Plants

Organs - examples

Organs - examples

• roots

• leaves

• stems

Tissues - examples

• dermal

• vascular

• ground

Cells - examples

• parenchyma cells

• collenchyma cells

• sclerenchyma cells

• cells of the xylem

• cells of the phloem

Plant Organs

draw resources

• minerals and water from the soil

• CO2 and light from above ground

form a root system and a shoot system

Root System

• roots and associated things underground

Roots

• anchor a vascular plant in the soil

• absorb minerals and water

• often store carbohydrates

Primary root

• originates in the embryo

• the first root to emerge from a germinating seed

• branches to form lateral roots

Evolution of plants

as plants moves further from the water they grew more complex vascular systems in order to get water to all parts of the plant

Taproot System

• one main vertical root (taproot)

  • prevents the plant from toppling over

• lateral roots

  • carry out most of the absorption

Fibrous Root System

• many smaller roots emerging from the stem

Prop Roots

stabilize plant in unstable soil

Green Roots

carry out photosynthesis

• plants without leaves carry out photosynthesis in their roots

Pneumatophores

project above the surface of the water

• important in areas where the water is murky and its difficult to take in substances from underwater

Stems

• raise and separate leaves, exposing them to sunlight

• raise reproductive structures to facilitate dispersal of pollen and fruit

• consist of an alternating system of nodes and internodes

Nodes

points at which the leaves are attached to the stem

Internodes

Stem segments between the nodes

Axillary Bud

• precursor of a branch or lateral shoot at the junction between the stem and a leaf

Apical Bud

• location where the shoot growth occurs (elongates the plant)

Rhizomes

modified underground plant stem that can send out roots and shoots

Stolons (runners)

stems that grow at the soil surface that form roots at the nodes

• shoot off from the mother plant and grow until they’re big enough to make a new plant

  • nutrients are carried through runners from mother to baby until the baby is big enough to provide it’s own nutrients

Tubers

• enlarged ends of rhizomes or stolons specialized for storing food

Leaves

• main photosynthetic organ

• consist of

  • flattened blade with specialized cells that contain chloroplasts for photosynthesis

  • a petiole

Petiole

Stalk that attaches the leaf blade to the stem at the node

Dermal Tissue

tissue that covers and protects the surface of the plant

• protects from damage

• prevents water loss

• regulates gas exchange

• comprised of thin epidermis, waxy cuticle and specialized guard/cork cells

Dermal Tissue Cells

• epidermal cells

• guard cells

• cork cells

Epidermal Cells

• usually consists of a single layer of thin cells

• produce a waxy substance called the cuticle that helps reduce water loss

Guard Cells

• specialized epidermal cells that create openings for gas exchange during photosynthesis

• they can also close the openings reducing water loss by evaporation

Cork Cells

• replace epidermal cells as a plant grows providing a thicker and more protective covering

• forms the outer layer of bark on trees

Vascular Tissue

layer under the dermal tissue (like our circulatory system)

• transports food, water, hormones and minerals between roots and shoots

• provides structural support

• xylem and phloem

Xylem

conducts water and minerals upward from the roots and the shoots

Phloem

transports sugars from where they are made to where they are needed

• generally from shoots down to roots but not always

Ground Tissue

• majority of the plant body

• important in storage, photosynthesis and support

• upper layer has tightly packed cells and is where most of the photosynthesis is taking place

• lower area has more spaced out and spongy cells allowing gasses to move around more freely

Pith

ground tissue that is internal to vascular tissue

Cortex

ground tissue that is external to vascular tissue

Parenchymal Cells

• comprises the filler or flesh of the plant

• contain chloroplasts

  • where most of the photosynthesis is taking place

• forms the cortex in roots, the pith and cortex in stems, the mesophyll of leaves, the pulp of fruits

• perform most metabolic functions of the plant

• can store starch in stems and roots

Collenchymal Cells

• provide structural support for young parts of the plant shoot

• elongates the cell

• thick cell walls

Sclerenchymal Cells

• make the plant hard and stiff

• dead at maturity

• act as supporting cells (very rigid)

• often occur in regions of the plant that have stopped growing

Cells in the Xylem

• conduct water and minerals

• dead elongated cells

• hollowed out

• cellular contents disintegrate leaving thick cell walls

• two types

  • tracheids and vessel elements

    • both tubular elongated cells

Cells in the Phloem

• conduct sugar

• alive but lack many organelles

• have more space than the average cells

  • lack organelles

• sieve cells

Sieve plates

• at the end of cells

• have pores that allow the flow of fluid between cells

Companion Cells

• have nuclei and ribosomes that serve sieve cells

Photosynthesis

chloroplasts in plant cells capture light energy and convert it into chemical energy that is stored in sugar

• 6 CO2 + 12 H2O + Light → C6H12O6 + 6 O2 + 6 H2O

Photosynthesis - Inside the Cell

• parenchyma cells in the palisade mesophyll contain 30—40 chloroplasts

• chloroplasts have 2 membranes surrounding the stroma

  • sacs called thylakoids contain chlorophyll (inside the stroma)

• Chlorophyll absorbs light energy resulting in the synthesis of organic molecules

Light Reactions

H2O + (Light) gives off O2

Calvin Cycle (dark reactions)

uses ATP from the light reactions and CO2 from the hair to make sugar

Water Transportation Systems

• Apoplastic route

• Symplastic route

• Transmembrane route

Apoplastic route

• transports water within the cell wall or extracellular space (or through dead cells)

Symplastic Route

• transport water through cells via plasmodesmata

Transmembrane Route

• transport water through cells with repeated crossing of cell membranes

Plant Cells inside the roots

• symplast

  • plant cell and whats inside

• Apoplast

  • outside of the cell membrane including the cell wall

Xylem Sap

water in the xylem

how does water move up the xylem

transpiration (water leaves from the leaves with helps draw more water upwards to the leaves)

• cohesion and adhesion

Cohesion

• water molecules stick together inside the plant to form a long chain so that when one moves up they all move up

Adhesion

• water molecules adhere to the inside walls of the vessel to prevent from falling back down

Stoma - open and close

Open

• water can leave through the opening and more water is pulled up the xylem

closed

• not much upward drive of water

• conserves water to prevent dehydration

Translocation

transport of the products of photosynthesis (sugar)

• moves from sites of production to sites of use/storage through the phloem

Phloem sap

water and sugar mixture in the phloem

Seed Vascular Plants

Two Clades

• Gymnosperms

• Angiosperms

Seed

embryo and nutrients surrounded by a protective coat

Gymnosperms

• non-flowering plants that produce a seed without a protective covering or attractive features

  • conifers (spruce, firs, pines)

  • cycads

  • ginkgoes

Angiosperms

• flowering plants that produce seeds in fruit

  • allow the seeds to be more easily dispersed by animals that carry them around and eat them

• most diverse plants

• 2 Major Groups

  • Monocots

  • Eudicots

Cotyledon

embryonic leaves in seed-bearing plants

• first leaves to appear from a germinating seed

Monocots

• 1 cotyledon

• parallel veins

• scattered vascular tissue

• usually fibrous root system

• pollen grain with one opening

• floral organs usually in multiples of 3

Eudicots

• 2 cotyledons

• veins usually netlike

• vascular tissue usually arranged in a ring

• taproot system

• pollen grain with 3 openings

• floral organs usually in multiples of 4 or 5

Monocots - Examples

• orchid

• barley

• pygmy date palm

Eudicots - Examples

• snow pea

• dog rose

• pyrenean oak

Ovary

• develops into a fruit

Stigma

• has a sticky substance to attract and hold in the pollen with the sperm

Petals

• colourful and attractive to attract pollinators

• Modified leaves

• collectively called the corolla

• nectaries

Cross Pollination

• one plants pollen lands on the stigma of another plant and fertilize it

Self-fertilization

• pollen gets into the stigma of the same plant to fertilize itself

Sepals

• first set of leaves that protects the flowers

• modified leaves that help enclose and protect a flower bud before it opens

• collectively called the calyx

• form the outermost part of the flower

• may be photosynthetic

Stamens

• pollen producing reproductive organs

• each composed of a filament that holds up the anther

• pollen grains develop in the anther

Carpels

ovule-producing reproductive organs

• ovary

  • sac-like structure that contains one or more ovules where female gametes develop

• style

  • long, slender neck of carpel where the ovary is located

• Stigma

  • sticky moist tip which receives pollen