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2 Lecture 11 Outline (Ch. 37) I.Mineral Acquisition II.Soil Conservation III. Essential Nutrients IV.Relationships with other organisms V.Lecture Concepts

3 Overview: A Nutritional Network Every organism –Continually exchanges energy and materials with its environment The branching root and shoot system provides high SA:V to collect resources –Plants’ resources are diffuse (scattered, at low concentration) What are these diffuse resources?

4 4 Light

5 Can a plant grow there? –Climate –Soil Quality Texture: type of soil particles Composition: organic and inorganic components Mineral Acquisition

6 After heavy rainfall, water drains away from the larger spaces in soil –But smaller spaces retain water because of its attraction to surfaces of clay and other particles The film of loosely bound water –available to plants (a) Soil water. A plant cannot extract all the water in the soil because some of it is tightly held by hydrophilic soil particles. Water bound less tightly to soil particles can be absorbed by the root. Soil particle surrounded by film of water Root hair Water available to plant Air space Mineral Acquisition

7 Acids derived from roots contribute to a plant’s uptake of minerals –When H + displaces mineral cations from clay particles Figure 37.3 (b) Cation exchange in soil. Hydrogen ions (H + ) help make nutrients available by displacing positively charged minerals (cations such as Ca 2+ ) that were bound tightly to the surface of negatively charged soil particles. H 2 O + CO 2 H 2 CO 3 HCO 3 – + Root hair K+K+ Cu 2+ Ca 2+ Mg 2+ K+K+ K+K+ H+H+ H+H+ Soil particle – – – – – – – – – Mineral Acquisition

8 Soil Conservation and Sustainable Agriculture In contrast to natural ecosystems agriculture depletes –mineral content of the soil –taxes water reserves –encourages erosion The goal of soil conservation strategies: minimize this damage Fertilizers – what’s the problem? Commercially produced fertilizers: Minerals are either mined or prepared industrially Irrigation – Why? Why not? –Can change the chemical makeup of soil Erosion – Why? Why should we care? Topsoil from thousands of acres of farmland is … –lost to water and wind erosion each year in the U.S.

9 Agricultural researchers –Are developing ways to maintain crop yields while reducing fertilizer and water use. Certain precautions –Can prevent the loss of topsoil Figure 37.5 Soil Conservation and Sustainable Agriculture

10 Essential Nutrients and Deficiencies Plants require certain chemical elements to complete their life cycle Plants derive most of their organic mass from the CO 2 of air –But they also depend on soil nutrients such as water and minerals Essential elements: Required for a plant to complete its life cycle

11 Essential elements in plants Nine of the essential elements are called macronutrients –Because plants require them in relatively large amounts The remaining eight essential elements are known as micronutrients –Because plants need them in very small amounts Table 37.1

12 Nitrogen, Soil Bacteria and Nitrogen Availability Plants compete fiercely for key nutrients like Nitrogen Nitrogen is needed for: Proteins, nucleic acids, chlorophyll, etc. Nitrogen-fixing soil bacteria convert atmospheric N 2 –To nitrogenous minerals that plants can absorb Figure 37.9 Atmosphere N2N2 Soil N2N2 N2N2 Nitrogen-fixing bacteria Organic material (humus) NH 3 (ammonia) NH 4 + (ammonium) H + (From soil) NO 3 – (nitrate) Nitrifying bacteria Denitrifying bacteria Root NH 4 + Soil Atmosphere Nitrate and nitrogenous organic compounds exported in xylem to shoot system Ammonifying bacteria

13 Symptoms of Mineral Deficiency The symptoms of mineral deficiency depend on –nutrient’s function –nutrient’s mobility within the plant Figure 37.7 Phosphate-deficient Healthy Potassium-deficient Nitrogen-deficient The most common deficiencies Are those of nitrogen, potassium, and phosphorus

14 Root nodulation Mycorrhizae Parasitic plants Carnivorous plants Relationship with other organisms

15 Symbiotic Nitrogen Fixation Symbiotic relationships between certain nitrogen-fixing bacteria and certain plants. –Mainly legume family (e.g. peas, beans) Why is this a symbiosis?

16 Nodules: Swellings of plant cells “infected” by Rhizobium bacteria Figure 37.10a (a) Pea plant root Nodules Roots Inside the nodule –Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell Figure 37.10b (b) Bacteroids in a soybean root nodule. In this TEM, a cell from a root nodule of soybean is filled with bacteroids in vesicles. The cells on the left are uninfected. 5  m Bacteroids within vesicle

17 Each legume is associated with a particular strain of Rhizobium Nodule development depends on a –chemical dialogue between Rhizobium bacteria and root cells of their specific plant hosts Figure 37.11

18 Mycorrhizae and Plant Nutrition Mycorrhizae –Symbiotic relationship between a root and fungus –Most but not all plants. The fungus gets: supply of sugars from the plant The fungus gives: Increases the surface area for water and mineral absorption Agriculturally, farmers and foresters … –Often inoculate seeds with spores of mycorrhizal to promote mycorrhizal relationships.

19 Two Common Types of Mycorrhizae In ectomycorrhizae –The mycelium of the fungus forms a dense sheath over the surface of the root Figure 37.12a Mantle (fungal sheath) Epidermis Cortex Mantle (fungal sheath) Endodermis Fungal hyphae between cortical cells (colorized SEM) 100  m

20 Two Common Types of Mycorrhizae In endomycorrhizae –Fungal hyphae extend into the root and form arbuscules Figure 37.12b EpidermisCortex Fungal hyphae Root hair 10  m Endodermis Vesicle Casparian strip Arbuscules

21 Epiphytes, Parasitic and Carnivorous Plants Figure Staghorn fern, an epiphyte EPIPHYTES PARASITIC PLANTS CARNIVOROUS PLANTS Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite Host’s phloem Haustoria Indian pipe, a nonphotosynthetic parasite Venus’ flytrap Pitcher plantsSundews Dodder

22 Self-Check Macronutrients (not a complete list) Sources; Any special methods for obtaining. Carbon Oxygen Hydrogen Nitrogen Phosphorus Magnesium

23 Lecture 11 concepts - Name the resources that plants need and must acquire. - Explain how plants uptake minerals via their roots. - What are the concerns for soil conservation? - Define macronutrient and micronutrient. List the macronutrients. - Describe how plants obtain carbon. - Explain how plants acquire nitrogen (more than one way). - Define ‘symbiosis’. Discuss the symbioses with bacteria and fungi. - Describe epiphytes, parasitic, and carnivorous plants. - Make a list of new vocabulary with definitions.