1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 37 Plant nutrition

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A Nutritional Network Every organism – Continually exchanges energy and materials with its environment For a typical plant – Water and minerals come from the soil, while carbon dioxide comes from the air

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The root system and shoot system – Ensure networking with both reservoirs of inorganic nutrients Figure 37.1

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plants require certain chemical elements to complete their life cycle Plants derive organic mass f/ CO 2 – Also depend on soil nutrients e.g. water and minerals Figure 37.2 CO 2, the source of carbon for Photosynthesis, diffuses into leaves from the air through stomata. Through stomata, leaves expel H 2 O and O 2. H2OH2O O2O2 CO 2 Roots take in O 2 and expel CO 2. The plant uses O 2 for cellular respiration but is a net O 2 producer. O2O2 CO 2 H2OH2O Roots absorb H 2 O and minerals from the soil. Minerals

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

6. Macronutrients and Micronutrients More than 50 elements identified in plants, but not all are essential Essential element is required for a plant to complete life cycle

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydroponic culture – Determines which chemicals elements are essential Figure 37.3 TECHNIQUE Plant roots are bathed in aerated solutions of known mineral composition. Aerating the water provides the roots with oxygen for cellular respiration. A particular mineral, such as potassium, can be omitted to test whether it is essential. RESULTS If the omitted mineral is essential, mineral deficiency symptoms occur, such as stunted growth and discolored leaves. Deficiencies of different elements may have different symptoms, which can aid in diagnosing mineral deficiencies in soil. Control: Solution containing all minerals Experimental: Solution without potassium APPLICATION In hydroponic culture, plants are grown in mineral solutions without soil. One use of hydroponic culture is to identify essential elements in plants.

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential elements in plants Table 37.1

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 9 essential elements are macronutrients (e.g. C,H,O,P,N,K) – Large amounts required 8 are micronutrients (e.g.Fe) – Small amts. required

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Common deficiencies Figure 37.4 Phosphate-deficient Healthy Potassium-deficient Nitrogen-deficient

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Soil Soil + climate – Major factors determining whether particular plants can grow well in a certain location Texture – Soil’s general structure Composition – Organic and inorganic chemical components

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Particles derived from the breakdown of rock found in soil – Also organic material (humus) Result is topsoil – A mixture of particles of rock and organic material

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Topsoil + other distinct soil layers, or horizons Figure 37.5 The A horizon is the topsoil, a mixture of broken-down rock of various textures, living organisms, and decaying organic matter. The B horizon contains much less organic matter than the A horizon and is less weathered. The C horizon, composed mainly of partially broken-down rock, serves as the “parent” material for the upper layers of soil. A B C

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Film of loosely bound water is usually available to plants Figure 37.6a (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

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Soil Conservation and Sustainable Agriculture In contrast to natural ecosystems – Agriculture depletes the mineral content of soil, taxes water reserves, and encourages erosion Goal of soil conservation strategies  Minimize damage

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fertilizers Commercially produced fertilizers (N P K) – Minerals that are either mined or prepared by industrial processes “Organic” fertilizers – e.g. manure, fishmeal, or compost

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Agricultural research – Maintain crop yields while reducing fertilizer use Genetically engineered “smart” plants – Inform the grower of nutrient deficiency Figure 37.7 No phosphorus deficiency Beginning phosphorus deficiency Well-developed phosphorus deficiency

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Irrigation Huge drain on water resources in arid regions – Can change the chemical makeup of soil

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Erosion Topsoil from thousands of acres of farmland – Lost to water and wind erosion each year

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prevention of topsoil loss Figure 37.8

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Goal of soil management – Sustainable agriculture, a variety of farming methods that are conservation-minded, e.g. No-till farming

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nitrogen often has the greatest effect on plant growth Plants require nitrogen f/: – Proteins, nucleic acids, chlorophyll, others

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Soil Bacteria Nitrogen-fixing bacteria convert atmospheric N 2 to form of N that plants can use 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

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two types of relationships plants have with other organisms are mutualistic – Symbiotic nitrogen fixation (Rhizobium) – Mycorrhizae

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic N 2 Fixation Provide plant w/ a built-in source of fixed N 2 Legume family (e.g. peas, beans)

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Root nodules – Composed of plant cells that have been “infected” by nitrogen-fixing Rhizobium bacteria Figure 37.10a (a) Pea plant root. The bumps on this pea plant root are nodules containing Rhizobium bacteria. The bacteria fix nitrogen and obtain photosynthetic products supplied by the plant. Nodules Roots

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each legume – Is associated with a particular strain of Rhizobium

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Development of a soybean root nodule Figure 37.11 Infection thread Rhizobium bacteria Dividing cells in root cortex Bacteroid 2 The bacteria penetrate the cortex within the Infection thread. Cells of the cortex and pericycle begin dividing, and vesicles containing the bacteria bud into cortical cells from the branching infection thread. This process results in the formation of bacteroids. Bacteroid Developing root nodule Dividing cells in pericycle Infected root hair 1 2 3 Nodule vascular tissue 4 3 Growth continues in the affected regions of the cortex and pericycle, and these two masses of dividing cells fuse, forming the nodule. Roots emit chemical signals that attract Rhizobium bacteria. The bacteria then emit signals that stimulate root hairs to elongate and to form an infection thread by an invagination of the plasma membrane. 1 4 The nodule develops vascular tissue that supplies nutrients to the nodule and carries nitrogenous compounds into the vascular cylinder for distribution throughout the plant.

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Crop rotation  Non-legume (e.g corn) planted one year, following year legume is planted

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae – Mutualistic associations of fungi and roots Fungus  steady supply of sugar f/ plant In return, the fungus i ncreases the surface area of water uptake

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae Figure 37.12a aEctomycorrhizae. The mantle of the fungal mycelium ensheathes the root. Fungal hyphae extend from the mantle into the soil, absorbing water and minerals, especially phosphate. Hyphae also extend into the extracellular spaces of the root cortex, providing extensive surface area for nutrient exchange between the fungus and its host plant. Mantle (fungal sheath) Epidermis Cortex Mantle (fungal sheath) Endodermis Fungal hyphae between cortical cells (colorized SEM) 100  m (a)

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mycorrhizae Figure 37.12b EpidermisCortex Fungal hyphae Root hair 10  m (LM, stained specimen) Cortical cells Endodermis Vesicle Casparian strip Arbuscules 2 Endomycorrhizae. No mantle forms around the root, but microscopic fungal hyphae extend into the root. Within the root cortex, the fungus makes extensive contact with the plant through branching of hyphae that form arbuscules, providing an enormous surface area for nutrient swapping. The hyphae penetrate the cell walls, but not the plasma membranes, of cells within the cortex. (b)

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Epiphytes, Parasitic Plants, and Carnivorous Plants Nutritional adaptations that use other organisms in nonmutualistic ways

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Exploring unusual nutritional adaptations in plants Figure 37.13 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 plants Sundews Dodder