Plants
Biology 112
Kingdom Plantae
 Multicellular
eukaryotes that have cell walls
made of cellulose
 Develop from multicellular embryos and carry
out photosynthesis using chlorophyll a and b
 All are autotrophs but a few live parasitically
or as saprobes
Plant Reproduction
 There

are two alternating phases
Sporophytes are spore producing plants
 Diploid
phase
 Produced using meiosis

Gametophytes produce gametes
 Haploid
phase
 Produced by mitosis
 Occurs after the spores have been produced
What plants need to survive
 Sunlight

photosynthesis
 Water

All of their cells require both
 Gas

and minerals
exchange
Plants require oxygen for respiration as well
as carbon dioxide for photosynthesis
 Movement

of water and nutrients
Taken up by their roots but make food in
their leaves
Early Plants
 The
appearance of plants created a lot
of change to terrestrial environments
 As a result, other organisms were able to
develop
 They began in the water, most likely
evolving from a multi-cellular like organism
similar to algae
 plants colonized land before animals did
 Many biologists believe plants coevolved
with fungi
First Plants
 Algae
are a plant’s evolutionary ancestor
 Share many similarities



Contain chlorophyll
Cell wall composition
DNA sequencing
 Earliest
plants were similar to today’s
mosses
 Dependent on water or at least a moist
environment
Overview of the Plant
Kingdom
 Three
features dictate the structural
arrangement of plants



Water conducting tissues
Seeds
Flowers
 There
are four major groups: conebearing, ferns, mosses and flowering
plants
Bryophytes (Mosses and
relatives)
 Also
called non-vascular plants because
they do not have vascular tissue
(conducts water and other nutrients)
 Depend on water for reproduction
 Draw up water by osmosis which keeps
them low to the ground
 Produce sperm that must swim to reach
the egg – therefore water is required
Mosses
 Moist
environments
 Soil may lack
nutrients
 Can tolerate low
temperatures
 Contain a thin
shoot with small
leaves
 They have rhizoids
instead of roots
Liverworts
 Flat
leaves
attached to the
ground
 Some are in the
shape of a liver
 Reproductive
structures called
gemmae – cup-like
structures
Hornworts
 Instead
of
gammae,
hornworts produce
a reproductive
structure that looks
like a horn
Life Cycle of Bryophytes
 The
gametophyte is the dominant,
recognizable stage of the life cycle that
carries out the plant’s photosynthesis
 The sporophyte is the reproductive
structure
 A spore develops into a protonema and
then develops rhizoids
 Some plants produce both male and
female on a single plant
Human Use of Mosses
 Sphagnum
moss is a group of mosses that
grow in acidic environments
 Acts as a natural sponge
 Large deposits can turn into peat, which
can be used as a fuel
 Added to soil to increase its ability to
absorb water
 Also increases a soil’s acidity