Test 4 - Plant

Avascular (non-vascular) plants

No veins; small; live in moist environments. Examples: algae, moss

Vascular plants

Have veins (xylem/phloem) that carry sugar and water

Seedless vascular plants

Reproduce via spores, not seeds. Example: ferns

Gymnosperms

"Naked" seeds (no enclosure); most produce cones. Examples: pine, redwood, junipers, cedars

Angiosperms

Seeds enclosed in an ovary; produce flowers at some point in life cycle

Shoot system

Typically above ground; function = photosynthesis + reproduction (flowers develop into fruit)

Root system

Typically below ground; function = anchoring the plant + absorbing water and minerals

Monocot cotyledons

1

Dicot cotyledons

2

Monocot flower parts

Multiples of 3

Dicot flower parts

Multiples of 4 and 5

Monocot leaf veins

Parallel

Dicot leaf veins

Branched/net-like

Monocot root system

Fibrous (no single main root)

Dicot root system

Taproot (one main root)

Monocot stem vascular bundles

Scattered throughout stem

Dicot stem vascular bundles

Arranged in a ring/circle

Monocot root vascular tissue

Arranged in a circle (pith in center)

Dicot root vascular tissue

In the center (often X-shaped)

Monocot pollen grain pores

1

Dicot pollen grain pores

3

Monocot leaf attachment

Blade wraps around stem (sheath), no petiole

Dicot leaf attachment

Attached via a petiole (stalk)

Only 100% foolproof way to tell monocot vs dicot

Counting cotyledons in the seed

Vascular tissue arrangement rule

Stem: ring = dicot, scattered = monocot. Root: circle with pith = monocot, center = dicot

3 plant tissue types

Dermal, vascular, and ground tissue

Dermal tissue

Always on the outside of the plant (like "skin"); includes epidermis, guard cells, and root hairs

Guard cells

Define the stoma (stomata) in leaves; let CO2 in, let water out

Root hairs

Modified epidermal cells on roots that increase surface area for absorption

Vascular tissue

Tubular cells that transport water and sugar; includes xylem and phloem

Xylem

Carries water and dissolved minerals; one-way flow UP; larger cells, stains red, thick-walled

Phloem

Carries sugars made in leaves; flows BOTH directions; smaller cells than xylem; made of sieve tube members and companion cells

Sieve tube members

Cells that make up phloem; have no nucleus but are alive

Companion cells

Control the metabolism of sieve tube members in phloem

Ground tissue

Everything that isn't dermal or vascular; the majority of plant tissue; includes parenchyma, collenchyma, sclerenchyma

Parenchyma

Thin-walled, living, most abundant cell type; carries out photosynthesis (mesophyll cells in leaves)

Collenchyma

Thicker primary cell wall; provides structural support; living

Sclerenchyma

Thick secondary cell wall; gives rigidity/strength; typically dead at maturity

Whorls

Circles in which flower parts are arranged, from outside in

Sepals

Outermost whorl, collectively called the calyx; green, leaf-like; provide protection to the developing flower

Calyx

The collective term for sepals

Petals

Collectively called the corolla; function is attraction of pollinators (color, scent)

Corolla

The collective term for petals

Stamen

Male reproductive part of a flower; consists of anther and filament

Anther

Top of the stamen; where pollen is made

Filament

Stalk holding up the anther

Carpel (pistil)

Female reproductive part of a flower; consists of stigma, style, and ovary

Stigma

Top of the carpel; where pollen lands; has receptors specific to the correct pollen species

Style

Neck-like structure of the carpel; pollen tube grows down through it

Ovary (flower)

Bottom, bulbous part of the carpel; contains one or more ovules

Double fertilization

One fertilization produces a zygote; a second fertilization produces energy-rich nutritive tissue for the seed

Ovule

Structure inside the ovary that becomes a seed after fertilization

Meristem

Undifferentiated tissue (plant equivalent of stem cells); retained throughout the plant's life

Apical meristem

Located at the very tip (apex) of shoots/roots; totally undifferentiated

Protoderm

Primary meristem that becomes dermal tissue

Ground meristem

Primary meristem that becomes ground tissue

Procambium

Primary meristem that becomes vascular tissue (xylem and phloem)

Vascular cambium

Lateral meristem that gives rise to secondary xylem (most of wood) and secondary phloem

Cork cambium

Lateral meristem that gives rise to periderm (protective covering/bark, replaces epidermis)

Secondary growth

Growth that increases girth (produces wood); common in dicots, rare in monocots

Imbibition

When a seed absorbs water, ruptures the seed coat, and allows O2 in so growth can begin

Radicle

The embryonic root; the first structure to emerge from a germinating seed

Seed germination order in dicots

Radicle emerges first, then cotyledons emerge above ground, then true leaves

Annual plant

Completes life cycle in 1 year (seed to flower/fruit to death); little/no secondary growth. Examples: corn, marigolds, tomatoes

Biennial plant

Completes life cycle in 2 years: Year 1 vegetative growth only, Year 2 flowers/fruits/seeds then dies. Examples: carrots, foxglove

Perennial plant

Continues flowering/fruiting year after year once mature. Example: apple trees

Early wood

Lighter, bigger cells in a tree ring, formed in spring ("spring wood")

Late wood

Darker, smaller cells in a tree ring, formed in winter

Tree ring width

Indicator of growing conditions that year (narrow = drought; wide = good conditions)

Why are there no growth rings in the tropics?

Temperature and rainfall don't vary seasonally there (warm and rainy year-round)

Cohesion-Tension Theory

Explains water transport: transpiration pulls water up as hydrogen-bonded water molecules cohere, creating continuous pull from leaves to roots

Percent of water absorbed by roots used in photosynthesis

About 2% - the rest is lost via transpiration

Auxin

Hormone (e.g., IAA) that stimulates cell elongation; concentrates on the dark side of stem, causing phototropism

Gibberellins

Hormone that promotes stem elongation (height); not related to light; Mendel's short pea plants lacked gibberellic acid

Cytokinins

Hormone (e.g., zeatin) that stimulates cell division (cytokinesis)

Abscisic acid (ABA)

Dormancy hormone: closes stomata, keeps seeds dormant, keeps buds from blooming prematurely

Ethylene

Gas hormone that promotes fruit ripening

Darwin's phototropism experiment

Cutting the tip or covering it with opaque material stopped phototropism; covering with transparent material did not - concluded the tip senses light

Boysen-Jensen experiment

Replacing a cut tip with porous gelatin still allowed phototropism; replacing it with non-porous mica stopped it - concluded a diffusible hormone (auxin) causes the response

ABA and wild oat dormancy example

Wild oat seeds produce ABA to prevent germination from a single stray summer rain; several rains are needed to wash away enough ABA for germination in fall

Ethylene and tomato ripening example

Store tomatoes are picked green and gassed with ethylene to turn red, but sugar content stays low since they're off the plant

Positive tropism

Growth toward a stimulus

Negative tropism

Growth away from a stimulus

Phototropism

Growth response to light; shoots show positive phototropism due to auxin concentrating on the dark side

Gravitropism (geotropism)

Growth response to gravity; roots show positive gravitropism (grow down), shoots show negative gravitropism (grow up)

Thigmotropism

Growth response to physical contact/touch; touched side grows slower, causing winding around objects (e.g., vine tendrils)

Chemotropism

Growth response to chemicals; positive toward beneficial chemicals, negative away from harmful chemicals

Day-neutral plants

Flower regardless of day length; cued by temperature instead (vernalization)

Vernalization

Requires a period of cold followed by a period of warmth to bloom. Examples: tulips, daffodils

Long-day plants

Flower when day length exceeds a critical value; tend to bloom in spring/early summer. Example: spinach

Short-day plants

Flower when day length is shorter than a critical value; tend to bloom late summer into fall. Examples: cocklebur, xanthium

Critical nuance about "day length" flowering

These plants actually respond to NIGHT length, not day length; interrupting a long night with a flash of light prevents short-day plants from flowering

Fruit (botanical definition)

The mature ovary of a flower; anything that contains seeds, even if commonly called a vegetable (e.g., zucchini, pumpkin, peanuts)

Vegetable (culinary definition)

Plant parts without seeds: leaves (lettuce), roots (carrot, turnip), etc. - not a real botanical category

Seed dispersal by wind

Example: maple seeds (winged, "helicopter" shape), dandelion seeds

Seed dispersal by animal caching

Example: squirrels and blue jays bury nuts/acorns; not all are retrieved, so some germinate

Seed dispersal via digestive tract

Example: apples, raspberries - seeds pass undigested and are deposited with natural fertilizer

Seed dispersal by sticking to fur

"Velcro" seeds stick to animal fur and fall off or are groomed off elsewhere

The Beal experiment

Buried seeds from ~20 plant species deep underground and periodically tested germination over decades; proved long-term seed dormancy is possible