CHAPTER 39 Plant Responses to Environmental Challenges

Chapter 39: Plant Responses to Environmental Challenges

CHAPTER 39Plant Responses to

Environmental Challenges


Chapter 39: Plant Responses to Environmental ChallengesPlant–Pathogen InteractionsPlant–Pathogen Interactions

Plants and Herbivores: Benefits and LossPlants and Herbivores: Benefits and Losseses

Water Extremes: Dry Soils and SaturatedWater Extremes: Dry Soils and Saturated Soils Soils

Too Much Salt: Saline EnvironmentsToo Much Salt: Saline Environments


Chapter 39: Plant Responses to Environmental ChallengesHabitats Laden with Heavy MetalsHabitats Laden with Heavy Metals

Hot and Cold EnvironmentsHot and Cold Environments


Plant–Pathogen Interactions• Plants and pathogens evolve together. Plants and pathogens evolve together.

Review Figure Review Figure 39.139.144


Figure 39.1

Figure 39.1Figure 39.1

figure 39-01.jpg


Plant–Pathogen Interactions • Plants can strengthen their cell walls Plants can strengthen their cell walls

when attacked.when attacked.66


Plant–Pathogen Interactions • Plant chemical defenses include PR Plant chemical defenses include PR

proteins and phytoalexins.proteins and phytoalexins.77


Plant–Pathogen Interactions • In the hypersensitive response, cells In the hypersensitive response, cells

produce phytoalexins and then die, produce phytoalexins and then die, trapping pathogens in dead tissue.trapping pathogens in dead tissue.

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Plant–Pathogen Interactions • The hypersensitive response is often The hypersensitive response is often

followed by systemic acquired followed by systemic acquired resistance.resistance.

• Salicylic acid activates further Salicylic acid activates further synthesis of PR proteins and triggers synthesis of PR proteins and triggers responses in other parts of the plant.responses in other parts of the plant.

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Plant–Pathogen Interactions • The hypersensitive response is The hypersensitive response is

nonspecific. nonspecific.

• A more specific response, gene-for-A more specific response, gene-for-gene resistance, matches up alleles in gene resistance, matches up alleles in a plant’s resistance genes and a a plant’s resistance genes and a pathogen’s avirulence genes. pathogen’s avirulence genes. Review Figure Review Figure 39.339.3

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Figure 39.3


figure 39-03.jpg


Plants and Herbivores: Benefits and Losses• Grazing by herbivores increases the Grazing by herbivores increases the

productivity of some plants. productivity of some plants. Review Figure Review Figure 39.539.5

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Figure 39.5

Figure 39.5 Figure 39.5

figure 39-05.jpg


Plants and Herbivores: Benefits and Losses • Some plants produce secondary Some plants produce secondary

products as chemical defenses against products as chemical defenses against herbivores. Review Table herbivores. Review Table 39.139.1

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Table 39.1

Table 39.1Table 39.1

table 39-01.jpg


Plants and Herbivores: Benefits and Losses • Hormones, including systemin and Hormones, including systemin and

jasmonates, participate in the jasmonates, participate in the pathways leading to defensive pathways leading to defensive chemical production. Review Figure chemical production. Review Figure 39.639.6

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Figure 39.6


figure 39-06.jpg


Plants and Herbivores: Benefits and Losses • To avoid poisoning themselves, plants To avoid poisoning themselves, plants

may confine toxic substances they may confine toxic substances they produce to special compartments, or produce to special compartments, or produce them only after cell damage, produce them only after cell damage, or may form enzymes and receptors or may form enzymes and receptors that are not affected by the that are not affected by the substances.substances.

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Water Extremes: Dry Soils and Saturated Soils• Desert annuals evade drought by Desert annuals evade drought by

living only long enough to take living only long enough to take advantage of the brief period during advantage of the brief period during which the soil has enough moisture to which the soil has enough moisture to support them.support them.

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Water Extremes: Dry Soils and Saturated Soils • Some leaves have adaptations to dry Some leaves have adaptations to dry

environments: environments: a thickened cuticle, a thickened cuticle, epidermal hairs, epidermal hairs, sunken stomata, sunken stomata, fleshy leaves, stems and spines fleshy leaves, stems and spines altered leaf display angles.altered leaf display angles.

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Water Extremes: Dry Soils and Saturated Soils • Other adaptations to dry environments Other adaptations to dry environments

include long taproots and root systems include long taproots and root systems that that

die back seasonally.die back seasonally.2121


Water Extremes: Dry Soils and Saturated Soils • The submerged roots of some plants The submerged roots of some plants

form pneumatophores to allow oxygen form pneumatophores to allow oxygen uptake from the air. uptake from the air.

• Aerenchyma in submerged plant parts Aerenchyma in submerged plant parts stores and permits the oxygen stores and permits the oxygen diffusion.diffusion.

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Too Much Salt: Saline Environment• A saline environment restricts water A saline environment restricts water

availability to plants. availability to plants.

• Halophytes are adapted to such Halophytes are adapted to such environments.environments.

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Too Much Salt: Saline Environments • Most halophytes accumulate salt, and Most halophytes accumulate salt, and

some have salt glands that excrete the some have salt glands that excrete the salt to the leaf surface.salt to the leaf surface.

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Too Much Salt: Saline Environments • Halophytes and xerophytes have some Halophytes and xerophytes have some

adaptations in common.adaptations in common.2525


Too Much Salt: Saline Environments • Aluminum, mercury, lead, and Aluminum, mercury, lead, and

cadmium are among the heavy metals cadmium are among the heavy metals toxic to plants toxic to plants

at high concentrations.at high concentrations.2626


Habitats Laden with Heavy Metals • Rather than excluding heavy metals, Rather than excluding heavy metals,

tolerant plants deal with them after tolerant plants deal with them after taking them up. taking them up.

• A given plant’s tolerance is limited to A given plant’s tolerance is limited to only one or two.only one or two.

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Hot and Cold Environments• High temperatures destabilize cell High temperatures destabilize cell

membranes and some proteins.membranes and some proteins.2828


Hot and Cold Environments • Adaptations to elevated temperatures Adaptations to elevated temperatures

include the production of heat shock include the production of heat shock proteins.proteins.

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Hot and Cold Environments • Low temperatures cause membranes Low temperatures cause membranes

to lose their fluidity.to lose their fluidity.3030


Hot and Cold Environments • Ice crystals can puncture organelles Ice crystals can puncture organelles

and plasma membranes.and plasma membranes.3131


Hot and Cold Environments • Adaptations to low temperatures and Adaptations to low temperatures and

freezing include a change in freezing include a change in membrane fatty acid composition and membrane fatty acid composition and production of antifreeze proteins.production of antifreeze proteins.

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CHAPTER 39 Plant Responses to Environmental Challenges

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