copyright © 2003 pearson education, inc. publishing as benjamin cummings plants
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
PLANTS
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Plants are multicellular photosynthetic eukaryotes
– They share many characteristics with green algae
– However, plants evolved unique features as they colonized land
What is a plant?
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
PLANTLEAFperformsphotosynthesis
CUTICLEreduces waterloss; STOMATAallow gas exchange
STEMsupports plant(and may performphotosynthesis)
Surrounding watersupports the alga
ALGA
WHOLE ALGAperformsphotosynthesis;absorbs water,CO2, andminerals fromthe water
HOLDFASTanchors the alga
ROOTSanchor plant;absorb water andminerals from the soil (aidedby mycorrhizalfungi)
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• Unlike algae, plants have vascular tissue
– It transports water and nutrients throughout the plant body
– It provides internal support
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Two main lineages arose early from ancestral plants
Plant diversity provides clues to the evolutionary history of the plant kingdom
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
PA
LE
OZ
OIC
Radiation offlowering plants
ME
SO
ZO
ICC
EN
OZ
OIC
Ch
aro
ph
yc
ea
ns
(a
gro
up
of
gre
en
alg
ae
)
Bry
op
hy
tes
(e
.g.,
mo
ss
es
)
Se
ed
les
s v
as
cu
lar
pla
nts
(e.g
., f
ern
s,
ho
rse
tail
s)
Gy
mn
os
pe
rms
(e.g
., c
on
ife
rs)
Ang
iosp
erm
s
First seed plants
Early vascular plants
Origin of plants
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• One lineage gave rise to bryophytes
– These are plants that lack vascular tissue
– Bryophytes include mosses, which grow in a low, spongy mat
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• Vascular plants are the other ancient lineage
• Ferns and seed plants were derived from early vascular plants and contain
– xylem and phloem
– well-developed roots
– rigid stems
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PARTS OF A VASCULAR PLANT
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• Ferns are seedless plants whose flagellated sperm require moisture to reach the egg
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• A major step in plant evolution was the appearance of seed plants
– Gymnosperms
– Angiosperms
• These vascular plants have pollen grains for transporting sperm
• They also protect their embryos in seeds
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• Gymnosperms, such as pines, are called naked seed plants
– This is because their seeds do not develop inside a protective chamber
• The seeds of angiosperms, flowering plants, develop in ovaries within fruits
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PLANT TISSUES
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• Angiosperms, or flowering plants, are the most familiar and diverse plants
• There are two main types of angiosperms
– Monocots include orchids, bamboos, palms, lilies, grains, and other grasses
– Dicots include shrubs, ornamental plants, most trees, and many food crops
The two main groups of angiosperms are the monocots and the dicots
PLANT STRUCTURE AND FUNCTION
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• Monocots and dicots differ in seed leaf number and in the structure of roots, stems, leaves, and flowers
SEED LEAVES LEAF VEINS STEMS FLOWERS ROOTS
MONOCOTS
Onecotyledon
Main veins usually parallel
Vascular bundles incomplex arrangement
Floral parts usuallyin multiples of three
Fibrousroot system
Twocotyledons
Main veins usually branched
Vascular bundles arranged in ring
Floral parts usually in multiples of four or five
Taprootusually present
DICOTS
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• Root system
– Provides anchorage
– Absorbs and transports minerals and water
– Stores food
• Root hairs increase the surface area for absorption
The plant body consists of roots and shoots
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• Shoot system
– Consists of stems, leaves, and flowers in angiosperms
– Stems are located above the ground and support the leaves and flowers
– Leaves are the main sites of photosynthesis in most plants
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PARTS OF A FLOWERING PLANT
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• The terminal bud is located at the tip of a stem – It is the growth point of the stem
• Axillary buds can give rise to branches
• In apical dominance, the terminal bud produces hormones that inhibit the growth of axillary buds
– This results in a taller plant that has greater exposure to light
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• Roots and stems are adapted for a variety of functions
– Storing food
– Asexual reproduction
– Protection
• Plant breeders have improved the yields of root crops by selecting varieties, such as the sugar beet plant, with very large taproots
Many plants have modified roots and shoots
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• Modified stems include
– runners, for asexual reproduction
– rhizomes, for plant growth and food storage
– tubers, for food storage in the form of starch
STRAWBERRYPLANT
POTATOPLANT
IRISPLANT
Runner
TuberTaproot
Rhizome
Rhizome
Root
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• Modified leaves include tendrils and spines– Tendrils help plants to climb
– Spines may protect the plant from plant-eating animals
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
NUTRITION
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ELEMENTS NEEDED IN PLANT NUTRITION
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
GROWTH REGULATION
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• Light is central to the life of a plant
• Photosynthesis is the most important chemical process on Earth
– It provides food for virtually all organisms
• Plant cells convert light into chemical signals that affect a plant’s life cycle
Life in the Sun
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• Light can influence the architecture of a plant– Plants that get adequate light are often
bushy, with deep green leaves
– Without enough light, plants become tall and spindly with small pale leaves
• Too much sunlight can damage a plant
– Chloroplasts and carotenoids help to prevent such damage
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• Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
AN OVERVIEW OF PHOTOSYNTHESIS
Carbondioxide
Water Glucose Oxygengas
PHOTOSYNTHESIS
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• Plants, some protists, and some bacteria are photosynthetic autotrophs
– They are the ultimate producers of food consumed by virtually all organisms
Autotrophs are the producers of the biosphere
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• On land, plants such as oak trees and cacti are the predominant producers
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• In aquatic environments, algae and photosynthetic bacteria are the main food producers
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• In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts
• A chloroplast contains:
– stroma, a fluid
– grana, stacks of thylakoids
• The thylakoids contain chlorophyll
– Chlorophyll is the green pigment that captures light for photosynthesis
Photosynthesis occurs in chloroplasts
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• The location and structure of chloroplasts
LEAF CROSS SECTION MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Intermembrane space
Outermembrane
Innermembrane
ThylakoidcompartmentThylakoidStroma
Granum
StromaGrana
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Are plants useful
to man?
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How are plants useful to man?
List the ways you use plants everyday.
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We eat plants for breakfast,
lunch and dinner.
What plants have you
eaten today?
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We use plants to make our clothing.
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We use plants to make medicines.
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We use plants to build furniture
and buildings.
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Plants are useful in
cleaning the air
we breathe.
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Man is very dependent on plants.
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