DAT - Plants

Three parts of a seed

Embryo (early plant within the seed), Seed Coat (hard outer protective layer), Endosperm (storage with nutrients)

Plumule

Top portion of plant that develops into the leaves

Epicotyl

Top of the shoot

Cotyledons

First leaves to appear on a seedling; Contain nutrients from seed

Hypocotyl

Bottom of young shoot

Radicle

First part to emerge; Develops into the roots

Germination

Seed sprouting into a seedling; Water is most important factor

Meristem

Regions at which plant growth occurs; Made of plant stem cells

Primary Growth

Vertical (occurs at apical meristem); Universal

Horizontal Growth

Horizontal at lateral meristems (Vascular cambium and Cork cambium); Not universal (mainly in woody plants)

Vascular Cambium

Ring of meristematic tissue between primary xylem and primary phloem

Primary Xylem

Transports water and dissolved minerals from the roots to the shoot and leaves in young plants (and provides structural support)

Primary Phloem

Transports nutrients from leaves to shoot and roots

Secondary Xylem

Cells on inside of the ring form the wood; New xylem produced every year

Secondary Phloem

Cells on outside of the ring form inner bark; New phloem replaces old

Cork Cambium

Ring of meristematic tissue outside of phloem; Produces cork (dead bark cells which waterproof the outside of the plant)

Ground Tissue

Structural Support; Most of a plant’s mass; All non-vascular and non-dermal tissue

Vascular Tissue

Transports water and nutrients from source to sink

Sieve Cells

Elongated cells without organelles that connect for nutrient transport

Companion Cells

Cells with organelles that connect to sieve cells and support their functions

Tracheids

Long, thin cells that transport water through pits in tapered ends

Vessel Elements

Short, stout cells that transport water through cell wall perforations

Dermal Tissue

Outer layer of plant (protection and regulation); Waxy cuticle limits water evaporation

Casparian Strip

Impenetrable substance in cell walls of root endodermis; Made of fat and wax; Water cannot penetrate the casparian strip, and is forced out of cell walls and into endodermal cell’s cytoplasm where it is filtered

What causes stomata closing?

CO2 too high; High temps

Transpiration

Loss of water vapor through stomata

Mesophyll Cells

Involved in photosynthesis and gas exchange between upper and lower epidermis

Bundle Sheath Cells

Surround and protect vascular bundles

Cohesion-Tension Theory

Transpiration leads to transpiration pull (a cohesive force between similar molecules that pulls water up the column

Root Pressure

Water enters roots osmotically from the soil; Osmotic gradient drives water into xylem

Pressure-Flow Hypothesis

Source cells produce sugar and lead it into the phloem; Increased sugar concentration creates a gradient that pulls water into the phloem; Turgor pressure in the phloem increases; Bulk-flow movement of sugar from leaves to roots

Ethylene

Gaseous hormone promoting fruit ripening

Auxins

Hormones stimulating cell growth

Phototropism

Growth towards light

Plant Tropisms

Growth in a particular direction; Auxins concentrated on one side of a plant cause asymmetric growth

Thigmotropism

Growth in response to contact (ex. vining plant)

Cytokinins

Regulate cell differentiation and division in coordination with auxins

Gibberellins

Promote stem and shoot elongation, elimination of seed dormancy, plant flowering, fruit production, and leaf and fruit death

Abscisic Acid

Promotes seed dormancy, closes stomata, and inhibits growth; Functions during stress

Alternation of Generations

Plants alternate between reproductive states; Gametophyte Stage has a haploid phase with one set of chromosomes; Sporophyte Stage has a diploid phase with two sets of chromosomes

Plant Reproductive Cycle

1. Haploid gametophytes produce haploid gametes

2. Haploid gametes from 2 separate organisms fuse, forming a diploid zygote

3. Diploid zygotę undergoes mitosis and forms a diploid sporophyte

4. Diploid sporophytes can produce haploid spores via meiosis

5. Haploid spores produce a haploid gametophyte via mitosis

Homosporous Plants

Produce only 1 type of spore; Spores eventually develop into a bisexual gametophyte (capable of producing both sperm and egg)

Heterosporous Plants

Produce 2 types of spores; Megaspores develop into an embryo sac which produces an egg; Microspores develop into pollen grains which will produce sperm

Bryophytes

Liverwort, Hornwort, Moss, etc.; Short, nonvascular plants found in moist environments; Grow horizontally to stay close to the water; Most of their life cycle is spent as a gametophyte

Rhizoids

Hair-like projections that help with water absorption and anchorage

Tracheophytes

Vascular plants capable of growing vertically due to root system with anchorage; Contain xylem and puddles; Most of their life cycle is spent as spherocytes; Seeded and Seedless versions

Seedless Tracheophytes

Lycophytes, Pteridophytes, Club moss, Quillworks, Fern, Horsetail; Mostly homosporous with independent gametophyte and sporophyte life cycles; Produce motile, flagellated sperm

Seeded Tracheophytes

Hetereosporous plants; Gymnosperms and Angiosperms

Gymnosperms

Produce unprotected seeds and non-flagellated sperm, which are dispersed by the wind

Angiosperms

Flowering plants that produce fruits with seeds enclosed in an ovary; Non-flagellated sperm is carried by pollen and dispersed by wind/animals; Most abundant plant type

Stamen

Male plant sex organ

Anther

Site of microspore production (can produce pollen)

Filament

Supports anther

Pistil

Female plant sex organ

Stigma

Top of pistil where pollen lands for germination

Style

Tube connecting stigma to ovary

Ovary

Stores ovule, which houses embryo sac

Monocots

Single cotyledon; Floral parts in multiples of 3; Long, narrow leaf and parallel veins; Vascular bundles scattered; Fibrous, fine root system; Ex. Corn

Dicots

Two cotyledons; Floral parts in multiples of 4 or 5; Broad leaf with network of veins; Vascular bundles in a ring; Single taproot with branching

Nitrogen Fixation

Plants and Nitrogen-fixing bacteria symbiotic relationship; Plants produce food for the bacteria via photosynthesis, and the bacteria fix atmospheric nitrogen into usable forms for the plant

Nitrogen-Fixing Bacteria

In root nodules; Convert N2 to NH3 and NH4+

Nitrifying Bacteria

Convert NH3 and NH4+ into NO2- and NO3-

Nitrates

Taken up by plants and incorporated into amino acids and chlorophyll

Detritus

From dead plants and animals; Provides soil with nitrogen

Denitrifying Bacteria

Convert nitrates back to atmospheric N2