Chapter 1 Essential elements Plant nutrition is a term that takes into account the interrelationships of mineral elements in the growth medium as well as their role in plant growth. Plant nutrition is a term that takes into account the interrelationships of mineral elements in the growth medium as well as their role in plant growth. Concept of plant nutrition Complex interactions involving weathering of rock minerals, decaying( of organic matter, such as humus and residues of plant,animals, and microbes, take place to form inorganic minerals in soil. Complex interactions involving weathering of rock minerals, decaying( of organic matter, such as humus and residues of plant,animals, and microbes, take place to form inorganic minerals in soil. Roots absorb mineral nutrients as ions in soil water. Many factors influence nutrient uptake for plants. Roots absorb mineral nutrients as ions in soil water. Many factors influence nutrient uptake for plants. This interrelationship involves a complex balance of mineral elements essential and beneficial for optimum plant growth. This interrelationship involves a complex balance of mineral elements essential and beneficial for optimum plant growth. Concept of plant nutrition Essential elements The material of living plants consist of organic matter, water and minerals. The percentage distribution of these three components is in the following order of magnitude: The material of living plants consist of organic matter, water and minerals. The percentage distribution of these three components is in the following order of magnitude: Water 70%(fresh matter) Water 70%(fresh matter) Organic material 27%(fresh matter) Organic material 27%(fresh matter) Minerals 3% (fresh matter) Minerals 3% (fresh matter) The term essential mineral element (or mineral nutrient) was proposed by Arnon and Stout (1939). The term essential mineral element (or mineral nutrient) was proposed by Arnon and Stout (1939). They concluded three criteria( ) must be met for an element to be considered essential( ). They concluded three criteria( ) must be met for an element to be considered essential( ). Essential elements Three criteria of Essential elements 1. A plant must be unable to complete its life cycle in the absence of the mineral element. 1. A plant must be unable to complete its life cycle in the absence of the mineral element. 2. The function of the element must not be replaceable by another mineral element. or deficiency symptoms can not be remedied by supplying some other element 2. The function of the element must not be replaceable by another mineral element. or deficiency symptoms can not be remedied by supplying some other element 3. The element must be directly involved in plant metabolism. 3. The element must be directly involved in plant metabolism. Sixteen Essential Elements Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulfur (S) Iron (Fe) Manganese (Mn)Copper (Cu) Zinc (Zn) Molybdenum (Mo)Boron (B) Chlorine (Cl) Nutrient Composition of Plants Relative amounts of essential elements in plant tissues Two ways to classify the essential elements 1.Classified by whether it is used in large or small amounts (Macronutrients or micronutrients) 2.Classified by its function in the plant (What the element does in the plant) Macronutrients and Micronutrients A.Macronutrients are elements that are used in relatively large amounts (% or g/kg). B.Micronutrients are elements that are used in relatively small amounts ( g/g or mg/kg). The concentration of macronutrients in plant tissue is often more than 1000x greater than the concentration of micronutrients. Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) Phosphorus (P) Potassium (K) Calcium (Ca) Magnesium (Mg) Sulfur (S) N, P, and K are called primary macronutrients Ca, Mg, and S are called secondary macronutrients Macronutrients Micronutrients Iron (Fe) Manganese (Mn) Copper (Cu) Zinc (Zn) Molybdenum (Mo) Boron (B) Chlorine (Cl) 1-1 Stout P.R. mol/gg/g% Mo Cu Zn Mn B Fe CI S P Mg Ca K N O C H Concentrations of essential elements in leaves Data, represent the lowest concentrations found in recently matured leaves of healthy plants. Higher levels are commonly found Among the all of nutrients, N, P and K are three most important ones in crops production because the amount of plant required is bigger but their availability are lower in the soil, so they are often deficiency to crop in the field, and they are needed to compensated by fertilizers. Among the all of nutrients, N, P and K are three most important ones in crops production because the amount of plant required is bigger but their availability are lower in the soil, so they are often deficiency to crop in the field, and they are needed to compensated by fertilizers. Three primary fertilizers ( or primary macronutrients 1-2 N P 2 O 5 K 2 O kg Requirement of N, P 2 O 5 and K 2 O of some kinds of crops (kg/tone biomass) NP2O5P2O5 K2OK2O 9311 628 6312 528 525 Crop Base Yield tonnes/h a Estimated Nutrient Removal kg/ha Corn Wheat Wheat+straw Soybeans Canola Cotton (seed+lint) Sugar beets Nutrient Removal by Crops N P 2 O5 K2OK2O Factors that affect the mineral content in the plant 1.Genotypes: Ability of the plant to take up nutrients 2.Availability of the nutrient in the soil or water etc. 3.Portion of the plant (leaf compared to fruit) 4.Age of the plant The special functions of the element must not be replaceable by another mineral element No matter how much is required by the plant, or how much content is it in plant,the every essential element is same important to the plant physiology and plant growth; its function of every essential element cannot substitute by another mineral element completely. No matter how much is required by the plant, or how much content is it in plant,the every essential element is same important to the plant physiology and plant growth; its function of every essential element cannot substitute by another mineral element completely. Beneficial elements are those that can compensate for toxic effects of other elements or may replace mineral nutrients in some other less specific function such as the maintenance of osmotic pressure. Beneficial elements are those that can compensate for toxic effects of other elements or may replace mineral nutrients in some other less specific function such as the maintenance of osmotic pressure. The beneficial elements have not been deemed essential for all plants but may be essential for some. The beneficial elements have not been deemed essential for all plants but may be essential for some. Beneficial elements Cobalt for instance is essential for nitrogen fixation in legumes. Cobalt for instance is essential for nitrogen fixation in legumes. Silicon, Equisetum and many grasses (particularly rice) require silicon, deposited in cell walls, has been found to improve heat and drought( ) tolerance and increase resistance to insects and fungal infections. Silicon, Equisetum and many grasses (particularly rice) require silicon, deposited in cell walls, has been found to improve heat and drought( ) tolerance and increase resistance to insects and fungal infections. Beneficial elements Silicon, acting as a beneficial element, can help compensate for toxic levels of manganese, iron, sodium and aluminum as well as zinc deficiency. Silicon, acting as a beneficial element, can help compensate for toxic levels of manganese, iron, sodium and aluminum as well as zinc deficiency. Na is required by species using the C 4 pathway of photosynthesis, Where it is supposed to maintain the integrity of chloroplasts and thus allow the uptake of pyruvate Na is required by species using the C 4 pathway of photosynthesis, Where it is supposed to maintain the integrity of chloroplasts and thus allow the uptake of pyruvate Beneficial elements Plant nutrients and toxins are important components of food chains that begin with plants and include animals-wild, domestic, and human Plant nutrients and toxins are important components of food chains that begin with plants and include animals-wild, domestic, and human Deficiencies of the essential elements frequently limit plant growth or quality. Even when the plants themselves do not suffer from a deficiency, they sometimes provide animals with a diet deficient in certain elements, for example, Mo, Se, Co, Cu, P, Na, Ca, or I Deficiencies of the essential elements frequently limit plant growth or quality. Even when the plants themselves do not suffer from a deficiency, they sometimes provide animals with a diet deficient in certain elements, for example, Mo, Se, Co, Cu, P, Na, Ca, or I Essential elements and food chain A more holistic approach( to plant nutrition would not be limited to nutrients essential to survival but would include mineral elements at levels beneficial for optimum growth and food chain. A more holistic approach( to plant nutrition would not be limited to nutrients essential to survival but would include mineral elements at levels beneficial for optimum growth and food chain. More toxic element Plants frequently contain unnecessary high and sometimes toxic concentrations of an essential or nonessential element. Most commonly toxic to plant are AI and Mn (in acid soils), Na, and CI (in saline soils), boron, and copper. Plants frequently contain unnecessary high and sometimes toxic concentrations of an essential or nonessential element. Most commonly toxic to plant are AI and Mn (in acid soils), Na, and CI (in saline soils), boron, and copper. Elements such as copper, lead, arsenic, cadmiun, molybdenum, and selenium are sometimes present at concentrations that injure foraging animals, though the plant itself is little affected. Elements such as copper, lead, arsenic, cadmiun, molybdenum, and selenium are sometimes present at concentrations that injure foraging animals, though the plant itself is little affected. Phytoremediation ( Plant are very adaptive( ) Plant are very adaptive( ) The plants, which can uptake and accumulation high level metal, is known as hyperaccumulators. The plants, which can uptake and accumulation high level metal, is known as hyperaccumulators. Now 45 plant families are known to contain metal-accumulating species. Now 45 plant families are known to contain metal-accumulating species. The decontamination of soil by means of plants uptake of organic and /or inorganic contaminants is called phytoremediation. The decontamination of soil by means of plants uptake of organic and /or inorganic contaminants is called phytoremediation. Specific function Structural components (C, H, O, N, P, S) Enzymes activators (K, Ca, Mg, Mn, Zn) Redox reaction (Fe, Cu, Mn, Mo) Elements of uncertain function (B,CI) The function of essential nutrients NON-SPECIFIC OSMOTIC FUNCTIONS The generation of turgor in walled cells depends on the accumulation of inorganic and organic solutes within the vacuoles and cytoplasm of plant K + is energetically much cheaper than organic solutes. Indeed K + is typically the preferred cation for turgor generation in land plants. For halophytes NaCl is an important osmoticum but it is restricted to the vacuole The function of essential nutrients C, H, O, N, and S are the major components of the plant tissue. Essential elements of atomic groups which are involved in enzymic processes P, B, and Si are important in esterfication ( )processes. P esters are involved in the energy transfer reactions Classified by function K, Na, Mg, Ca, Mn, and Cl control the movement of water and ions between cells. Non-special functions (osmotic potentials) and special function (enzyme activation) K, Na, Mg, Ca, Mn, and Cl control the movement of water and ions between cells. Non-special functions (osmotic potentials) and special function (enzyme activation) Fe, Cu, Zn, and Mo enable electron transport by valency change. Fe, Cu, Zn, and Mo enable electron transport by valency change. 2. Flow of the nutrients from soil to the root nutrient How do plant roots and nutrients come into contact? Root interception Mass flow Diffusion Root Interception( Roots grow through soil and come into contact with the surfaces of soil particles. The root surfaces are able to take up the nutrients from soil clay mineral. Root Interception Roots only occupy about 1-2% of the total soil volume, so the amount of nutrients take up in this way is relatively small. But It is most significant for: 1.High concentrations in soil solution such as Ca and Mg(?) 2.Nutrients required in small amounts (e.g. Zn, Mn, and other micronutrients) Mass Flow (or bulk flow) Nutrients are transported as water moves from the soils to the plant roots. or soil solution (containing dissolved nutrients) moves down gradients of water potential The characteristics of mass flow Wet soil dry soil Higher water potential lower water potential All nutrients move in the same direction Rate of nutrient movement depends on concentration in solution - affected by uptake and replacement volume of solution - affected by soil moisture and by soil pore sizes rate of flow - affected by transpiration( , evaporation and drainage Mass Flow (or bulk flow) Mass flow supplies most of the required amounts of NO 3 -, SO 4 2-, Cl -, and H 3 BO 3 It often supplies more than the required amounts of Ca, Mg. It can meet or supply a significant portion of the requirements for Cu, Mn, and Mo. Mass Flow (or bulk flow) Factors that affect nutrient transport by mass flow 1.Soil water content if the soil is dry water move very slowly. 2.Temperature if the temperature is low, water uptake by the plant is reduced and nutrient transport declines. 3.Air humid Diffusion( Diffusion occurs when an ion is transported from a place of higher concentration to a place of lower concentration. Diffusion As plants take up nutrients, there is a reduction in the nutrient concentration near to the root (rhizosphere). So the nutrient concentration in bulk soil solution is higher then that in rhizosphere, then nutrients will begin to move into the area near to the root surface. Nutrient concentration is different at the root surface compared to the soil solution. If the difference in the concentration is very large, then diffusion can occur more rapidly. Diffusion is an important mechanism for the movement of NH 4 +,P, K, Fe, and Zn. Canola Corn Diffusion of nutrients Movement in solution is independent of direction of flow of solution Nutrient moves down concentration gradient Rate for each nutrient depends on concentration gradient (driving force) diffusion coefficient in soil (D) (ease of movement) D=Di f Dcs/Dc Diffusion coefficient in water (Di) buffering capacity of soil (Dcs/Dc) tortuosity of pathway in soil (f) soil moisture (continuity of water-filled pores)() Di = diffusion coefficient of ions in soil (m 2 s -1 ) ion ion wet soil -10 kPa dry soil kPa NO 3 - NO 3 - (low buffering capacity) (low buffering capacity) K + K H 2 PO 4 - H 2 PO 4 - (high buffering capacity) (high buffering capacity) values are much lower than for diffusion in pure water( )due to: tortuosity( ) of pathway increased viscosity( close to surfaces exclusion of ions by surface charge on particles Processes involved in nutrient replacement replacement at root surface replacement at root surfaceNP diffusion diffusionrapidslow mass flow mass flow+++(+) N has low buffering capacity and high concentration in soil solution N is VERY MOBILE (easily gets to roots; easily leached out of soil) P has high buffering capacity and low concentration in soil solution (