Plant Nutrients July 2024 PDF

Plant Nutrients Prof. Sriyani E. Peiris Intended Learning Outcome Discuss Plant nutrients and their contributions to plant growth and development Nutrients: Macro, micro, beneficial minerals Nutrient deficiencies of plants Ion uptake by cells and roots Nitrogen fixation  Mineral Nutri...

Plant Nutrients Prof. Sriyani E. Peiris Intended Learning Outcome Discuss Plant nutrients and their contributions to plant growth and development Nutrients: Macro, micro, beneficial minerals Nutrient deficiencies of plants Ion uptake by cells and roots Nitrogen fixation  Mineral Nutrition in plants Plants are: Capable of making all necessary organic compounds from inorganic compounds and elements in the environment (autotrophic) Supplied with all the carbon, hydrogen, and oxygen they could ever need (CO2, H2O) Required to obtain all other elements from the soil so in a sense plants act as soil miners How plants obtain, distribute, metabolize, and utilize mineral nutrients. Mineral”: An inorganic element acquired “ mostly in the form of inorganic ions from the soil Nutrient”: A substance needed to survive or “ necessary for the synthesis of organic compounds  Mineral Nutrients – Elements acquired mainly in the form of inorganic ions from the soil  How do mineral nutrients enter the biosphere? Predominantly through the root systems of the plants Plants do not depend on the high energy compound synthesized by the other organisms Absorb -> Translocate to various parts of the plant -> Use for biological functions Cycle through all organisms Absorption of Mineral Nutrients Very efficient Large surface area of roots Ability to absorb at low concentrations in soil Helped by, Mycorrhizal fungi N-fixing bacteria  Plant Minerals in Agriculture High yield -> Fertilization with mineral nutrients Yield linearly increase with the amount of fertilizer absorbed  Plant uses less than half of the fertilizer applied Remaining? – Leach into surface water / ground water – Attach to soil particles – Contribute to air pollution Solutions? – Traditional – recycle – Phytoremediation - Slow releasing fertilizer  Why is mineral nutrition important? Fertilization increases crop production Kg/ha Kg/ha  Element Composition in Plants >90% of plant C, H, O, N In certain tissues – High N, P, K levels – Eg:- young tissues Over 60 different elements have been found – Eg:- Au, Ag, As, Hg, Pb  Essential Elements Plant cannot complete life cycle without it Components of essential plant metabolite or constituent – Eg :- Mg in chlorophyll No other element can substitute for it Has defined physiological role If the plant is provided with these elements and energy, it can synthesize all the compounds it needs for normal growth  Essential Mineral Nutrients Co2in the atmosphere 17 essential elements – 3 non-minerals (C, H, O) 0.041% Most abundant From CO2 or H2O – 14 others absorbed by soil P, K, N, S, Ca, Fe, Mg, B, Mn, Cl, Cu, Zn, Ni, Mo Some are considered beneficial but not essential – Na, Si, Co – Can have species specific difference Classification According to the relative concentration within the plant – Macronutrients – Micronutrients Often present in plant in greater concentration than needed  Macro nutrients – Present in plant material at concentration > 0.1% or 1000ppm Micro nutrients – Present in plant material at concentration < 0.01% or 100ppm Categories of Essential plant nutrients All mineral nutrients together make up less than 4% of plant mass, yet plant growth is very sensitive to nutrient deficiency. Micronutrients are present in very low concentrations Very low concentrations, but still essential because of specialized roles in metabolism Categories according to the biochemical role and physiological function Constituents of macromolecules or carbon compounds – (DNA, RNA, lipids, sugars, etc) Help in energy storage and structure – Involved in energy transfer reactions – (P) Electrolytes to maintain the osmotic concentration, enzyme cofactors, photosynthesis – (Na, Mg, Ca, Mn, Cl) Redox components – (Fe, Cu, Zn, Mo) Mineral Nutrients and their functions Group 1 N- Constituents of amino acids, nuleotides, coenzymes hexosamines etc. S- Compound of cysteine, methionine and proteins. Constituent of lipolic acid ,coenzyme A, thiamine pyrophosphate. Glutathione, biotin adenosine-5- phosphosulphateand 3 phosphoadenosine. Group 2 P- Component of sugar phosphate, nucleic acid, nucletides, coenzymes, phospholipids, phytic acids etc. Has a key role in reactions that involve ATP. Si – Deposited as amorphous silica in cell wall Contributes to cell wall mechanical properties including rigidity and elasticity B- Complexes with mannitol, mannan, polymanniuronic acid and constituents of cell walls. Involve in cell elongation and nucleic acid metabolism. Group 3 K- Required as a cofactor for more than 40 enzymes. Principal cation in establishing cell turgor and maintaining cell electroneutrality Ca- Constituent of the middle lamella of cell walls. Required as a cofactor by some enzymes Involve in hydrolysis of ATP and phospholipids. Acts as a second messanger in metabolic regulation. Group 3 cont…. Mg- Constituent of the chlorophyl molecule. Required by many enzymes involved in phosphate transfer. Cl- Required for the photosynthetic reactions involved in O2 evolution Mn- Required for activity of some dehydrogenases, decarboxylases, kinases, oxidases and peroxidases. Involved with other cation activated enzymes and photosynthetic O2 evolution. Na- Involved with the regeneration of phosphoenolpyruvate in C4 and CAM plants. Substitutes for potassium in some function Group 4 Fe- Constituent of cytochromes and nonheme iron proteins involved in photosynthesis. N2 fixation and respiration. Zn- Constituent of alcohol dehydrogenase, glutamic dehydrogenase, carbonic anhydrase, etc. Cu- Component of ascorbic acid oxidase, tyrosinase, monoamine oxidase, uricase, cytochrome oxidase, phenolase laccase, and plastocyanin.  Group 4 cont…. Ni- Constituents of urease, In N2- fixing bacteria, constituents of hydrogenases. Mo- Constituents of nitrogenase, nitrate reductase and xanthine dehydrogenase The proportional weights of various element in plants Carbon, hydrogen, oxygen Others Macronutrients (3.5%) Micronutrients (0.5%) N, P, K, Ca, Mg, S Fe, Cl, Mn, B, Zn, Cu, Mo ◼ Macronutrients : minerals found in >1000 ppm concentration ◼ Micronutrients : minerals found in 2 μm, or even 4 μm in at least one dimension.These are silicate minerals with a layered structure. They have a net negative charge due to isomorphous substitution and broken edges. Organic matter: Organic matter, particularly humus, contains functional groups like carboxyl (-COOH) and phenolic (-OH), which also contribute negative charges. Negative Charges and Cation Attraction: Negative charges on the clay and organic matter surfaces attract and hold positively charged ions (cations) through electrostatic forces. These cations are not permanently bound to the soil particles but are held loosely, allowing them to be exchanged with other cations in the soil solution. Cation Exchange Process: When the soil solution (the water present in soil) contains a higher concentration of a particular cation, it can replace cations held on the soil particles. Example, if the soil solution is rich in calcium ions (Ca²⁺), these can replace sodium ions (Na⁺) held on the clay particles. Measurement of CEC: CEC is measured in milliequivalents per 100 grams of soil (meq/100g). This unit reflects the number of cation charges that a given quantity of soil can hold. Soils with high clay and organic matter content generally have higher CEC values because they have more sites for cation exchange.  Importance of CEC: Nutrient availability: High CEC soils can hold more nutrients, making them available to plants over time. Soil fertility management: Understanding CEC helps in managing soil amendments like lime and fertilizers, as it influences the soil's buffering capacity and its ability to supply nutrients to plants. Soil pH: CEC also interacts with soil pH. For instance, soils with low CEC often require more frequent lime applications to maintain a stable pH.  Cation Exchange Capacity - CEC Depends on, – Soil composition Ca, Mg, K, H ions are stuck to soil particles High CEC – Particle size – pH dependent Bicarbonate ion  Cation exchange Anions enter Cations enter root root hairs via hairs via channels cotransporters or carriers http://housecraft.ca/author/jpriest/page/4/ Cation Exchange The fine hairs of the roots are negatively charged, and attract the cations. The plant releases a Hydrogen ion (H+) to maintain the overall balance. In cation exchange, plant roots are trying to take in cations like potassium (K+), magnesium (Mg++), calcium (Ca++), and ammonium (NH4+) in exchange for the Hydrogen (H+).  Cation exchange capacity is soil pH dependent :  nutrient availability  soil microbes : fungi – acidic; bacteria – alkaline  root growth : slightly acidic soil (pH 5.5 & 6.5) Acid soil ----- rocks release K+, Mg2+, Ca2+, Mn2+  solubility of SO42-, H2PO4-, HCO3- So, availability to roots  Soil pH  due to : - decomposition of organic matter - Rainfall decomposition of org. Matter : CO2 + H2O → H+ + HCO3- (microbial decomposition) : NH3 + O2 → HNO3 (nitric acid) H2SO4 (sulfuric acid) H+ displace K+, Mg2+ ----- K+, Mg2+ etc. Available --- pH  Anion Exchange In anion exchange, the plant absorbs molecules like phosphate (HPO4-) and nitrogen (NO3-) and return things like bicarbonates (HCO3-) and hydroxyls (OH-). Other key anions include phosphates (PO4), sulfates (SO4-) and chlorides (Cl-) Soils that have an anion exchange capacity typically contain weathered kaolin minerals, iron and aluminum oxides, and amorphous materials. Anion exchange capacity depends upon the pH of the soil and increases as the pH of the soil decreases.  Plant roots – the primary route for Meristematic zone mineral nutrient acquisition – Cells divide both in direction of root base to form cells that will become the functional root and in the direction of the root apex to form the root cap Elongation zone – Cells elongate rapidly, undergo final round of divisions to form the endodermis. Some cells thicken to form casparian strip Maturation zone – Fully formed root with xylem and phloem – root hairs first appear here  Root absorbs different mineral ions in Calcium different areas – Apical region Iron – Apical region (barley) – Or entire root (corn) Potassium, nitrate, ammonium, and phosphate – All locations of root surface In corn, elongation zone has max K accumulation and nitrate absorption – In corn and rice, root apex absorbs ammonium faster than the elongation zone does – In several species, root hairs are the most active phosphate absorbers  Why should root tips be the primary site of nutrient uptake? Tissues with greatest need for nutrients – Cell elongation requires Potassium, nitrate, and chlorine to increase osmotic pressure within the wall – Ammonium is a good nitrogen source for cell division in meristem – Apex grows into fresh soil and finds fresh supplies of nutrients Nutrients are carried via bulk flow with water, and water enters near tips Maintain concentration gradients for mineral nutrient transport and uptake  Root uptake soon depletes nutrients near the roots Formation of a nutrient depletion zone in the region of the soil near the plant root – Forms when rate of nutrient uptake exceeds rate of replacement in soil by diffusion in the water column – Root associations with Mycorrhizal fungi help the plant overcome this problem  Nutrients move from fungi to root cells Ectotrophic Mycorrhizal – Occurs by simple diffusion from the hyphae in the hartig net to the root cells Vesicular arbuscular mycorrhizal fungi – Occurs by simple diffusion from the arbuscules to the root cells – Also, as arbuscules are degenerating as new ones are forming, the nutrients may be released directly into the host cell  Mycorrhizal associations Not unusual – 83% of dicots, 79% of monocots and all gymnosperms Ectotrophic Mycorrhizal fungi – Form a thick sheath around root. Some mycelium penetrates the cortex cells of the root – Root cortex cells are not penetrated, surrounded by a zone of hyphae called Hartig net – The capacity of the root system to absorb nutrients improved by this association – the fungal hyphae are finer than root hairs and can reach beyond nutrient-depleted zones in the soil near the root  Vesicular arbuscular mycorrhizal Mycorrhizal associations fungi – Hyphae grow in dense arrangement , both within the root itself and extending out from the root into the soil – After entering root, either by root hair or through epidermis hyphae move through regions between cells and penetrate individual cortex cells. – Within cells form oval structures – vesicles – and branched structures – arbuscules (site of nutrient transfer) – P, Cu, & Zn absorption improved by hyphae reaching beyond the nutrient-depleted zones in the soil near the root  Manipulating mineral transport in plants Increase plant growth and yield Increase plant nutritional quality and density Increase removal of soil contaminants (as in phytoremediation) Fertilizers  Good for plantation crops, Tea, Rubber, Coconut Gypsum salt- Calcium sulphate Triple Super Phosphate H2PO4 2-, Calcium M HPO42-, PO43 - Muriate of Potash (K+) carbonate  High K mixture Good for reproductive stage Contains only N- for flowering good for vegetative Balance mixture – for vegetative growth. growth. 10-10-10 mean 10% of N,P,K each. 20-20- Contains only 45% 20 means20-20-20 mean 20% of N,P,K each Triple Super Phosphate Good for root growth. In some plants encourage flowering  Fertilizer mixtures Yara Mila Foliar applications Albert solution for hydroponics  Slow releasing fertilizers Slow-release fertilizers release their nutrients slowly after each irrigation. The benefits to the farmer are that the plants don't receive toxic amounts of fertilizers all at once. The rate of release is determined by how soluble the ingredients of the fertilizer are, among other things like existing soil and weather conditions. How to apply fertilizers First wet the medium /soil Add fertilizer Mix with the medium until fertilizers are covered.  https://www.youtube.com/watch?v=W6E_MyVjQX4  Nutritional needs of plants Plant tissues contain > 60 kinds of elements Are all of these elements essential for growth ? Why are they essential ? How does the plant absorb them ? How are they utilized ? What effects if it is lacking ?  Mineral Nutrition How plants acquire and use mineral nutrients Why is mineral nutrition important? What are the essential mineral nutrients? classification systems Mineral nutrients in the soil nutrient availability adsorption to soil particles effects of pH Roots and mineral nutrient acquisition root structure depletion zones Mycorrhizae What is the contribution of mycorrhizae in nutrient absorption. Thank you