AP Biology Unit IX
- All About Plants
Plant Anatomy and Growth- Chapter 35
Plant Transport - Chapter 36
Plant Nutrition - Chapter 37
Plant Reproduction and Development - Chapter 38
Plant Control Systems - Chapter 39
Unit 9 - All About Plants: Structure, growth, transport, nutrition, and reproduction (focus on angiosperms)
Essential Questions: ·
What are the major components of the plant body?
· How do genetics and the environment combine to affect plant growth?
· What are the different plant tissues and what are their properties?
· How do plants grow and develop?
· What factors affect and control plant growth and development?
· How does differential gene expression cause cell differentiation and the different structures of plant
development?
· How do materials move through plants?
· What role do leaves, vascular tissue, and roots play in transport?
· How do the properties of water play a role in transport?
· How do the processes of diffusion, osmosis, and pressure affect movement of materials through plants?
· What are the nutritional requirements of plants and where do plants get them?
· What role does soil play in plant nutrition?
· What roles to plants play in chemical cycles in the ecosystem?
· What is the role of nitrogen on plant nutrition?
· How do relationships between plants and other organisms benefit each other and work to cycle nutrients?
· In what ways are some plants parasitic?
· How do plants reproduce sexually?
· How do plants reproduce asexually?
· How is biotechnology changing agriculture?
· How do plants regulate their systems?
· In what ways do plants respond to environmental stimulus?
Objectives:
Identify and describe the major plant organs.
Identify and describe plant tissues.
Discuss how the environment and genes work to both impact plant growth and development.
Explain plant growth and development.
Discuss how gene control and expression control plant growth and development.
Discuss transport between cell and across membranes in plants.
Discuss water potential and how it affects the movement of water within plants.
Discuss the movement of water and mineral into the root and into the vascular cylinder.
Explain the process of transpiration powered by water potential.
Review the properties of water and explain how this facilitates the movement of water through plan
Explain translocation in plants from source to sink.
Explain the pressure flow process.
Identify the nutritional requirements of plants.
Discuss the importance of soil and how successful agriculture depends on good soil.
Discuss the importance of nitrogen to plants and the role plants and the associated bacteria have
the nitrogen cycle.
Explore the relationship between bacteria and plants.
Explore the relationship between fungus and plant roots.
Discuss parasitic and carnivorous pants.
Review the reproductive cycles of mosses, ferns, pines focusing on alternation of generations.
Discuss the significance of flowers.
Identify and give the functions of the parts of a typical flower.
Illustrate the sexual reproduction of flowering plants. From pollen formation, ovule maturation,
pollination, double fertilization, seed development, fruit development.
Discuss the significance of pollen from an adaptive standpoint.
Discuss the significance of fruit from an adaptive standpoint.
Explain types of asexual reproduction on plants.
Discuss recent advances in biotechnology that are impacting agriculture.
List and describe the different plant hormones.
Describe plant movement (tropisms).
Discuss plants responses to environmental stresses.
Plant Anatomy
angiosperms
Plant Organs
stores
Roots - specialized for absorption of water and minerals, acts as an anchor, and
excess food (starch)
Stems - conducts water and minerals, supports plant, lifts up leaves for display, store
food, and in young plants photosynthesis
Leaves - trap light for food production, some specialized leaves can acts as spines,
tendrils, succulents (hold water), trap food ( Venus Flytrap)
Flowers - Reproductive structures
Plant Tissues - plant organs are composed of plant tissues
Ground Tissue - makes up the bulk of the plant body
roots, lengthening of
represents primary growth
and secondary
increases the thickness.
rise to a sturdier
epidermis
Meristem : growing tissue, regions of embryonic cells
- Apical meristems - at ends of shoots and
stems and roots
- Vascular Cambium - lateral meristem in roots
growth stems that
- Cork Cambium - lateral meristem that gives
covering that replaces
Simple tissues
- Parenchyma - makes up most of the soft
moist, primary
growth,
pliable, thin walled and multi sided = generic heal
wounds, mesophyll - type of parenchyma in leaves
containing chlorophyll other types play role in storage,
secretion and
- Collenchyma - flexible support, elongated
cells with uneven
thickening, Cell walls
contain Pectin (sticky polysaccharide
helps bind fibers)
- Sclerenchyma - support mature plants and
seeds. Thick cell
walls with Lignin. Lignin
strengthens and water proofs.
Consists of
fibers - long tapered cells
Vascular Tissue - provides system of conduction and support
- Xylem : conducts water and dissolved minerals. vessel members and
tracheids are dead at maturity. The walls have lignin
and form water
collecting pipelines
- Phloem - conducts sugars and other solutes. main cells are sieve-tube
members, stay alive at maturity. Typically there are
companion cells
(parenchyma) help loading the sugars
Dermis Tissue
- epidermis - covering tissue, single layer of unspecialized cells, coated by
waxes and cutin = cuticle. Restricts water loss and
resists attacks from
microorganisms
stoma - openings in leaf epidermis. Guard cells are specialized to open
and
close the stomata.
- peridermis - replace the epidermis in the roots and stems with secondar
growth.
Structure of shoots
Vascular bundles - scattered vs in rings
Cortex
pith
Leaves (page ___ )
variations - regular, needle, succulents
deciduous vs evergreen
simple vs compound
veins - parallel vs netlike
thin and flat = high surface area to volume ratio. arrangement - so that
maximizes exposure without shading other leaves.
leaf epidermis - reduces water loss, have stomata under, can have
epidermal
hairs
Mesophyll
internal
Upper epidermis
Palisade mesophyll
Spongy mesophyll
vascular bundle
lower epidermis
stoma - guard cells
Roots
primary root with lateral roots = Taproot - Dicots
monocots - primary root short lived replaced by adventitious roots from
the stem, then lateral roots branch = fibrous root system
internal structure - zones of cell division, elongation, and differentiation
root cap protects apical meristem
root hairs - extensions of the root epidermis, increase greatly the surface
area for absorption
pericycle gives rise to lateral roots
Secondary growth - Woody Plants
Annuals
Biennials
Perennials
evolutionary advantage of woody structure
Plant Physiology
Plant Nutrition and Transport
Soil: particles of minerals mixed with humus (decomposing organic
material).Mineral particles come in three sizes : Sand, Silt, Clay. Clay consists
of aluminosilicates with negatively charged ions. Positively charged ions and
water cling to the clay. This is important to plants. Too much clay bad. LOAM equal proportions of sand, silt, and clay. Amount of humus important. best
between 10-20% humus
Nutrients: elements that are essential for a given organism. Play a role in
metabolism.
For plants the essential elements are:
Macronutrients
oxygen hydrogen carbon - get these from H2O and CO2, photosyn.
These elements are dissolved in water in ionic forms that bind to clay.
Nitrogen Potassium
Calcium Magnesium
Phosphorus
Sulfur
Micronutrients
Chlorine Iron
Molybdenum
Boron
Manganese
Zinc
Copper
Loss of nutrients form the soil
Leaching - removal as water percolates through the soil. Occurs
more in sandy soils that don't have enough clay.
Erosion - move ment of land due to wind and water.
Absorption of water and minerals
Plants spend tremendous amounts of energy growing root systems. Soil
where concentration of water and mineral ions are greater, stimulates growth.
Specialized Absorptive structures
root hairs - extensions of epidermal cells
root nodules - local swellings
bacteria and fungi live in mutaulistic relationships with roots.
There is plenty of nitrogen in the air, but plants cant fix it. Nitrogen fixing
Bacteria can break the triple bond of N2 and attach the nitrogen to organic compounds
that plants can use. Legumes (string beans, peas, alfalfa, clover) have these bacteria in
the nodules of their roots.
Mychorrhizae - Fungus that lives in association with roots. Helps absorption
of minerals.
Water Transport Through Plants
Plants use only a portion of the water they absorb. Much of the water is lost through
the stomata.
Transpiration - evaporation of water from leaves, stems, and other plant parts
Cohesion-Tension theory
xylem - transports water through cells called tracheids and vessel members. These
cells are dead at maturity, so there can be no "active" pulling.
The water is being pulled up by the drying force of the air. Creates negative pressure
(tensions).
1. Drying power of the air causes TRANSPIRATION (evaporation from plant parts
exposed to the air). This puts water confined in the conducting tubes of xylem in a
state of tension. (from veins in leaves down through stems into roots)
2. Unbroken, fluid columns of water show COHESION; the hydrogen bonds between
the water molecules makes them stick together.
3. As long as water molecules are leaving from one end, the tension pulls water into
the roots to replace them.
Water conservation
Cuticle - epidermal cells secrete *translucent waxes ( water insoluble lipids with long fatty acid tails). These waxes are
embedded with Cutin
(insoluble lipid polymer). Blocks water loss and * restricts the diffusion of CO2 and O2 *.
Does not, however, block sunlight.
Control of water loss at the stomata
Since cuticle restricts diffusion of gases, there needs to be a way for gases to enter and exit the leaf. ** STOMATA*
Problem is you get loss of water.
A pair of specialized cells called guard cells surround each opening.
When the guard cells are filled with water the turgor pressure causes them to pucker, thus opening up the stoma.
When the cells lose water the cells sag against each other, thus closing the stoma.
In most plants the guard cells stay open during the day to allow photosynthesis, water is lost but gases are
exchanged. At night when photosynthesis cannot proceed they close to conserve water. Also CO2 builds up inside
the leaf due to respiration.
Detailed mechanism of guard cells
Guard cells open and close due to amount of water and carbon dioxide in them.
1. Sun up
2. photosynthesis begins
3. carbon dioxide levels drop in guard cells
4. The decrease in CO2 levels triggers active transport of potassium ions into guard cells.
5. Water follows K+ into guard cells due to osmosis. Causes stomata to open.
6. As sun goes down CO2 levels go back up (b/c no photosynthesis going on)
7. K+ and water move out of the guard cells and stomata close.
**CAM Plants (such as cacti) conserve water differently. They can't have their stomata open during the day b/c they
would lose too much water due to extreme dry air and heat. They open their stomata at night and fix carbon via the
C4 pathway. The next day they use the carbon dioxide for photosynthesis.
Movement of organic compounds through the plant.
PHLOEM - the vascular tissue that conducts organic materials throughout plants.
Consists of sieve tubes ( living cells) and companion cells (live). Sieve tube cells
rapidly transport sugars. The companion cells help load organic compounds into sieve
tube cells.
Leaf cells make carbohydrates. They use some of those products for themselves, the
remainder are transported roots, stems, buds, flowers, and fruits. The carbohydrates
are converted to starch and stored in plastids (leucoplasts). Proteins and fats which
are made from carbohydrates and amino acids are stored in seeds or fruits (avocados).
Carbohydrates transported in the form of SUCROSE.
Translocation - transport of sucrose and other organic materials through the phloem.
High pressure drive the process. (5x press. of auto tire)
Pressure Flow Theory
Phloem translocates organic compounds along gradients of decreasing pressure and
solute concentration. Flows from areas of high pressure to areas of lower pressure
and lower concentration gradients. Flows from source to sink. Source is anywhere
where organic compound are being loaded into sieve tubes. Sinks are anywhere
organic compounds are being unloaded, used, or stored.
Detailed mechanism
1. In a leaf products of photosynthesis ( in mesophyll cells ) diffuse into companion
cells.
2. Companion cells actively (against the conc. gradient) move the material into the
sieve tubes.
3. Water follows increased concentration gradient, thus increasing turgor pressure.
4. The pressure pushes the material away from the source towards the sink.
5. Pressure and concentration gradients decrease between the source and the sink.
6. Solutes are unloaded at the sinks.
PLANT REPRODUCTION
Coevolution of flowers and pollinators.
Reproduction
Higher plants have sporophyte generation dominant. Show alternation of
generation
Draw below
Flowers - Structures and their functions
Petals - attract pollinators ( all petals = corolla)
Sepals (all sepals = calyx)
Carpel - female reproductive structure
Stigma - collects pollen
Style - lifts stigma up
Ovary - contains ovules becomes the fruit
Ovule - contains eggs becomes the seed
Stamen - male reproductive structure
Anther - makes the pollen
Filament - raises the anther up
Perfect flowers : have both male and female parts.
Imperfect flowers : have only male or female parts.
Some plant have male flowers and female flowers.
Some species have male and female flowers on separate plants.
Draw Picture Here
Pollen development
Each anther has four pollen sacs. Cells in the pollen sacs undergo meiosis and cell division to form
microspores. These haploid cells form a thick wall that resists decomposers. The microspores divide once or twice to
produce the pollen grain (= gametophyte). One of the nuclei will become the sperm.
Egg development
on the inner surface of the ovary a mass of cells forms the ovule. Inside the ovule a cell divides by
meiosis and forms four haploid spores (megaspores) . Typically all megaspores disintegrate except one. The one
remaining haploid spore ( gametophyte ) divides three times by mitosis with some cytoplasmic division. At the end there
are seven cells. One cell is the egg, one cell has two nuclei, the other five cells not important (called - synergids)
Pollination and Fertilization
Pollination - transfer of pollen from anther to stigma. Via wind, water, or biotic vectors.
Pollen lands on stigma and germinates. Forms a pollen tube down through the style to the
ovule. Sperm nuclei (plural) travel down the tube to the ovule.
Fertilization - One sperm nucleus fuses with the egg to form the zygote. The other sperm nucleus fuses
with both nuclei of the endosperm. This results in triploid (3N) nutritive tissue. Two fusions = DOUBLE FERTILIZATION
Embryo development
Zygote in the ovule starts dividing by mitosis. The embryo has lobes of meristematic tissue that give rise to
cotyledons (embryonic leaves). Monocots have one cotyledon, dicots have two. In dicots the embryo absorbs
nutrients from the endosperm and stores them in the cotyledons. In monocots the endosperm is not tapped into until
germination.
Seed Development
By the time the embryo matures the ovule becomes detached from the wall of the ovary. Its integuments (outer
covering) thicken and harden into a seed coat. The embryo, food reserves (endosperm), and coat constitute the
seed.
Fruit Development
Fruit = Mature Ovary
They consist of one or more ovaries. The ovary swells and the flower parts fall off. The ovary will continue to grow
into the fruit. Sometimes other parts of the flower are incorporated into the fruit.
Some fruits are fleshy, some are dry ( acorn, pea pod).
Three divisions of the fleshy fruit are:
endocarp - innermost portion around the seed or seeds
Mesocarp - fleshy portion
exocarp - skin
Fruit and Seed dispersal
Function of fruits is seed dispersal. Why disperse? competition
Different fruits are specialized to disperse seed via wind, water, animals.
Asexual reproduction in plants
Natural
Vegetative growth - new roots and shoots grow right out of extensions or fragments of a parent plant.
Offspring are genetic clones of the parent.
Parthenogenesis - when an embryo develops from an unfertilized egg. May be stimulated by certain
hormones. This embryo is 2N (diploid)?! How? Fusion of the products of mitosis of the egg.
Induced Propagation
- whole plants can grow from cuttings or fragments of shoots
- twig or bud from one plant grafted onto some closely related species
ex: grapevines
Tissue Culture Propagation - Frederick Steward
carrots - shows specialized cells retain genetic info to make all other types of cells. Used
to clone plants that show favorable
mutations
Plant Growth and Development
Dormancy - evolutionary significance of a dormant stage ........
stage of arrested development
Seed germination - when a seed ends dormancy and begins to grow.
Factors that influence germination:
temperature, moisture, oxygen in the soil, and the length of the day
SPRING
Steps:
- imbibition - process by which water moves into a seed. The water is attracted to
the hydrophyllic groups of proteins in the endosperm or cotyledons.
- As more water moves in the seed swells and the coat ruptures.
- As the seed opens up more oxygen reaches the embryo and respiration rates
increase and the cell division increases.
- The root meristem is first to activate.
- Germination is over when the root breaks through the seed coat
Hormonal effects on growth and development
Growth is the increase in the number, size, and volume of cells. Quantitative
Development is the emergence of specialized body parts. Qualitative
Hormones play a role in the selective expression of genes. By different genes being
expressed, cells become differentiated and different patterns of development ensue.
Since the DNA governs the synthesis of enzymes, the hormones influence how and
when the enzymes function.
Five categories of Plant Hormones
- Gibberellins : Promote stem lengthening, help buds and seeds break dormancy. In
some species they influence flowering
- Auxins : affect the lengthening of stems and responses to gravity and light. Also
make coleoptiles grow longer. Indoleacetic acid (IAA) is an important natural auxin. It
is used to thin over crowded seedlings. Some auxins are used to prevent premature
fruit drop. Other auxins are used as herbicides. In certain concentrations these auxin
will kill some plants but not others.
- Cytokinins : stimulate cell divisions, found in abundance in root and shoot meristems,
and in maturing fruits. Natural and synthetic versions have been used to prolong shelf
life of cut flowers and other produce.
- Ethylene : induces aging processes like fruit ripening and leaf drop.
- Abscisic acid : induce bud dormancy and inhibit cell growth or premature seed
germination. Also help stomata close when a plant is low on water.
- Other hormones can be made by root and leaf cells. One kind associated with shoot
tips inhibits growth of lateral buds. = Apical dominance. Gardeners often pinch of
shoots to keep this from happening = bushier bushes
http://www.tensas.k12.la.us/pigpen/BIology%20101/Plant%20Growth%20and%20Develop
ment.ppt#256,1,Plant Growth and Development
http://www-users.york.ac.uk/~drf1/tropism/jcf_1.htm
Tropisms
A plant movement in response to some stimulus. Example roots growing down towards
gravity, shoot growing up towards light. Plant hormones control these movements by
adjusting the rates of cellular division and elongation.
Geotropism (gravitropism): How do roots "know" which direction is down
and shoots know which direction is up? Redistribution of auxins ( and growth inhibiting
hormone) and / or increased/decreased sensitivity to auxins. If one side is having its
growth inhibited while the other side is still growing then the plant bends.
Phototropisms : when plants adjust rate and direction of growth in response
to light. related to a growth stimulating hormone. Auxin moves towards cells less
exposed to light.
Thigmotropism : Change in plant growth in response to touch. Both Auxin
and ethelyene may have a role. Vines, Tendrils
Responses to mechanical stress : example wind blown at beach. Shaken tomatoes
http://plantsinmotion.bio.indiana.edu/plantmotion/movements/tropism/tropisms.ht
ml
Biological clocks
Internal timing mechanisms. Trigger shifts in daily, bring about seasonal adjustments in
growth, development, and reproduction. Controlled by blue-green pigment phytochrome.
Circadian rhythm - daily Cycle (24 hrs), Example: rhythmic leaf movement
Photoperiodism : biological response to change in relative length of the daylight hours to dark hours. Possibly triggered
by Pfr (activated phytochrome).
Long Day Plants : produce flowers in spring
Short Day Plants : produce flowers in late summer or early fall
Day neutral Plants : flower when they are mature enough
Light flash interrupts dark signal
Senescence
Abscisson = dropping of flowers, leaves, fruits and other parts
sum total of processes that lead to the death of a plant or some of its parts.
the recurring cue is decreased length of day. others could be drought, wounds, and nutrient deficiencies. Triggers
decline in IAA production in leaves and fruits.
MORE
Dormancy - short days and long cold nights, or dry nitrogen defice
vernalization - low-temperature stimulation of flowering