Plants
multicellular, autotrophic eukaryotes
photosynthetic
thick cell walls made of cellulose
stem and leaves have waterproof coat = cuticle
Evolved 500 million years ago- no leaves
psilophytes
evolved from filamentous green algae
thallophyte (thallus) -n plant with no rools, stems or leaves (seaweed)
Adaptations
cuticle- prevents water loss
leaf cells carry out photosynthesis
roots- pull up water and food and anchor plant
stem- structural support, conduit from roots to leaves
green stems are photosynthetic
Nonvascular Plants (Bryophyta)
mosses and hornworts
no vascular tissue
tissue a few cell layers thick (water moves btw cells by osmosis)
Vascular Plants
have vascular tissue- tubelike cells - water/food move thru
can live away from water because of transport system
tissues can be thicker than nonvascular plants, can grow larger
Reproductive Strategies
Nonvascular plants require film of water for sperm to swim
thru to get to egg
Vascular Plants produce seeds- contain embryo, food, and
protective coat (protect from drying)
Alternation of Generations
All plant life cycles consist of 2 stages
Gametophyte generation- development of gametes (haploid)
Sporophyte generation- development of spores (diploid)
spores of nonvasc. plants released into environment,
grow into haploid gametes
Vascular plants - spores retained by parent
Seeds- reduced sporophyte plants in protective coat
Spores- male and female reproductive
male gametophyte develops inside pollen grain
female gametophyte develops inside ovule
Seed Plants
Conifers (Gymnosperms- no fruit)- needle or scale like leaves
Repro. structrure- cones (male and female)
Flowering Plants (angiosperms -fruit)- 2 divisions
Monocots- 1 seed leaf- grasses, orchids, lillies, palms
Dicots- 2 seed leaves
Deciduous plants- lose all leaves at same time (reduces
water loss)
Pollenation- pollen grain finds stamen (self and cross)
Fertilization- pollen grain fuses with ovule (does not req. water)
Plant Tissues
epidermis- covers all parts of plant, produces waxy layer
root hairs- extension of root dermal cells
absorb nutrient and water from soil
trichomes- "stem hairs," reduce evaporation, can produce toxins
stomata- openings in cuticle of leaf
allows and controls water loss and gas exchange
found on green stems and upper and lower surface of
leaves (fewer on upper)
guard cells- control opening and closing of stomata
Vascular tissues
Xylem: transports water and minerals from the roots up
cells usually dead at maturity
capillary action
Phloem: transports sugars
living tubular cells
Meristematic cells
regions of actively dividing cells- "growth areas"
Apical- growth at tips of roots and stems
Lateral- increases diameter of plant
Structure of Plants
Seeds:
Advantage- food supply for embryo
protection from harsh conditions
Germination- seed begins to grow into a plant
Cotyledon- tiny leaves in embryo
store or absorb food
often first leaves to emerge
Radicle- first part to grow
embryonic root grows down
Hypocotyl- portions of stem nearest the seed
brings out cotyledons and plants first leaves
Epicotyl- stem that grows from hypocotyl
Flowers:
petals- bright colored, perfumed to attract pollinators
gametes: sperm (pollen) and egg (ovule)
fruit- ripened ovary of flower
pistil- female sex organs
stigma- at top of pistil
sticky for pollen grains to land
style- stalk that connects stigma to ovary
ovary- contains ovules (when fert., becomes seeds)
becomes fruit
stamen- male sex organs
anther- produces pollen
filament- connects anther to flower
sepals- outermost portion of flower
protective coating for flower bud
Leaves:
primary function to trap light
contain vascular tissues (located in veins that run thru
mesophyll)
mesophyll- under epidermis, photosynthetic tissue
transpiration- loss of water thru stomata (90% loss)
translocation- movement of sugars from leaves thru phloem
3 types: simple, complex (leaflets), needles
petiole- stalk that joins leaf to stem
Roots:
underground
anchor plant
absorb water and nutrients
"sink"- any place that stores sugars
2 types- according to needs
taproot- central and fleshy
smaller branching roots
fibrous- numerous roots branching from central pt.
Life Spans of Anthophyta (flowering plants)
1. Annuals- live 1 year or less
nor woody
drought resistant seeds survive winter
2. Biennials- live 2 years, in winter, above ground dies
large storage roots- carrots, beets
3. Perennials- live several years, seeds and flowers periodically
Plant responses
Hormones: chem produced in one part of an organism and
transported to another part to cause a physiological change
Auxins: promote cell elongation
Indolacetic acid: increases rate of cell division
produced in apical meristem
weakens connective tissue between cellulose
fibers in cell wall
Auxins produced in apical meristem prevent growth of side
branches
high [auxin]= fruit formation and prevents dropping fruit
Gibberellins- "grow tall"- stimulates cell elongation
increased seed germination and bud development
Cytokinins- stimulate cell division/ cytokinesis
increase protein prodution
produced in root meristems
Ethylene Gas- increases fruit ripening
weakens cells walls and stimulates starch => sugar
Tropic Responses
Tropism: plants response to external stimulus that comes from
defined direction
positive- plant grows toward
negative- plant grows away
Not reversible, but if direction of stimulus changes, so will
direction of plant growth
Phototropism: growth toward light
unequal distribution of auxin in stem
more in side away from light, so more cells grow on
that side - plant bends toward light
Gravitropism: direction of plant growth due to gravity
Thigmotropism growth response to touch (vines wind)
Nastic Response: not dependent on direction of stimulus
reversible
Venus fly-trap
Photoperiodism- response of flowering plants to difference in
the duration of lght and dark periods in day
period of dark controls flowering
3 types: long day, short day, day neutral
