Chapters 22-25

Plants

Characteristics

Eukaryotes Multicellular Cell walls of cellulose Carry out photosynthesis using pigments

chlorophyll a and b Life cycle

Gametophyte (1N) > gametes (1N) > fertilization > zygote > sporophyte (2N) > meiosis > spores (1N) > mitosis > gametophyte

Evolved from green algae

3 Types of Tissues Dermal tissue – outer covering

In leaves covered by cuticle – waxy layer Vascular tissue – conducts nutrients through plant

Xylem – conducts water Composed of dead cells called tracheids and vessel

elements that act as pipes. Phloem – conducts food

Composed of sieve tube elements – contain openings to allow sugars through

Also, companion cells – surround for support Ground tissue – btw others

Parenchyma – site of most photosynthesis Collenchyma – flexible walls, help support – celery Sclerenchyma – thick, rigid, strong

Structure I Roots – underground organs that absorb

water and minerals, anchors, prevents erosion 2 types

Taproot – 1 main root – carrots Fibrous roots – many similar

branches Structure

Epidermis – outer layer Covered in root hairs – increase

surface area for absorption Cortex – middle – ground tissue Endodermis – inner

Aka vascular cylinder Contains xylem & phloem

Root cap – covers apical meristem

Structure II Leaves – bundles of photosynthetic

vascular tissue Structure

Blades – flattened section Petiole – attaches to stem Specialized ground tissue

Palisade mesophyll – absorbs light Spongy mesophyll – connects to the outside via

stomata (openings) to allow carbon dioxide in and oxygen out

Guard cells – control opening/closing of stomata Functions

Photosynthesis Transpiration – loss of water through leaves Gas exchange

Structure III Stem

3 functions Produce leaves, branches, & flowers Hold leaves up to sunlight Transport substances between roots and leaves

Structure Nodes – where leaves attach Internode – region btw nodes Buds – at nodes – tissue that can produce new

stems and leaves Primary growth – occurs in meristematic tissue at the

apical meristem – increase in length Secondary growth – increase in width

Occurs in lateral meristematic tissue – vascular cambium & cork cambium

Classification I

Bryophytes 3 phyla Vascular tissue absent – results in small size Flagellated sperm - must stay close to water No true roots or leaves Gametophyte - dominant life cycle Ex. Mosses, liverworts, hornworts

Classification II Pteridophytes

2 phyla Vascular tissue

present Appearance of true

roots & leaves Sporophyte – now

the dominant life cycle

Ex. Ferns, club mosses, horsetails

Classification III Gymnosperms

Appearance of seeds (embryo of a plant encased in a protective covering with a food supply) which are produced in cones - plants were able to reproduce without water Male gametophyte – pollen

Ex. Gnetophytes, Cycads, Ginkgoes

Conifers – pine, juniper, spruce Aka evergreens

Classification IV Angiosperms

Aka flowering plants Cotyledons – embryonic seed leaves

Monocots – 1 seed leaf, parallel veins Vascular bundles in stem are scattered

Dicots – 2 seed leaves, branched veins Vascular bundles in stem are arranged in a ring

May be subdivided based on stem characteristics Woody or Herbaceous

Life spans Annuals - complete a life cycle 1 year Biennials - complete a life cycle in 2 years Perennials - live for more than 2 years

Alternation of Generations

Gametophyte (1N) > gametes (1N) > fertilization > zygote (2N) > sporophyte (2N) > meiosis > spores (1N) > gametophyte

Gymnosperms Gametophytes are found in cones

Pollen cones – maleOvulate cones – female

Pollen is carried by wind from male to female

Alternation of Generations Angiosperms

Gametophytes are found in flowers Structure

Sepals - outermost petals – green – enclose bud before opening Petals - brightly colored – attract pollinators Stamen

Filament - thin stalk Anther - produce male gametophytes (pollen)

Pistil Aka carpel Stigma - top – sticky Style – stalk Ovary - contains female gametophytes – becomes fruit

Life cycle – Double Fertilization Pollen sticks to stigma Pollen tube forms and grows down style to ovary 1 sperm fertilizes egg = embryo A 2nd sperm joins with other cells to form the endosperm (food supply)

Angiosperm life cycle

Flowers

Sepal Petals Stamen

Anther Filament

Carpel Stigma Style Ovary

Pollination

Seed Dispersal

May be dispersed by wind, water, or animals

May remain dormant until conditions are right

Germination – early stage of growth

Plant Hormones Hormone – chemical substance that control’s a plants

growth, development, and responses Target cell – part affected by a particular hormone Auxins cause:

Phototropism – growth toward light Gravitropism – causes branches to grow up and

roots to grow down Apical dominance - delays the appearance of new

lateral buds (which grow into side branches) Cytokinins - stimulate cell division, growth of lateral

buds, and sprouting Gibbreellins - promotes overall growth Ethylene - stimulates fruits to ripen

Plant responses Tropisms – response to an external stiumulus Types

Gravitropism - response to gravity Phototropism - response to light Thigmotropism – slower changes in growth

in response to touch Vines

Rapid responses – quick movement in response to touch Mimosa, venus fly trap

Photoperiodism Timing of seasonal activities Phytochrome - pigment responsible Short-day plants - flower when days are

short Ex. Poinsettias

Long-day plants - flower when days are long

Dormancy - period when growth/activity decrease or stop Usually during winter for deciduous plants