Plants - Home - Dr B M Salameh

Report
Plants
The Kingdom
Plantae
Common characteristics
1. Multicellular
2. Eukaryotic
3. Photoautotrophic
First: Some terms to know
• Gametophyte: a multi-celled haploid body
(stage) that produces haploid (n) gametes.
• Zygote: a diploid body formed when gametes
fuse at fertilization.
• Sporophyte: a multi-celled diploid (2n) body
that grows by mitosis from a zygote, produces
spore-bearing structures.
• Spores: resting structures, able to survive
harsh conditions, germinate to form
gametophytes.
Adaptations to Land
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Root systems
Shoot systems
Vascular tissues
Waxy cuticle for water
conservation
Properties of Plants
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Photosynthetic
Plant cells have a cell wall (cellulose)
Organs: roots, stems, leaves
Sessile: non-mobile, stay in one place
Indeterminate growth
Life cycle:
Gametophyte
Sporophyte
Milestones in Plant Evolution
charophytes
bryophytes lycophytes
horsetails ferns
cycads ginkgos conifers gnetophytes flowering plants
seed plants
plants with true leaves
vascular plants
land plants
(closely related groups)
The Non-Vascular Plants:
Bryophytes
• Small, nonvascular, non-woody
• Gametophyte dominates life cycle;
has leaf-like, stem-like, and rootlike parts
• Usually live in wet habitats
• Flagellated sperm require water to
reach eggs
Moss Life Cycle
Development of
mature
sporophyte (still
attached to
gametophyte)
Zygote
Fertilization
Diploid Stage
Meiosis
Haploid Stage
Spores
released
male
gametophyte
tip
Sperm
Egg
Male gametophyte
female
gametophyte
tip
Female gametophyte
Vascular Plants
• Majority of plants
• Have internal tissues that carry water
and solutes (Xylem and Phloem)
• Two groups
– Seedless vascular plants
– Seed-bearing vascular plants
Seedless Vascular Plants
• Produce spores but no seeds
• Main groups:
Lycophytes
Horsetails
Ferns
Life Cycle of a Fern
Seedless Vascular Plants
• Like bryophytes:
– Live in wet, humid places
– Require water for fertilization
• Unlike bryophytes:
– Sporophyte is free-living and
has vascular tissues
Rise of Seed-Bearing Plants
• Seeds appeared about 360 million
years ago
• Seed ferns and gymnosperms were
dominant at first
• Angiosperms arose later
Pollen
• Pollen grains are sperm-bearing male
gametophytes that develop from
microspores
• Allows transfer of sperm to egg without
water
• Can drift on air currents, or be carried
by pollinators
Seeds
• Ovules are female reproductive
structures that become seeds
• Consist of:
– Female gametophyte with egg cell
– Nutrient-rich tissue (endosperm)
– Jacket of cell layers that will form
seed coat
Seed-Bearing Vascular Plants
• Gymnosperms arose first
– Conifers
– Others…
• Angiosperms arose later
– Monocots
– Dicots
Special Traits of
Seed-Bearing Plants
• Pollen grains
– Arise from microspores
– Develop into male gametophytes
– Can be transported without water
• Seeds
– Megaspores inside ovules
– Embryo sporophyte inside nutritive tissues
and a protective coat
– Can withstand hostile conditions
Gymnosperms
• Plants with “naked seeds”
• Seeds don’t form inside an ovary
• Four groups
Conifers
Ginkgos
Cycads
Gnetophytes
Conifer Characteristics
• Widest known, largest number of living
species
• Woody trees or shrubs
• Most are evergreen
• Bear seeds on exposed cone scales
• Most produce woody cones
Pine Cones
• Woody scales of a “pine cone” are the
parts of where megaspores formed
and developed into female
gametophytes
• Male cones, where microspores and
pollen are produced, are not woody
Pine Cones
Male and
female cones
Pine
Life
Cycle
Female cone
Sporophyte
(Pine Tree)
Ovule
Male cone
Seed
Pollen sac
Fertilization
Egg
Pollen tube
View inside
ovule
Meiosis
Microspores
Megaspores
Angiosperms
• Flowering plants
• Defining feature: Ovules and (after
fertilization) seeds are enclosed in an
ovary
• Two classes: Monocots and Dicots
Flower
Parts
Pollination by animals
Life Cycle of Angiosperms
Vascular Tissues
Xylem = absorbs water and
nutrients up through the roots
- movement only in the upward
direction
Phloem = distributes sugars,
amino acids, & organic nutrients
- movement is multi-directional
Monocots vs. Dicots
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Monocots
1 cotyledon
Parallel veins
Fibrous root
Flower parts in 3’s
Stem organization:
- Scattered bundles
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Dicots
2 cotyledons
Net-like veins
Tap root
Flower parts in 4’s / 5’s
Stem organization:
- Bundles in a ring
Monocots vs. Dicots
Monocots vs. Dicots
A Fungus is Not a Plant
There are many significant differences between fungi
and plants, including
– fungi are hetertrophs
– fungi have filamentous bodies (Hyphae, Mycelium)
– fungi have nonmotile sperm
– fungi have cell walls made of chitin
– fungi have nuclear mitosis
Many fungi produce spores.

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