Chapter 10 Flashcards
Plants include
all multi-celled, eukaryotic, photosynthetic autotrophs
Biologists believe that modern, multi-celled plants evolved from
the green algae Chlorophyta that lived in fresh water
Biologists believe that modern, multi-celled plants evolved from
the green algae Chlorophyta that lived in fresh water
Plants can be classified as
bryophytes or tracheophytes
Bryophytes
primitive plants that lack vascular tissue
Byrophytes must live in moist environments because
they have no roots or xylem and must absorb and transport water by osmosis
Why are bryophates tiny?
because they lack the lignin-fortified tissue necessary to support tall plants on land
What do bryophates include?
mosses, liverworts, and hornworts
Tracheophytes
transport vessels, xylem, and phloem
What do tracheophytes include?
- ancient seedless plants like ferns that reproduce by spores
- modern plants that reproduce by seeds
Tracheophytes with seeds are further subdivided into
gymnosperms
angiosperms
Gymnosperms
conifers, the con-bearing plants that produce seeds on the surface of cones
Gymnosperms have various modifications to make them more resistant to
wind, cold, and drought
Some of these modifications include
needle shaped leaves
a thick and waxy cuticle
stomates located in stomatal crypts to reduce water loss even further
Examples of gymnosperms
cedars sequoias redwoods pines yews junipers
Angiosperms
flowering plants in which seeds develop inside ovaries of flowers
Angiosperms: After pollination, the ovary
becomes the fruit
Angiosperms are the most diverse and
plentiful plants on Earth
Examples of angiosperms
roses daisies fruits nuts grains grasses
Examples of angiosperms
roses daisies fruits nuts grains grasses
Examples of angiosperms
roses daisies fruits nuts grains grasses
Angiosperms are further subdivided into
monocotyledons (monocots) and eudicots which include complex flowering plants called dicotyledons (dicots)
Angiosperms are further subdivided into
monocotyledons (monocots) and eudicots which include complex flowering plants called dicotyledons (dicots)
Characteristic: Cotyledons (seed leaves)
Monocots vs. Dicots
M: one
D: two
Characteristic: vascular bundles in stem
Monocots vs. Dicots
M: scattered
D: in a ring around the edge
Characteristic: leaf venation
Monocots vs. Dicots
M: parallel
D: netlike
Examples of monocots are the grasses:
wheat, corn, oats, lawn grass, and rice
also, palm trees
Monocots provide the
food for most of the world
Examples of dicots are
daisies roses carrots and most other flowering plants oak walnut cherry and most other trees
The cladogram from plants shows the
evolutionary relationships among the four main groups of living plants using the presence or absence of 3 derived traits: vascular tissue, seeds, and flowers
Plants began life in the seas and
moved to land as competition for resources increased
Plants began life in the seas and
moved to land as competition for resources increased
What are the biggest problems a plant faces on land?
supporting a plant body and absorbing and conserving water
Modifications that enable plants to live on land include:
cell walls roots/root hairs stomates cutin gametes/zygotes/gamentangia sporopollenin seeds and pollen
Cell walls made of cellulose support the plant whose cells
unsupported by a watery environment, must maintain their own shape
Roots and root hairs absorb
water and nutrients from the soil
Stomates open to exchange
photosynthetic gases and close to minimize excessive water loss
The waxy coating on the leaves, cutin,
helps prevents excess water loss from the leaves
In some plants, gametes and zygotes form within a
protective jacket of cells called gametangia that prevents drying out
Sporopollenin is a
tough polymer, is resistant to almost all kinds of environmental damage and protects plants in a harsh terrestrial environment
Where is sporopollenin found?
in the walls of spores and pollen
Seeds and pollen have a protective
coat that prevents desiccation. They are also a means of dispersing offspring
Reduction of primitive gametophyte (n)
generation occurs
Reduction of primitive gametophyte (n)
generation occurs
Why do plants continue to grow as long as the live?
because they have meristem tissue that continually divides, generating new cells
Plants grow in two ways:
primary and secondary
Primary growth is
vertical , the elongation of the plant down into the soil and up into the air
Primary growth:
new cells arise from the constantly dividing growth layer called the
apical meristem which is located at the buds of shoots and the tips of roots
Primary growth:
root growth is concentrated
near the root tip
Three zones of cells at different stages of primary growth are located at the root growth:
zone of cell division called apical meristem
zone of elongation
zone of differentiation
The root tip is protected by a
root cap that secretes a substance that helps digest the earth as the root tip grows through the soil
Zone of cell division contains
meristem cells that are actively dividing and are responsible for producing new cells that grow down into the soil
The zone of cell division is the region we observe
under the microscope in labs when you were studying cells undergoing mitosis
The zone of cell division is the region we observe
under the microscope in labs when you were studying cells undergoing mitosis
Zone of elongation
cells in this zone elongate and are responsible for pushing the root cap downward and deeper into the soil
Zone of differentiation
cells in this zone undergo specialization into 3 primary meristems that give rise to 3 tissue systems in the plant:
- the epidermis
- the ground tissue
- the xylem and phloem
Secondary growth means
lateral growth or an increase in girth
Whats provided by secondary growth?
new cells are provided by the lateral meristem
In herbaceous (nonwoody) plants , like vegetables and flowers,
there is only primary growth because these plants only live for one season
In herbaceous (nonwoody) plants , like vegetables and flowers,
there is only primary growth because these plants only live for one season
Woody plants are protected by
bark and live for many years
In woody plants, secondary growth is responsible for the
enlargement of the trunk , for each year of growth another ring is added
In woody plants, secondary growth is responsible for the
enlargement of the trunk , for each year of growth another ring is added
Roots
the function of the roots is to absorb nutrients from the soil, anchor the plant, and store food
Roots
the function of the roots is to absorb nutrients from the soil, anchor the plant, and store food
Epidermis
covers the entire surface of the root and is modified for absorption
Root hairs
- slender cytoplasmic projections from the epidermal cells
- extend out from each cell and greatly increase the root’s absorptive surface area
Cortex
main function is storage
-consists of parenchyma cells
Parenchyma cells that contain
many plastids for the storage of starch and other organic substances
Stele
the function of this vascular cylinder is transport
Stele consists of
vascular tissues (xylem and phloem) surrounded by 1 or more layers of tissue called the pericycle from which lateral roots arise
Endoderm
the vascular cylinder is surrounded by a tightly packed layer of cells called the endodermis
What is each endoderm cells wrapped with?
Casparian strip, a continuous band of waxy material that is impervious to water and dissolved minerals
Function of endoderm
to select what minerals enter the vascular cylinder and the body of the plant
Absorption
plants use roots to absorb nutrients/water and then these must be absorbed by the cells themselves
Absorption
plants use roots to absorb nutrients/water and then these must be absorbed by the cells themselves
Movement of water and solutes across a plant is called
lateral movement
Lateral movement is done along the
symplast and apoplast
Symplast
continous system of cytoplasm of cells interconnected by plasmodesmata
Apoplast
a network of cell walls and intercellular spaces within a plant body that permits extensive extracellular movement of water within a plant
Mycorrhizae
supply the plant with water and minerals
-symbiotic structures consisting of the plant’s roots intermingled with the hyphae (filaments) of a fungus that greatly increase the quantity of nutrients that a plant can absorb
Where are mycorrhize located?
in mature plants of many species where older regions of roots lack root hairs
Rhizobium
a symbiotic bacterium that lives in the nodules on roots of specific legumes
-fixes nitrogen gas from the air into a form of nitrogen the plant requires
Taproot
a single, large root that gives rise to lateral branch roots
In many dicots,
the primary root is the taproot
Some taproots ‘tap’
Some are modified for
water deep in the soil
storage (ex. carrots, beets, turnip)
What does a fibrous root system do?
Where are fibrous root systems found?
holds the plant firmly in place
common in monocots like grasses
Why do grasses make fine ground cover?
they minimize soil erosion
Adventitious roots
Including 2 examples
roots that arise above ground
aerial and prop roots
Aerial roots
roots that stick up out of the water and serve to aerate the root cells
Where are aerial roots found?
in trees that grow in swamps or salt marshes like mangroves
English ivy has aerial roots that enable
the ivy to cling to the sides of buildings
Prop roots
roots that grow aboveground out from the base of the stem and help support the plant
Example of plants with prop roots
tall plants like corn
Stem
- function = support
- transport water and minerals from the soil and nutrients from the leaves to the rest of the plant
Vascular tissue runs the length of the stem in strands called
vascular bundles
Each vascular bundle contains
xylem on the inside
phloem on the outside
meristem tissue between the two
The ground tissue of the stem consists of
cortex and pith (parenchymal tissues modified for storage)
The leaf is organized to
maximize sugar production while minimizing water loss
Parts of leaf:
epidermis-upper and lower
protection
Parts of Leaf:
waxy cuticle-made of cutin
minimize water loss
Parts of leaf:
guard cells-modified epidermal cells, contain chloroplasts
control the opening of the stomates
Parts of Leaf:
palisade mesophyll-tightly packed
photosynthesis
Parts of Leaf:
spongy mesophyll-loosely packed
photosynthesis
diffusion and exchange of gases into and out of these cells
Parts of Leaf:
veins-located in the mesophyll
carry water and nutrients from the soil to the leaves and carry sugar, the product of photosynthesis, from the leaves to the rest of the plant
Respiration –> CO2 –>
Photosynthesis –> O2 –>
Photosynthesis
Respiration
When plant cells carry out cellular respiration,
they take in oxygen and give off carbon dioxide
When plant cells carry out photosynthesis
they take in carbon dioxide and give off oxygen and water vapor
Plants exchange these gases between
air sacs in the spongy mesophyll and the exterior of the leaf by opening their stomates
Transpiration
loss of water from the leaf
If stomates were kept open all the time
the plant would lose so much through transpiration it could not survive
How do plants minimize excessive water loss?
when the sun is shining brightly and photosynthesis is running at top speed, stomates are open
at night, most plants close their stomates
How long must plants keep their stomates open?
long enough to allow photosynthesis to take place but not so long that they lose too much water
Guard cells
modified epithelial cells that control the opening and closing of the stomates in response to changes in water pressure
What happens when guard cells absorb water by osmosis?
they become turgid, they curve like hot dogs, causing the stomate to open
What happens when guard cells lose water?
they become flaccid and the stomate closes
Plants consist of 3 main tissue types
dermal
vascular
ground tissue
an ‘extra’ one is meristem tissue or growth tissue only found in growing tips of shoots and roots
Dermal Tissue
the outer protective covering of plants and usually consist of a single layer of epidermal cells
Some leaves are also covered with tiny, spikelike projections called
trichomes, which also protect the leaf
For the most part, epidermal cells do not
contain chloroplasts and cannot photosynthesize
An important exception are guard cells, which are
modified epidermal cells that contain chloroplasts and can photosynthesize
Vascular Tissue
transports water and nutrients up and down the plant
2 types of vascular tissue
xylem and phloem
Xylem
consists of tracheids and vessel elements
Phloem
consists of sieve tube elements and companion cells
Ground tissue make up all plant tissue besides
dermal and vascular tissue
Ground tissue consists of 3 cell types
parenchyma, collenchuma, and sclerenchyma
Parenchyma cells are the traditional-looking plant cell
- primary cell wall and secondary cell wall
- cytoplasm contains 1 or 2 large vacuoles
- when cell is turgid w/ water, cells lend support to the plant
- these cells are found in in all parts of plant, some contain chloroplast and other don;t
Collehnchyma cells
have unevely thickened primary cell walls but lack secondary cell walls
‘strings of celery’ consist of collenchyma
Sclerenchyma cells have
very thick primary and secondary cell walls that are fortified with lignin
-purely for support
Xylem and phloem
transport water, nutrients, and gases
Xylem consists of 2 types of elongated cells
tracheids and vessel elements
Secondary cell walls of tracheids are hardened with
lignin and function to support the plant and transport nutrients and water
Xylem makes up
wood
What is xylem’s role in transport?
carries water and nutrients from the soil up to the tallest leaves against gravity with no expenditure of energy
How do xylem transport water/nutrients?
transpirational pull
cohesion tension
Transpiration
evaporation of water from leaves
Cohesion
water molecules are attracted to each other and stick together
What does the transpirational pull-cohesion tension theory state?
that for each molecule of water that evaporates from a leaf by transpiration, another molecule of water is drawn in in at the root to replace it
What drives/causes transpiration?
absorption of sunlight
What factors affect the rate of transpiration and loss of water from a leaf?
- high humidity slows transpiration, low humidity speeds it up
- wind can reduce humidity near stomates and thereby increase transpiration
- increased light intensity increases photosynthesis, thereby increasing both the amount of water vapor to be transpired and the rate of transpiration
- closing stomates stops transpiration
Phloem vessels are made of chains of 2 types of cells:
What do they do?
sieve tube elements and companion cells
-carry sugar from photosynthetic leaves to rest of plant by a process called translocation
Sugar is stored in the roots, unlike transport in xylem,
this process requires energy
Plants can reproduce
sexually and asexually
Plants can clone themselves or reproduce asexually by
vegetative propagation
Process of vegetative propagation
a piece of the vegetative part of a plant, the root, stem, or leaf, produces an entirely new plant genetically identical to the parent plant
examples, grafting, cuttings, bulbs, runners
What is the sexual organ of a plant?
the flower
Parts of the Flower include
petals, sepals, pistils/carpels, ovary, ovule, style, stigma, stamen, anther, filament
Parts of the Flower:
petals
brightly colored, modified leaves found just inside the circle of sepals ; attract animals that will pollinate the plant
Sepals
- outermost circle of leaves
- are green and closely resemble ordinary leaves
- enclose the bud before it opens and protects the flower while it develops
Pistils or Carpels
female part of the flower
produce female gametophytes
each consists of an ovary, stigma, and style
Ovary
swollen part of pistil that contains the ovule, where 1 or more ova are produced by meiosis
Ovule
structure within the ovary where the ova (female gametophytes) are produced
Style
long, usually thin stalk of the pistil
Stigma
sticky top of the style where pollen lands and germinates
Stamen
male part of the flower, made up of anther and filament
Anther
male part of the flower where sperm (pollen) are produced by meiosis
Filament
threadlike structure that supports the anther
What does sexual reproduction begin with?
pollination
Step 1 of Pollination
one pollen grain containing 3 haploid nuclei- one tube nucleus and 2 sperm nuclei- lands on the sticky stigma of the flower
Step 2 of Pollination
the pollen grain absorbs moisture and germinates or sprouts, producing a pollen tube that burrows down the style into the ovary
Step 3 of Pollination
the 2 sperm nuclei travel down the pollen tube into the ovary
Step 4 of Pollination
Once inside the ovary, the 2 sperm nuclei enter the ovule through the micropyle
Step 5 of Pollination
1 sperm nucleus fertilizes the egg and becomes the embryo (2n) and the other sperm nucleus fertilizes the 2 polar bodies and becomes the triploid (3n) endosperm or cotyledon, the food for the growing embryo
Double fertilization
2 fertilizations occur
Double fertilization
2 fertilizations occur
What happens after fertilization?
the ovule becomes the seed and the ripened ovary become the fruit
In monocots, food reserves
remain in the endosperm
In dicots, the food reserves of the endosperm are
transported to the cotyledons and consequently, the mature dicot seed lacks endosperm
In coconuts, the endosperm is
liquid
Double fertilization can be seen as:
- Sperm + Ovum –> Embryo = 2n
2. Sperm + 2 Polar bodies –> cotyledon (food for the growing embryo) = 3n
What does a seed consist of?
protective seed coat, an embryo, and the cotyledon or endosperm-food for the growing embryo
The embryo of the seed consists of the
hypocotyl
epicotyl
radicle
Hypocotyl
Epicotyl
Radicle of embryonic root
becomes the lower part of the stem and the roots
becomes the upper part of the stem
the first organ to emerge from the germinating seed
The food source in a monocot is
endosperm instead of cotyledon
The sexual life cycle of plants is characterized by
the alternation of generations in which haploid (n) and diploid (2n) generations alternate with each other
What does the gametophyte (n) produce?
gametes by mitosis that fuse during fertilization to yield 2n zygotes
Each zygote develops into a
sporophyte (2n) that produces haploid spores (n) by meiosis
Each haploid spore forms a new
gametophytes, and the cycle continues
Remember:
The gametophyte generation
The sporophyte generation
haploid n
diploid 2n
Antheridium
structure that produces sperm, develops on the gametophytes
Archegonium
structure that produces eggs, develops on the gametophyte
Gametophyte
haploid adult plant
Megaspores
produced by large female cones and will develop into female gametophytes
Microspores
produced by small male cones and will develop into male gametophytes or pollen grains
Protonema
branching, 1-celled-thick filaments produced by germinating moss spores, becomes the gametophyte in moss
Sporangia
located on the tip of the mature sporophyte, where meiosis occurs, producing haploid spores
Sporophyte
a diploid adult plant
Sori
raised spots located on the underside of sporophyte ferns, clusters of sporangia
Mosses
green, carpetlike plants seen growing in damp forests, sometimes on fallen logs
-primitive plants
Mosses: The gametophyte generation
dominates the life cycle
this means that the organism is haploid (n) for most of its life cycle and the sporophyte (2n) is dependent on the gametophyte
Mosses:
Gametophyte obtains
Sporophyte obtains
nutrients by photosynthesis
nutrients from the gametophyte
The fern is a
seedless vascular plant and is intermediate between the primitive bryophytes and the flowering vascular plants
In ferns, the sporophyte generation is
larger and independent from the gametophyte
Ferns
both the gametophyte and the sporophyte
sustain themselves by photosynthesis
Seed plants are
advanced, vascular plants
Seed plants are divided into
flowering plants and conifers
Flowering plants (angiosperms), the gametophyte generation exists inside the
sporophyte generation is totally dependent on the sporophyte
In a gymnosperm (cone-bearing) like a pine tree,
the gaemtophyte generation develops from haploid spores that are retained within the sporangia
What do plant hormones do?
coordinate growth, development, and response to environmental stimuli
Hormones are produced in very small quantities however they have a profound effect because
the hormone signal is amplified
Plant’s response to a hormone depends on
relative amounts not absolute amounts
Examples of plant hormones
auxins cytokinins gibberllins abscisic acid (ABA) ethylene
Auxins enhance
apical dominance, the preferential growth of a plant upward (toward the sun) rather than laterally
-terminal buds actually suppresses lateral growth by suppressing development of axial buds
How do auxins stimulate stem elongation and growth?
by softening the cell wall
First plant hormone discovered was auxin.
What is IAA? 2,4-D?
Indoleacetic acid is a naturally occuring auxin
2,4-D is used as a wee killer (human made)
Auxins are used as rooting powder to
develop roots quickly in a plant cutting
What results in seedless tomatoes?
a synthetic auxin sprayed on tomato plants will induce fruit production without pollination
Cytokinins
-stimulate cytokinesis and cell division
Function on cytokinins
they delay senescence (aging) by inhibiting protein breakdown
(florists spray cut flowers with cytokinins to keep them fresh)
Gibberellins
- promote stem and leaf elongation
- induce bolting, the rapid growth of a floral stalk
When a plant which normally grows close to the ground, enters the reproductive stage,
it sends up a very tall shoot on which the flower and fruit develop
-this is to ensure pollination/seed dispersal
ABA Abscisic Acid
- inhibits growth and promotes seed dormancy
- enables plants to withstand drought
- closes stomates during times of water stress
Ethylene
this plant hormone is a gas
-promotes ripening, which in turn, triggers increased production of ethylene gas
Tropism
the growth of a plant toward or away from a stimulus
Examples of tropisms
thigmotropisms (touch)
geotropisms or gravitropisms (gravity)
phototropisms (light)
Positive Tropism vs. Negative Tropism
+ –> a growth of a plant toward a stimulus
- –> a growth away from a stimulus
Phototropisms result from an
unequal distribution of auxins that accumulate on the side of the plant away from the light
Since auxins cause growth,
the cells on the shady side of the plant enlarge and the stem bends toward the light
Geotropisms result from an
interaction of auxins and statoliths, specialized plastids containing dense starch grains
