Download Plant Anatomy and Physiology

Plant Anatomy and Physiology
Chapters 24-28
I.
Plant Kingdom Major Characteristics
(Chap. 24)
A. Photosynthetic (Autotrophic) –
make their own “food” molecules
through photosynthesis
1. CO2 + H2O + light 
C6H12O2 + O2
2. other requirements: plant
nutrients (NO3, PO4, SO4, etc),
pigments to capture sunlight, and
enzymes
3. chloroplast – site of
photosynthesis
a. thylakoids with grana –
contain plant pigments,
stroma – chemical soup,
contain their own DNA, can
replicate inside a plant cell
4. pigments: chlorophyll a– main
light trapping pigment (b, c);
other accessory pigments trap
light of different wavelengths
and also protect chlorophyll
from harmful light intensities
B.
Cellulose cell walls
C. Eukaryotes – cells contain a
nucleus with many other membrane
bound organelles
D. Specialized organs (root, stem,
leaf) and tissues (dermal – epidermis;
vascular – xylem – conducts water
and minerals and phloem – conducts
food/sugars and water; ground –
parenchyma, fills organs; and
meristematic – cell division and
growth)
E.
Complex life cycles consist of two
phases: sporophyte (diploid – 2N) –
produces spores; gametophyte
(haploid – N), produces gametes.
F.
Reproduce with seeds
(multicellular with embryo, seed coat,
and food – endosperm) and spores
(unicellular)
II. Vascular plants (conducting cells)
versus non-vascular plants (do not
contain specialized conducting cells)
A. Phyla or divisions
1. Non-vascular: Bryophyta –
mosses, Hepatophyta –
liverworts: both reproduce with
spores
2. Vascular but spore producing:
Lycophyta – club mosses,
Sphenophyta – scouring rushes
or horsetails, Pterophyta – ferns
3. Vascular (seed producing) with
cones: Coniferophyta
(Gymnosperms) – conifers
(redwoods, spruce, pine,
junipers); Cycadophyta – cycads
(more abundant in prehistoric
forests); Gnetophyta, and
Ginkgophyta - ginkgos
4. Vascular (seed producing) with
flowers: Anthophyta
(angiosperms) – Monocots vs
Dicots
B.
Life Cycle of a Moss –
gametophyte generation is dominant,
sporophyte grows on top of
gametophyte
1. simplest land plants
2. grow near water
3. very small (2-5 cm)
4. flagellated sperm
C. Life Cycle of a Fern – sporophyte
and gametophyte are two distinct,
separate plants; sporophyte is the
larger and dominant generation
1. vascular – do have xylem and
phloem
2. underground, horizontal stems –
rhizomes
3. flagellated sperm
D. Life Cycle of a Pine – sporophyte
is clearly dominant, gametophyte is
greatly reduced - formed from the
megasporangium and megaspore –
female gametophyte, and
microsporangium and microspores –
male gametophyte (pollen)
1. seeds are “naked”
(gymnosperms) and not enclosed
in a “fruit”
2. seeds are formed in cones (male
and female)
3. needles are “leaves”
4. grow in harsh (cold)
environments, poor soils
5. evergreen or non-deciduous – do
not lose their leaves in the winter
6. double fertilization occurs
7. generally wind pollinated
8. sperm nuclei in pollen grains
E.
Life Cycle of a Flowering Plant –
most and diverse of all plant groups;
sporophyte is clearly dominant,
gametophyte is greatly reduced –
formed from the megasporangium
and megaspore – female gametophyte,
and the microsporangium and
microspores – male gametophyte
(pollen)
1. seeds are enclosed in a “fruit”
that forms from the ovary
2. many are deciduous – lose leaves
in the winter and become
“dormant”
3. insect pollinated
4. monocots and eudicots are the
two major subgroups
a. monocots – one cotyledon or
seed leaf, parallel veins in
leaves, flower parts in 3’s or
multiples of 3’s, scattered
vascular bundles in stem,
usually herbaceous (nonwoody), fibrous root system
with xylem and phloem in a
ring
b.eudicots – two cotyledons or
seed leaves, branching or
palmate veins in leaves, flower
parts in 4’s or 5’s or multiples,
vascular bundles in a ring in
stem, herbaceous or woody,
tap root system with phloem
in between xylem arms – star
shaped
5. sperm nuclei in pollen grains
6. double fertilization
F.
Adaptations of plants to a
terrestrial environment
1. obtaining water and minerals –
roots and symbiotic fungi
(mycorrhizae)
2. transport of water and minerals
– xylem and phloem
3. preventing evaporation of water
– waxy cuticle
4. obtaining gases for
photosynthesis – stomata
5. obtaining sunlight for
photosynthesis - leaves
6. supporting body for upright
growth – xylem filled with lignin
(wood)
7. growth and responses to
environmental changes –
hormones
8. reproduction – gametophyte is
protected and freed from
dependence on water, sperm
found in pollen grains
9. dispersal – wind, insects, and
other animals distribute pollen
and seeds
III. Plant Organs and Tissues (Chap 25-26)
A. Root – absorbs water and
minerals – transports them to the
stem and leaves; stores starch;
attachment/anchoring in the soil
1. root hairs increase surface area
for absorption
2. layers: epidermis, cortex,
endodermis with Casparian
strip, pericycle, xylem and
phloem
a. xylem – conducts water and
minerals; 2 types of cells –
tracheids (smaller with
slanted end walls with pores)
and vessel elements (larger in
diameter with perforation
plates); both types are hollow
and non-living when
functional
b.phloem – conducts sugars and
water from leaves down the
stem and into the roots; 3
types of cells – sieve tube
members (contain cytoplasm
but no nucleus) and
companion cells (contain a
nucleus and are directly
connected to sieve tube
members)
B.
Stem – support, transport, food
production (photosynthesis), and gas
exchange
1. layers: epidermis, cortex,
vascular bundles of xylem and
phloem
2. growth: vascular cambium and
cork cambium – produce
secondary growth – widening of
stem (lateral meristems)
3. primary growth – all roots and
stems lengthen from a growing
tip or apical meristem region
C. Leaves – food production
(photosynthesis) and gas exchange
through stomata
1. layers: upper and lower
epidermis, mesophyll – palisade
and spongy layers with air
spaces, vascular bundles
2. stomata with “guard cells” for
gas exchange – mechanism of
opening/closing involves changes
in osmotic pressure
3. how are water and minerals
transported up from the roots,
through the stem and into the
leaves? - transpirational pull
and negative pressure, root
pressure – positive, and capillary
action (adhesion and cohesion)
4. how are sugars and water
transported downward from the
leaf? - mass flow or bulk flow
with sink
D. Seed – multicellular reproductive
structure produced by flowering
plants (Anthophyta) and cone bearing
plants (Coniferophyta)
1. embryo
2. food (endosperm)
3. seed coat
IV. Plant regulation and responses –
Chapter 27 - HORMONES
A. auxin
1. source: young tissues – shoot
apical meristem, young leaves,
coleoptile tip, developing fruits
and seeds
2. actions: meristem growth –
apical dominance, cell division
and enlargement, gravitropism,
positive phototropism, root
formation, xylem differentiation
B.
cytokinins
1. source: roots
2. actions: cell division, growth,
release of lateral buds from
auxin inhibition, inhibition of
dormancy, inhibition of
senescence
C.
D.
E.
F.
gibberellins
1. source: embryo, young leaves,
buds, upper stem
2. actions: leaf growth, phloem
differentiation, stem elongation,
pollen tube growth, inhibition of
root formation, stimulation of
auxin production, stimulation of
fruit development, seed
germination, release of buds
from dormancy
abscisic acid
1. source: mature leaves and roots
2. actions: dormancy in seeds,
initiation of senescence, reactions
to stress, opening/closing of
stomata
ethylene
1. source: meristems, ripening
fruits, wounded or senescing
tissue (unique – gaseous state)
2. actions: ripening and abscission
of fruit, seed germination and
growth, counteracts auxin
Plant responses
1. gravitropism – roots grown down
(positive) and stems grow up
(negative): auxin (inhibits root
cell growth and promotes stem
cell growth); statoliths “settle”
to the bottom of cells
2. phototropism (positive) – stems
grow towards light: auxin and
cell growth/elongation
3. thigmotropism – (curling and
wrapping around objects –
“touch”: cells on contact side
grow less than those on opposite
side
4. Nastic movements result from
touch, shaking, or thermal
stimulation: examples – closing
of leaves of the “sensitive plant”
and “pitcher plant” are due to
ion transport out of specific cells
(pulvinus and/or trichomes – act
as triggers to receive the
stimulus), changes in osmotic
potential of leaf cells  leaf
closes or folds.
5. flowering and photoperiodism
(response to changes in the
length of daylight) involve a
change in the relative amounts of
two variation of phytochrome
pigments
a. Pr (phytochrome red) absorbs
red light and is converted to
Pfr
b.Pfr (phytochrome far red)
absorbs far red light and is
converted to Pr
c. Direct sunlight contains more
red light, darkness contains
more far red light
d.Day  more Pfr present;
Night  more Pr present
e. Plants respond to changes in
the relative amounts of these
two pigments
f. Short day plants flower when
the day length is shorter than
a certain critical time period –
respond to an uninterrupted
period of darkness that is
longer than a certain length
(cocklebur – 8.5 hours of
darkness)
Long day plants flower when
the day length is longer than a
critical period – respond to an
period of darkness shorter
than a certain minimum
(clover and spinach)
Day neutral plants flower at a
certain stage in their life cycle
regardless of the photoperiod