AP Biology Unit IX - All About PlantsPlant Anatomy and Growth- Chapter 35Plant Transport - Chapter 36Plant Nutrition - Chapter 37Plant Reproduction and Development - Chapter 38Plant 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 plants.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 in 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 Anatomyangiosperms

Plant OrgansRoots - specialized for absorption of water and minerals, acts as an

anchor, and stores excess food (starch)Stems - conducts water and minerals, supports plant, lifts up leaves for

display, store food, and in young plants photosynthesisLeaves - 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 tissuesGround Tissue - makes up the bulk of the plant body

Meristem : growing tissue, regions of embryonic cells

- Apical meristems - at ends of shoots and roots, lengthening of stems and roots represents primary growth

- Vascular Cambium - lateral meristem in roots and secondary growth stems that increases the thickness.

- Cork Cambium - lateral meristem that gives rise to a sturdier covering that replaces epidermis

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 secondary growth.

Structure of shootsVascular bundles - scattered vs in ringsCortexpith

Leaves (page ___ )variations - regular, needle, succulentsdeciduous vs evergreensimple vs compoundveins - parallel vs netlikethin 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

internalUpper epidermisPalisade mesophyllSpongy mesophyllvascular bundlelower epidermisstoma - guard cells

Rootsprimary root with lateral roots = Taproot - Dicotsmonocots - 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 PlantsAnnualsBiennialsPerennials

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:Macronutrientsoxygen 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

MicronutrientsChlorineIron Boron Manganese ZincCopper Molybdenum

Loss of nutrients form the soilLeaching - 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 mineralsPlants spend tremendous amounts of energy growing root

systems. Soil where concentration of water and mineral ions are greater, stimulates growth.

Specialized Absorptive structuresroot hairs - extensions of epidermal cellsroot 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 PlantsPlants 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 theoryxylem - 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 conservationCuticle - 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 stomataSince 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 cellsGuard 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 cells4. 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 TheoryPhloem 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 mechanism1. 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.

ReproductionHigher plants have sporophyte generation dominant. Show

alternation of generation

Draw below

Flowers - Structures and their functionsPetals - attract pollinators ( all petals = corolla) Draw Picture HereSepals (all sepals = calyx)

Carpel - female reproductive structureStigma - collects pollen

Style - lifts stigma upOvary - contains ovules becomes the fruit

Ovule - contains eggs becomes the seed

Stamen - male reproductive structureAnther - makes the pollenFilament - 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.

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 developmenton 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 FertilizationPollination - 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

Pollen development

Embryo developmentZygote 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 DevelopmentBy 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 DevelopmentFruit = Mature OvaryThey 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 seedsMesocarp - fleshy portionexocarp - skin

Fruit and Seed dispersalFunction of fruits is seed dispersal. Why disperse? competitionDifferent fruits are specialized to disperse seed via wind, water, animals.

Asexual reproduction in plantsNatural

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 Stewardcarrots - shows specialized cells retain genetic info to make all other types of

cells. Used to clone plants that show favorable mutations

Plant Growth and DevelopmentDormancy - 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

SPRINGSteps:- 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 developmentGrowth is the increase in the number, size, and volume of cells. QuantitativeDevelopment 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%20Development.ppt#256,1,Plant Growth and Development

TropismsA 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

Biological clocksInternal 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

http://www-users.york.ac.uk/~drf1/tropism/jcf_1.htm

http://plantsinmotion.bio.indiana.edu/plantmotion/movements/tropism/tropisms.html

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

SenescenceAbscisson = 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