2N zygote (single cell, fertilized egg)

Pollen Grain Germination

• tube cell forms pollen tube.

• generative cell divides by mitosis/cytokinesis to produce 2 sperm

Sexual Cycle: FEMALE: pollen tube process

• pollen tube enters micropyle of ovule; digest nucellus.

• pollen tube delivers perm to location of the egg.

• pollen tube enter one synergid then releases its contents and synergid ruptures.

• tube nucleus degrades and 2 sperms release into large central cell

• micropyle closes up

Sexual Cycle: FEMALE: double fertilization

“fusion”

• both sperms fuse with other nuclei

• 1N egg + 1N sperm = 2N zygote (fertilized egg)

• 1N sperm + 2N polar nuclei = 3N primary endosperm cell

Sexual Cycle: FEMALE: post fertilization

• within ovule

• 2N zygote grows by mitosis/cytokinesis into 2N multicellular embryo

• 3M primary endosperm grows by mitosis/cytokinesis into 3N multicellular endosperm(nutritive tissue for embryo)

  • inside the ovule

  • 2N integuments HARDEN to form SEED COATS! *

Sexual Cycle: FEMALE: ending, seed dispersal, agents

• Ovule with 2N zygote mature into seed with 2N multicellular embryo and ovary enlarges with sugars/H2O into a fruit(mature ovary) with enclosed seeds(mature ovules).

• seed dispersal

  • seeds enclosed within fruit

• has pollinating agents

  • wind

  • water

  • animals (MAJORITY)

Sexual Cycle: FEMALE: seed germination

• seed with 2N embryo enter period of dormancy

• dormancy broken by a combination of internal and external(environmental) factors

• radical (1st root) emerges and grows down

• shoot (2nd) emerges and grows up

Plant Genetics

the study of genes, genetic variation, and heredity specifically in plants.

Plant Genetics: DNA

• deoxyribonucleic acid

• the building block of life

• made up of individual nucleotides

• 4 potential nitrogenous bases

DNA’s 4 potential nitrogenous bases

1. Adenine (A)

2. Thymine (T)

3. Cytosine (C)

4. Guanine (G)

A and T

C and G

Plant Genetics: DNA: how traits are coded

• genotype:

  • genetic information of certain traits

  • sequence of the nucleotide bases

• phenotype:

  • physical expression of that trait

  • ex: tall or short

Plant Genetics: Monohybrid Cross

• 2 parents with different genes/traits

• dominant and recessive

• homozygous and heterozygous

Dominant trait

• visible trait

• uppercase

Recessive trait

• marked trait

• lowercase

Homozygous

• 2 copies of same allele

  • ex: AA or aa

  • Homo dominant

    • AA

  • Homo recessive

    • aa

Heterozygous

• 2 different alleles

  • ex: Aa

Punnet Squares

• parent 1 on y-axis

• parent 2 on x-axis

• used to determine genotype ratio, phenotype ratio, and percentage of genotype and phenotype.

Mutations

• change in order or structure of genetic information (DNA)

  • most are neutral, don’t affect

  • some can be lethal/harmful and some can be beneficial

  • ex:

    • white/albino squirrels

      • rare recessive mutation

      • no pigment in fur

      • red eyes

Mutations provide what?

• genetic variation

• change in one base substitution can create 2 completely different proteins

  • ex:

    • ATCGTTCG: protein 1

    • AGCGTTCG: protein 2

    • sunlight goes onto T in protein 1 altering it and then altering/changing the base substitution and creating a different protein.