Plant Nutrition (??? ??)

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Plant Nutrition(??? ??)

• Chapter 33

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???? ???? ?????????(Tillandsia usneoides)? ??????
?? ??? ??? ????? ????, ?? ??? ?? ???? ?? ?? ??
???? ??.

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33.1 Plant Nutritional Requirements

• Plants require macronutrients(????) and
  micronutrients(????) for their metabolism
• Nutrient deficiencies cause abnormalities in
  plant structure and function

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Mineral Nutrient Limitations

• Soil never contains sufficient quantities of all
  necessary plant nutrients
• Leaching(??) in moist to wet soils
• Arid climates lack water in soils
• Herbivores obtain concentrated soil nutrients by
  eating plants

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Tropical Rain Forest
?? 33.1. ?????? ??? ????.
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Hydroponics(????)

• Ashes(? ??) from plants lack certain volatile
  elements and include nonessential ones
• Hydroponic culture(????) grows plants in solution
• Remove one nutrient at a time, observe growth
• Essential elements(????)
• Necessary for growth/reproduction
• Cannot be substituted
• One or more roles in metabolism

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Research Hydroponic Culture
?? 33.2. ????.
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Macronutrients and Micronutrients

• Macronutrients(????) essential in large
  quantities
• C,H, O 96 of dry mass, come from air, not
  considered minerals
• N, P, Ca, S, Mg
• Micronutrients(????) essential in trace
  quantities
• Hard to exclude (Cl)
• May be enough in seeds for multiple generations
  (Ni)
• Some micronutrients specific to plant types

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Nutrient Deficiencies

• Different plants have different needs for (or
  toxicity to) elements
• Soil determines where and how well plants grow
• Nutrient deficiencies have symptoms with clues to
  metabolic function
• Stunted growth, leaf color, dead spots, abnormal
  stems, chlorosis?(?)???
• Young vs. older growth deficiencies indicate
  mobility of limiting element

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?? 33.3. 7?? ?? ??? ?? ??? ???? ???? ?? ??.
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33.2 Soil

• Components of a soil and the size of the
  particles determine its properties
• Characteristics of soil affect root-soil
  interactions

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Soil

• Soil-mineral particles, compounds, ions,
  decomposing organics(???? ?? ???), water, air,
  organisms
• Sand, silt(?? ???), and clay(??) particles
• Humus(???) Decomposing organics
• Relative amount of soil particles determine soil
  properties
• Loam(??) Equal parts of all, best for plant
  growth

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Soil Development

• Organisms and plant roots
• Bacteria, fungi, nematodes and worms, insects,
  vertebrates
• Fertile soil has faster organic matter turnover
• Soil development produces soil horizons(?? ???)

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Soil Horizons(?? ???)

• O horizon(?? ????)
• Top organic-matter dominated
• A horizon(?? ??? ?? ???)
• Topsoil(??) below O, most roots
• B horizon
• Subsoil(???) accumulates nutrients, woody roots
• C horizon
• Rock fragments, parent material

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?? 33.4. ???? ?? ???? ???.
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Water Availability

• Soil solution(????) available for plant uptake
  after gravity drainage
• Coats soil particles, partially fills pore spaces
• Sandy soil looser, holds less water than clay
  soils
• Humus(???) increases water availability
• When water content of soil is low, water binds
  tightly to particles
• Roots must have lower ? than soil

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?? 33.5. ????? ??.
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Mineral Availability (1)

• Mineral cations (Mg, Ca2, K) adsorped(????) to
  negative soil particules
• Cation exchange(??? ??) replaces mineral with H
  produced by roots or carbonic acid(??)
• Anions (NO3-, SO42-, PO4-) weakly bound to soil
• Move freely and leach easily

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?? 33.6. ????? ???? ??? ??.
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Mineral Availability (2)

• Soil pH changes availability of mineral elements
• Acidic or basic soils have unavailable elements
• Weathering and ecosystem cycling maintain
  available elements in soil
• Fertilizer does not add humus

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33.3 Obtaining and Absorbing Nutrients

• Root systems allow plants to locate and absorb
  essential nutrients
• Nutrients move into and through the plant body by
  several routes
• Plants depend on bacterial metabolism to provide
  them with usable nitrogen
• Some plants obtain scarce nutrients in other ways

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Root Systems

• Extensive root systems are adaptations to limited
  mineral nutrients
• May be more than half of total plant mass
• Roots grow as long as plant lives
• Roots have mechanisms to increase uptake
• Root hairs
• Membrane transporters
• Mycorrhizae(?? 28.3? ??) symbiotic with fungi

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Nutrient Movement

• Nutrients taken up actively, or passively via
  transpiration
• Apoplastic (xylem) or symplastic movement
• Casparian strip
• Phloem moves nutrients from sources to sinks
• Tissue/organ can change from source to sink
  (spring vs. fall foliage)

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Nitrogen Limitations

• Nitrogen (N)(??)
• Abundant element in air, most limiting to plant
• Triple bond requires specific enzyme
• Nitrogen cycle provides soil nitrogen
• Nitrogen fixation(????) incorporates atmospheric
  N2 into plant-available compounds
• Nitrogen-fixing bacteria
• Lightning(??) (small amounts)

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Nitrogen Cycling

• Bacterial ammonification(????? ??) breaks organic
  N compounds into NH4
• Plants take up NH4, but prefer NO3-
• Bacterial nitrification?(?)??? oxidizes NH4 to
  NO3-
• High rates of nitrification, except in acidic
  soils
• Plants convert NO3- to NH4 to assimilate N into
  organic compounds

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?? 33.7. ??? ?????? ??? ?? ??.
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Nitrogen Fixation

• Most N is fixed by plant symbioses with bacteria
• Plant provides organic molecules for respiration
  energy, bacteria provide NH4
• Legumes form root nodules(???) with
  Rhizobium(?????) or Bradyrhizobium(???)
• Bacterial nod genes expressed with flavonoid
  signal from plant
• Infection thread(???) allows bacterial invasion
• Bacteroids(?????) enclosed in nodule
  (leghemoglobin(???????) and nitrogenase)

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?? 33.8. ???? ??? ??. (a) ??? ???, (b) ??? ??
???? ??? ??. ???? ?????? ??? ???, (c) ?????? ???,
?????? ???? ?? ?? ???, ??? ?? ???? ????? ??? ???
????.
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?? 33.9. ?????? ??????? ?????(Rhizobium)? ????
???? ??? ??? ??? ??.
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Other Nutrient Adaptations

• Carnivorous(??) plants digest animals
  extracellularly
• Most common in N-poor areas such as bogs(??)
• Parasitic plants obtain some or all nutrients
  from other plants (some conduct photosynthesis)
• Haustorial roots(???) tap into host vascular
  tissue
• Epiphytes(????) grow on other plants (not
  parasites)
• Trap water and nutrients

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?? 33.10. ???? ?? ?? ??? ????? ?? ???. (a)
????, (b) ????, (c) ????, (d) ????.