Introduction to Plant Science

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Introduction to Plant Science

• AGRI 1203

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1000 Point Course 700 objective, 300 subjective

• Final/ Journal
• Daily Assignments
• Mid Term
• Notebooks
• Power Point Presentation
• Final
• (other projects to be announced throughout the
  course)

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The Importance of Plants in Our Daily Lives

• Plants provide us with the basis of survival.
• Wheat and Barley are among the oldest known
  cultivated crops.
• Plants can thrive without people and animals
  however, people and animals can NOT survive
  without plants.
• Plants provide us with food, oxygen, fossil
  fuels, vaccines, medicines, and prevent the
  erosion of soil.

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Importance of Plants (continued)

• Herbivores consume approximately 10 of the plant
  biomass produced in a typical food chain.
• Carnivores capture and consume about 10 of the
  energy stored by the herbivores.

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The Significance of the Binomial System of Naming
Plants

• There are over 500,000 different recognized
  plants in the world.
• The Binomial System was developed by Carolus
  Linnaeus.

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The Significance of the Binomial System of Naming
Plants (continued)

• First word is the genus
• Second word is the species
• Third word is the authority of abbreviation

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Introduction to Plants

• The parts of a plant can be divided into two
  groups, sexual reproductive parts and vegetative
  parts. Sexual reproductive parts are those
  involved in the production of seed. They include
  flower buds, flowers, fruit, and seeds. The
  vegetative parts include leaves, roots, leaf
  buds, and stems. Although the vegetative parts
  are not directly involved in sexual reproduction,
  they are often used in asexual or vegetative
  forms of reproduction, such as cuttings.

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Introduction to Plants

• The kingdom Plantae encompasses water-dwelling
  red and green algae as well as terrestrial
  plants, which have evolved to support themselves
  outside of the aquatic environment of their
  ancestors.
• The terrestrial plants, which include bryophytes
  (mosses) as well as the more highly evolved
  vascular plants, called tracheophytes.

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Introduction to Plants

• As a consequence of their move onto land,
  terrestrial plants require structures that
  support their weight, prevent desiccation (drying
  out), aid in reproduction, and transport water,
  nutrients, and the products of photosynthesis
  throughout the parts of the plant.
• Bryophytes have not yet made the complete
  transition to land, and are thus still dependent
  upon a moist environment to assist in
  reproduction and nutrient transport.
• The more highly evolved tracheophytes, on the
  other hand, have developed internal systems of
  transport and support called vascular systems,
  which have allowed them to become fully
  terrestrial.

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Common Plant Characteristics

• As explored in Common Plant Characteristics ,
  most terrestrial plants (both bryophytes and
  tracheophytes) share some general structural and
  functional features.
• Plant bodies are divided into two regions, the
  underground root portion and the aerial shoot
  portion (including stem, leaves, flowers, and
  fruits).
• These different regions of the plant are
  dependent on each other, as each performs
  different essential functions.

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Common Plant Characteristics

• Land plants also share certain more specific
  adaptations that are essential to survival out of
  water.
• These include an impermeable waxy cuticle on the
  outer aerial surfaces, jacket cells around the
  reproductive organs, and stomata that allow gas
  exchange without risking excessive water loss.
• All Plants are also autotrophic, meaning that
  they produce their own food and do not use other
  organisms to supply organic nutrients the way
  animals do.
• Finally, the life cycle of plants follows a
  pattern called the alternation of generations, in
  which they fluctuate between haploid and diploid
  generations and sexual and asexual modes of
  reproduction.

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Plant Classification

• Terrestrial plants, as noted above, are
  classified as bryophytes and tracheophytes.
• Bryophytes, such as mosses and liverworts, are
  still dependent on a moist environment for
  reproductive and nutritive functions even though
  they are technically "terrestrial."
• Bryophytes also have very little internal
  support, limiting the heights to which they can
  grow.

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Plant Classification

• As a phylum, Bryophytes, are lower on the
  evolutionary scale than tracheophytes, which have
  adapted completely to life on land.
• Tracheophytes (also known as vascular plants)
  possess well-developed vascular systems, which
  are comprised of tissues that form internal
  passageways through which water and dissolved
  nutrients can traverse the entire plant.

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Plant Classification

• Vascular plants are thus far less reliant on
  moist environments for survival.
• At the same time, Vascular systems also provide a
  strong system of support to the plant, allowing
  some tracheophytes to grow to immense heights.
• The tracheophytes can be further broken down into
  two kinds of seed-producing plants, gymnosperms
  (conifers) and angiosperms (flowering plants).

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Plant Classification

• The male gametes of gymnosperms and angiosperms
  are carried by pollen each of these types of
  plants also produce seeds, which protect the
  embryos inside from drying out in a terrestrial
  environment.
• Angiosperms, with their flowers and fruits, have
  adapted even further to the terrestrial
  environment flowers, by attracting insects and
  other pollen-bearing animals, aid in the transfer
  of pollen to female reproductive organs.
• Angiosperm fruits, developed from ovaries,
  protect the seeds and help in their dispersal.
• Finally, angiosperms themselves are divided into
  two classes--monocots and dicots--based on
  differences in embryonic development, root
  structure, flower petal arrangement, and other
  factors.

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Structures and Functions

• The seed, which develops from an ovule after
  fertilization has occurred, surrounds the plant
  embryo and protects it from desiccation.
• Each seed consists of an embryo, food source, and
  protective outer coat, and can lie dormant for
  some time before germinating.
• The roots of a plant function in the storage of
  nutrients, the acquisition of water and minerals
  (from the soil), and the anchoring of the plant
  to the substrate.

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Structures and Functions

• Tiny root hairs, which extend from the root
  surface, provide the plant with a huge total
  absorptive surface and are responsible for most
  of the plant's water and mineral intake.
• Plant stems (or trunks, as they are called in
  trees) function primarily in nutrient transport
  and physical support.
• The leaves contain chlorophyll and are the major
  sites of photosynthesis and gas exchange.
• Flowers contain the reproductive organs of
  angiosperms.

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Essential Processes

• Plants carry out a number of processes that are
  essential to their survival.
• Internal water and sugar transport are largely
  carried out within the vascular system, ensuring
  that the entire plant receives water and food
  even though these materials are brought in or
  produced only in certain parts of the plant.

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Essential Processes

• Plant hormones determine the timing and
  occurrence of many of the processes of the plant,
  from germination to tissue growth to
  reproduction.
• Plants can also respond to light, touch, and
  gravity in various ways.

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Life Cycle

• The life cycle of plants depends upon the
  alternation of generations, the fluctuation
  between the diploid (sporophyte) and haploid
  (gametophyte) life stages.
• Reproduction in most plants can occur both
  sexually and asexually.
• In sexual reproduction, fertilization occurs when
  a male gamete (sperm cell) joins with an egg cell
  to produce a zygote.

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Life Cycle

• In gymnosperms and angiosperms (the seed plants),
  the ovule containing the egg cell becomes a seed
  after fertilization has occurred.
• In angiosperms (flowering plants), the embryo is
  given added protection by an ovary, which
  develops into a fruit.
• Plants can also reproduce asexually through
  vegetative propagation, a process in which plants
  produce genetically identical offshoots (clones)
  of themselves, which then develop into
  independent plants.
• This asexual means of reproduction can occur
  naturally through specialized structures such as
  tubers, runners, and bulbs or artificially
  through grafting.

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Classification Based on Life Span

• From a horticultural perspective, life span is a
  function of climate and usage.
• Many garden plants (including tomatoes and
  geraniums) grown as annuals in Colorado would be
  perennials in climates without freezing winter
  temperatures.

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Annuals

• Complete their life cycle (from seedling to
  setting seed) within a SINGLE growing season.
• However, the growing season may be from fall to
  summer, not just spring to fall.
• These plants come back from seeds only.

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Summer annuals

• Germinate from seed in the spring and complete
  flowering and seed production by fall, followed
  by plant death, usually due to cold temperatures.
  
• Their growing season is from spring to fall.
• Examples marigolds, squash, and crabgrass. These
  are also called warm season annuals.

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Winter annuals

• Germinate from seed in the fall, with flowering
  and seed development the following spring,
  followed by plant death.
• Their growing season is from fall to summer.
• Examples winter wheat and annual bluegrass.
• These are also referred to as cool season
  annuals.
• Many weeds in the lawn (such as chickweed and
  annual bluegrass) are winter annuals.

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Biennials

• Germinate from seed during the growing season and
  often produce an over-wintering storage root or
  bulb the first summer.
• Quite often they maintain a rosette growth habit
  the first season, meaning that all the leaves are
  basal.
• They flower and develop seeds the second summer,
  followed by death.

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Biennials

• In the garden setting, we grow many biennials as
  annuals (e.g., carrots, onions, and beets)
  because we are more interested in the root than
  the bloom.
• Some biennial flowers may be grown as short-lived
  perennials (e.g., hollyhocks).

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Perennials

• Live through several growing seasons, and can
  survive a period of dormancy between growing
  seasons.
• These plants regenerate from root systems or
  protected buds, in addition to seeds.

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Perennials

• Herbaceous perennials develop over-wintering
  woody tissue only at the base of shoots (e.g.
  peony and hosta) or have underground storage
  structures from which new stems are produced.
• (Please note Golden Vicary Privet can be either
  herbaceous or woody as grown in Colorado.)

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Perennials

• Spring ephemerals have a relatively short growing
  season but return next season from underground
  storage organs (e.g. bleeding heart, daffodils).
• Woody perennials develop over-wintering tissue
  along woody stems and in buds, (e.g. most trees
  and shrubs grown in Colorado).
• Combination plants are usually classified as
  annual, biennial or perennial on the basis of the
  plant part that lives the longest. For example,
  raspberries have biennial canes and perennial
  roots

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Classification by Climatic Requirements
Temperature Requirements

• Tropical plants originate in tropical climates
  with a year-round summer like growing season
  without freezing temperatures.
• Examples include cocoa, cashew and macadamia
  nuts, bananas, mango, papaya, and pineapple.

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Classification by Climatic Requirements
Temperature Requirements

• Sub-tropical plants cannot tolerate severe winter
  temperatures but need some winter chilling.
• Examples include citrus, dates, figs, and olives.
• Temperate-zone plants require a cold winter
  season as well as summer growing season and are
  adapted to survive temperatures considerably
  below freezing point.
• Examples include apples, cherries, peaches,
  maples, cottonwoods, and aspen.
• In temperate zones, tropical and sub-tropical
  plants are grown as annuals and houseplants.

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Classification by Climatic Requirements
Temperature Requirements

• Cool season plants thrive in cool temperatures
  (40 to 70 degrees Fahrenheit daytime
  temperatures) and are somewhat tolerant of light
  frosts.
• Examples include Kentucky bluegrass, peas,
  lettuce, and pansies.
• Warm season plants thrive in warm temperatures
  (65 to 90 degrees Fahrenheit daytime
  temperatures) and are intolerant of cool
  temperatures.
• Examples include corn, tomatoes and squash.

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Classification by Climatic Requirements
Temperature Requirements

• Tender plants are intolerant of cool
  temperatures, frost and cold winds.
• Examples include most summer annuals, including
  impatiens, squash, and tomatoes.
• Hardy plants are tolerant of cool temperatures,
  light frost and cold winds (e.g., spring
  flowering bulbs, spring-flowering perennials,
  peas, lettuce).

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Classification by Climatic Requirements
Temperature Requirements

• Hardiness refers to a plants tolerance to winter
  climatic conditions.
• Factors that influence hardiness include minimum
  temperature, recent temperature patterns, water
  supply, wind and sun exposure, genetic makeup,
  and carbohydrate reserves.
• Cold hardiness zone refers to the average annual
  minimum temperature for a geographic area.
• Temperature is only one factor that influences a
  plants winter hardiness.
• The USDA Hardiness zone map http//www.usna.usda
  .gov/Hardzone/ushzmap.html

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Classification by Climatic Requirements
Temperature Requirements

• Heat zone refers to the accumulation of heat, a
  primary factor on how fast crops grow and what
  crops are suitable for any given area. This is
  only one factor that influences a plants heat
  tolerance. On a heat zone map, the Colorado Front
  Range falls into zones 5 to 7.

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The Four Major Plant Parts

• Roots
• Stems
• Leaves
• Flowers

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Plant Root

• Underground parts of most plants
• Absorb water and minerals
• Store starch as food reserve
• Anchor the plant

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ROOTS

• A thorough knowledge of the root system of plants
  is essential if their growth, flowering, and
  fruiting responses are to be understood.
• The structure and growth habits of roots have a
  pronounced effect on the size and vigor of the
  plant, method of propagation, adaptation to
  certain soil types, and response to cultural
  practices and irrigation.
• The roots of certain vegetable crops are
  important as food.

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ROOTS

• Roots typically originate from the lower portion
  of a plant or cutting.
• They possess a root cap, have no nodes and never
  bear leaves or flowers directly.
• The principal functions of roots are to absorb
  nutrients and moisture, to anchor the plant in
  the soil, to furnish physical support for the
  stem, and to serve as food storage organs.
• In some plants they may be used as a means of
  propagation.

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ROOTS

• A primary (radicle) root originates at the lower
  end of the embryo of a seedling plant.
• A taproot is formed when the primary root
  continues to elongate downward.
• This makes them difficult to transplant and
  necessitates planting only in deep, well-drained
  soil.
• The taproot of carrot, parsnip, and salsify is
  the principal edible part of these crops.

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ROOTS

• A lateral, or secondary root is a side or branch
  root which arises from another root.
• A fibrous root system is one in which the primary
  root ceases to elongate, leading to the
  development of numerous lateral roots.
• These then branch repeatedly and form the feeding
  root system of the plant.

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ROOTS

• A fibrous root is one which remains small in
  diameter because of a lack of significant cambial
  activity.
• One factor which causes shrubs and dwarf trees to
  remain smaller than standard trees is the lower
  activity rate of the cambium tissue which
  produces a smaller root system.
• If plants that normally develop a taproot are
  undercut so that the taproot is severed early in
  the plants life, the root will lose its taproot
  characteristic and develop a fibrous root system.
  

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ROOTS

• This is done commercially in nurseries so that
  trees, which naturally have tap roots, will
  develop a compact, fibrous root system.
• This allows a higher rate of transplanting
  success.
• The quantity and distribution of plant roots is
  very important because these two factors have a
  major influence on the absorption of moisture and
  nutrients.
• The depth and spread of the roots is dependent on
  the inherent growth characteristics of the plant
  and the texture and structure of the soil.

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ROOTS

• Roots will penetrate much deeper in a loose,
  well-drained soil than in a heavy, poorly-drained
  soil.
• A dense, compacted layer in the soil will
  restrict or stop root growth.
• During early development, a seedling plant
  nutrients and moisture from the few inches of
  soil surrounding it.
• Therefore, the early growth of most horticultural
  crops which are seeded in rows benefits from band
  applications of fertilizer, placed several inches
  to each side and slightly below the seeds.

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ROOTS

• As plants become well-established, the root
  system develops laterally and usually extends far
  beyond the spread of the branches.
• For most cultivated crops roots meet and overlap
  between the rows.
• The greatest concentration of fibrous roots
  occurs in the top foot of soil but significant
  numbers of laterals may grow downward from these
  roots to provide an effective absorption system a
  couple of feet deep.

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Root Systems

• Taproots have a dominant main segment and are a
  characteristic of many dicot plants
• Fibrous roots have no dominant segment

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Parts of a Root

• Internally, there are three major parts of a
  root.
• The meristem is at the tip and manufactures new
  cells.
• It is an area of cell division and growth.

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Parts of a Root

• Behind it is the zone of elongation, in which
  cells increase in size through food and water
  absorption.
• These cells by increasing in size, push the root
  through the soil.
• The third major root part is the maturation zone,
  in which cells undergo changes in order to become
  specific tissues such as epidermis, cortex, or
  vascular tissue.

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Parts of a Root

• The epidermis is the outermost layer of cells
  surrounding the root.
• These cells are responsible for the absorption of
  water and minerals dissolved in water.
• Cortex cells are involved in the movement of
  water from the epidermis and in food storage.

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Parts of a Root

• A layer of suberized (a fatty material in some
  cells), known as the Casparian strips, has
  regulatory effect on the types of minerals
  absorbed and transported by the roots to stems
  and leaves.
• Vascular tissues conduct food and water and are
  located in the center of the root.

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Parts of a Root

• However, some monocots have the vascular system
  of their roots distributed around the root
  center.
• Externally there are two areas of importance.
• Root hairs are found along the main root and
  perform much of the actual work of water and
  nutrient absorption.

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The Function of Root Hairs

• Root hairs are found behind the root cap
• They absorb moisture and minerals which are
  conducted to the larger roots and stem of the
  plant

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Root Hairs
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Root Hairs
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Parts of a Root

• The root cap is the outermost tip of the root,
  and consists of cells that are sloughed off as
  the root grows through the soil.
• The root cap covers and protects the meristem and
  also senses gravity and directs in what direction
  the root grows.

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Roots as Food

• The enlarged root is the edible portion of
  several vegetable crops.
• The sweet potato is a swollen root, called a
  tuberous root, which serves as a food storage
  area for the plant.
• Carrot, parsnip, salsify, and radish are
  elongated taproots.

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Stems

• Act as channels through which water and
  photosynthetic food products pass.
• Stems may be above or below ground

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Above Ground Stems

• Small Stems carrots and dandelion
• Climbing Stems ivy and pod beans
• Creeping Stems (Stolons) bentgrass

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Below Ground Stems

• Tubers potatoes
• Bulbs tulip and crocus
• Rhizomes zoysiagrass

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Stems

• Stems are structures which support buds and
  leaves and serve as conduits for carrying water,
  minerals, and sugars.
• The three major internal parts of a stem are the
  xylem, phloem, and cambium.
• The xylem and phloem are the major components of
  a plants vascular system.

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Stems

• The vascular system transports food, water, and
  minerals and offers support for the plant.
• Xylem vessels conduct water and minerals, while
  phloem tubes conduct food.
• The vascular systems of monocots and dicots
  differ.

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Stems

• While both contain xylem and phloem, they are
  arranged differently.
• In the stem of a monocot, the xylem and phloem
  are paired into bundles these bundles are
  dispersed throughout the stem.
• But in the stem of a dicot, the vascular system
  forms rings inside the stem.

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Stems

• The ring of phloem is near the bark or external
  cover of the stem and is a component of the bark
  in mature stems.
• The xylem forms the inner ring it is the sapwood
  and heartwood in woody plants.
• The difference in the vascular system of the two
  groups is of practical interest to the
  horticulturist because certain herbicides are
  specific to either monocots or dicots.
• An example is 2, 4, -D, which only kills dicots.

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Types of Stems

• A shoot is a young stem with leaves present.
• A twig is a stem which is less than one year old
  and has no leaves since it is still in the
  winter-dormant stage.
• A branch is a stem which is more than one year
  old and typically has lateral stems.
• A trunk is a main stem of a woody plant.

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Types of Stems

• Most trees have a single trunk.Trees are
  perennial woody plants, usually have one main
  trunk, and are usually more than 12 feet tall at
  maturity.
• Shrubs are perennial woody plants that may have
  one or several main stems, and are usually less
  than 12 feet tall at maturity.
• A vine is a plant which develops long, trailing
  stems that grow along the ground unless they are
  supported by another plant or structure.

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Types of Stems

• Some twining vines circle their support clockwise
  while others circle counter clockwise.
• Climbing vines are supported by aerial roots,
  slender tendrils which encircle the supporting
  object, or tendrils with adhesive tips.

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Modified Stems

• Although typical stems are above-ground trunks
  and branches, there are modified stems which can
  be found above ground and below ground.
• The above-ground modified stems are crowns,
  stolons, and spurs, and the below-ground stems
  are bulbs, corms, rhizomes, and tubers.
• A crown is a region of compressed stem tissue
  from which new shoots are produced, generally
  found near the surface of the soil.
• Crowns (strawberries, dandelions, African
  violets) are compressed stems having leaves and
  flowers on short internodes.

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Modified Stems

• A spur is a compressed fruiting branch.
• Spurs are short, stubby, side stems that arise
  from the main stem and are common on such fruit
  trees as pears, apples, and cherries, where they
  may bear fruit.
• If severe pruning is done close to fruit-bearing
  spurs, the spurs can revert to a long,
  nonfruiting stem.

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Modified Stems

• A stolon is a horizontal stem that is fleshy or
  semi-woody and lies along the top of the ground.
• A runner is a type of stolon.
• It is a specialized stem that grows on the soil
  surface and forms a new plant at one or more of
  its nodes.

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Modified Stems

• Strawberry runners are examples of stolons.
• Remember, all stems have nodes and buds or
  leaves.
• The leaves on strawberry runners are small but
  are located at the nodes which are easy to see.
• The spider plant also has stolons.

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Modified Stems

• A tuber is an enlarged portion of an underground
  stem like potato tubers, tulip bulbs, and iris
  rhizomes are underground stems that store food
  for the plant.
• The tuber, like any other stem, has nodes that
  produce buds.
• The eyes of a potato are actually the nodes on
  the stem.

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Modified Stems

• Each eye contains a cluster of buds.
• A rhizome is a specialized stem which grows
  horizontally at or just below the soil surface.
• They act as a storage organ and means of
  propagation in some plants and are similar to
  stolons.
• Some rhizomes are compressed and fleshy such as
  those of iris they can also be slender with
  elongated internodes such as bentgrass.

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Modified Stems

• Johnsongrass is a hated weed principally because
  of the spreading capability of its rhizomes.
• Tulips, lilies, daffodils, and onions are plants
  that produce bulbs--shortened, compressed,
  underground stems surrounded by fleshy scales
  (leaves) that envelop a central bud located at
  the tip of the stem.

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Modified Stems

• If you cut through the center of a tulip or
  daffodil bulb in November, you can see all the
  flower parts in miniature within the bulb.
• Many bulbs require a period of low-temperature
  exposure before they begin to send up the new
  plant.
• Both the temperature and length of this treatment
  are of critical importance to commercial growers
  who force bulbs for holidays.

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Modified Stems

• Corms are not the same as bulbs.
• They have shapes similar to bulbs, but do not
  contain fleshy scales.
• A corm is a solid, swollen stem whose scales have
  been reduced to a dry, leaflike covering.

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Modified Stems

• Some plants produce a modified stem that is
  referred to as a tuberous stem.
• Examples are tuberous begonia and cyclamen.
• The stem is shortened, flattened, enlarged, and
  underground.
• Buds and shoots arise from the crown and fibrous
  roots are found on the bottom of the tuberous
  stem.

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Modified Stems

• In addition, some plants such as the dahlia and
  the sweet potato produce an underground storage
  organ called a tuberous root, which is often
  confused with bulbs and tubers.
• However, these are roots, not stems, and have
  neither nodes nor internodes.
• It may sometimes be difficult to distinguish
  between roots and stems, but one sure way is to
  look for the presence of nodes.

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Modified Stems

• Stems have nodes roots do not. Stems are
  commonly used for plant propagation.
• Above-ground stems can be divided into sections
  that contain internodes and nodes.
• They are utilized as cuttings and will produce
  stems that are good propagative tissues.

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Modified Stems

• Rhizomes can be divided into pieces.
• Bulbs form small bulblets at the base of the
  parent bulb.
• Cormels are miniature corms that form under the
  parent corm.
• Tubers can be cut into pieces containing eyes and
  nodes.
• All of these will produce new plants.

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Texture and Growth of Stems

• Woody stems contain relatively large amounts of
  hardened xylem tissue in its core, and are
  typical of most tree fruits and ornamental trees
  and shrubs.
• A cane is a stem which has a relatively large
  pith and usually lives only one or two years.

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Texture and Growth of Stems

• Examples of plants with canes include rose,
  grape, and blackberry.
• Herbaceous or succulent stems contain only small
  amounts of xylem tissue and usually live for only
  one growing season.
• If the plant is perennial, it will develop new
  shoots from the root.

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Life Cycles of Plants

• Plants are classified by the number of growing
  seasons required to complete a life cycle.
• Annuals pass through their entire life cycle from
  seed germination to seed production in one
  growing season and then die.
• Biennials are plants which start from seeds and
  produce vegetative structures and food storage
  organs the first season.

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Life Cycles of Plants

• During the first winter a hardy evergreen rosette
  of basal leaves persists.
• During the second season flowers, fruit, and
  seeds develop to complete the life cycle.
• The plant then dies.
• Carrots, beets, cabbage, celery, and onions are
  biennial plants.
• Hollyhock, Canterbury Bells, and Sweet William
  are biennials which are commonly grown for their
  attractive flowers.

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Life Cycles of Plants

• Plants which typically develop as biennials may,
  in some cases, complete the cycle of growth from
  seed germination to seed production in only one
  growing season.
• This situation occurs when drought, variations in
  temperature or other climatic conditions are
  experienced.
• These cause the plant to physiologically pass
  through the equivalent of two growing seasons, in
  a single growing season.

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Life Cycles of Plants

• This phenomenon is referred to as bolting.
• Perennial plants live for many years, and after
  reaching maturity, typically produce flowers and
  seeds each year.
• Perennials are classified as herbaceous if the
  top dies back to the ground each winter and new
  stems grow from the roots each spring.
• They are classified as woody if the top persists,
  as in shrubs or trees.

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Stems as Food

• The edible portion of cultivated plants such as
  asparagus and kohlrabi is an enlarged succulent
  stem.
• The edible parts of broccoli are composed of stem
  tissue, flower buds, and a few small leaves.
• The edible part of potato is a fleshy underground
  stem called a tuber.
• Although the name suggests otherwise, the edible
  part of the cauliflower is proliferated stem
  tissue.

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Leaves

• Make Food for the Plant

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LEAVES

• The blade of a leaf is the expanded, thin
  structure on either side of the midrib.
• The blade is usually the largest and most
  conspicuous part of a leaf.
• The petiole is the stalk which supports the leaf
  blade.

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LEAVES

• It varies in length and may be lacking entirely
  in some cases where the leaf blade is described
  as sessile or stalkless.
• The principal function of leaves is to absorb
  sunlight for the manufacturing of plant sugars in
  a process called photosynthesis.
• Leaves develop as a flattened surface in order to
  present a large area for efficient absorption of
  light energy.

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The Function of the Chloroplasts

• Chloroplasts are plastids containing chlorophyll
• Absorb energy of light
• Separate H (hydrogen) from 02 (oxygen) in a
  molecule of H2 O (water)

110
Respiration

• Opposite of Photosynthesis
• Respiration is the release of energy from a plant
  that was captured and stored by photosynthesis
• Equation of Respiration
• C6H1206 6H2O 6O2 6CO2 12H2O energy

111
Transpiration

• Transpiration is the upward pull of water started
  by the evaporation of molecules

112
Photosynthesis

• Photosynthesis is the process by which green
  plants manufacture food
• Light Energy (solar) is converted to chemical
  energy
• Photosynthesis Equation
• 6CO2 6H2O sunlight C6H12O6 6O2

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The Function of the Phloem

• Phloem is active in conducting photosynthetic
  sugars from the leaves to the root

114
The Function of the Xylem

• The xylem conducts water and minerals from the
  soil to above ground plant parts

115
Monocots and Dicots

• Plants having a single cotyledon (seed leaf) are
  monocots
• Plants having more than one cotyledon
• Student Assignment Compare and contrast the
  difference in seed leafs between corn and green
  beans.

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LEAVES

• The leaf is supported away from the stem by a
  stem-like appendage called a petiole. The base of
  the petiole is attached to the stem at the node.
• The small angle formed between the petiole and
  the stem is called the leaf axil.
• An active or dormant bud or cluster of buds is
  usually located in the axil.

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LEAVES

• The leaf blade is composed of several layers.
• On the top and bottom is a layer of thickened,
  tough cells called the epidermis.
• The primary function of the epidermis is
  protection of leaf tissue.

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LEAVES

• The way in which the cells in the epidermis are
  arranged determines the texture of the leaf
  surface.
• Some leaves have hairs that are an extension of
  certain cells of the epidermis.
• The African violet has so many hairs that the
  leaf feels like velvet.

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LEAVES

• Part of the epidermis is the cuticle, which is
  composed of a waxy substance called cutin that
  protects the leaf from dehydration and prevents
  penetration of some diseases.
• The amount of cutin is a direct response to
  sunlight, increasing with increasing light
  intensity.

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LEAVES

• For this reason, plants grown in the shade should
  be moved into full sunlight gradually, over a
  period of a few weeks, to allow the cutin layer
  to increase and to protect the leaves from the
  shock of rapid water loss or sun scald.
• The waxy cutin also repels water and can shed
  pesticides if spreader-sticker agents or soaps
  are not used.

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LEAVES

• This is the reason many pesticide manufacturers
  include some sort of spray additive to adhere to
  or penetrate the cuticle.
• Some epidermal cells are capable of opening and
  closing.
• These cells guard the interior of the leaf and
  regulate the passage of water, oxygen, and carbon
  dioxide through the leaf.

124
LEAVES

• These regulatory cells are called guard cells.
• They protect openings in the leaf surface called
  stoma.
• The opening and closing of the cells are
  determined by the weather.

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The Function of the Stoma

• Stomas are openings within the epidermis
• They allow air to enter the leaf and water vapor
  and oxygen to move out

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LEAVES

• Conditions that would cause large water losses
  from plants (high temperature, low humidity)
  stimulate guard cells to close.
• Mild weather conditions leave guard cells in an
  open condition.
• Guard cells will close in the absence of light.

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The Function of the Guard Cell

• One of the two epidermal cells in a plant leaf
• Guard Cells enclose a stoma

128
LEAVES

• A large percentage of stomata occur in the lower
  epidermis.
• The middle layer of the leaf is the mesophyll and
  is located between the upper and lower epidermis.
  
• This is the layer in which photosynthesis occurs.

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LEAVES

• The mesophyll is divided into a dense upper
  layer, called the palisade layer, and a spongy
  lower layer that contains a great deal of air
  space, called the spongy mesophyll.
• The cells in these two layers contain
  chloroplasts which are the actual sites of the
  photosynthetic process.

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Types of Leaves

• A number of rather distinct types of leaves occur
  on plants.
• Leaves commonly referred to as foliage are the
  most common and conspicuous, and as previously
  stated, serve as the manufacturing centers where
  the photosynthetic activity of the plant occurs.

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Types of Leaves

• Scale leaves or cataphylls are found on rhizomes
  and are also the small, leathery, protective
  leaves which enclose and protect buds.
• Seed leaves, or cotyledons, are modified leaves
  which are found on the embryonic plant and
  commonly serve as storage organs.
• Spines and tendrils, as found on barberry and
  pea, are specialized modified leaves which
  protect the plant or assist in supporting the
  stems.

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Types of Leaves

• Storage leaves, as are found in bulbous plants
  and succulents, serve as food storage organs.
  Other specialized leaves include bracts, which
  are often brightly colored. The showy structures
  on dogwoods and poinsettias are bracts, not
  petals.
• Conifers, (pines, firs, spruce, laurel, etc.)
  have "needles" as leaves. They normally have waxy
  cuticles with sunken stomata to help deter
  desiccation. Also, most have resin canals on
  either side of the vascular system. The resin is
  thought to help deter and guard against insect
  damage.

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Venation of Leaves

• The vascular bundles from the stem extend through
  the petiole and spread out into the blade.
• The term venation refers to the patterns in which
  the veins are distributed in the blade.
• Two principal types of venation are
  parallel-veined and net-veined.

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Venation of Leaves

• Parallel-veined leaves are those in which there
  are numerous veins which run essentially parallel
  to each other and are connected laterally by
  minute, straight veinlets.
• Possibly the most common type of parallel-veining
  is that found in plants of the grass family where
  the veins run from the base to the apex of the
  leaf.
• Another type of parallel-venation is found in
  plants such as banana, calla, and pickerelweed,
  where the parallel veins run laterally from the
  midrib.
• Parallel-veined leaves occur on plants which are
  part of the monocotyledon group.

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Venation of Leaves

• Net-veined leaves, also called
  reticulate-veined, have veins which branch from
  the main midrib(s) and then subdivide into finer
  veinlets which then unite in a complicated
  network.
• This system of enmeshed veins gives the leaf more
  resistance to tearing than most parallel-veined
  leaves.
• Net-venation may be either pinnate or palmate.
• In pinnate venation, the veins extend laterally
  from the midrib to the edge, as in apple, cherry
  and peach.

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Venation of Leaves

• Palmate venation occurs in grape and maple
  leaves, where the principal veins extend outward,
  like the ribs of a fan, from the petiole near the
  base of the leaf blade.
• Net-veined leaves occur on plants which are part
  of the dicotyledon group.

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Leaves as a Means of Identifying Plants

• Leaves are useful in identifying species and
  varieties of horticultural plants.
• The shape of the leaf blade and the type of
  margin are of major importance as identifying
  characteristics.
• Simple leaves are those in which the leaf blade
  is a single continuous unit. A compound leaf is
  composed of several separate leaflets arising
  from the same petiole.

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Leaves as a Means of Identifying Plants

• A deeply lobed leaf may appear similar to a
  compound leaf, but if the leaflets are connected
  by narrow bands of blade tissue it may be
  classified as a simple leaf.
• If the leaflets have separate stalks and if these
  stalks are jointed at the point of union with the
  main leafstalk, the leaf is considered to be
  compound. Some leaves may be doubly compound,
  having divisions of the leaflets.

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Shape of the Leaf Blade

• The following are some common shapes which are
  found in leaves and leaflets
• Linear Narrow, several times longer than wide
  approximately the same width.
• Elliptical2 or 3 times longer than wide
  tapering to an acute or rounded apex and base.
• Ovate Egg-shaped, basal portion wide tapering
  toward the apex.
• Lanceolate Longer than wide tapering toward the
  apex and base.
• Cordate Heart-shaped, broadly ovate tapering to
  an acute apex, with the base turning in and
  forming a notch where the petiole is attached
• head lettuce, the leaves form a large, naked bud
  and are the edible product.

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Shape of the Leaf Apex and Base

• The following are common shapes found in leaves
• Apex
• Acuminate Tapering to a long, narrow point.
• Acute Ending in an acute angle, with a sharp,
  but not acuminate, point.
• Base
• Obtuse Tapering to a rounded edge.
• Sagittate Arrowhead-shaped, with two pointed
  lower lobes.
• Truncate Having a relatively square end.

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Appex
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Base
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APPEX
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BASE
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Leaf Margins

• Studying leaf margins is especially useful in the
  identification of certain varieties of fruit
  plants.
• Entire A smooth edge with no teeth or notches.
• Sinuate Having a pronounced sinuous or wavy
  margin.
• Crenate Having rounded teeth.
• Dentate Having teeth ending in an acute angle,
  pointing outward.
• Serrate Having small, sharp teeth pointing
  toward the apex.
• Incised Margin cut into sharp, deep, irregular
  teeth or incisions.
• Lobed Incisions extend less than halfway to the
  midrib.
• Cleft Incisions extend more than halfway to the
  midrib.

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Leaf Arrangement along a Stem

• The various ways leaves are arranged along a stem
  are also used to help identify plants.
• Rosulate arrangement is one in which the basal
  leaves form a rosette around the stem with
  extremely short nodes.
• Opposite leaves are positioned across the stem
  from each other, two leaves at each node.
• Alternate or spiral leaves are arranged in
  alternate steps along the stem with only one leaf
  at each node.
• Whorled leaves are arranged in circles along the
  stem.

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Types of Leaf Arrangements
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Leaves as Food

• The leaf blade is the principal edible part of
  several horticultural crops including chive,
  collard, dandelion, endive, kale, leaf lettuce,
  mustard, parsley, spinach, and Swiss chard.
• The edible part of leek, onion, and Florence
  fennel is a cluster of fleshy leaf bases.

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Leaves as Food

• The petiole of the leaf is the edible product in
  celery and rhubarb.
• In plants like Brussels sprouts, cabbage, and
  head lettuce, the leaves form a large, naked bud
  and are the edible product.

164
Naming Plants

• Binomial nomenclature is the scientific system of
  giving a double name to plants and animals.
• The first, or genus name, is followed by a
  descriptive or species name. Modern plant
  classification, or taxonomy, is based on a system
  of binomial nomenclature developed by the Swedish
  physician Carolus Linnaeus (1707-1778).

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Naming Plants

• Prior to Linnaeus, people had tried to base
  classification on leaf shape, plant size, flower
  color, etc.
• None of these systems proved workable.

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Naming Plants

• Linnaeuss revolutionary approach was to base
  classification on the flowers and/or reproductive
  parts of a plant and to give plants a genus and
  species name.
• This has proven to be the best system since
  flowers are the plant part least influenced by
  environmental changes.
• For this reason a knowledge of the flower and its
  parts is essential to plant identification.

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Flowers

• Protection (sepals are the outer most part of the
  flower that protect its internal parts).
• Pollination (petals attract insects with nectar)
• Fertilization (stamens male, pistil female)

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FLOWERS

• The sole function of the flower, which is
  generally the showiest part of the plant, is
  sexual reproduction.
• Its attractiveness and fragrance have not evolved
  to please man but to ensure the continuance of
  the plant species.
• Fragrance and color are devices to attract
  pollinators that play an important role in the
  reproductive process.

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Parts of the Flower

• As the reproductive part of the plant the flower
  contains the male pollen and/or the female ovule
  plus accessory parts such as petals, sepals, and
  nectar glands.
• The pistil is the female part of the plant.
• It is generally shaped like a bowling pin and
  located in the center of the flower.
• It consists of the stigma, style, and ovary.

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Parts of the Flower

• The stigma is located at the top, and is
  connected to the ovary by the style.
• The ovary contains the eggs which reside in the
  ovules.
• After the egg is fertilized the ovule develops
  into a seed.

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Parts of the Flower

• The stamen is the male reproductive organ.
• It consists of a pollen sac (anther) and a long
  supporting filament.
• This filament holds the anther in position so the
  pollen it contains may be disbursed by wind or
  carried to the stigma by insects, birds or bats.

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Parts of the Flower

• Sepals are small green, leaflike structures on
  the base of the flower which protect the flower
  bud.
• The sepals collectively are called the calyx.

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Parts of the Flower

• Petals are highly colored portions of the flower.
  
• They may contain perfume as well as nectar
  glands.
• The petals collectively are called the corolla.

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Parts of the Flower

• The number of petals on a flower is often used in
  the identification of plant families and genera.
• Flowers of dicots typically have sepals and/or
  petals in multiples of four or five.
• Monocots typically have these floral parts in
  multiples of three.

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Parts of Flowers

• The stamen has two parts anthers and filaments.
• The anthers carry the pollen.
• These are generally yellow in color.
• Anthers are held up by a thread-like part called
  a filament.

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Parts of Flowers

• The pistil has three parts stigma, style, and
  ovary.
• The stigma is the sticky surface at the top of
  the pistil it traps and holds the pollen.
• The style is the tube-like structure that holds
  up the stigma.
• The style leads down to the ovary that contains
  the ovules.

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Classification of FLOWERS

• Complete flowers possessing petals and sepals
• Incomplete flowers possessing either petals or
  sepals
• Perfect flowers containing both pistil and
  stamen
• Imperfect flowers containing either the pistil
  or stamen

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Parts of Flowers

• Flowers can have either all male parts, all
  female parts, or a combination.
• Flowers with all male or all female parts are
  called imperfect (cucumbers, pumpkin and melons).
  
• Flowers that have both male and female parts are
  called perfect (roses, lilies, dandelion).

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Parts of Flowers

• A complete flower has a stamen, a pistil, petals,
  and sepals.
• An incomplete flower is missing one of the four
  major parts of the flower, the stamen, pistil,
  petals, or sepals.

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Students are to illustrate the following

• Complete/ Perfect Flower
• Incomplete/Perfect Flower
• Complete/ Imperfect Flower
• Incomplete/ Imperfect Flower

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Types of Flowers

• If a flower has a stamen, pistils, petals, and
  sepals, it is called a complete flower.
• If one of these parts is missing, the flower is
  designated incomplete.
• If a flower contains functional stamens and
  pistils, it is called a perfect flower. (Stamen
  and pistils are considered the essential parts of
  a flower.)
• If either of the essential parts is lacking, the
  flower is imperfect.

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Types of Flowers

• Pistillate (female) flowers are those which
  possess a functional pistil(s) but lack stamens.
• Staminate (male) flowers contain stamens but no
  pistils.
• Because cross-fertilization combines different
  genetic material and produces stronger seed,
  cross-pollinated plants are usually more
  successful than self-pollinated plants.
• Consequently, more plants reproduce by
  cross-pollination than self-pollination.

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Types of Flowers

• As previously mentioned, there are plants which
  bear only male flowers (staminate plants) or bear
  only female flowers (pistillate plants).
• Species in which the sexes are separated into
  staminate and pistillate plants are called
  dioecious.
• Most holly trees and pistachio trees are
  dioecious therefore, to obtain berries, it is
  necessary to have female and male trees.

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Types of Flowers

• Monoecious plants are those which have separate
  male and female flowers on the same plant. Corn
  plants and pecan trees are examples.
• Some plants bear only male flowers at the
  beginning of the growing season, but later
  develop flowers of both sexes examples are
  cucumbers and squash.

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How Seeds Form

• Pollination is the transfer of pollen from an
  anther to a stigma. This may occur by wind or by
  pollinators.
• Wind-pollinated flowers lack showy floral parts
  and nectar since they don't need to attract a
  pollinator.
• Flowers are brightly colored or patterned and
  contain a fragrance or nectar when they must
  attract insects, animals, or birds.

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How Seeds Form

• In the process of searching for nectar these
  pollinators will transfer pollen from flower to
  flower.
• The stigma contains a chemical which stimulates
  the pollen, causing it to grow a long tube down
  the inside of the style to the ovules inside the
  ovary.
• The sperm is released by the pollen grain and
  fertilization typically occurs.

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How Seeds Form

• Fertilization is the union of the male sperm
  nucleus (from the pollen grain) and the female
  egg (in the ovule).
• If fertilization is successful, the ovule will
  develop into a seed.

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Types of Inflorescences

• Some plants bear only one flower per stem and are
  called solitary flowers.
• Other plants produce an inflorescence, a term
  which refers to a cluster of flowers and how they
  are arranged on a floral stem.
• Most inflorescences may be classified into two
  groups, racemes and cymes.

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Types of Inflorescences

• In the racemose group, the florets, which are
  individual flowers in an inflorescence, bloom
  from the bottom of the stem and progress toward
  the top.
• Some examples of racemose inflorescence include
  spike, raceme, corymb, umbel, and head.

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Types of Inflorescences

• A spike is an inflorescence in which many
  stemless florets are attached to an elongated
  flower stem or peduncle, an example being
  gladiolus.
• A raceme is similar to a spike except the florets
  are borne on small stems attached to the
  peduncle.
• An example of a raceme inflorescence is the
  snapdragon.

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Types of Inflorescences

• A corymb is made up of florets whose stalks and
  pedicels are arranged at random along the
  peduncle in such a way that the florets create a
  flat, round top.
• Yarrow has a corymb inflorescence.
• An umbel is similar except that the pedicels all
  arise from one point on the peduncle.

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Types of Inflorescences

• Dill has an umbel inflorescence.
• A head or composite inflorescence is made up of
  numerous stemless florets which is characteristic
  of daisy inflorescence.
• In the cyme group, the top floret opens first and
  blooms downward along the peduncle.

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Types of Inflorescences

• A dischasium cyme has florets opposite each other
  along the peduncle.
• Babys breath inflorescence is an example.
• A helicoid cyme is one in which the lower florets
  are all on the same side of the peduncle,
  examples being freesia and statice
  inflorescences.

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Types of Inflorescences

• A scorpioid cyme is one in which the florets are
  alternate to each other along the peduncle.
• Examples are tomato and potato inflorescences.

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Buds

• A bud is an undeveloped shoot from which
  embryonic leaves or flower parts arise.
• The buds of trees and shrubs of the temperate
  zone typically develop a protective outer layer
  of small, leathery, bud scales.
• Annual plants and herbaceous perennials have
  naked buds in which the outer leaves are green
  and somewhat succulent.

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Buds

• Buds of many plants require exposure to a certain
  number of days below a critical temperature
  (rest) before they will resume growth in the
  spring.
• This time period varies for different plants.
• The flower buds of forsythia require a relatively
  short rest period and will grow at the first sign
  of warm weather.

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Buds

• Many peach varieties require 700 to 1,000 hours
  of temperatures below 45F (7C) before they will
  resume growth.
• During rest, dormant buds can withstand very low
  temperatures, but after the rest period is
  satisfied, buds become more susceptible to
  weather conditions and can be damaged easily by
  cold temperatures or frost.

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Buds

• A leaf bud is composed of a short stem with
  embryonic leaves, with bud primordia in the axils
  and at the apex.
• Such buds develop into leafy shoots.
• Leaf buds are often less plump and more pointed
  than flower buds.

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Buds

• A flower bud is composed of a short stem with
  embryonic flower parts.
• In some cases the flower buds of plants which
  produce fruit crops of economic importance are
  called fruit buds.
• This terminology is objectionable because flowers
  have the potential for developing into fruit.

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Buds

• This development may never occur because of
  adverse weather conditions, lack of pollination
  or other unfavorable circumstances.
• The structure is a flower bud and should be so
  designated since it may never set fruit.

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Types of Buds

• Buds are named for the location which they
  inhabit on the stem surface.
• Terminal buds are those which are located at the
  apex of a stem.
• Lateral buds are borne on the sides of the stem.
• Most lateral buds arise in the axis of a leaf and
  are called axillary buds.

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Types of Buds

• In some instances more than one bud is formed.
• Adventitious buds are those which arise at sites
  other than in the terminal or axillary position.
• Adventitious buds may develop from the internode
  of the stem at the edge of a leaf blade from
  callus tissue at the cut end of a stem or root
  or laterally from the roots of a plant.

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Buds as Food

• Enlarged buds or parts of buds form the edible
  portion of some horticultural crops.
• Cabbage and head lettuce are examples of
  unusually large