Transcript Plant Kingdom Evolutionary requirements

PLANT KINGDOM
EVOLUTIONARY
REQUIREMENTS
By: Serena Young
PARTS OF A PLANT (FLOWER)
4 MAJOR FACTORS THAT ALLOW
PLANTS TO LIVE ON LAND
• Retaining Moisture
• Cuticle & stomata
• Transporting Resources
• Vascular system
• Growing Upright
• lignin
• Reproducing on Land
• Pollen grain & seeds
RETAINING MOISTURE
• Plants retain moisture for photosynthesis
• The surface of the plant is covered with a
cuticle which is a waxy, waterproof layer
that helps hold in moisture
stoma 
• In the cuticles, there are tiny holes called
stomata which allow for gas exchange
between the plant and the atmosphere
• Special cells allow the stomata to close for
water retention, or to open to allow air to
move in and out
• Diffusion and osmosis are taking place
moving water and elemental products in
or out of the cell
Cuticle 
TRANSPORTING RESOURCES
• While plants must get sunlight and carbon
dioxide from the air, they must also get
water and nutrients from the soil
• Taller plants get more sunlight and carbon
dioxide, but how will they get water and
nutrient from the soil?
• The vascular system is a collection of
specialized tissues in some plants that
transports water and mineral nutrients up
from the roots and brings sugar down from
the leaves
• The vascular system allows plants to grow
higher off the ground because resources
are carried up and down to different parts
of the plants
• The xylem carries water and mineral
nutrients up from the roots
• The phloem carries sugar down from the
leaves
GROWING UPRIGHT
• Plant height may also be limited by the plant’s ability to hold its own weight
• The basis of the plant is held up by the roots
• Plants need a structure to support their weight and provides space for
vascular tissues
• Lignin hardens the cell walls of some vascular system and is responsible for
the strength of wood and provides stiffness to the stems of other plants
• The result is a plant keeping its upright structure as they grow toward the sun
Seeds
Pollen
REPRODUCING ON LAND
• In all plants, eggs are fertilized within the tissue of the parent plant and develop into
an embryo
• Some plants need water to reproduce and other do not
• Pollen and seeds are adaptations that allow plants to reproduce without water
• Pollen is blown by the wind or by animals, each pollen grain contains cells that will
divide to form sperm
• These sperm are looking for a female egg to fertilize in the ovaries
• Seeds protect and provide nutrients for developing embryos, protecting it from wind
and sunlight
• Once a seed is in the right conditions, the embryo can develop into an adult plant
SEED PLANTS
• Seed plants have many advantages over their ancestors:
• Seed plants can reproduce without water
• Seedless plants depend on water for sperm to swim through to fertilize an egg
• Seed plants use pollen which is carried by the wind or on the body of an animal pollinator such as a
bee
• Pollination occurs when pollen (sperm) meets female reproductive parts of the same species
• Each pollen grain then divides to form sperm and fertilization occurs when the sperm reaches the egg
• Seeds nourish and protect plant embryos
• Each seed has a protective coat that has a plant embryo and a food supply
• A seed can survive a long time in a dormant state, during which it can withstand harsh conditions
(drought or cold) that might kill an adult plant
• When conditions are favorable, the embryo will begin growing, using the food supply provided by the
seed
• Seeds allow plants to disperse to new places
• Wind, water, or animals often carry seeds far from the individual plant that produced them
• Many seed plants have adaptations that aid in the dispersal of seeds, such as the “wings” that carry
maple seeds in the wind
• Since seeds can remain dormant, the embryo will not begin to develop until it reaches a suitable
environment
SEED PLANTSGYMNOSPERM AND ANGIOSPERM
• Scientists believe that seed plants evolved as the earth’s climate changed from
warm ad moist to hot and dry during the Devonian period (410- 360 million years
ago)
• Fossils have proved that seed plants can be grouped according o whether their
seeds are enclosed in fruit
• An angiosperm is a seed plant that has seeds enclosed in some type of fruit
• A gymnosperm is a seed plant whose seeds are not enclosed in fruit
• Most are cone-bearing and evergreen (example- pine tree)
• A woody cone is the reproductive structure of most gymnosperms
• It contains hard protective scales
• Pollen is produced in male cones, while eggs are produced in female cones
• Seeds also develop on the scales of female cones, which protect fertilized eggs
• There are 3 living phyla of gymnosperms: cycads, Ginkgo biloba, and confiers
CONIFERS
• They are gymnosperms
• Many conifers are evergreen and some lose their needles in the winter
• They are well adapted to high altitudes, sloping hillsides, and poor soil which
allows them to thrive in the mountainous regions
• They tend to grow old and tall which means that they have well working
vascular systems that use the phloem and xylem to move minerals, sugar,
and water up and down the plants
COTYLEDONS, MONOCOTS,
DICOTS, & WOOD
• Flowering plants are based on two basic kinds of seeds: seeds with one or two
cotyledons
• A cotyledon is an embryonic leaf inside a seed
• As an embryo develops into a seedling, the seed leaf of some species remains inside
the seed coat
• Flowering plants whose embryos have one seed leaf are called monocotyledons
(monocots). Monocot plants usually have parallel veins in long, narrow leaves.
• Flowering plants whose embryos have two seed leaves are called dicotyledons
(dicots). Dicots have leaves with netlike veins.
• Some flowering plants develop woody stems, while others do not.
• Wood is a fibrous material made up of dead cells that are part of the vascular
system of some plants. Woody plants have lignin, making the cell wall stronger.
FLOWERING PLANTS
• They are angiosperms
• A flower is the reproductive structure of flowering plants. They protect a
plant’s gametes and fertilized eggs
• A fruit is the mature ovary of a flower
PLANT CELL TYPES
• Plant cells have cell walls, plastids, and a large vacuole
• Cells are organized into tissues
• Plant tissues are made of 3 basic cell types:
• Parenchyma cell
• Collenchyma cell
• Sclerenchyma cell
PARENCHYMA CELL
• It is the most common type of plants cell and it stores starch, oils, and water
for the plant
• These cells have thin walls and large water-filled vacuoles in the middle
• Photosynthesis occurs in the chloroplasts with parenchyma cells in the leaves
• Both the chloroplasts and the colorless plastids in parenchyma cells within
the roots and stems store starch
• They have the ability to divide throughout their entire lives, so they are
important in healing wounds to the plants and regenerate parts
COLLENCHYMA CELL
• They have cell walls ranging from thick to thin which provide support while
still allowing the plants to grow
• Flexibility is a unique feature of the collenchyma cell
• Their cells walls do not contain lignin, so they are stretchy and can change
size
• As a young leaf grows, collenchyma cells can elongate and still give the leaf
a structure
SCLERENCHYMA CELL
• It is the strongest of the 3 cells
• These cells have the second cell wall that is hardened by lignin, which makes these
cells very tough, durable, and rigid
• Since they can’t grow with the plant, sclerenchyma cells are found in parts of the
plant that aren’t lengthening anymore
• Many of these cells die when they reach maturity
• The cytoplasm and organelles of these dead cells disintegrate, but the rigid cell
walls are left behind as skeletal support for the water-conducting tissues or for the
plant itself
• Sclerenchyma cells form a major part of fruit pits and the hard outer shell of nuts
• They are also found in stems and leaf veins and are responsible for the gritty texture
of pears
TISSUE SYSTEMS
• Plants organs are made of 3 tissue systems:
• Dermal tissue
• Ground tissue
• Vascular tissue
• A tissue is a group of cells working together to perform a certain function
• The tissue systems of plants may consist of simple tissues from the basic cell
types parenchyma, collenchyma, and sclerenchyma
• They may also be made of complex tissues that have additional types of
cells
• Neighboring cells are usually connected by plasmodesmata which are
strands of cytoplasm that pass through opening in cell walls and connect
living cells
• Through the plasmodesmata, cells of a plant tissue can share water,
nutrients, and chemical signals
DERMAL TISSUE
• Dermal tissue covers the outside of a plant and protects it in a variety of
ways
• It is called epidermis and it is made up of live parenchyma cells in the nonwoody parts of plants
• On leaves and some stems, epidermal cells may secrete a waxy-coated
substance that becomes the cuticle
• Dermal tissue made of dead parenchyma cells makes up the outer bark of
woody plants
GROUND TISSUE
• Dermal tissue surrounds the ground tissue
• Ground tissue makes up most of the inside of a plant
• It provides support and stores materials in roots and stems
• In leaves, ground tissue is packed with chloroplasts, where photosynthesis
makes food for the plant
• Ground tissue consists of all 3 of the simple tissues: parenchyma tissue,
collenchyma tissue, and sclerenchyma tissue (most common- parenchyma)
• The ground tissue of cacti has many parenchyma cells that store water
VASCULAR TISSUE
• Ground tissue surrounds the vascular tissue
• The system of vascular tissue transports water, mineral nutrients, and organic
compounds to all parts of the plants
• Plants can transport necessarily fluids and nutrients throughout their systems
• A plant’s vascular system is made up of two networks of hollow tubes and
each network consists of a different type of vascular tissue that works to
move different resources throughout the plant
• Xylem is the vascular tissue that carries water and dissolved mineral nutrients
up from the roots to the rest of the plant
• Phloem is the vascular tissue that carries the products of photosynthesis
through the plant
VASCULAR SYSTEM
• water and dissolve minerals move up the roots to the rest of the plant through the xylem
• One type of specialized cell in xylem is called a tracheid (long and narrow)
• Water can flow from cell to cell in tracheids through openings in the thick cell walls
• Some types of flowering plants have an additional xylem cell called a vessel element
• The cohesion-tension theory proposes that physical properties of water allow the rise of water through a plant (attracting
to each other)
• However, water molecules are also attracted to the xylem wall due to adhesion (attracting to other substances)
• Transpiration is when water vapor is lost (evaporation)
• As leaves transpire, the outer flow of water lowers the pressure in the leaf’s xylem, creating a vacuum that pulls water
upward
• Phloem carried sugars from photosynthesis down to the stems and roots
• Phloem is a complex tissue made mostly of cells called sieve tube elements (have holes to let the phloem fluids, or sap
move through the plan)
• Phloem sap can move in any direction, depending on the plant’s need
• The pressure flow model is a theory that explains how food, or sap, moves through a plant. Phloem sap moves from a
sugar source (high concentration of sugars) to a sugar sink (uses or stores sugars). The pressure changes, keeping
nutrients moving.
• At a source, many plants use ATP to pump or load sugar into phloem at a high concentration (water- low and flows into
phloem through osmosis). This creates high pressure at the sugar source. Sugar concentration of the sink end is lessened
as sugar is unloaded into the sink.
• The overall result is higher pressure at the source end and lower at the sink end.
ROOTS AND STEMS
• Roots act as an anchor for plant support
• Roots absorb water, transport, and store nutrients
• The center of the root is the vascular cylinder (made of xylem and phloem tissues)
• Root hairs are tiny projections in cells
• The root cap covers the tip of the root and is a small cone of cells that protects the growing part of the root as it pushes
through the soil
• The meristem is undifferentiated plant issue from which new cells are formed
• Apical meristems are areas of growth that lengthens the tips of roots and stems
• Roots have 2 basic forms:
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Fibrous root- systems make fine branches in which most of the roots are the same size
Taproot- systems have a long, thick, vertical root with smaller branches (get water deep in ground)
• All plants require water and certain mineral nutrients for growth, development, and function
• The pattern of plant growth depends on the location of the meristem within the plants
• There is primary growth which makes stems grow taller or roots grow longer and secondary growth which adds width in
the stems and roots of woody plants (tree trunk)
• The age of a tree can be determined y counting the annual ring and the climate by how thick the ring is
LEAVES
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Most leaves share similar structures
The blade is usually broad and flat, and it collects the sunlight for plants
The blade connects to the stem by a thin stalk called a petiole
A bud that grows between the petiole ad the stem of a plant, called an
axillary bud, marks where a leaf ends
Leaves have an outer covering of dermal tissue and internal system of
vascular tissue surrounded by ground tissue
The dermal tissue is covered by a waxy cuticle (water resistant covering)
The cuticle protects the inner tissues and limits evaporation from the plant
Between the 2 dermal layers of a leaf is parenchyma tissue called mesophyll
(veins made up by the vascular tissues of phloem and xylem)
LEAVES CONTINUED
• Upper portion of the mesophyll has chloroplasts that are useful for photosynthesis
• Lower portions has the stomata and it is the site of transpiration and gas exchange
• A pair f guard cells surround each stoma, and can open and close
• During the day, stomata of most plants open, allowing CO2 necessary for
photosynthesis to enter
• Potassium ions from nearby cells accumulate in the guard cells, which causes water
to flow into the guard cells, opening the stoma
• When the stoma is open, water evaporates from the leaves
• When the plant is losing water faster than gaining it, the guard cells deflate ad close
the stomata, causing the plant to run low on CO2 for photosynthesis
LEAF CHARACTERISTICS
• Certain leaf structures can be used to identify plants
PLANT LIFE CYCLES
• Plants complete their life cycle by alternating between 2 phases that allow
the plants to reproduce sexually and disperse to new areas
• Sporophyte phase involves a diploid plant body that produces spores
• Gametophyte phase involves a haploid plant body that produces gametes
• Alternation of generations is the type of life cycle which alternates between
haploid and diploid phases
• Life cycle of moss has a dominate gametophyte phase. The capsule at the
tip of the moss sporophyte contains spore-producing sacs called sporangia.
When the pores are mature, the capsule opens and releases them. A moss
gametophyte produced gametes in special reproductive structures. Males
produce sperm and females produce an egg. A sperm swims through water
to reach an egg and when it fertilizes it, the sporophyte phase begins again.
PLANT LIFE CYCLES CONTINUED
• The life cycle of ferns has a dominant sporophytic phase for all vascular plants. Sori are
clusters of sporangia. Spores are released from sporangia when they are mature. A fern
gametophyte is often called a prothallus (plant body). It anchors itself to the soil using
rhizoids (thread-like structures). When water is present, male structures release sperm
which swim toward an egg. When the egg is fertilized, a zygote grows above the
prothallus. The mature sporophyte is the familiar fern plant. Newly forming fronds
(underside of a fern leaf) are called fiddleheads which produce spores on the underside
of each frond, and the cycle repeats.
• The life cycle of conifers has a familiar form for all seed plants, sporophytes. Seed plants
produce 2 spores which develop into a female and male gametophytes. Female cones
are larger and more scaly than male cones. Each female pine cone has 2 ovules that
produce spores. One spore of each ovule will develop into a microscopic female
gametophyte, and the rest will die. Male spores are produces inside male cones, which
only live for a few weeks. Male spores develop into pollen grains. Male cones release
pollen which can stick onto a female cone. After pollination, eggs are produced inside
the ovule and a pollen tube begins to grow from the pollen grain toward an egg. 2
sperm also develop inside the pollen grain. The sperm travel down the pollen tube which
will fertilize an egg, forming a zygote, and then an embryo. At the same time, the ovule
develops into a protective pine seed. Each scale of a female pine cone can be home
to 2 developing pine seeds. Once the seeds are mature, the scales open up and release
them. The life cycle begins again with a new sporophyte.
REPRODUCTION IN FLOWERING PLANTS
• The outer-most layer of a flower is made of sepals (modified leaves that protect the
developing flower)
• The layer just inside the sepals is made up of petals (modified leaves)
• A stamen is the male structure of a flower and a carpel is the female one. Female
gametophytes are produced inside the ovary (found at base of flower)
• When a pollen grain reaches the stigma (tip) of the same plant species, the flower has
been pollinated
• In flowering and vascular plants, the sporophyte is the dominant phase
• Fertilization in the flower starts with production of male and female gametophytes and
then double fertilization.
• Double fertilization is when one sperm fertilizes the egg and the other combines with the
polar nuclei in the embryo sac. The cell now has a tripoid (3n). It will become the
endosperm (food supply for the developing embryo).
• After fertilization, the next sporophyte generation begins. The ovule becomes a seed
(contains embryo and endosperm with a seed coat). Using the nutrients provided by the
endosperm, the embryo develops 1 or 2 cotyledons (seed leaves). While the seed
develops, the ovary grows into a fruit.
SEED DISPERSAL & GERMINATION
• Animals, wind, and water can spread seeds
• Seeds begin to grow when environmental conditions are favorable
• Dormancy- state of inactivity during which an organism or embryo is not growing
• Inside the seed coat, an embryo can withstand extremes that would kill a young
seedling
• Germination- when the embryo breaks out of the seed coat and begins to grow
into a seedling
• The embryo starts to take up water, which causes the seed to swell and the coat to
crack
• Then the embryonic root called a radicle breaks through the cracks
• A young shoot called a plumule eventually breaks through the surface of the soil
• Some species of dicots have cotyledons of other dicots emerge above ground with
the growing shoot, when the leaves emerge from the shoot, they begin to make food
through photosynthesis, then the plant is called a seedling
ASEXUAL REPRODUCTION
• Sexual reproduction produces genetic diversity and asexual reproduction allows a
well adapted plant to make many copies of itself
• Regeneration is the process by which a new plant can grow from a fragment of a
non-reproductive structure, such as a root, stem, or leaf
• Vegetative reproduction is a type of asexual reproduction in which stems, leaves, or
roots attached to the parent plant reproduce new individuals
• Many plants have structures that are specifically adapted for vegetative
reproduction:
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Stolons (stems that grow horizontal to the ground)
Rhizomes (horizontal underground stems)
Tubers (underground stem modified for storage)
Bulbs (underground stems surrounded by modified leaves adapted for storage,
covered with a protective, papery skin)
HORMONES
• Plant hormones regulate plant functions
• A hormone is a chemical messenger produced in one part of an organism
that stimulates or suppresses the activity of cells in another part
• Some hormones in plants are:
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Gibberellins
Ethylene
Cytokinins
Auxins
GIBBERELLINS & ETHYLENE
• Gibberellins produce dramatic increases in size
• They are involved in ending seed dormancy, starting germination, and
promoting the rapid growth of young seedlings
• They are responsible for the large size of many fruits and rapid upward
growth of some flower stalks
• Ethylene causes ripening and is naturally produced by plants
• Fruits or vegetables, such as tomatoes, are shipped to far away places and
when they arrive, they are exposed to ethylene gas to ripen before they are
sold
CYTOKININS & AUXINS
• Cytokinins stimulate cytokinesis (final stage if cell division)
• They are produced in growing roots and developing seeds and fruits and are
involved in the growth of side branches
• A property of cytokinins are used to slow the aging of plant organs
• Auxins are involved of the lengthening of plant cells produced in the apical
meristem (growing tip)
• Auxins stimulate growth of the primary stem, preventing growth of new branches
• Gardeners use the property of auxins to control branching patterns by cutting off
the tip of the growing stem (less auxin in stem, and side branches are encouraged
to grow)
• The lengthening of cells triggered by auxins also controls some forms of tropism, the
movement of a plant in response to an environmental stimulus
• If a stimulus (sun) hits one side of a stem, auxins will build up in the cells on the
shaded side of the stem…the cells elongate and grow/bend toward the light
PLANT RESPONSES
• Phototropism is the tendency of a plant to grow toward the light
• Thigmotropism is the plant’s response to touch
• Gravitropism is the up and down growth of a plant
• Photoperiodism is signals from the changing lengths od day and night
through the year
• Rapid responses do not involve growth and are often adaptations that help
to protect plants from predators