Transcript Plant Structure, Growth & Reproduction

Kingdom PLANTAE
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Multi-celled /
eukaryotic
Autotrophic /
chloroplast
Cell wall - cellulose
Kingdom PLANTAE
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Plant Evolution
Plants: Alternation of
Generation
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Gametophyte (n): Haploid, produces
eggs and sperms which then unite to
form sporophyte
Sporophyte (2n): Diploid which goes
through meiosis to produce spores
which grow into gametophytes
Plants: Alternation of
Generation
Plants: Alternation of
Generation - MOSSES
Plants: Alternation of
Generation - FERNS
Plants: Flowers Alternation of
Generation
Plants: Flowers
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Most plants are
angiosperms,
flowering plants
Angiosperm
seeds protected
and dispersed
in fruits, which
develop from
ovaries
Plants: Flowering Plants
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Angiosperms, or flowering plants, are
most familiar and diverse plants
Two main types of angiosperms
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Monocots: orchids, bamboos, palms, lilies,
grains, and other grasses
Dicots: shrubs, ornamental plants, most
trees, and many food crops
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Comparison between dicot and monocot
seeds
Seed coat
Embryonic
shoot
Embryonic
leaves
Embryonic
root
Cotyledons
COMMON BEAN (DICOT)
Fruit tissue
Cotyledon
Seed coat
Endosperm
CORN (MONOCOT)
Embryonic
leaf
Embryonic
shoot
Sheath
Embryonic
root
Figure 31.11B
Plants: Monocots vs Dicots
Plants: Flowering Plant
Reproduction
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The angiosperm
flower is a
reproductive
shoot consisting
of
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sepals
petals
stamen
carpels
Anther
Carpel
Stigma
Ovary
Stamen
Ovule
Sepal
Petal
Figure 31.9A
Plants:
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Stamens - male reproductive organs
of plants
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Pollen grains develop in anthers, at the tips
of stamens
Carpels - female reproductive organs
of plants
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Ovary at the base of the carpel has ovule
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Life cycle of angiosperm involves several
stages
Ovary, containing
ovule
Embryo
Fruit,
containing seed
Seed
Mature plant with
flowers, where
fertilization occurs
Seedling
Germinating seed
Figure 31.9B
Figure 31.10
Plants: The ovule develops
into a seed
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After fertilization, ovule becomes seed
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Fertilized egg inside seed - embryo
Other fertilized cell - endosperm, stores
food for the embryo
Resistant seed coat protects the embryo
and endosperm
Triploid cell
OVULE
Zygote
Two cells
Cotyledons
Endosperm
Seed coat
Shoot
Embryo
Root
SEED
Figure 31.11A
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Seed dormancy is an important evolutionary
adaptation in which growth and
development are suspended temporarily
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It allows time for a plant to disperse its seeds
It increases the chance that a new generation
of plants will begin growing only when
environmental conditions favor survival
Plant: Asexual Reproduction
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Asexual reproduction:
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Bulbs: parts of root split and form new
bulb (ex. tulip)
Tubers: modified underground stem have
buds (ex. potato)
Runners: plant stem run above ground (ex.
Strawberry)
Rhizomes: woody underground stem (ex.
Iris)
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Modified stems
include
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runners, asexual
reproduction
rhizomes, plant
growth and food
storage
tubers, food
storage as starch
STRAWBERRY
PLANT
Runner
POTATO
PLANT
Rhizome
IRIS
PLANT
Rhizome
Tuber
Taproot
Root
Figure 31.4B
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Asexual runners
Figure 31.14D
Plant: Asexual Reproduction
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Vegetative propagation: cuttings or bits of
tissue increase agricultural productivity
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But it can also reduce genetic diversity
Cutting: cut stem form roots
Layering: bent stem touching ground form
roots
Grafting: stock of one grafted on stem (scion)
of another
Plants: Shoot and Root System
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Root system
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Provides anchorage
Absorbs and transports
minerals and water
Stores food
Shoot system
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Consists of stems,
leaves, and flowers in
angiosperms
Stems: located above
ground and support
leaves and flowers
Leaves: main sites of
photosynthesis in most
plants
Plant: Cell Structure
Plants: 3 Tissue Systems
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Instead of organs,
plants have roots,
stems, and leaves
are made of three
tissue systems
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The epidermis
The vascular tissue
system
The ground tissue
system
PLANTS: Epidermis and Vascular
Tissue
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The epidermis covers and protects the plant
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The cuticle is a waxy coating secreted by epidermal
cells that helps the plant retain water
The vascular tissue contains xylem and phloem
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It provides support and transports water and nutrients
Xy: high (water)
Phlo: lo (nutrients)
Rise of water: transpiration pull, capillary action, root
pressure
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Phloem transports
food molecules
made by
photosynthesis
Figure 32.5B
Figure 32.3
Plants: Vascular & Ground
Tissue
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Vascular tissue:
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Xylem: inside, bring water up; usually dead cells
act as tube
Phloem: outside bundle, brings nutrients down
Pith: storage and structure
Cambium: growth tissue – divide into xylem and
phloem (2nd growth)
The ground tissue system functions mainly
in storage and photosynthesis
VASCULAR
TISSUE
SYSTEM
Xylem
Phloem
Epidermis
GROUND
TISSUE
SYSTEM
Cortex
Endodermis
Figure 31.6B
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These microscopic cross sections of a dicot
and a monocot indicate several differences
in their tissue systems
Figure 31.6C
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Three tissue systems in dicot leaves
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Epidermis: stomata (singular, stoma)
surrounded by guard cells – regulate
opening/closing of stomata
Figure 31.6D
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Ground tissue system of a leaf – mesophyll,
site of photosynthesis
Figure 31.6D
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Vascular tissue: xylem and phloem
Figure 31.6D
Plants: Guard cells control
transpiration
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Guard cells: control transpiration
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Opening and closing of stomata - adaptation to
help plants regulate water content / adjust to
changing environmental conditions
H2O Guard cells
H2O
H2O
H2O
H2O
H2O
K+
H2O
Vacuole
H2O
H2O
H2O
Stoma opening
Stoma closing
Figure 32.4
Plant Growth: Primary vs
Secondary
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Most plants continue to grow as long as
they live (as opposed to animals that stop
growing)
Two types of growth:
- primary growth (length)
- secondary growth (width)
Plants: Primary Growth
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Growth from tissue meristems
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Meristems: unspecialized, dividing cells
(like our stem cells)
Apical meristems: tips of roots and
stems and terminal buds ; length
growth
Primary growth (length growth) new cell productions
Terminal bud
Axillary buds
Arrows =
direction
of growth
Root
tips
Figure 31.7A
Cortex
Epidermis
DIFFERENTIATION
Vascular
cylinder
CELL
DIVISION
ELONGATION
Root hair
Cellulose
fibers
Apical meristem
region
Root
cap
Figure 31.7B
Plants: Secondary growth
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Secondary growth: Increase in a
plant's width
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Lateral meristem (also called
cambium):
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Vascular cambium (located between
xylem and phloem)
Cork cambium (not in grasses or herbs,
but found in woody dicots, ex. oaks)
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Vascular cambium thickens stem by
adding layers of secondary xylem, or wood,
next to its inner surface
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Also produces secondary phloem- tissue of
bark
Cork cambium produces protective cork
cells located in bark
Figure 31.8A
Plants: Secondary Growth
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Everything outside vascular cambium –
bark
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Secondary phloem
Cork cambium
Protective cork cells
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Woody log result of several years of
secondary growth (inside “dead”; outside
“growing”)
Sapwood
Rings
Wood
rays
Heartwood
Sapwood
Vascular cambium
Secondary phloem
Bark
Cork cambium
Cork
Heartwood
Figure 31.8B
Plant: Behavior = Tropism
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Plant behavior:
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Phototropism
Gravitropism
Geotropism
thigmotropism
Figure 33.1A
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Phototropism is the bending toward light
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It may result
from auxin
moving from
the illuminated
side to the
shaded side of
a stem
Figure 33.1A
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Gravitropism is a response to gravity
Figure 33.9A
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Thigmotropism - response to touch
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Responsible for coiling of tendrils and vines
around objects
Enables plants
to use other
objects for
support while
growing
toward sunlight
Figure 33.9B
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Phototropism
Shaded
side of
shoot
Light
Illuminated
side of
shoot
Figure 33.1B
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Hormone controls phototropism
Light
Control
Figure 33.1C
Tip
removed
Tip covered
by opaque
cap
Tip
covered
by transparent cap
DARWIN AND DARWIN (1880)
Base
covered
by opaque
shield
Tip
separated
by gelatin
block
Tip
separated
by mica
BOYSEN-JENSEN (1913)
Shoot tip placed on agar block.
Chemical (later called auxin)
diffuses from shoot tip into agar.
Agar
Control
Block with
chemical
stimulates
growth.
Offset blocks with
chemical stimulate
curved growth.
Other controls:
Blocks with no
chemical have
no effect.
NO LIGHT
Figure 33.1D
Plants: Hormones
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Hormones affect:
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cell elongation
cell differentiation
Table 33.2
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Auxin: stimulates cell division –
phototropism and geotropism
Positive and negative geotropism (b/c
unequal distribution of hormone, unequal
growth & root grows faster)
Plants: Hormones
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Cytokinins: promote cell division
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Produced in actively growing roots, embryos,
and fruits
Opposite auxin, so plant coordinates
growth of root and shoot systems
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Cytokinins – develop side growth
Ex grow branch
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Auxin – stimulate length growth
w/o auxin, plant becomes thicker b/c cytokinins
Terminal bud
No terminal bud
Figure 33.4
Plants: Hormones
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Gibberellins:
stimulate cell
elongation and cell
division in stems
and leaves
Gibberellins: can
stimulate seed
growth
Figure 33.5A
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Gibberellins with auxin - influence fruit
development
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Grapes
at right treated with
gibberellin,
left not
Figure 33.5B
Plants: Hormones
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Abscisic acid (ABA) inhibits germination of
seeds
Ratio of ABA & gibberellins determines
whether seed remain dormant or germinate
Also “stress hormone” – close stomata
when too dry
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Seeds of many plants
remain dormant until
ABA inactivated or
washed away
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Ex. flowers grow
from seeds after
rainstorm in
Mojave Desert
Figure 33.6
Plants: Hormones
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Ethylene: triggers fruit ripening
Given off as cells age
Figure 33.7A
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Fruit growers use ethylene to control
ripening
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Apple farmers slow down ripening action of
natural ethylene
Tomato farmers pick unripe fruit and then pipe
ethylene into storage bins to promote ripening
Plants: Circardian Rhythms
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Circadian rhythms: internal biological clock
controls daily cycles
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Even in the absence of
environmental cues, they
persist with periods of
about 24 hours
But such cues are needed
to keep them synchronized
with day and night
Figure 33.10