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Mineral Nutrition

Mineral Nutrition. Nutrients. 1. Definition 2. Categories 3. Essential versus Non-Essential 4. Evidence. Fig 37.2. Julius Sachs 1860’s. Mineral Nutrition - Overview. 1. Some minerals can be used as is: e.g. K + ions for guard cell regulation

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Mineral Nutrition

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  1. Mineral Nutrition

  2. Nutrients 1. Definition 2. Categories 3. Essential versus Non-Essential 4. Evidence

  3. Fig 37.2 Julius Sachs 1860’s

  4. Mineral Nutrition - Overview • 1. Some minerals can be used as is: • e.g. K+ ions for guard cell regulation • 2. Some minerals have to be incorporated into other compounds to be useful: • e.g. Fe+ in the cytochrome complex of the light reactions • 3. Some mineral compounds have to be altered to be useful: • NO3- must be converted to NH4+ inside the plant

  5. Chemical composition of plants 1. 80–85 % of an herbaceous plant is water. 2. Water is a nutrient since it supplies most of the hydrogen and some oxygen incorporated into organic compounds by photosynthesis. 3. But > 90% of the water absorbed is lost by transpiration. 4. Water’s primary function is to serve as a solvent. 5. Water also is involved in cell elongation and turgor pressure regulation

  6. Chemical composition of plants: dry weight 1. 95% “organic” – C, H, O from air & water, assimilated by photosynthesis 2. 5% inorganic minerals

  7. Essential Nutrients 1. Nutrients that are required for a plant to grow from a seed and complete its life cycle. 2. 2 types: macronutrients & micronutrients

  8. Macronutrients • Elements required by plants in relatively large amounts. CHOPKNS Ca Mg

  9. Micronutrients • 1. These elements are required by plants in relatively small amounts (<0.1% dry mass). • 2. Major functions: • A. cofactors of enzymatic reactions • B. Light reactions of photosynthesis • C. Optimal concentrations highly species specific • Fe, B, Cl, Mo, Cu, Mn, Ni, & Zn

  10. Table 37.1

  11. Mineral Deficiencies • dependent on: • 1. the role of the nutrient in the plant • 2. its mobility

  12. Immobile Nutrients 1. Once they have been incorporated into plant tissue, they remain (can’t return to phloem). 2. Boron, calcium, and iron 3. Growth = normal until the mineral is depleted from soil; new growth suffers deficiency and thus youngest tissues show symptoms first.

  13. Mobile Nutrients 1. can be translocated by phloem to younger (actively growing) tissue. 2. Cl, Mg, N, P, K, and S 3. When mineral is depleted, nutrients translocated to younger tissue. 4. Thus older tissues show deficiency & then die What is the adaptive value of nutrient mobility?

  14. Mineral Deficiency • 1. Not common in natural populations. Why? • A. Plants have adapted to soil components • 2. Common in crops & ornamentals. Why? • A. Human selection for biggest, fastest plants. Need more nutrients than the soil provides • B. Crop growth depletes the soil because no organic matter return • 3. Deficiencies of N, P, and K are the most common. • 4. Shortages of micronutrients are less common and often soil type specific. • 5. Overdoses of some micronutrients can be toxic.

  15. Mineral Deficiency Symptoms 1. Chlorosis – leaves lack chlorophyll: yellow, brittle, papery. Typically lack of N or Fe. 2. Necrosis – the death of patches of tissue 3. Purpling – deficiency of N or P, causes accumulation of purple pigments 4. Stunting – lack of water, N

  16. Fig 37.4

  17. Soils

  18. Soil Formation 1. Forces 2. Horizons

  19. 3. Orders

  20. 4. Locations

  21. Soils 1. What do soils give to plants?? A. minerals B. nitrogen–fixing bacteria C. mycorrhizal fungi D. water E. oxygen

  22. Soil properties influence mineral nutrition • 1. Chemistry – determines which minerals are present and available, thus affecting plant community composition • 2. Physical nature – affects porosity, texture, density of soil, which affects #1 • 3. Soil organisms – • A. decomposition & mineral return • B. Interact with roots to make nutrients available • C. Nitrogen! The only mineral that the plant can ONLY get from reactions mediated by soil organisms.

  23. Soil texture & composition 1. Soil is created by weathering of solid rock by: water freeze/thaw, leaching of acids from organic matter, carbonic acid from respiration + water. 2. Topsoil is a mixture of weathered rock particles & humus (decayed organic matter). 3. Texture: sand, silt, clay Large, spaces for water & air Small, more SA for retaining water & minerals

  24. More about topsoil….. 1. Bacteria, fungi, insects, protists, nematodes, & Earthworms! Create channels for air& water, secrete mucus that binds soil particles 2. Humus: reservoir of nutrients from decaying plant & animal material 3. Bacterial metabolism recycles nutrients

  25. Availability of soil nutrients 1. Cations in soil water adhere to clay particles (negatively charged surface) 2. Anions do not bind; thus they can leach! (NO3, HPO4, SO4) 3. Cations become available for root uptake by cation exchange – H+ displaces cations on the soil particle surface 4. H+ from carbonic acid – formed from water + CO2 released from root respiration 5. Humus – negatively charged & holds water & nutrients. Thus very important in the soil!!!!!

  26. Thus soil pH is important! • 1. Low pH = high H+ concentration • A. More cations released • B. Too much acid – cations leach…..mineral deficiency • 2. High pH • A. Not enough H+ for cation release….mineral deficiency

  27. Fig 37.6

  28. Soil conservation • 1. Natural systems: decay recycles nutrients • 2. Agricultural systems: crops harvested, depleting soil of nutrients & water • 3. Thus irrigation & fertilizer • 4. Fertilizers: N:P:K • A. Synthetic: plant-available, inorganic ions. Faster acting. • a. Problem: • b. leaching, acidifying the soil • B. Organic: slow release by cation exchange, holds water, thus less leaching

  29. Phytoremediation 1. Use of plants to extract toxic metals from soil 2. Benefits: easier to harvest the plants than to remove topsoil!

  30. NITROGEN

  31. Why nitrogen? • 1. Air is 80% Nitrogen, but….. • 2. Macronutrient that is most often limiting. Why? • Is almost always taken up as anions (NO3-) • 3. What’s it used for? • Proteins (AAs), nucleic acids, chlorophyll production

  32. The Nitrogen Cycle N2 N2 fixation Denitrification Uptake Decomposition NO3 Nitrification Ammonification NH4 Organic N Leaching Immobilization

  33. Nitrogen Metabolism in Plants • 1. Steps: • A. N fixation – conversion of N2 to NH3 • B. Ammonification – conversion of NH3 or organic N into NH4+ • C. Nitrification – conversion of NH4+ to NO3- • D. N reduction – conversion of NO3- back to NH4+ within plant. • E. N assimilation – incorporation of NH4+ into AAs, nucleic acids of the plant

  34. But N is also lost…. 1. Leaching – loss of NO3- by soil water movement 2. Denitrification – conversion of NO3- back to N2

  35. All steps within the soil are mediated by bacteria!!!! Fig 37.9

  36. A. Nitrogen Fixation • This process is catalyzed by the enzyme nitrogenase, requires energy (ATP), and occurs in three ways: • a. Lightening – converts N in air to inorganic N that falls in raindrops • b. Non-symbiotic – certain soil bacteria • c. Symbiotic

  37. c. Symbiotic Nitrogen Fixation * Legumes: peas, beans, alfalfa *The legume/bacteria interaction results in the formation of nodules on roots *Plant – gets ample inorganic N source *Bacteria – gets ample carbon source

  38. Fig 37.10

  39. d. Fixation in Nonlegumes • * Here in the NW: alder • * Azolla (a fern) contains a symbiotic N fixing cyanobacteria useful in rice paddies. • * Plants with symbiotic N fixers tend to be first colonizers. Why?

  40. C. Nitrification a. Unfortunately NH4+ is a highly desirable resource for free–living bacteria, oxidizing it to NO3-. b. Consequently the predominant form of N available to roots is NO3-.

  41. D. Nitrate Reduction A. NO3- must be reduced back to NH4+ in order to be incorporated into organics. B. This process is energetically expensive but required.

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