Transcript Seed Vascular Plants

Plants
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They are distinguished from algae because
they are embryophytes (plants with embryos)
Land plants have: (charophyceans don’t)
see p. 602-603.
- Apical meristems – found at the tips of
roots and shoots; a dividing region of
nondifferentiated cells.
- Alternation of generations - alternate
between adult haploid – gametophyte
and adult diploid - sporophyte
- Walled spores produced in sporangia
adult sporophyte has a structure called
sporangia which produces haploid spores
from a diploid sporocyte. Spores are
walled in sporopollenin.
- Multicellular gametangia that produce
gametes.
Female version: archegonia – produces
1 egg.
Male version: antheridia – produces
sperm, many are flagellated
- Multicellular, dependent embryos
Embryos develop inside the female parent,
receives nourishment from placental
transfer cells. Therefore, known as
embryophytes.
Also, many plants have a waxy cuticle to
prevent dessication (drying out) and pathogen
infection.
Many have special metabolic pathways to
produce secondary compounds to deter
predators,block uV light, etc.
Plant divisions
Nonvascular (a.k.a. Bryophytes)
- No extensive transport system
- Includes mosses, liverworts and
hornworts
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Nonvascular Plants (Bryophytes)– Mosses
- Many live in moist environments (b/c
no vascular tissue.
- mosses and liverworts have stomata
- sphagnum moss produces peat (partially
decayed organic matter)
- have rhizoids; long filaments of cells to
anchor the moss, no role in water or
mineral absorption, not made of tissue.
- Life cycle – see diagram on page 607
alternation of generations
(know all terms)
Vascular Plants (a.k.a. Tracheophytes)
- 2 groups:
Seedless Plants
- ferns
Seed Plants: embryos are packaged with
a supply of nutrients in a protective coat.
2 types:
Gymnosperms – “Naked seed plants,” no
chambers for a seed (mostly
conifers).
Angiosperms – “Flowering plants,” seeds
develop in ovaries/chambers. Ovary
originates as flowers and develop
into fruits.
Vascular Plants (Tracheophytes)
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Evolved in the early Carboniforous. Most
early plants (bryophytes and ferns) were
limited to moist environments by
swimming sperm.
All vascular plants have:
1. Life cycles with a dominant (large and
complex) sporophyte, gametophyte
is very reduced.
2. Roots that are present to anchor the
plant and absorb nutrients and water.
3. Transport using vascular tissues
known as xylem and phloem.
xylem – conducts most water and
minerals.
- includes tracheids (dead,
tube-shaped cells)
- cells are strengthened by
lignin (protein – allows them
to grow tall.)
phloem – living, sugar-conducting
cells arranged in tubes
- distribute sugars, amino
acids, and organic products.
4.Leaves are present to increase surface
area for photosynthesis.
2 main types of leaves:
Microphylls – small, spine-shaped
with a single vein
Megaphylls – highly branched, larger
have a vascular system
(p. 613)
There are also some spore-bearing
leaves called sporophylls.
microphyll
megaphyll
Seedless Vascular Plants
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Ferns! See fern life cycle on p. 611
(alternation of generations)
Seed Vascular Plants
- Have a microscopic gametophyte (that’s
so cute!) It stays inside the female
sporophyte for protection.
- Most plants have 2 kinds of spores (p. 620)
Megasporangia produces a megaspore
which develops into female gametophyte
Microsporangia produces a microspore
which develops into male gametophyte
-Have Ovules – (female) which consist of
megasporangium, a megaspore and
sporophyte tissue called integument.
-Have Pollen grains (male) – which develop
from microspores and contain the male
gametophyte protected by sporopollenin.
-Pollenation occurs when pollen is
transferred to the ovule. Pollen grains land,
germinate, and grow a pollen tube that
delivers the male gametophyte.
Most sperm are nonflagellated.
- The fertilized ovule will develop into a seed.
The seed contains: embryo, food and a
protective seed coating called the integument.
- The seed resists harsh environments by
lying dormant.
- Seeds increase dispersal rate for
offspring.
Gymnosperms: “naked seeds” (not in ovary)
-Many seeds are exposed on modified
leaves (usually from cones). Therefore,
they are known as conifers.
- Life cycle – see p. 624
Angiosperms (Phylum Anthophyta):
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“Flowering Plants”:
- Flowers are specialized for sexual reproduc.
- Pollination occurs with the help of wind (like
gymnosperms), insects, etc. (more directed.)
Flower Anatomy – see p. 625
sepals and petals – sepal protects flowers.
- petals attract pollinators.
stamens (microsporophylls) – produce
male microspores that make pollen
grains containing a male gametophyte.
parts: filament (stalk) and
anther (terminal sac, pollen is
produced there)
.
Carpels (megasporophylls) – make
megaspores that become
gametophytes.
Sometimes, 1 carpel or group of
carpels is called the pistil.
parts: stigma – sticky tip that receives
pollen.
style – leads to the ovary
ovary – at base of carpel, has
one or more ovules.
receptacle – attaches carpel
to stem.
Fruits – they are thick ovaries at maturity
(Ex: pea pod, see p. 626)
- they protect seeds and aid in dispersal
- pollination triggers a hormone change
that causes the ovary walls to thicken
and become pericarp.
- Fleshy pericarp: peaches, apples
- Dry pericarp: nuts, beans, grains
- Fruit ripening is stimulated by the
hormone ethylene.
Life Cycle of an Angiosperm – see p. 627
- Most species cross pollinate (p. 627)
- Double pollination occurs in most:
1. Diploid zygote is formed from
one fertilized egg.
The sporophyte embryo
develops with a rudimentary
root and one or two seed leaves.
(monocots – one, dicots – two p.631)
2. Second sperm fuses with 2 nuclei
in the central cell of the
(polar)
gametophyte. Forms an endosperm
with starch and amino acids for
nourishment.
- Angiosperm seed germination will begin
after moisture and temperature conditions
are ideal. This is triggered by hormones
called gibberellins.
-Root growth and stem elongation are
triggered by a hormone called auxins.
Chapter 36 – Transport in Plants – 3 Types 7
See p. 765
1.Individual Cell Transport of water and
solutes.
Proton Pumps – p. 769. Builds
up a membrane potential outside
of the cell (uses ATP). Cotransport
through chemiosmosis transports
substances back into the cell.
Ex: sugar (sucrose) loading from leaves
K+ in guard cells (look at diagram
of guard cells in book, p. 777), NO3from root cells
Root Hairs on a root cell help to increase
surface area.
Some plants have a symbiosis with a
fungus to form structures called
mycorrhizae (p. 767), which are fungal
Hyphae that help absorb water and
minerals.
2. Short Distance Transport between
several cells. (water and solute transport
at the tissue and organ level)
3 Pathways (p. 768)
1 – Can pass through each cell membrane
(through aquaporins and proteins)
2 – Pass through Symplast, which is a
cytosol continuum of plasmodesmata
3 – Pass through Apoplast, which is a
continuum of cell walls and
extracellular spaces (very direct route)
3. Long Distance Transport (xylem and phloem)
Xylem – unidirectional transport from
roots to leaves. P. 775
Increases water loss because of
transpiration through stomata (90%
is lost – can wilt if not replaced)
Xylem Loading – water and mineral
absorption pathway to xylem: p. 773
Epidermis (via root hairs)
↓
to cortex (made of ground tissue)
↓
to endodermis via symplast
(waxy Casparian Strip forces water
to go through a membrane to
prevent minerals and water from
leaking out.)
↓
To xylem
Xylem Transport:
- At night, roots pump minerals into the
xylem. This decreases the water
potential inside, forcing water to diffuse
in from the cortex. This generates
root pressure, an upward push of xylem
sap. If too much water flows in,
guttation results at the leaves.
- Transpiration results in an upward pull
from: adhesion, cohesion, surface
tension and negative pressure at
the water/air interface, negative
water potential at leaves.
Phloem: transfers organic nutrients
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known as translocation.
- In angiosperms, sucrose is transferred
from mesophyll cells to phloem by
specialized phloem cells called
seive-tube members.
- Phloem sap can be up to 30% sucrose.
(& some amino acids, minerals,
hormones)
- Direction of transport is variable, but is
always from a sugar source to a sugar
sink.
Source – organ that produces
sugar or breaks down starch
Sink – a net consumer or storer of
sugar (growing roots, buds,
stems and fruits)
Loading of Phloem – see p. 780
Mesophyll cells → symplast or apoplast
→ sometimes via companion cells
(with ingrowth of cell walls) known as
transfer cells → seive tube members
of phloem.
Loading into companion cells is usually
done through active transport via proton
pump and cotransport. (This is because
seive tube sucrose content is 2-3 times
higher than mesophyll.)
- Unloading of phloem is usually done through
diffusion at a sugar sink.
-Movement through phloem occurs through
pressure flow of sugar solution (p. 781)
Increased pressure builds up at the
source. Lower pressure is at the sink.
This causes the xylem water to diffuse
into the phloem and move from source
to sink and take sucrose with it
(rate is about 1m/hour.)
Ch. 35 – Plant Structure, Growth and Develop.
Growth:
Annuals – complete their life cycles
in 1 year or less
Biennials – live 2 years
Perennials – live many years (trees,
shrubs, some grasses)
Plant tissues:
Dermal (epidermis, endoderm)
- single layer of tightly packed cells
to cover and protect
Ex: root hairs, cuticle
Vascular (transport tissues)
Ground Tissue – bulk of plant tissue is
ground tissue which is found
between the dermis and vascular
tissues. Mostly made of
parenchyma cells. Functions in
photosynthesis, storage, support,
and metabolism.
Specialized Cells:
Parenchyma Cells – thin, flexible (no
secondary cell wall), most common
type, can divide for repair.
Found in: photosynthetic cells,
stems, roots, fruits, and usually
have plastids.
Collenchyma cells – grouped in strands,
help support young shoots.
No secondary cell wall (no lignin);
therefore, they can grow.
Ex: celery strings
Sclerenchyma Cells – supporting cells
with thick secondary cell walls with
lignin. Cannot elongate when
mature. Many are dead at
maturity (lose protoplasts.)
2 types:
sclereids – short and irregular
shaped, like in seed coats,
nut shells or pear grit.
fibers – fibers that are long, thin,
and tapered like hemp or
flax.
More Plant Growth:
Apical Meristems – tips of roots and
buds of shoots.
- Responsible for increase in
length, primary growth.
(lateral meristems help with
secondary growth, increase in
width: vascular tissue and cork
cambium)
See p. 747 (bottom) for apical meristem
Root cap – for protection
Zone of Division – includes root apical
meristem. New cells produced
here (mitotic division.)
Zone of Elongation – cells elongate,
push tip
Zone of Maturation – cells complete
differentiation and mature.
This produces epidermis, ground
tissue and vascular tissue.
Tissue organization of stems and roots:
(on your own) p. 750 and lab manual
(p. 106)
Tissue organization of leaves see p. 751
cuticle
upper epidermis
palisade meophyll (tighter)
spongy mesophyll – spread out
(increases gas exchange)
veins (xylem and phloem) covered with
bundle sheath cells for protection
lower epidermis
cuticle