Chapter 27, pages 552-555
Basic Botany-3 0:00-9:52
Five Kingdoms-5 0:00-7:51
I. Characteristics of the Kingdom Plantae
A. Adapted for land habitation in every conceivable habitat all over the earth
B. Plants vary in size from the size of a pinhead to the giant sequoia tree of California
C. Plants are multicellular
1. Plants show division of labor among their cells
a. Chlorophyll a and b
b. Xanthophylls - yellow
c. Carotene - orange
3. Cuticle covers the aerial parts to prevent dehydration
4. Stomata are found in the epidermis of the aerial plant parts for gas exchange
a. CO2 for trapping energy and carbon fixation into sugar
b. O2 for releasing energy
a. Gametangium
(1) General name for a sex organ
(2) Contains a sterile layer of cells that surrounds the gametes and protects them
b. Archegonium
(1) Female gametangium
(2) Produces a single egg
c. Antheridium
(1) Male gametangium
(2) Produces many sperm
6. Development of the zygote
a. Egg is fertilized within the archegonium
b. The zygote develops into a multicellular embryo within the archegonium
c. The embryo develops and differentiates further into a mature plant
II. Division Bryophyta
A. Characteristics
1. Terrestrial
2. Thallus
a. Filamentous in only one part of the life cycle of mosses
b. Blocks or sheets of parenchyma tissue in the liverworts and hornworts
3. Asexual reproduction
a. Fragmentation by the dichotomous habit
b. Gemmae
4. Sexual reproduction
a. Gametophyte
(1) The visible and vegetative generation of the bryophytes
(2) Because the sperms must swim through water to
fertilize
the egg,
bulk
water is necessary for fertilization to
occur
b. Sporophyte
(1) Grows out of and attached to the venter of the archegonium
(2) Gets all its nourishment from the parent gametophyte plant
(3) Sometimes it is necessary to use a microscope to
see this generation in
some species
5. No true roots, stems, leaves, or flowers
B. Classification
1. Class Hepaticae - liverworts
2. Class Anthocerotae - hornworts
C. Class Hepaticae
1. Characteristics
a. Least specialized of the bryophytes
b. 8,500 species in this class world wide
c. Habitat - in moist and shady places
d. Thallus
(1) Flat and ribbon-like sheet of parenchymatous tissue
(2) Air chambers with a pore at the top occur in the upper part of the thallus
(3) Rhizoids
(a) Root-like structures on the lower side of the thallus
(b) Each rhizoid is a single protoplasmic extension of the epidermis
(4)
Scales
(filaments
of several cells) are frequently encountered on the lower
surface of the leaf
e. Sporophyte plant grows attached to and covered by gametophyte tissue
2. Marchantia as an example
a. Gametophyte
(1) Thallus
(a) The thallus forms large
mats of plants on moist rocks and soil in damp
shady
spots
(b) The upper part of the
thallus contains an
air
chamber with a
pore
at
the top
(c) The lower part of the
thallus contains
scales
and
rhizoids
on the
surface
i) The scales are filamentous and multicellular
ii) The rhizoids are protoplasmic extensions of the epidermal cells
(2) Asexual reproduction in GAMETOPHYTE ONLY
(b) Gemmae cups
(3) Sexual reproduction
(a) Plants dioecious
(b) Antheridia
i) Borne on discs called antheridial heads
ii) Antheridial
head raised on a
stalk
above the thallus called an
antheridiophore
(c) Archegonia
i) Borne on an 8-lobed disc called an archegonial head
ii) Archegonial head raised on a stalk called an archegoniophore
iii) Structure of the archegonium
a) Venter
b) Egg
c) Neck
e) Neck canal
(d) Opening of neck canal
i) Egg matures
ii) Cover cells separate
iii)
Portions of the cells in the center of the neck dissolve to form the
neck canal
(e) Fertilization
i)
Antheridia
split open and release the sperm in a jelly-like mass
when there is plenty of free water for the sperm to swim in
ii) Sperm
swim through the film of water on the surface of the
thallus
and other objects toward the
archegonium
and egg by a
chemotactic response
b. Sporophyte
(1) Zygote forms when the egg and sperm unite in the venter
(2) Zygote divides by mitosis to form an embryo
(3) The embryo continues to divide by mitosis and differentiate into the:
(a) Foot
(b) Seta
(c) Capsule or Sporangium
(d) Calyptra
(4) Structure of the sporangium
(a) Outer sterile layer
(b) Inner sporogenous region
i) Elater cells
ii) Sporogenous cells
a)
Diploid
spore mother cells divide by
meiosis
to form a
tetrad
of tetraspores
b) Each tetraspore is haploid
c) Each tetrad breaks up into separate spores
(5) When the spores are fully mature, the
capsule
and
calyptra
breaks open
and releases the spores.
Dispersal
of the spores is aided by the
elaters.
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