Introduction to Plants

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Introduction to Plants

• Chapter 22.1

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Basic Plant Structure
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Plants Are

1. Multicellular
2. Eukaryotic
3. Autotrophic
4. Use Chlorophyll a or b

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How Did Plants Originate?

• First land plants appeared 500 mya
• Resembled present day mosses
• Released nitric acids on rock surfaces which
  created soil
• Likely colonies of protists adapted to dry
  environmentbut how?

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Links Between Algae and Plants

• Both have protective cell walls
• Both contain chlorophyll used in photosynthesis
• Both store food in the form of starches

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Plants Must Adapt To Live On Land

• Absorb nutrients from surroundings
• Prevent desiccation
• Reproduce without the aid of water
• If plants adapt to these strategies, they can
  evolve on land
• Why would a plant want to move onto the land?

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A. Preventing Water Loss

• Cuticle waxy coating that prevents tissues from
  drying out
• Stomata-openings in the cuticle that allow gas
  exchange to take place and also regulate water
  loss

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Prevent Desiccation?

• Desiccation Drying Out
• As plants evolved further away from water, they
  needed to evolve a waterproof structure/coating
  (cuticle)
• But, this structure needs pores (stomata)
• WHY?
• Think about what the plant needs for
  photosynthesis
• CARBON DIOXIDE!

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Stomata
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B. Autotrophic

• Leaf-organ that enables the plant to trap and
  absorb light energy

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Leaf Layers via microscope
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C. Stabilization and Nutrient Absorption

• (Accomplished with roots and mycorrihizea)
• Roots-organ that is used to reach and transport
  water and minerals, anchor plants and store food
• Earliest roots are rhizoids
• Fossils show fungi helped plants before roots
  evolved

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The Root

• Main function absorb water
• Functional Part root hair
• Structure from outside in
• Epidermis with root hair protection
• Cortexsupport/storage
• Vascular Bundle Phloem, Vascular Cambium, Xylem
  
• Vascular Cam growth of new vascular tissue

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Root Structure
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D. Transportation System

• Stem- Transport of water, food, and
• minerals
• Support of plant
• Storage of materials

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Structures of the Stem

• Epidermis (bark or green)protection
• Cork cambium new growth of bark/ epidermis
• Cortex thick layer, sometimes contains
  chloroplasts, mostly for support
• Vascular Bundle contain transport tissues
  towards the middle of the stem
• Xylem transports water and minerals (generally
  in the middle)

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More Structures

• Phloem transports sugars to all cells, located
  outside the xylem
• Vascular cambium separates the X and P,
  contains new cells for vascular growth
• Pith central portion of stem of tree, for
  storage

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E. Reproduce Without Water

• Spores/Cones/Seed-protective coat which prevents
  a developing embryo from drying out
• Advent of pollen and seeds make it possible to
  reproduce far away from water
• Pollen plant sperm, light weight and wont dry
  out, carried via wind, water, animal, etc

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Pollen Images via SEM