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
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