chapter 36: plant nutrition chapter 36 plant nutrition

Chapter 36: Plant Nutrition

CHAPTER 36Plant Nutrition


Chapter 36: Plant NutritionThe Acquisition of NutrientsThe Acquisition of Nutrients

Mineral Nutrients Essential to PlantsMineral Nutrients Essential to Plants

Soils and PlantsSoils and Plants


Chapter 36: Plant NutritionNitrogen FixationNitrogen Fixation

Sulfur MetabolismSulfur Metabolism

Heterotrophic and Carnivorous Seed Heterotrophic and Carnivorous Seed PlantsPlants


The Acquisition of Nutrients• Plants are photosynthetic autotrophs, Plants are photosynthetic autotrophs,

producing all the compounds they producing all the compounds they need from carbon dioxide, water, and need from carbon dioxide, water, and minerals. minerals.

• They obtain energy from sunlight, They obtain energy from sunlight, carbon dioxide from the atmosphere, carbon dioxide from the atmosphere, and nitrogen-containing ions and and nitrogen-containing ions and mineral nutrients from soil.mineral nutrients from soil.

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The Acquisition of Nutrients • Plants explore their surroundings by Plants explore their surroundings by

growing rather than by locomotion.growing rather than by locomotion.

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Mineral Nutrients Essential to Plants• Plants require fourteen essential Plants require fourteen essential

mineral elements, all of which come mineral elements, all of which come from soil. from soil.

• Several essential elements fulfill Several essential elements fulfill multiple roles. Review Table 36.1multiple roles. Review Table 36.1

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Table 36.1

Table 36.1Table 36.1

table 36-01.jpg


Mineral Nutrients Essential to Plants • The six mineral nutrients required in The six mineral nutrients required in

substantial amounts are substantial amounts are macronutrientsmacronutrients

• The eight required in much smaller The eight required in much smaller amounts are micronutrients. Review amounts are micronutrients. Review Table 36.1Table 36.1

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Mineral Nutrients Essential to Plants • Deficiency symptoms suggest what Deficiency symptoms suggest what

essential element a plant lacks. essential element a plant lacks. Review Table 36.2Review Table 36.2

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Table 36.2

Table 36.2Table 36.2

table 36-02.jpg


Mineral Nutrients Essential to Plants • Biologists discovered the essentiality Biologists discovered the essentiality

of each mineral nutrient by growing of each mineral nutrient by growing plants on nutrient solutions lacking the plants on nutrient solutions lacking the test element. Review Figure 36.2test element. Review Figure 36.2

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Figure 36.2

Figure 36.2Figure 36.2

figure 36-02.jpg


Soils and Plants

• Soils have complex structure, with Soils have complex structure, with living and nonliving components. living and nonliving components.

• They contain water, gases, and They contain water, gases, and inorganic and organic substances. inorganic and organic substances.

• They typically consist of two or three They typically consist of two or three horizontal zones called horizons. horizontal zones called horizons. Review Figures 36.3 and Table 36.3Review Figures 36.3 and Table 36.3

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Figure 36.3


figure 36-03.jpg


Table 36.3Table 36.3Table 36.3

table 36-03.jpg


Soils and Plants

• Soils form by mechanical and chemical Soils form by mechanical and chemical weathering of rock.weathering of rock.

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Soils and Plants

• Plants obtain some mineral nutrients Plants obtain some mineral nutrients by ion exchange between the soil by ion exchange between the soil solution and the surface of clay solution and the surface of clay particles. Review Figure 36.5particles. Review Figure 36.5

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Figure 36.5


figure 36-05.jpg


Soils and Plants

• Farmers use fertilizer to make up for Farmers use fertilizer to make up for deficiencies in soil mineral nutrient deficiencies in soil mineral nutrient content, and apply lime to raise low content, and apply lime to raise low soil pH.soil pH.

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Soils and Plants

• Plants affect soils in various ways, Plants affect soils in various ways, helping them form, adding material helping them form, adding material such as humus, and removing such as humus, and removing nutrients.nutrients.

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Nitrogen Fixation

• A few soil bacteria species are A few soil bacteria species are responsible for almost all nitrogen responsible for almost all nitrogen fixation. fixation.

• Some live free in the soil; others live Some live free in the soil; others live symbiotically as bacteroids within symbiotically as bacteroids within plant roots.plant roots.

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Nitrogen Fixation

• In nitrogen fixation, nitrogen gas (NIn nitrogen fixation, nitrogen gas (N22) ) is reduced to ammonia (NHis reduced to ammonia (NH33) or ) or ammonium ions (NHammonium ions (NH44

++) in a reaction ) in a reaction catalyzed by nitrogenase. Review catalyzed by nitrogenase. Review Figure 36.7Figure 36.7

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Figure 36.7 – Part 1

Figure 36.7 – Part 1Figure 36.7 – Part 1

figure 36-07a.jpg




figure 36-07b.jpg


Nitrogen Fixation

• Nitrogenase requires anaerobic Nitrogenase requires anaerobic conditions, but bacteroids in root conditions, but bacteroids in root nodules require oxygen for respiration. nodules require oxygen for respiration.

• Leghemoglobin helps maintain the Leghemoglobin helps maintain the oxygen supply to bacteroids.oxygen supply to bacteroids.

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Nitrogen Fixation

• Nodule formation requires an Nodule formation requires an interaction between the root system of interaction between the root system of a legume and a legume and RhizobiumRhizobium bacteria. bacteria. Review Figure 36.8Review Figure 36.8

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figure 36-08a.jpg




figure 36-08b.jpg


Nitrogen Fixation

• Nitrogen-fixing bacteria reduce Nitrogen-fixing bacteria reduce atmospheric Natmospheric N22 to ammonia, but most to ammonia, but most plants take up both ammonium and plants take up both ammonium and nitrate ions. nitrate ions.

• Nitrifying bacteria oxidize ammonia to Nitrifying bacteria oxidize ammonia to nitrate. nitrate.

• Plants take up nitrate and reduce it Plants take up nitrate and reduce it back to ammonia, something animals back to ammonia, something animals are incapable of doing. Review Figure are incapable of doing. Review Figure 36.936.9

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Nitrogen Fixation

• Denitrifying bacteria return NDenitrifying bacteria return N22 to the to the atmosphere, completing the biological atmosphere, completing the biological nitrogen cycle. Review Figure 36.9nitrogen cycle. Review Figure 36.9

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Figure 36.9


figure 36-09.jpg


Sulfur Metabolism

• Plants take up sulfate ions and reduce Plants take up sulfate ions and reduce them, forming cysteine and them, forming cysteine and methionine. methionine.

• Cysteine is the major precursor for Cysteine is the major precursor for other sulfur-containing compounds in other sulfur-containing compounds in plants and in animals, which must plants and in animals, which must obtain organic sulfur from plants.obtain organic sulfur from plants.

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Heterotrophic and Carnivorous Seed Plants• A few heterotrophic plants are A few heterotrophic plants are

parasitic on other plants.parasitic on other plants.

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Heterotrophic and Carnivorous Seed Plants • Carnivorous plants are autotrophs that Carnivorous plants are autotrophs that

supplement their nitrogen supply by supplement their nitrogen supply by feeding on insects.feeding on insects.

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