Soil, Plant Nutrition & Roots

1. Soil, Plant Nutrition & Roots Chapters 29, 30, 24

2. Exam 1 Avg = 86.4%

3. humus Soils and Plant Nutrition • Plants require nutrients from soil • In eastern US, 200 yr to form 2 cm topsoil (even slower in western where arid) • What is soil? • A mixture of: • Mineral particles (sand, silt, clay) • Decomposing organic matter (humus) • Air • Water • Living Organisms

4. clay sand silt Mineral Particles • Sand 0.05-2.0 mm • Silt 0.002-0.05 mm • Clay < 0.002 mm • Clay soils •  soil water holding capacity, but all water not available for plants •  infiltration rates so  runoff • Loamy soils • even mixture of particle sizes • best for agricultural

5. Many soils in southeastern Nebraska were formed in parent materials deposited by the glaciers, usually referred to as glacial drift, glacial till or glacial outwash. Much of the parent material deposited in ancient times has been covered by windblown material. The windblown silty material is called loess. It covers most of Nebraska to varying depths, except in the Sandhills and western portions of the Panhandle.

6. Where does soil come from? • Weathering of parent material (bedrock) • Soil horizons • O horizon • organic, few cm thick • humus – organic decay products • contained within A horizon in some classifications • A horizon • topsoil, 10-30cm thick • greatest physical, chemical, and biological activity • B horizon • subsoil, larger particles, 30-60cm • leaching from A horizon by water percolation • iron oxide, clay particles, little organic material • mixed with A horizon when plowed • C horizon • soil base • partially weathered parent material, 90-120 cm

7. Extent of North American glaciation Soil Forming Factors • Parent material • Climate • Living organisms • Topography • Time

8. Cedar Rapids Iowa http://www.treehugger.com June 2008 Rainfall http://www.srh.noaa.gov 2008 Iowa Floods Soil erosion 20 tons/acre 40,000lbs/acre Some farms in Iowa have no topsoil remaining (Mary Skopec, Iowa DNR)

9. chlorophyll Essential Elements for Plants Required for normal growth & reproduction No other element can replace Direct or indirect action in plant metabolism Macronutrients (9) • required in greater amounts • What do these macronutrients do? C, H, O - basic organic constituents N, K, Ca, P - oh my gosh, some very essential organics: amino acids, nucleotides, ATP, NADPH, cell wall, regulatory, osmoregulation Mg, S - chlorophyll, electron transport chain, amino acids

10. Chlorosis Magnesium deficiency Iron deficiency

11. amine group

16. Essential Elements (continued) Micronutrients(8) • required in lesser quantities Fe, Mn, Cu, Zn, B, Mo, Cl, Ni • What do these micronutrients do? essential for enzyme function, organ and organelle function, photosynthesis Manganese: involved in photosynthetic reaction in which oxygen is produced from water Copper: associated with enzymes involved in redox reactions Iron: component of enzymes involved in the transfer of electrons Etc…..

17. Plant Growth Medium for fern gametophytes (C-fern) • Macronutrients NH4NO3, KH2PO4, MgSO4, CaCl2 • Micronutrients MnSO4, CuSO4, ZnSO4, H3BO3, (NH4)6Mo7O24, FeSO4

18. Nickel

19. Roots • Roots are 50-80% of plant biomass in prairie • Plants “forage” for dilute nutrients in environment

20. Root functions • Anchor plant into ground • Storage of energy reserves • Absorption of water and dissolved minerals from soil • Conduction of water and dissolved nutrients to shoot

21. Taproot System • First root formed is the radicle • In dicots, radicle grows into taproot • Branch roots grow from taproot

22. Fibrous Root System • Mostly in monocots • Extensive mass of similarly sized roots • Radicle short-lived, replaced by adventitious root system • adventitious means not belonging to • roots growing from stem

23. Root Structure • Root cap • protection from desiccation, lubrication, water and nutrient absorption • Zone of Cellular Division • densely packed cells undergoing mitosis • Zone of Elongation • growing cells • Zone of Maturation • differentiating cells

25. Epidermis: • one cell thick, usually no cuticle; absorbs water Cortex: • just interior to epidermis, waxy protective layer • parenchyma tissue: most of cortex, often contains starch • endodermis: tightly packed cells with casparian strip Stele: • tissue inside cortex • pericycle: interior to endodermis - a meristem for branch roots • vascular bundle: xylem as a cross with phloem in armpits Dicot Root Monocot Root

27. Endodermis change through aging Dicot - young stele Dicot - mid-aged stele Dicot - old stele

28. Casparian Strip • integral band-like portion of primary wall and middle lamella in endodermal cells • lignin and suberin “valve” • regulates water because water • must move symplastically through the endodermal cells • through plasmdesmata between cells • rather than apoplastically • through intercellular spaces

29. Casparian Strip

31. Root hairs

32. - - - - O O O O H H H H H H H H + + + + + + + + Unique Properties of Water due to molecular structure a polar molecule - excellent solvent hydrogen bonding between water molecules cohesion tensile strength between water and other molecules adhesion capillarity - from cohesion and adhesion

35. H2O Leaf Anatomy

36. 85-95% of plants is water • 95% of H20 taken up by plant transpired back into atmosphere

37. as water evaporates from the leaf surface, a column of water is pulled upward from the soil water Cohesion-tension theory cohesion and adhesion cause water to rise in plants

39. tracheid vessel elements

40. Note distribution of pits in walls of all xylem elements (tracheids and vessels) Size comparison of xylem elements

41. pits perforation plate (end walls)

42. Problems with water movement • air bubbles • cavitation • water column rupture • embolism • filling with air or water vapor • solution • move water around embolism

43. Is there a limit to water column? How tall are the tallest trees? What are the tallest trees?

44. Tallest Tree Coast Redwood Sequoia sempervirens Redwood National Park California Height = 116m (379.1 feet) named Hyperion; Steve Sillett, Humboldt State U. Estimated Age = 2,000+ yrs Save the Redwoods League

45. Giant Redwood -Sequoiadendron giganteum Top: lithograph showing a party of 32 people dancing on the stump of the Discovery Tree, North Calaveras Grove Bottom: 30-foot section of the General Noble Tree, which was displayed at the Columbian Exposition in Chicago in 1893 and later at the Mall in Washington, DC; it was subsequently taken to the US government's Arlington Experiment Farm, where it was "misplaced" http://en.wikipedia.org/wiki/Image:Giant_sequoia_exhibitionism.jpg

46. Transpiration and Productivity Leaves adapted for photosynthesis abundant stomata large number vein endings Tradeoff CO2 in - photosynthesis H2O out - transpiration • H2O limits biomass production in most areas • Evapotranspiration • transpiration & soil evaporation • problematic in arid areas