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Introduction to Plants. Mrs. M. Rightler. Earliest Plants. Algae Phytoplankton Lived in the sea. Problem Drying Out Making Food Reproduction Gravity & Support Getting water & nutrients. Solution Waxy cuticle, stomata Formed leaves Develops spores & seeds Bark (cork) & vessels

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Introduction to plants l.jpg

Introduction to Plants

Mrs. M. Rightler


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Earliest Plants

  • Algae

  • Phytoplankton

  • Lived in the sea


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Problem

Drying Out

Making Food

Reproduction

Gravity & Support

Getting water & nutrients

Solution

Waxy cuticle, stomata

Formed leaves

Develops spores & seeds

Bark (cork) & vessels

Roots & vessels

Problems with life on land


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Types of Plants

  • Avascular

    • Bryophytes

    • nonseed plants

  • Tracheophytes

    • vessels for transport and support


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Mosses & Liverworts: The Bryophytes

  • First land plants

  • AVASCULAR = very small

  • 500 m.y.a.

  • Must grow in moist environments

  • Used for fuel (peat)


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Reproduction in Bryophytes

  • Mosses have a protonema (liverworts do not)

  • Sexual reproduction

    • Antheridium – makes sperm

    • Archaegonium – makes eggs

  • Asexual reproduction

    • Fragmentation

    • Formation of gemmae


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Tracheophytes

  • Vessels

    • XYLEM = transports water & dissolved minerals from roots to leaves

    • PHLOEM = transports sugars from leaves to rest of plant

  • Spores or seeds for reproduction


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Club Mosses (Lycophyta)

  • Leaves produce spores

    • Strobilus = spore-bearing leaves

    • Prothallus = produces antheridia & archaegonia


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Horsetails (Sphenophyta)

  • Jointed stems

  • Reproduction similar to club moss


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Ferns (Pterophyta)

  • 400 m.y.a.

  • Dominant form = sporophyte

  • Structure

    • Rhizome = underground stem

    • Fronds = leaves

    • Sori = store spores on underside of fronds


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Gymnosperms

  • Gymno = “naked” Sperm = “seed”

  • First plants to produce seeds

    • No flowers

    • No fruit


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Why Make Seeds?

  • Has own food supply

  • Protective coat against harsh conditions

  • Some are designed for travel to new areas


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Sporophytes produce:

  • MICROSPORE

    • Produce male gametophyte

    • Produce pollen

  • MEGASPORE

    • Produce female gametophyte

    • Produce ovule (makes archaegonia with egg cells)


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Gymnosperm Reproduction

  • Pollen grains carried by wind

  • Land on ovule, develop pollen tube

  • Sperm move through tube to fertilize egg

    • Fertilized egg = ZYGOTE

    • EMBRYO = young, diploid sporophyte plant

    • COTYLEDONS = food storage for embryo, become first leaves


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Why Pollen Instead of Spores?

  • Plant can live in very dry areas

  • Fertilization does not require water

  • Pollen has protective coat and food supply for sperm


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Why Ovules Instead of Archaegonia?

  • Protective tissues prevent drying out

  • Ovule holds archaegonia and protects eggs from elements


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Minor Gymnosperm Groups

  • Cycadophyta (1st in Triassic Era)

  • Ginkgophyta

    • Only one species today Ginkgo biloba

    • Most lived 200 m.y.a.

  • Gnetophyta – only three genera

    • Gnetum – house plants

    • Ephedra – weight loss, allergies & asthma

    • Welwitschia


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Coniferophyta (largest group)

  • Needle or scale-like leaves

  • Bear seeds in woody cones

  • Can live in very cold climates

  • Most are evergreens

  • Have wood

    • Made of thick-walled vessels (TRACHEIDS)

    • Tracheids are xylem


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Angiosperms

  • Angio – “flower” Sperm – “seed”

  • Extremely diverse

  • All have seeds enclosed in fruit


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Cambium

  • Any growth tissue in plants

  • Types of cambium

    • Vascular = produces xylem & phloem

    • Cork = produces cork (bark)


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Overall Structures [121]

  • Roots

  • Stems

  • Leaves

  • Flowers


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Roots [124]

  • Absorb water & nutrients

  • Hold plant in place

  • Root types:

    • Fibrous

    • Tap

    • Prop

    • Aerial


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Stems [123]

  • Support leaves & flowers

  • Sometimes photosynthesis

  • Transport (contain xylem & phloem)

  • Types

    • herbaceous – green & flexible

    • Woody – stiff, have cork layer, usually brown


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Leaves [119]

  • Cuticle = protection

  • Stomata = gas exchange, water loss (transpiration)

  • Epidermis = protection, color

  • Mesophyll

    • Palisade = most PHOTOSYNTHESIS

    • Spongy = Vascular bundles run through it


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Flowers [131]

  • Pistils = female reproductive structures

  • Stamens = male reproductive structures

  • Complete flowers

    • Have petals & sepals

    • Have male and female parts

  • Incomplete flowers = missing one or more parts


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Monocots

mono = “one”

cot = “seed leaf”

Approx. 60,000 species

Flowers = multiples of 3

Leaf veins parallel

Dicots

di = “two”

cot = “seed leaf”

Approx. 170,000 species

Flowers = multiples of 4 or 5

Leaf veins branching

Types of Angiosperms [115]


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Plant Tropisms

  • Tropism = plant response to external stimulus

    • Positive: plant moves towardstimulus

    • Negative: plant moves away from stimulus

  • Types:

    • Phototropism = light

    • Gravitropism = gravity

    • Thigmotropism = touch

      (nastic movement – direction does not matter)


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Plant Hormones

  • Hormone – chemical produced in one part of an organism that has an effect on a different part of the organism

  • Types

    • Auxins – regulate growth

    • Gibberellins – speeds growth, germination

    • Abscisic acid – dormancy, close stomata, stress

    • Ethylene – ripens fruit


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