SOIL & MINERAL NUTRITION

• MINERAL NUTRITION - During soil formation, rocks are converted gradually into dissolved ions and inorganic compounds. Because they are derived from the rock minerals, their role in plant nutrition is mineral nutrition.

  -Covers a variety of plant metabolism
• SOIL -   covers a variety of substances.

  -       important to plants not only in supplying minerals and harboring nitrogen-fixing bacteria, but also in holding water, supplying air to roots, and acting as a matrix that stabilizes plants, preventing them from blowing over.
• HYDROPONIC SOLUTION – technique of growing plants using a water-based nutrient solution rather than soil.
• • ESSENTIAL ELEMENTS An element required for normal growth and reproduction.

  -are called the major or macro essential elements because they are needed in large quantities by plants.
• MAJOR (MACRO) ESSENTIAL ELEMENTS -are needed in relatively large concentration. Macronutrients
• MINOR (MICRO, TRACE) ESSENTIAL ELEMENTS - are needed only in low concentrations. Micronutrients.
• • TRACE ELEMENTS group of minor or micro essential elements.
• CRITERIA FOR ESSENTIALITY:

  1. The element must be necessary for complete, normal plant development through a full life cycle.
  2. The element itself must be necessary, and no substitute can be effective.
  3. The element must be acting within the plant, not outside it.
• CHLOROSIS - A common symptom of mineral deficiency, a yellowing of leaves due to lack of chlorophyll.

  -Are often brittle and papery.
• Deficiencies of either nitrogen or phosphorus cause another common symptom, the accumulation of anthocyanin pigments that give the leaves either a dark color or a purple hue.
• • NECROSIS the death of patches of tissue (necrosis can also be caused by bacterial, viral, and fungal infections)
• -The location of the necrotic spots depends on the particular element: Potassium deficiency causes leaf tips and margins to die, whereas manganese deficiency causes the leaf tissues between veins to die even though all of the veins themselves remain alive and green.
• • MOBILITY An important diagnostic aspect is whether symptoms appear in young leaves or older leaves
• • IMMOBILE ELEMENTS nutrients which do not move throughout the plant.

  -Boron, calcium, and iron.

  -After they have been incorporated into plant tissue, they remain in place.

  -They do not return to the phloem and cannot be moved to younger parts of the plant.
• MOBILE ELEMENTS - Nutrients that are mobile in the plant will move to new growth areas, so the deficiency symptoms will first show up in older leaves.

  -chlorine, magnesium, nitrogen, phosphorus, potassium, and sulfur.

  -even after they have been incorporated into a tissue, they can be translocated to younger tissue.

  -The mobile elements are salvaged and moved to growing regions.
• MOBILE ELEMENTS - Nutrients that are mobile in the plant will move to new growth areas, so the deficiency symptoms will first show up in older leaves.

  -chlorine, magnesium, nitrogen, phosphorus, potassium, and sulfur.

  -even after they have been incorporated into a tissue, they can be translocated to younger tissue.

  -The mobile elements are salvaged and moved to growing regions.
• • WEATHERING Soils are derived from rock by this process.

  -breaking down or dissolving of rocks and minerals on Earth’s surface.
• The initial rock may be volcanic (granite, basalt), metamorphosed (marble, slate), sedimentary (sandstone, limestone), or other types.
• TWO THINGS are important: Rock has a crystalline structure, and trapped within the structure are numerous types of contaminating ions and elements.
• PHYSICAL WEATHERING – breakdown of rock by physical forces such as wind, water movement, and temperature changes.

  -Ice is an important agent.
• Physical weathering produces a variety of sizes of soil particles:

  • COARSE SAND - the largest ones that are technically important to soil are grains of this.

  -a size range of 2.0 to 0.2 mm.

  • FINE SAND Particles only one tenth this large of course sand (0.2 to 0.02 mm).
  • SILT one tenth of fine sand (0.02 to 0.002 mm).
  • CLAY PARTICLES – also known as MICELLES.

  -The finest particles, smaller than 0.002 mm in diameter.
• FIELD CAPACITY - Water that remains in the soil is held by capillary adhesion/cohesion and is said to be the field capacity of the soil.

                    -amount of soil moisture or water content held in soil after excess water has drained away.
• • CHEMICAL WEATHERING involves chemical reactions, and the most important agents are acids produced by decaying bodies, especially those of plants and fungi.
• Two fundamental processes of weathering convert rock to soil:

  1. Physical weathering
  2. Chemical weathering
• • ACID RAIN also called acid precipitation.

  -Rain that has become acidic due to air pollution; it can damage plant cuticle as well as speed the leaching of minerals from soil.
• EUTROPHICATION - The process that occurs as rivers and lakes receive too many mineral nutrients (usually as pollution from fertilized fields);
• EUTROPHICATION -they develop an overabundance of algae, much of which dies and decays, depleting the oxygen in the water and harming fish.
• • MYCORRHIZA the joining of a fungus and the root of a plant in which the fungus grows around or through the root providing nutrients and water to it and receiving food from it
• The roots of 90% of all species of plants form a symbiotic association with soil fungi, and this relationship is called a mycorrhiza
• Vesicular/arbuscular mycorrhiza (vam) - a kind of mycorrhizae whose hyphae penetrate the cells of plant roots by producing balloon-shape structures (vesicles) or dichotomously—branching invaginations (arbuscules).
• NITROGEN METABOLISM - nitrogen is relatively inert chemically and is useless to almost all organisms; it must be converted to chemically active forms.

  -The biosynthesis of amino acids in plants and the animal body
• This process, called nitrogen metabolism, consists of: (1) nitrogen fixation, (2) nitrogen reduction, and (3) nitrogen assimilation.
• • NITROGEN FIXATION conversion of N2 gas into nitrate, nitrite, or ammonium, all forms of nitrogen that are substrates for a variety of enzymes.
• NITROGENASE - The enzyme responsible for nitrogen fixation.
• NITROGENASE -is a giant enzyme complex composed of two distinct enzymes (dinitrogenase composed of four proteins, and dinitrogenase reductase composed of two proteins).
• NITROGEN REDUCTION - is the process of reducing nitrogen in the nitrate ion, NO3-, from an oxidation state of +5 to the –3 oxidation state of ammonium, which is also the oxidation state of nitrogen in amino acids, nucleic acids, and many other biological compounds.
• • NITROGEN ASSIMILATION is the actual incorporation of ammonium into organic molecules in the plant body.
• TRANSAMINATION – The transfer of an amino group from one molecule to another.
• OTHER ASPECTS OF PROKARYOTES AND NITROGEN

  • NITRIFYING BACTERIA - They oxidize ammonium to nitrite (Nitrosomonas, Nitrosococcus), and others oxidize nitrite to nitrate (Nitrobacter, Nitrococcus).
  • NITRIFICATION – the entire process above is called nitrification.
  • DENITRIFICATION - is a process in which certain bacteria (Hyphomicrobium, Pseudomonas) reduce nitrate to gaseous nitrogen, N2.
• Whereas nitrification results in nitrate that plants cannot use as easily as ammonium, denitrification results in nitrogen gas, which plants cannot use at all.