gen bio 2 finals (3rdqtr) [chapter1]

plants nd em

Rhizomes

Specialized stem, example being ginger. Serves as storage of starch and protein, which permit perennial growth

Carbon, Hydrogen, Oxygen

Major constituent of organic plant material; assimilation of oxidation-reduction reactions.
Function: Forms carbohydrates, proteins, fats; main structural component
If absent: No food production → plant dies
Function: Part of organic compounds; involved in photosynthesis
If absent: Growth stops; plant wilts and dies
Function: Needed for respiration and energy release
If absent: Respiration stops → plant dies

Boron

Cell wall synthesis; enzymatic reactions and metabolic pathways; mitotic activity for root development
Function: Cell wall formation; sugar transport
If absent: Death of shoot tips; poor fruit and seed formation

Calcium

Structural component of the cell wall and cell membrane; counter-ion in the vacuole
Function: Cell wall formation; membrane stability
If absent: Death of growing tips; weak roots and stems

Chlorine

Water splitting system for photosystem II; stomatal opening regulation
Function: Photosynthesis; water balance
If absent: Wilting; reduced root growth

Copper

Cofactor for metalloproteins and enzymes; photosynthetic electron transport; cell wall metabolism and hormone signaling; oxidative stress response
Function: Enzyme activity; photosynthesis
If absent: Leaf curling; weak stems

Iron

Regulatory component of proteins and metabolites in roots and leaves
Function: Chlorophyll synthesis; electron transport
If absent: Yellowing of young leaves

Magnesium

Chlorophyll synthesis; cofactor in activation of ATPase

Function: Component of chlorophyll; enzyme activation
If absent: Yellowing between veins of older leaves (interveinal chlorosis)

Manganese

Photodestruction of chlorophyll and chloroplast structure; enzyme activator; precursor of amino acid, hormones (auxins) and lignins

Function: Enzyme activation; photosynthesis
If absent: Pale leaves with brown spots

Molybdenum

Enzyme activation (e.g., nitrate reductase, catalase, ribonuclease); chlorophyll synthesis

Function: Nitrogen metabolism
If absent: Poor nitrogen use; yellowing leaves

Nickel

Endosperm development and dehydrogenase activity; urease activation for urea breakdown; root nodule growth

Function: Nitrogen metabolism (urease enzyme)
If absent: Accumulation of toxic urea; poor growth

Nitrogen

General plant growth of roots, stem, leaf, flowers and fruits; chlorophyll synthesis

Function: Proteins, enzymes, chlorophyll formation, leaf development
If absent: Stunted growth; yellowing of older leaves

Phosphorus

Energy transferring process for photosynthesis and respiration (ADP-ATP synthesis); structural component of phospholipids, nucleic acids, coenzymes, and nucleotides.

Function: Energy transfer (ATP), DNA/RNA, root development
If absent: Poor root growth; delayed flowering; dark green or purplish leaves, stunted growth, delayed maturity.

Potassium

Cell extension and stomatal regulation; enzyme activation; photosynthetic activity

Function: Enzyme activation; stomatal regulation, needed for osmotic balance within plant cells
If absent: Weak stems; leaf edges turn yellow/brown

Sulfur

Assimilation of oxidation-reduction reactions; participates in various enzymatic processes

Function: Amino acids and protein synthesis
If absent: Yellowing of young leaves; slow growth

Zinc

Enzymatic function and reactivity; stem elongation; protein and starch synthesis

Function: Growth hormone (auxin) synthesis
If absent: Short internodes; small leaves

Auxins

What:

Indole-acetic acid (aromatic compound)

Growth functions

• Cell elongation in stems

• Apical dominance (suppresses lateral buds)

• Root initiation

Defense / stress role

• Helps regulate wound responses and tissue regeneration

If absent

• Stunted growth

• Loss of apical dominance

• Poor root formation

Example

• A shoot bending toward light (phototropism)

Gibberellins

What: Diterpenoid steroid-like compound

Growth functions

• Stem elongation

• Seed germination (enzyme production)

• Flowering in some plants

Defense / stress role

• Helps recovery after stress by promoting growth

If absent

• Dwarf plants

• Poor seed germination

Example

• Barley seeds producing amylase during germination

Cytokinins

What: Adenine derivative

Growth functions

• Cell division

• Delays leaf senescence (aging)

• Promotes lateral bud growth

Defense / stress role

• Enhances resistance to pathogens by maintaining leaf health

If absent

• Early leaf yellowing

• Reduced branching

Example

• Leaves staying green longer after cutting

Ethylene

What: Gaseous hydrocarbon (C2H4)

Growth functions

• Fruit ripening

• Leaf and flower senescence

• Abscission (leaf fall)

Defense / stress role

• Activates defense genes during pathogen attack

If absent

• Fruits do not ripen

• Delayed leaf fall

Example

• Bananas ripening faster when kept together

Abscisic Acid

What: Sesquiterpenoid compound

Growth functions

• Growth inhibitor

• Induces seed dormancy

Defense / stress role

• Closes stomata during drought

• Helps plant survive stress

If absent

• Excessive water loss

• Seeds germinate too early

Example

• Stomata closing during dry conditions

Salicylic Acid

What: Phenolic compound

Growth functions

• Minor role in growth regulation

Defense role

• Activates systemic acquired resistance (SAR)

• Protects against pathogens

If absent

• Weak immune response

• Increased disease susceptibility

Example

• Whole-plant resistance after a local infection

Jasmonic Acid

What: Cyclopentanone fatty acid derivative

Growth functions

• Regulates root growth and senescence

Defense role

• Defense against herbivores and wounding

If absent

• Severe damage from insects

Example

• Production of toxins after insect attack

What:Steroid-based hormone

Growth functions

• Cell elongation & division, vascular differentiation, seed germination

Defense role

• Enhances stress tolerance, pathogen defense

If absent

• Dwarfism, weak vascular tissue, poor germination

Example

• Stem elongation in dwarf plants

Positive Feedback Mechanism

The response enhances or amplifies the original stimulus

Example: Ethylene production during fruit ripening.
One ripe fruit releases ethylene → triggers more ethylene → ripens neighboring fruits faster.

Negative Feedback Mechanism

The response counteracts or reduces the initial stimulus

Example: Regulation of stomatal opening by Abscisic Acid (ABA).

• During drought, ABA increases → stomata close → prevents water loss.

• When water is sufficient, ABA decreases → stomata reopen.

Artificial Insemination

Injection of sperm into the female reproductive tract by artificial means

Purpose: Allows selective breeding without natural mating

Example: Dairy cows bred with high-yield bull sperm

In Vitro Fertilization

Fertilization of egg and sperm outside the body (in a lab), then the embryo is implanted into the uterus.

Purpose: Helps in infertility treatment

Example: Human IVF clinics

Embryo Transfer Technology

Fertilized embryos are transferred from donor female to surrogate female.

Purpose: Produces multiple offspring from high-quality animals

Example: Cattle, buffalo breeding programs

Cloning

Producing genetically identical organisms from a single cell or parent.

Purpose: Preserve desirable traits

Example: Dolly the sheep

CRISPR-Cas9 Gene Editing

A precise tool for cutting and modifying genes

Purpose: Disease resistance, better production

Example: Pigs resistant to certain viruses

Genetic Engineering

Inserting foreign DNA into an organism to express new traits

Purpose: Pest resistance, herbicide tolerance

Example: Bt cotton, Golden Rice

Stem Cell Technology

Using undifferentiated cells to repair or regenerate tissues

Purpose: To treat diseases, repair tissues, and advance research.

Example: Treating diseases like Parkinson’s or spinal cord injury

Genetically Modified Organisms (GMOs)

plants modified to enhance yield, resistance, or nutritional value.

Phototropism

• Stimulus: Light

• Direction:

  • Positive → growth toward light

  • Negative → growth away from light (rare)

• Example: Shoots bending toward sunlight

• Hormone involved: Auxin (redistributed to shaded side → cell elongation)

Gravitropism

• Stimulus: Gravity

• Direction:

  • Positive → growth toward gravity (roots)

  • Negative → growth away from gravity (shoots)

• Example: Roots growing down, shoots growing up

Hydrotropism

• Stimulus: Water / moisture

• Direction: Growth toward moisture

• Example: Root tips growing toward wetter soil patches

Thigmotropism

• Stimulus: Mechanical touch or contact

• Direction: Growth wraps around or along a support

• Example: Tendrils of climbers like pea plants wrapping around a support

Chemotropism

• Stimulus: Chemicals

• Direction: Growth toward or away from chemical signals

• Example: Pollen tube growth toward ovule guided by chemical signals

• Other Example: Roots growing toward nutrient-rich soil

Thermotropism

• Stimulus: Temperature changes

• Direction: Growth toward favorable temperature

• Example: Some plants’ flowers or leaves move toward warmth to aid pollination

Electrotropism

• Stimulus: Electric current or field

• Direction: Growth toward or away from electric field

• Example: Certain root tips respond to electric stimuli (rarely studied)

Heliotropism

• Stimulus: Sunlight

• Direction: Daily movement of leaves or flowers toward sun

• Example: Sunflower heads tracking the sun (heliotropism)

Photoperiodism

• Definition: The response of plants to the relative lengths of day and night, especially in flowering.

• Type: Physiological response, not a directional growth

• Purpose / Significance:

  • Ensures flowering occurs during optimal season

  • Helps synchronize reproduction with environmental conditions