mcgeeshsscience

plant notes

Page history last edited by Karen McGee 7 mos ago

Plant Notes

Kingdom Plantae – multicellular eukaryotes that have cell walls made of cellulose. They

carryout photosynthesis (photosynthetic autotrophs; phototrophs)

using the green pigments chlorophyll a and b.

Plant Life Cycle

Alternation of generations: alternate between a diploid (2N) sporophyte that produces haploid spores by meiosis and a haploid gametophyte that produces haploid gametes by mitosis. The gametes unite to form the diploid sporophyte. The haploid spores produced by the sporophyte form the gametophyte.

*Differentiate between vascular and nonvascular plants.*

Nonvascular plants lack vascular tissue, tubular conducting tissue that conducts water and nutrients. (xylem and phloem)

Vascular plants contain vascular tissue, xylem and phloem, that forms a transport system for the plant, conducting water and nutrients throughout the plant.

Nonvascular plants are called bryophytes. The bryophytes include mosses, liverworts, and hornworts.

Vascular plants are called tracheophytes. The tracheophytes include all other plants such as ferns, conifers and flowering plants.

*Relate the structure of plant tissue to its function.*

1. epidermal tissue – outer covering – usually a single layer of cells

leaves: trichomes protect leaf, produce a fuzzy appearance

contains guard cells that regulate water loss and gas

exchange

roots: forms root hairs that increase surface area for more water

absorption

ground tissue – cells that lie between dermal and vascular tissues

Three Types of Ground Tissue

parenchyma – most abundant ground tissue

thin cell walls, large central vacuoles

leaves: parenchyma packed with chloroplasts – site of

most photosynthesis

collenchyma – strong flexible cell walls support larger plants – strings of

celery

3. sclerenchyma – extremely thick, rigid cell walls, make ground tissue

tough and strong – stone cells in pears

vascular tissue – forms a transport system that moves water and nutrients

throughout the plant

Two Types of Vascular Tissue

xylem – water-conducting tissue

Two Types of Cells in Xylem Tissue

1. tracheids – long narrow cells

walls impermeable to water

found in all seed plants

mature cells die, cytoplasm disintegrates and neighboring

cells connect

2. vessel elements – found in angiosperms

mature cells die and become hollow

the ends of cell walls disintegrate producing a

continuous tube

The combination of root pressure, capillary action, and transpiration provides enough force to move water through the xylem tissue of the tallest plants.

Transpiration – most powerful of the forces. The major force in water transport is

driven by evaporation of water from leaves during transpiration.

Capillary action – tendency of water to rise in a tube. Due to cohesion and

adhesion.

cohesion – molecules of like substances attracted to each other

(water sticks to water)

adhesion – molecules of unlike substance attracted to each other

(water sticks to other surfaces)

Water rises in tracheids and vessel elements by capillary action.

Root pressure – water pressure created in roots when the Casparian strip prevents

the flow of water out of the vascular cylinder of roots. Root

pressure is the starting point for the movement of water through

the vascular system of the plant.

phloem – food-conducting tissue

Two Types of Phloem Cells

sieve tube elements – main phloem cells

end walls have tiny holes

mature cells lose their nuclei and other organelles,

remaining organelles hug the side of cell to create a

pipeline through which sugars and other goods are

carried in water

2.companion cells – surround sieve tube elements

keep their nuclei and organelles

support sieve tube elements

aid in movement of substances in and out of phloem

When nutrients are pumped into or removed from the phloem system, the change in concentration causes a movement of fluid in the same direction. As a result, phloem is able to move nutrients in either direction to meet the nutritional needs of the plant.

4. Meristematic Tissue – the only plant tissue that produces new cells by mitosis

undifferentiated tissue – not specialized for a specific

function

meristem – cluster of tissue responsible for continuing

growth throughout a plant’s life

Three Types of Meristem

1. apical meristem – tip of stems and roots – increases

length of stems and roots

2. floral meristem – apical meristem that produces

flowers

3. vascular cambium – increases width of stems and

roots

*Describe the structure and function of the major parts of a plant.*

1. Roots:

Functions of Roots

1. water and mineral transport

2. anchor the plant

Two Types of Roots

1. taproot – a primary root grows long and thick

secondary roots remain small

found mainly in dicots

a carrot is a taproot

2. fibrous roots – roots branch and no root grows larger than the rest

found mainly in monocots

grasses have fibrous roots

Structure of Roots

epidermis – outer layer

cortex – ground tissue

endodermis

central cylinder – vascular tissue

root hairs – extensions that increase surface area and water absorption

Roots grow in length from apical meristem protected by the root cap.

Casparian strip prevents water from moving out of the vascular cylinder, which

creates root pressure to help force water upward.

2. Stems:

Functions of Stems

1. produce leaves, branches, and flowers

2. hold leaves up to sunlight

3. transport substance between roots and leaves

Monocot Stem Structure:

Vascular bundles are scattered throughout the stem

Epidermis anchors vascular bundles and ground tissue

Vascular bundle contains xylem and phloem

phloem – outside of bundle

xylem – inside of bundle

Vascular bundles are surrounded by ground tissue (parenchyma)

Dicot Stem Structure:

Vascular tissue arranged in a ring around the stem

Mature Stem:

Cork

Cork Cambium – produces the outer covering – meristematic tissue

Cortex – parenchyma (ground tissue) outside the vascular tissue

Vascular Tissue:

phloem – conducts food down from leaves

vascular cambium – produces vascular tissue, meristematic tissue

increases thickness of stem

xylem – transports water and minerals upward to leaves

Pith – central parenchyma (ground tissue)

3. Leaves:

Functions of Leaves

1. absorb sunlight

2. carryout photosynthesis

Blade – flattened section that collects sunlight

Petiole – attaches leaf to stem

Structure of Leaves

cuticle – waxy protective covering protects against water loss and injury

epidermis – outer cell layer

palisade mesophyll – specialized ground tissue that is the site of most

photosynthesis

Write the formula for photosynthesis.

spongy mesophyll – specialized ground tissue with many air spaces connected to

the outside of the leaf by stomata

stomata – openings in the lower epidermis that allow for gas exchange.

____________________ enters the leaf and ____________________

exits the leaf through stomata.

guard cells – specialized cells in the epidermis

control the opening and closing of stomata

Leaves lose water (transpiration) to allow carbon dioxide to enter for

photosynthesis. If plants lose too much water guard cells shrink and

collapse closing the stomata, preventing water loss but also shutting

down photosynthesis. What process causes the cell to shrink? What is

the shrinking of a plant cell called? What have plant cells lost when

they collapse? So what keeps guard cells open?

4. Flowers

Functions of Flowers

1. sexual reproduction

2. attract pollinators

Flower Structure

sepals – outer layer of leaflike structures that protect the developing flower

petals – brightly colored – attract pollinators

stamens – male reproductive structure

filament – long, thin, stalk that supports the anther

anther – meiosis produces haploid gametophytes – pollen grains

(contain sperm nuclei)

pistil – female reproductive structure

stigma – sticky top that traps pollen grains

style – stalk that lead from stigma to ovary

ovary – base that contains ovules where ova (eggs) develop

ova fertilized by sperm nuclei from pollen grains form seeds

ovary forms the fruit that protects the seeds and aids in seed

dispersal

*Differentiate among cycads, gymnosperms, and angiosperms.*

Cycads, gymnosperms, and angiosperms are all seed plants. They reproduce from seeds. Seed plants are the dominant group of plants. Gymnosperms (naked seed) produce seeds on exposed bracts of cones. Cycads are gymnosperms. Angiosperms are the flowering plants. The flowers are the reproductive structures that produced seeds. The seeds are protected in the ovary which develops into a fruit. Cycads differ from most other gymnosperms, especially conifers in that they are tropical, resemble palm trees, and have separate sexes. Conifers are usually temperate or subarctic and sexes are not separate. Most conifers are wind pollinated. Most angiosperms are pollinated by other organisms although some are wind pollinated. Angiosperms are divided into two large groups: monocots and dicots.

*Compare and Contrast the life cycles of familiar organisms.*

Sexual Reproduction

Asexual Reproduction

Alternation of Generations

*Evaluate the medical and economic importance of plants.*

Many pharmaceutical drugs are produced from plants. Medicines used to treat heart problems and cancers are produced from plants. Aloe is even used by many to treat kitchen burns. Plants are responsible for almost all of our food production. We eat plants and feed plants to our livestock. They are the base of most food chains. They supply us with oxygen. We use plants to build and furnish our homes and make our clothing. Aesthetic value produces income for florists and nurserymen, increases the value of homes and creates an entire landscape industry. Plant products are used in most soaps and cleaners. They prevent erosion and anchor the soil. They provide shelter for wildlife which helps the food chain. They are used to produce energy such as ethanol.