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Plant Physiology and Soils Basic Botany Fall 2007 Brooke Wheeler.

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Presentation on theme: "Plant Physiology and Soils Basic Botany Fall 2007 Brooke Wheeler."— Presentation transcript:

1 Plant Physiology and Soils Basic Botany Fall 2007 Brooke Wheeler

2 Saturday September 22 Reading quiz Plant physiology Short break (talk with project group) Soils- play with dirt Transpiration lab

3 Plant Physiology Plant hormones Plant growth and trophisms Photosynthesis

4 External factors and plant growth Light- phototrophism (elongation influenced by auxin) Gravitropism (auxin concentration) Thigmotropism- growth response to touching a solid object Circadian rhythms (ex. leaves moving outward during the day)

5 Plant Hormones Chemical signals Regulators –Stimulate –Inhibit

6 Auxin Phototrophism –Elogation of shaded cells  bend towards light Gravitrophism or geotrophism –Upper root cells elongate due to lower levels, causing the root to grow downwards Promotes adventitious root growth on cuttings Prevents fruit and leaf abscission Fruit maturation


8  Normal All seeds Removed   Horizontal band of seeds removed Auxin promotes fruit development

9 Gravitropism

10 Cytokinin and root gravitropism


12 Gibberellin Elongation of shoots Seed germination Stimulation of flowering in some plants

13 Effects of Gibberellin

14 Thigmotropism -roots around rocks, shoots of climbers around supports -Differential growth rates

15 Senescence (Aging) You have a bunch of green bananas but your child will only eat a ripe banana. What might to you do in order to speed up the ripening process?

16 Senescence Ethylene –Ripening of fruit –Separation process –Breakdown of membranes, softer cell walls Abscisic acid –Leaf abscission Fall color? –Dormancy in some seeds

17 Mutant of maize Zea mays -decreased sensitivity of embryos to abscisic acid leads to premature germination

18 Diurnal movements Wood sorrel (Oxalis sp.) during day (above) and night (right)


20 Temperature and Day length




24 Photosynthesis Capture of light energy from sun 250 billion metric tons of sugar/yr Overall reaction CO 2 + H 2 O + Light energy  (CH 2 O) + O 2


26 Chloroplast from mesophyll cell of the pigweed, Amaranthus retroflexus

27 Elodea, pondweed Oxygen on leaves of submerged plant Van Niel first to propose that oxygen came from splitting water, not breakdown of CO2

28 Electromagnetic Spectrum

29 Light Wave model –All radiation travels in waves with distinctive wavelengths Particle model –Albert Einstein 1905 Particles of energy compose light (photons) Energy of a photon is inversely proportional to its wavelength (longer wavelength, lower energy)

30 Pigments! -substances that absorb light -varying absorption spectrums

31 Taraxacum officinale Mesophyll specialized for photosynthesis

32 Structure of chlorophyll a

33 Stomata in a leaf- need CO2 to diffuse in for photosynthesis

34 Photosynthesis

35 Overview of Photosynthesis


37 C4 photosynthesis- spatial separation -more efficient but higher energy - 5 ATP to fix one molecule of CO2 but C3 plants need 3 ATP -Maintain high ration of CO2 to O2 at sight of Rubisco activity -(Maize, sugarcane, sorghum) -evolved in tropics and are wll adapted to high light, high temp and dryness. CAM: Crassulacean Acid Metabolism -Cacti, and stonecrops ( family Crassulaceae) -Photosynthetic cells can fix CO2 in the dark- temporal separation

38 Sugarcane C4 Pineapple CAM

39 Soil Take a break first!

40 Plant Nutrition

41 Macronutrients Sulfur: soil Phosphorous: soil Calcium: soil Potassium: soil Nitrogen: soil/fungi Oxygen: air, water Carbon: air and soil Hydrogen: air

42 Micronutrients: from soil Magnesium Molybdenum Copper Zinc Manganese Boron Iron (Chlorine, Aluminum, sodium, silicon, cobalt)



45 Nutrient Cycling

46 Hubbard Brook Experiments

47 Legumes contain symbiotic bacteria called rhizobia within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants.

48 Not enough magnesium causes Chlorosis

49 Soil - an essential part of a plant’s environment -the source of plant nutrition

50 Soil Inorganic –Erosion of rock Organic –Humus –Decomposing plant and animal matter

51 Soil Properties Texture: Determines how much moisture can be held pH Organic matter content and fertility Living organisms Porosity Mineral content

52 Soil Texture Percent Silt Sand Clay


54 Factors in Soil Formation Parent Material Climate Living Organisms Topography Time

55 Mountain soil: Shallow, young soil

56 Piedmont Soil: Dark grey sandy loam toplayer, Red clay subsoil

57 Coastal soil: Very sandy

58 Major Soil Types ENTISOL Soils of limited development. Profile is largely that of the parent material. INCEPTISOL (from incept [Latin] = beginning) Moderate development of soil horizons. Horizons are those that form quickly. ARIDISOL (from aridus [Latin] = dry) Soils of arid regions. Limited change in parent materials, low precipitation. MOLLISOL (from mollis[Latin] = soft) Soils with friable surface horizons containing organic matter. Base saturation level is high. SPODOSOL (from spodus[Latin] = wood ash) Soils with illuvial B2 horizons containing free Fe and Al oxides, non-crystalline clavas and humus. Often partially cemented. ALFISOL Soil with B2 horizon with crystalline clay - moderate to high degree of base saturation. ULTISOL Soil with B horizon with crystalline clay - LOW degree of base saturation. OXISOL (from oxide[French]) Highly weathered soils containing B horizon primarily of sesquioxides or clays. VERTISOL (from verto [Latin] = turn) Soils that form large cracks on drying - "self ploughing" soils HISTOSOLS (from histos[Greek] = tissue) Soils with very high levels of organic matter. Definitions: Base saturation- percent base saturation measures a soil’s ability to store plant nutrients (how much of the cation exchange capacity is being used); the percentage of the cation exchange capacity occupied by basic cations (ex Ca2+, Mg2+, K+, Na+; they are called basic because enough OH- ions are present to make the system alkaline) Illuvial- having received nutrients removed from an upper layer in the soil; generally a B horizon which has solid materials deposited from the A horizon Cation exchange capacity- CEC- capacity of the clay and humus (organic matter) to hold exchangeable cations in the soil

59 The Southeast is dominated by ultisols

60 Soil map of US



63 Getting dirty Look at the four soil samples Describe them –What is the color? –What is the texture? –Sandy? Silty? Clay? Where might they be from?

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