Environmental Adaptations of Plants

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Environmental Adaptations of Plants
Topic 14.5

• Biology 1001
• November 30, 2005

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Introduction

• Seed pollen dispersal means that plants occupy
  numerous environments
• Plants have developed evolutionary adaptations to
  many environments
• These include morphological, physiological,
  anatomical reproductive modifications
• Environmental stressors can be biotic or abiotic,
  periodic or continuous
• Drought, flooding, cold, low light, and poor
  nutrient availability are abiotic stressors
• Herbivores and pathogens are biotic stressors

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Newfoundlands Environment

• Dwarf black spruce (Picea mariana) or tuckamore
  is an adaptation to a cold, windy coastal
  environment
• Influences the pattern of growth and form or
  morphology of the plant

Lise Sorensen
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Newfoundlands Environment

• Pitcher plant (Sarracenia purpurea)
• Adapted to low nutrient availability in peatland
  bogs

• Sarracenia purpurea (Botanical Latin, purple,
  referring to the colour of the mottled pitchers)
  is the floral emblem of Newfoundland and
  Labrador. Our pitcher plant is the stout little
  carnivore of Canadas peat-quilted swamps and
  jelly-earthed bogs, where it traps insects in
  leaves modified to hold water, hence pitcher
  plant. The slippery sides of each pitcher are
  lined with downward-pointing hairs that help
  insects slide into the pitcher but prevent them
  from escaping. Trapped without mercy, they
  struggle, fall exhausted back into the water, and
  drown in the liquid to which the plant has added
  a flesh-dissolving enzyme. The decomposed bodies
  of the insects provide essential nutrients for
  the pitcher plant.- Bill Casselman, Common
  Garden Words, Macarthur and Company, 1997

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PLANT Adaptations to Drought

• When water is scarce or only seasonally
  available, plants need to transpire but at the
  same time minimize water loss
• Adaptations of Plants That Endure Dry Periods
• Mechanisms to reduce transpiration rate during
  dry spells
• - Control of stomatal opening and closing
• - Inhibition of growth of young leaves
• - Leaves that roll or fold
• (- Loss of leaves by deciduous trees in the
  autumn
• - Needle-shaped leaves of conifers)
• Such mechanisms are a compromise because they
  also reduce photosynthesis
• Roots also respond to dry periods
• - Shallow root growth is inhibited
• - Deep roots continue to grow to where the soil
  is still moist
• See Topic 14.34 Notes and Text Reading
• () Loss of water due to freezing

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Leaves that fold - Oxalis

• Leaves that roll
• Ammophila arenaria

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Xerophytes are Plants Adapted to Arid Environments
See Topic 14.34 Text Reading

• Mechanisms to reduce water loss while transpiring
• Waxy cuticles, sunken stomata on the lower
  epidermis, trichomes (hairs)
• Photosynthetic stems that store water leaves
  that are spines
• Leaves of xerophytes may also have an abundance
  of fibers to provide support when turgour
  pressure is low

Nerium oleander Fig. 36.16
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Xerophyte Adaptations That Reduce Transpiration

• Crassulacean acid metabolism of succulents in the
  family Crassulaceae and ice plants
• Stomata stay closed during the day, open at night
  to take in CO2
• Store CO2 as malic acid (organic acid) in
  vacuoles
• Malic acid is broken down during the day to
  provide CO2

Crassula portulaceae 'Hobbit' - Baby Jade
Ice Plant Carpobrotus edulis
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ADAptations to life in water

• Excess water leads to oxygen deprivation
• The aerial roots of mangroves, called
  pneumatophores, provide access to oxygen
• Oxygen deprivation in other plants stimulates the
  production of the hormone ethylene, which causes
  some of the cells in the root cortex to undergo
  apoptosis, or programmed cell death

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Hydrophytes are Plants Adapted to An Aquatic
Environment

• Such plants are secondarily aquatic their
  ancestors evolved on land
• Adaptations include leaf heterophyly (floating
  and submerged leaves have different forms) and
  stomata on the upper surface of the leaf

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Reproductive Adaptations to Cold

• Sun-tracking flowers
• Hairy flowers that absorb IR radiation
• Higher rates of asexual reproduction stolons,
  rhizomes, bulbs on flowering stalks

Salix
Allium canadense
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PREDATION BY HERBIVORES

• Predation is important in chemical recycling
  because it returns nutrients to the soil
• Plant defenses to predation include
  developmental, mechanical and chemical
  modifications
• Grasses are supremely adapted to grazing,
  continuing to grow throughout the season due to a
  meristem at the base of the leaf
• Spines (modified leaves), thorns (modified
  stems), and prickles (epidemal outgrowths) are
  mechanical deterrents to predators

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Chemical Defense Against Predation

• Many plants produce secondary compounds that are
  poisonous or bitter tasting to animals often
  the source of our drugs
• Nicotine from tobacco (Nicotiana sp.)
• Caffeine from coffee (Coffea arabica)
• Morphine, codeine, and heroin from poppies
  (Papavar sp.)
• Strychnine from the tropical vine Strychnos
  toxifera
• Jackbeans produce canavanine, which replaces
  arginine in the proteins of the herbivore

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Coffea Nicotiana?