Plant Form and Function:

1
Plant Form and Function

• How Do Plants Live in the World?

2
What Important Events Define the History of Plant
Life ?

• Photosynthesis changed the world
• Eukaryotic cells and multicellularity enabled
  plants to diversify
• Plants moved from water to land
• Vascular plants dominate the terrain

3
Important Events in Plant Evolution
4
Photosynthesis Changed the World

• Plants use chlorophyll to capture the energy of
  sunlight for use in photosynthesis
• Oxygen is the by-product and has accumulated over
  the past 2.5 billion years.

5
Evolution of Eukaryotic Cells

• Occurred before plants became multicellular.
• Evolution of eukaryotic cells due to
  endosymbiosis.
• Evidence to support the theory Mitochondria and
  chloroplasts.
• Many examples of living prokaryotes that share
  features of mitochondria and chloroplasts found
  in eukaryotes.

6
Evolution of Multicellular Cells

• Advantages of multicellularity
• Cellular organisms have opportunity for cellular
  specialization.
• Decreased vulnerability to changes in
  temperature, humidity, and nutrient availability
  that comes with increased size

7
Origin of Multicellularity
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8
Plants Moved From Water To Land

• Several evolutionary adaptations made this
  possible
• Multicellularity.
• To prevent water loss
• A waxy cuticle.
• An epidermal layer.
• Structures that protect and enclose the delicate
  gametes and embryo.

9
Plants Moved From Water To Land

• Several evolutionary adaptations made this
  possible
• Alternation of Generations
• Their life cycle is divided into two stages

10
Plants Moved From Water To Land

• Life cycle of vascular plants
• Have vascular tissues for moving food and water.
• Includes evergreens and flowering plants.

11
Plants Moved From Water To Land

• Another evolutionary adaptation that occurred in
  most vascular plants is
• Seed formation
• Has helped contribute to the success of vascular
  plants

12
Vascular Plants Dominate the Terrain
13
Vascular Plants Dominate the Terrain

• Most successful vascular plant are angiosperms.
• Most diverse
• Defining characteristic is the flower.

14
What Do Plants Need and How Do They Get It?

• Plant form and function is best understood in
  terms of their needs
• Light
• Gases
• Water
• Nitrogen and other nutrients

15
Plants Need Light

• Needed for photosynthesis.
• Asymmetric branch pattern allows for greatest
  exposure to light.
• Leaf
• Greatest amount of photosynthesis.
• Allow for maximum light absorption
• Can do solar tracking

16
Plants Need Light

• Leaf interior promotes light absorption
• Palisade layer
• Spongy mesophyll

17
Plants Need Gases

• Plants need carbon dioxide (CO2)
• Raw material for making sugar.
• Stomates allow CO2 to enter cells.
• Water can be lost through stomates

18
Stomata
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19
Plants Need Gases

• C4 plants
• Can trap CO2 on hot, dry days
• Trap CO2 in palisade or spongy cells
• Only about 3 of plants

20
Plants Need Gases

• CAM plants
• Desert dwelling plants
• Stomates must be closed all day long to prevent
  water loss.
• Stomates only open at night
• Carbon dioxide enters and is stored in 4-carbon
  molecule .
• CO2 molecule is released during the day in order
  for photosynthesis to occur.

21
Plants Need Water

• Roots
• Anchor plant to ground and absorb moisture and
  minerals
• Root structure specially designed for absorption

22
Plants Need Water

• Root hairs maximize absorption.
• Found on root surface
• Delicate extensions dramatically increase surface
  area

23
Plants Need Water

• Arrangement of cells in the root
• Water is absorbed at epidermal layer and moves
  from cell to cell through the cortex by diffusion

24
Plants Need Nitrogen

• Nitrogen-fixation
• Process in which certain microbes fix atmospheric
  nitrogen into organic compounds.
• Some plants have a symbiotic relationship with
  these microbes.

25
Plants Need Other Nutrients

• Plants obtain minerals through their roots.
• When water enters the plant roots, so do
  minerals.
• Move up the body of the plant to the leaves and
  stems.

26
Plants Need Nitrogen and Other Nutrients
27
How Do Higher Plants Transport Substances and
Support Themselves?

• All large multicellular organisms must have some
  way of transporting substances through their
  bodies, including plants.
• In some plants, the same tissues are responsible
  for
• Moving water
• Providing support

28
Translocation

• The movement of fluids within the plant body
• Phloem
• Living vascular tissue near the periphery of the
  stem
• Made of columns of sieve tubes
• Sap (sugar-rich fluids made by photosynthesis)
  moves through the phloem

29
Transpiration

• Evaporation of water through the stomates of
  plant leaves.
• Creates a negative pressure
• Allows water to move upward plant from roots
• Also prevents plants from overheating.

30
Water and Minerals Move Through the Xylem

• Xylem
• Vascular tissue usually found nearer the core, or
  center, of the stem.
• Composed primarily of dead cells that form a
  hollow interconnected network of tubules.

31
Plants Need Mechanical Support

• Reaching for the sun means growing upward
• Opposing gravity.
• In soft-stemmed plants, mechanical support
  provided by turgor pressure.
• In woody plants, mechanical support provide by
  xylem.
• Reinforced with lignin.

32
How Do Plants Grow?

• Plant growth is indeterminate.
• Occurs at the meristem
• Cells divide by mitosis within meristem tissue.
• Found at the
• tip of shoots and roots
• In periphery of the woody trees and shrubs

33
Three Main Tissue Types in Plants
34
How Do Plants Grow?

• Apical meristem
• Found at tip of shoots and roots.
• Responsible for lengthwise growth.
• Called primary growth.

35
How Do Plants Grow?

• Vascular cambium
• Meristematic tissue that produces new bundles of
  xylem and phloem.
• Increases the girth of the stem or roots.
• Called secondary growth.

36
How Do Plants Grow?

• Cork cambium
• Layer of meristem produced from cells of the
  ground tissues.
• Produces a new layer of cells called cork.
• Also contributes to secondary growth.

37
Plants Have Hormones

• Phototrophism
• Growing plant will bend toward the light.
• Due to the presence of auxins.
• Class of molecules.

38
Plants Have Hormones

• Auxins
• Stimulate cell elongation.
• Play a role in causing the growing plant root to
  bend down.
• Involved in fruit development.

39
Plants Have Hormones

• Gibberellins
• Class of 100 similar chemical compounds.
• Produced at tips of roots and stems.
• Stimulates plant growth.
• Most concentrated in seeds.
• Facilitates growth of embryo and germination.

40
Plants Have Hormones

• Abscisic Acid (ABA)
• Hormones that slow growth
• Needed on cold days or excessively hot days.
• Released when water is scarce.
• Plant growth is a balance between ABA and
  gibberellins.

41
Plants Have Hormones

• Ethylene
• Causes fruit ripening
• As fruit ages, it releases more ethylene
• Activates enzymes that digest the cell walls of
  plants.
• Enables plant to respond to environment by by
  aging or planned cell death

42
Plants Reproduce Sexually

• Zygotes are formed by the fusion of male and
  female gametes
• In angiosperms, flowers are the sex organs that
  produce gametes.

43
Sexual Reproduction in Flowering Plants

• Male reproductive organs stamens
• Have anthers
• Contain cells that give rise to pollen

44
Sexual Reproduction in Flowering Plants

• Female sex organ carpel
• First houses the ovule,
• Then the female gametophyte
• And finally, the embryo

45
Fertilization in Flowering Plants
46
Fertilization in Flowering Plants
47
Pollination

• How does pollen get from the male anther to the
  female ovary?
• Wind
• Water
• Animal pollinators
• Flowers attract animal pollinators.

48
Seeds and Fruits

• After fertilization, ovule develops into a seed.
• Seed remains dormant until conditions for growth
  are appropriate.
• Ovary that surrounds the seed, or some other
  parental structure, may develop into the fruit.