Bio 106 WSU Exam 2

Macronutrients

Nutrients required in larger amounts as raw materials to create organic molecules.

List of key macronutrients

Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium.

Role of carbon in organic molecules

Serves as the structural backbone of organic molecules.

Biological uses of nitrogen in plants

Required to build DNA, RNA, proteins, and chlorophyll.

Biological uses of phosphorus

Required for DNA, RNA, cell membranes, and ATP.

Carbon proportion in plant dry mass

Carbon makes up 45% of a plant's dry mass.

How plants absorb carbon

Carbon is absorbed from the air through stomata.

Fertilizer

enriched in nitrogen potassium and phosphorus

Soil

mix of organic matter and mineral particles: rocks sand silt, larger particles not good at retaining water or nutrients, smaller particles pack too close and exclude oxygen

Humus layer

rich in organic matter comes from decomposing leaves dead organisms feces or bacteria, humus prevents clay from packing together allowing air pockets for air circulation around roots, also increase cation exchange, houses bacteria fungi earthworms nematodes insects protists plant roots

How minerals exist in soil

Minerals exist in soil solution as charged ions.

How cation exchange works in soil

Positively charged mineral ions bind to negatively charged soil particles.

How roots release mineral cations from soil

Roots acidify the soil, causing cations to release into solution.

Usability of atmospheric N₂ for plants

Atmospheric N₂ diffuses into soil but cannot be directly used by plants.

Forms of nitrogen absorbed by plants

Plants absorb nitrogen as ammonium (NH₄⁺) and nitrate (NO₃⁻).

Function of ammonifying bacteria

They produce ammonium (NH₄⁺) by breaking down decaying organic matter.

Function of nitrifying bacteria

They convert ammonium (NH₄⁺) into nitrate (NO₃⁻).

Function of nitrogen-fixing bacteria

They convert atmospheric N₂ gas into ammonium (NH₄⁺).

Rhizobacteria

special group of N fixing bacteria live within nodules in the roots of legumes, mutualism bacteria release usable N plant provides shelter and sugars

Mycorrhizal fungi symbiosis

fungi wraps around roots, increase water and nutrient absorption capabilities, plant supplies fungi with carbs formed by photosynthesis,

Ectomycorrhizae

the mycelium forms a dense sheath over root surface, fungal hyphae penetrate cortex

Endomycorrhizae

extends into root and make small pockets in cortical cells.

Root system

anchor plant, bring nutrients and water, can store carbs

Shoot system

stems are structural and transport nutrients and water, leaves exchange gases with air and do photosynthesis

Taproots

penetrate soil deeply with lateral roots branching off, supports tall plants(prevent toppling), absorption occurs in lateral roots

Fibrous roots

multiple slender roots emerge from stem, form underground mat of interwoven branching roots, prevents grazers from uprooting plant, anchors topsoil

Absorption

occurs primarily at root tips, root hairs(thin extensions of individual cells,

Stems

main function is to elongate and orient shoot to maximize: photosynthesis positioning leaves towards sun and avoid neighbor plants, reproduction facilitating dispersal of pollen and fruit, structure: nodes points where leaves emerge, internodes segments between nodes, apical bud growing shoot tip, axillary bud where a branch can form

Leaves

main function photosynthesis, capture light, exchange gas with atmosphere, take part in water uptake, consists of flattened blade, the petiole(a stalk which joins the leaf to a node of the stem)

Tissue Layers

outerlayer(dermal tissue) protect plant, middle layer(ground tissue) bulk of plant carries out most functions, central layer(vascular tissue) circulatory system tubes distribute water and nutrients throughout body

Xylem

tubes that transport water and mineral upward from roots into the shoots, structure: dead tubular ends stacked end to end, the initial cell walls have lignin in them, when cells die walls remain, form long pipes have perforations between cells for water to flow

Xylem cells

vessel elements: wider shorter with larger openings, aligned end to end forming continuous tube, have perforation plates for flow from cell to cell, tracheids: long tapered, water flows cell to cell laterally via pits

Phloem

moves organic nutrients(sugars) from where they are made or stored to where they're needed

Phloem cells

sieve tube element cells: living cells connect end to end forming a tube, lack most organelles(nucleus ribosomes), connect end to end via sieve plates, companion cells supply proteins to sieve tube element cells

Ground tissue

anything that isn't dermal or vascular, fills in between dermal tissue and vascular tissue, includes various cells specialized for functions such as storage photosynthesis and support, ground tissue of roots and stems: pith(internal to vascular tissue), cortex(external to vascular tissue)

Indeterminate growth

Continuous growth throughout a plant's life.

Primary growth

Growth that elongates the plant shoots and roots longer or taller.

Secondary growth

Growth that increases the thickness or width of stems and roots.

Vascular cambium

Ring of meristematic cells producing secondary xylem inside and secondary phloem outside.

Cork cambium

Lateral meristem producing a tough, protective waxy outer layer replacing the epidermis.

Growth limitation of herbaceous plants

Restricted to primary growth only.

Meristems

Regions of unspecialized, actively dividing stem cells called initials.

Apical vs. axillary meristems

Apical meristems are at root and shoot tips; axillary meristems are at branch points.

Fate of dividing meristem cells

One cell differentiates into a specialized cell while the other remains a stem cell.

Primary growth in shoots

Apical meristem produces leaf primordia; internode cell elongation lengthens the shoot.

Function of the root cap

Protects the apical meristem and secretes lubricating slime as roots push through soil.

Eudicot stem vascular arrangement

Vascular bundles form a ring.

Monocot stem vascular arrangement

Vascular bundles are scattered throughout the stem.

Waxy cuticle function

Reduces water loss from the leaf surface.

Stomata and guard cells

Leaf pores flanked by guard cells that open for gas exchange and close to prevent water loss.

Leaf vascular tissue

Xylem and phloem bundled together into leaf veins.

Plant cell wall composition

Made of cellulose and pectin, acting like a mesh surrounding the cell membrane.

Symplast

The continuum of cytoplasm connected between plant cells.

Symplastic route

Movement of water and minerals from cell to cell through plasmodesmata.

Apoplast

The continuum of cell walls and extracellular spaces.

Apoplastic route

Movement of water and minerals through the network of cell walls.

Transmembrane route

Movement of water and minerals repeatedly exiting and entering cells across membranes and walls.

Casparian strip

Waxy strip blocking the apoplastic route, forcing final screening across cell membranes.

Root pressure

Active K⁺ accumulation in xylem increases solute concentration, driving osmotic water entry.

Cohesion

Attraction between water molecules holding the water column together.

Adhesion

Attraction of water molecules to other substances like xylem cell walls.

Cohesion-tension mechanism

Transpiration creates tension that pulls a continuous, cohesive column of water upward.

Stomatal opening mechanism

K⁺ enters guard cells, causing water influx via osmosis so cells elongate and bow.

Transpiration trade-off

Balancing the minimization of water loss against the maximization of gas exchange.

Phloem translocation bulk flow

Sugar loading into sieve tubes draws water from xylem, generating pressure that drives flow.

Auxin primary function

Stimulates plant growth by promoting cell elongation and cell wall loosening.

Auxin mechanism of cell loosening

Pumps H⁺ into cell walls, activating expansion enzymes that break microfibril bonds.

Auxin response to light

Moves to the dark side of the stem, stimulating cells there to elongate.

Cytokinins primary function

Stimulate cell division and shoot branching while inhibiting lateral root growth.

Cytokinin transport direction

Released from root tips and moves upward to the shoots.

Gibberellins growth mechanism

Stimulate cell division and elongation, working with auxin to loosen cell walls.

Gibberellins role in seed germination

Water triggers gibberellin release, breaking down stored starch into glucose for embryo development.

Abscisic acid (ABA) primary function

Inhibits growth, promotes seed dormancy, and closes stomata during drought stress.

ABA stomatal closure mechanism

Pumps K⁺ out of guard cells, causing osmotic water loss and cell flaccidity.

Ethylene primary functions

Ripens fruit, steers growth around obstacles, and promotes leaf abscission.

Mechanism of leaf abscission

Decreasing auxin makes the abscission zone sensitive to ethylene, weakening leaf attachment.

Photoreceptors

Pigment molecules that absorb specific light wavelengths to detect direction, color, and intensity.

Phytochromes light spectrum

Detect red and far-red light in the 630-730 nm wavelength range.

Phytochrome activation mechanism

Red light converts inactive phytochrome to active; far-red light turns it inactive.

Blue light photoreceptors function

Detect 400-500 nm wavelengths, influencing stem elongation and maximizing photosynthesis.

Photoperiodism

A plant's tracking of night length to time flowering.

Short-day vs. long-day plants

Short-day plants require long nights to flower; long-day plants require short nights.

Gravitropism responses

Roots show positive gravitropism (grow downward); stems show negative gravitropism (grow upward).

Statoliths

Specialized starch-filled plastids used by plant cells to detect gravity.

Thigmomorphogenesis

Long-term changes in plant form in response to persistent physical stress.

Environmental stressors

plants may create snorkels to prevent suffocation during a flood this releases ethylene causing some root cortex cells to die, for draught plants reduce respiration causing K+ to pump out of guard cells with water following making them close, salt stress: excess salt reduces water uptake and alters water potential responds by creating solutes, heat stress: plants can unravel vital proteins producing heat shock proteins to help proteins refold into functional form, cold stress: can cause ice crystals in cell walls and lose fluidity response is to alter cell membrane and increase sugars

Defenses

physical defense can include thorns trichomes spines, chemical defense distasteful or toxic compounds many used as medicines, behavioral defense release volatile chemicals to attract predators

Structures

Sepals enclose flower, petals attract pollinators, stamen(male structures) anther is where pollen is made filament holds it up high,Carpel(female structures) stigma is landing pad for pollen style is tube leading to ovary and ovary makes ovules, flowers are where eggs and pollen are made, structures facilitate fertilization of ovum by the sperm

Complete flowers

have all 4 organs

Incomplete flowers

missing one or more organs

Making sperm

packaged in the male gametophyte in the pollen grains, microsporangium manufactures microspores, microspore grows up into male gametophyte, male gametophyte is only 2 cells the generative cell will create 2 sperm cells and tube cell will make pollen tube, generative cell lives inside tube cell

Making the egg

megasporangium is inside ovule in the ovary, each megasporangium makes 1 megaspore, megaspore grows into female gametophyte, cell divides to make a 7 celled gametophyte with 8 nuclei, all cells are inside the central cell

Pollination

pollen grain lands on a stigma, tube cell stretches out into a pollen tube, pollen tube grows towards the ovary, generative cell divides into 2 sperm cells, both sperm cells enter the pollen tube and move to ovary, color birds see red bees dont but see yellow and uv white good at night, nectar at base must reach for it, smell most have sweet scents some mimic rotten flesh

Seed formation

fertilized egg is now a zygote after ovule develops into seed, first cell of sporophyte generation, central cell now triploid 3n, develops into endosperm, serves as food reserve in some, ovary develops into fruit, each ovule develops into seed, integument becomes seed coat, embryo grows consisting of embryonic root and shoot tissues, when it breaks out of seed it germination

Seed structure

endosperm becomes nutrient rich, embryo begins development, cotyledons form, upon germination cotyledon becomes embryonic first leaves, cotyledons supply nutrition plant embryo needs to germinate and become established, plant cant get food from environment until it has leaves and roots

Seed dormancy

can delay germination until environmental conditions are suitable, cues that are used to break dormancy heavy rain fire exposure to cold chemical abrasion,

Seed germination

seed imbibes water and begins to swell and rupture seed coat, water activates enzymes to digest endosperm releasing nutrients, embryo begins development(developing sporophyte), first: radical produced(embryonic root), second: shoot tip emerges(becomes above ground parts)

Nourishment

cotyledons/endosperms provide initial nourishment, prior to first leaves food is supplies by them, first foliage leaves take over feeding via photosynthesis,

Ovary

develops into fruit, other flower parts wither, fruit encloses seeds helps disperse seeds and animals eat fruit seeds adapted to survive digestive tract deposited elsewhere

Edible fruits

may be fleshy(apples oranges cherries), may be dry(nuts, beans, dandelions, grains) grains are fruits of grasses corn wheat rice oats