Plant Bio Test 3

Hormones

chemical messengers that regulate plant growth

most transported in phloem tissue (ATP)- ALL require expenditure of energy on part of plant for transport

interact with external environmental factors to determine growth (soil moisture/temp, day length, air temp, seasonality)

What do hormones control (6 things)

growth, seed germination, flowering, fruiting/seed production, shedding of leave, color change of leaves (breakdown of photosynthetic pigments)

2 broad categories of hormones

growth inhibiting: mostly fall/winter (certain times of year is not good)

growth promoting: mostly summer/spring

Auxins

first group of plant hormones described, GPH, produced in shoot tips, seeds, fruits, leaves, stems, NOT ROOTS

Auxin Effects

promote cell elongation, shoot elongation, production of wood, and fruit development.

inhibit bud development (produce new later shoots)

inhibit expression (droppings) of leaves, flowers, fruits

Cytokinin

originally detected in coconut milk

GPH

produced in seeds, fruits, and roots

Cytokinin Effects

promotes cell division, lateral bud development

inhibits leaf senescence/ change of color due to breakdown of pigments (especially chlorophyll)

Gibberellins/ Gibberellic Acid

many types (more than any other group)

GPH

found throughout plant, but concentrated in seeds

Gibberellins Effects

promotes stem elongation by stimulating cell division and elongation

promotes breakdowns of food reserves in germinating seeds: starch → glucose to be respired by cells to generate ATP for seed growth

adequate soil moisture

intake of water causes swelling and embryo hydration

embryo secrets gibberellins

transported to cells of another layer to secrete enzyme (alpha-amylase) for breakdown of endosperm →glucose (starchy stored food)

embryo is deciding the timing of germination

advantage of seed plants

Abscisic Acid (ABA)

GIH

found in large quantities in seeds, mature leaves, and dormant buds

ABA Effects

inhibits cell elongation

inhibits alpha-amylase production (curb early germination)

promote leaf senescence (loss of pigments)

promote production of storage carbs in seeds (keep endosperm from breaking down)

Ethylene

GIH but is actually gas from incomplete metabolism (not both ways in phloem)

Ethylene Effects

promote fruit ripening

promote abscission of leaves, fruits, and flowers

interacts with 3 GPH to determine cell size and shape (cells elongate too fast → weak cell walls)

Seed Germination

requires breaking of dormancy, combo of internal and external factors

typically over winter

Internal Factors for Seed Germination

hormones, stored food, H2O absorption, embryo swelling

External Factors for Seed Germination

sunlight, temp (air of soil), longer days (increased temps), soil moisture

Seed Germination Parts (3)

Seed Coat(s), embryo, and stored food

What happens as the seed coat cracks?

Shoot comes out, radicle emerges first

Seedling

result of cell reproduction (RAM or SAM) and increase in cell size

internal development: cells to tissues to organs to organism = Plant

Nutrient

substances metabolized by/incorporated into organism

What nutrients does photosynthesis need

CO2, H2O, K, N, Ca

Deficiency Symptoms

what happens in plants that receive too little of a nutrient

Essential Elements

play many roles in plant metabolism, often enzyme cofactors

Macronutrients

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

Micronutrients

‘trace’

required in at or less than .1 g/kg of plant dry mass

Limiting Factors of Nutrition

sunlight (photosynthesis), CO2 (photosynthesis), H2O (photosynthesis, elongation, and more), other mineral nutrients

How many essential elements must ALL plants have (some can have more)

16

What are the 16 essential elements

C, H, O from CO2 (air) and H2O (soil), 13 soil nutrients (absorbed dissolved in H2O through roots from soil, follow same path as H2O/xylem)

Soil Macronutrients (6)

Nitrogen (N), Potassium (K), Phosphorus (P), Calcium (Ca), Sulfur (S), Magnesium (Mg)

Nitrogen

component of proteins, nucleic acids, chlorophyll

Potassium

osmosis and ion balance, open/close stomata (gas exchange)

Phosphorus

component of nucleic acids, ATP, phospholipids (‘gatekeeper’)

Calcium

component of cell wall (support)

Sulfur

component of proteins, coenzymes

Magnesium

component of chlorophyll, enzyme coactivator

Soil Micronutrients (7)

Molybdenum (Mo), Copper (Cu), Zinc (Zn), Manganese (Mn), Chlorine (Cl), Boron (B), Iron (Fe)

Molybdenum

enzyme cofactor

Copper

enzyme cofactor

Zinc

enzyme cofactor

Manganese

enzyme cofactor, chloroplast membrane for O2 release with photosynthesis

Chlorine

split of H2O (generate electron energy), ion balance

Boron

enzyme cofactor, cell wall component, nucleic acid synthesis

Iron

enzyme cofactor, component of cytochromes (photosynthesis, cellular respiration), synthesis of chlorophyll

Most plants display sexual reproduction; what is this

2 gametes fuse to produce offspring with unique combination of genes

Plants undergo alteration of generations

2 multicellular life cycle stages: Diploid and Haploid

Diploid Life Cycle Stage

spore producing sporophyte by meiosis (2N to 1N)

Haploid Life Cycle Stage

gamete producing gametophyte via mitosis (1N to 1N)

Evolutionary Trends

sporophyte is larger and more complex where as the gametophyte is smaller and less complex

Moss

sporophytes are small and dependent on gametophyte

Flowering Plant

sporophyte larger, independent, more complex than gametophyte

dependent gametophyte are few-celled and within flowers

female is around 7 cell, male is around 2/3 cells

Flowers

only in angiosperms

all sizes, shapes, colors, and aromas

Essential Processes of Sexual Reproduction within the Flower

meiosis/cytokinesis (reduce chromosome #, 2N → 1N)

syngamy (fertilization, restore chromosome #, 1N egg + 1N sperm = 2N zygote

Ideal Flower

4 sets of highly modified leaves arranged in whorls at tip of highly modified stem

highly modified determinate (short term) shoot system

Whorls

Sepals, Petals, Stamens, Carpels

Whorls for Reproduction

Stamens and Carpels

Whorls NOT for Reproduction

Sepals and Petals

Sepals

make Caylx- All sepals, protect unopened flower

Petals

make Corolla- all petals, attract pollinators, contain color, smell, and nectar

Stamens

make Androecium- all stamens, male household, pollen (sperm)

Carpels

make Gynoecium- all carpels, female household, embryo sac (with egg)

Pistil (fused carpels)

stigma, style, ovary with ovules, become seeds, ovary with fruit

What is a part of the sporophyte generation, is 2N, and is attached to the receptacle

Pedicel (flower stalk), Receptacle (enlarged tip of pedicel), and 4 sets of highly modified leaves

What is a part of the 1N gametophyte generation

Pollen (sperm) and Egg (within embryo sac)

Pollen Formation (male side)

takes place within stamen

Anther

bilobed with 2 pollen chambers per lobe

c.s.- 2 N microspore mother cells

2N microspore mother cell within anther

2N cell undergoes meiosis and cytokinesis to create 4 1N microspores which then undergo mitosis and cytokinesis, but unequal and incomplete for some to create 4 2-celled pollen grain which contain a tube cell with a 1N nucleus and a generative cell with a 1N nucleus

EACH 2N MICROSPORE MOTHER CELL CAN PRODUCE 4 1N 2-CELLED POLLEN GRAINS

Pollination

transfer of pollen from anther to stigma of pistil

Self-pollination

transfer within same flower or between flowers of the same plant

Cross-pollination

transfer between flowers of different plants which causes genetic variation

Pollinating Agents

mechanisms used for transfer of pollen

Wind (small, lightweight pollen)

Water (with a few aquatic plants)

Animals (majority of plants, utilize ‘trick and reward’ system [nectar, color, aroma to attract animals])

Ovule Development (Female Side)

ovule = future seed, ovary = future fruit

enclosed within ovary of pistil (carpel), one to many ovules per ovary

Ovule attached to the central axis or wall of hollow ovary

Always enclosed, only in angiosperms

Megaspore Mother Cell

within ovule is 1 large 2N cell

Megaspore Mother Cell

1 2N megaspore undergoes mitosis and cytokinesis to create 4 1N megaspores, 3 are degraded leaving 1 functional 1N megaspore, this undergoes series of 3 mitosis and cytokinesis all of which are incomplete and unequal which creates 8 1N nuclei that only have 7 cells

Embryo Sac

female gametophyte, 8 nucleate, 7 celled structure

7 cells in the embryo sac

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

Syngamy

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

Pollen Grain Germination

tube cell forms pollen tube, generative cell divides by mitosis and cytokinesis to produce 2 1N sperm

Syngamy Steps

pollen tube enters micropyle of ovule, digest nucellus

pollen tube delivers sperm to location of egg

pollen tube enters 1 synergid, releases its contents, synergid ruptures

tube nucleus degrades, 2 sperm release into large central cell

micropyle closes up

fertilization!

Double Fertilization/Fusion

both sperm fuse with other nuclei

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

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

all other cells in embryo sac reabsorbed

Post Fertilization (within ovule)

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

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

indie ovule: 2N integuments harden to form seed coats

Post Fertilization, not just inside ovule

ovule with 2N zygote matures into seed with 2N multicellular embryo and ovary enlarges with sugars and H2O into fruit (mature ovary) with enclosed seeds (mature ovules)

Seed Dispersal (seeds enclosed within fruit)

wind, water, animals (majority)

Seed Germination

seed with 2N embryo enters period of dormancy which is broken by combination of internal and external (environmental) factors

Radicle (1st root) emerges and grows down

Shoot emerges and grows up

DNA

deoxyribonucleic acid

building block of life (contains info to build an organism)

made up of 4 nucleotides

4 Nitrogenous Bases

Adenine, Thymine, Guanine, Cytosine

A=T, G=C

Genotype

genetic information of a trait, sequence of nucleic bases

Phenotype

physical expression of trait

Central Dogma (don’t think we have to know this term, but helpful to know)

DNA (can replicate) → (transcription) RNA → (translation) Protein

Dominant vs Recessive

visible vs masked

How Many Alleles Per Gene

Each individual has 2

Homozygous

2 copies of same allele (AA or aa)

Heterozygous

2 different alleles (Aa)

Dominant Allele vs Recessive Allele

uppercase vs lowercase

Punnett Square AA x aa

100% Aa (hetero)

Phenotypic Ratio: 1:0

Genotypic Ratio: 0:1:0

Punnett Square Aa x Aa

AA, 2 Aa, aa

Phenotypic Ratio: 3:1

Genotypic Ratio: 1:2:1

Independent Assortment

traits/genes assort independently of one another

Mutations

change in order/structure of genetic information (DNA)

provides genetic variation

Example of a Mutation

Albinism in animals

Rare recessive mutation where pigment is removed from fur