Mineral Nutrition. Global Nutritional Deficiency. Beginning of mineral nutrition in plants

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1 Mineral Nutrition Mineral elements required by men or mice are mined by plants (land) and by algae (sea). Human daily needs Ca 1000 mg/day Mg 400 mg Fe 18 mg Iodine 150 ug Zn 15 mg Cu 2 mg Mn 2 mg E. Epstein (1972) Global Nutritional Deficiency 1. 1/2 of childhood deaths result from deficiency in minerals, like Fe, Zn, and Vitamins, e.g. A Increasing micronutrient metals in seeds and grains of staple foods is a global effort. WHO 2. Unbalanced diet and stressed lifestyles can cause malnutrition. Lec 6. OUTLINE : MINERAL NUTRITION of Plants Apart from C, H, and O, all other nutrients are absorbed from the soil. 1. What are essential nutrients? Macronutrient, micronutrient 2. What chemical forms of the nutrients are available to the plant? 3. How does each nutrient enter the plant? Gas: via stomates Mineral nutrients or ions: via roots How are nutrients taken up? [later] 4. How do plants tolerate toxic levels of nutrients or toxic heavy metals? E.g. Cu, Zn, Cd, Pb. 5. What are the major function(s) of each nutrient? Beginning of mineral nutrition in plants Van Helmont (1600s) planted a willow tree. Belgian What happens when nutrients are deficient? No Molybdate Lawr.ucdavis-ssi109

2 N deficiency in corn Lawr.ucdavis-ssc109 Fe deficiency Mg deficiency in corn Essential nutrients are those nutrients which are necessary for a plant to complete its life cycle, and for which no other element can substitute. Essential nutrient must have a clear function. A. Nutrient & Conc. required Macronutrients (elements): C, H, O, N, K, Ca, Mg, P, S Micronutrient: Cl, Fe, B, Mn, Zn, Cu, Mo, Ni > 1 mm < 1 mm (µm) K Deficiency Boron deficiency in almond Boron/BigPixB.html B. Biochemical Functions 1) carbohydrates, lipids, Proteins, nucleic acids CHO CHO CHON(S) CHONP 2) Coenzyme: Mg, Ca, Mn, Zn, Fe, Cu, Mo, Mn [redox rx] 3) Osmotic and electrical components: K +,Cl -, H +, Ca 2+ 4) B cross-links sugars in cell wall pectin

3 Boron cross-links pectin RGII Table 5.1 Taiz. Essential nutrients required by plants A. Macronutrient Available Conc in Dry matter Form umol/g µm [medium] H H 2 O 60,000 C CO 2 40,000 O O 2, CO 2 30,000 N NO 3-, NH + 4 1,000 16,000 K K ,000 Ca Ca ,000 Mg Mg ,000 P H 2 PO 4-, HPO ,000 S SO ,000 B. Micronutrient Available Form umol/g µm Cl Cl B BO Mn Mn Zn Zn Cu Cu Mo MoO Fe Fe Optional Ni Ni Si Si 28 1,000 Na Na Nutrient level is important for optimal growth 5-4. Soil ph affects Nutrient availability 5-6. Wheat Root A. Dry soil B. Irrigated soil

4 Pi level influence Lateral root development- Lupinus 5-8. Apex of root + 1 mm Pi -Pi 0 mm Recap 1. Plants require essential nutrients at varying levels. 2. Deficiency in nutrients reduce productivity 3. Too much can cause toxicity. Plants are able to adapt to soils with different levels of nutrients and can transport ions selectively. Questions? How do plants regulate how much it takes up? How do they get rid of excess nutrients? Transport of ions and metabolites: 1. How do plants take up, distribute, & sort nutrients in organs and in cells? 2. How do plants deal with excess ions and toxic metals? 3. What controls guard cell movement? Changes in ion levels and water movement 4. Form of communication TRANSPORT How are essential mineral nutrients taken up and distributed in the plant? Concepts 1. p-lipid bilayer is a remarkable barrier 2. Proteins catalyze transport of nutrients and metabolites just as enzymes catalyze chemical reactions. There are 3 main classes of transport proteins. Channels, Pumps Carriers 3. Transport can be active or passive. Passive and active transport of ions result in electric potential difference across membranes 4. Major Transport Proteins in Plants a. H+ pumping ATPases are the major ion pumps in plants b. Active transport of many nutrients and metabolites depend on H+coupled co-transport. Energy from H+ gradient is used to drive uphill movement of other nutrients. c. Channels allow rapid, passive transport of ions and metabolites. d. Water is transported via WATER CHANNELS or AQUAPORINS in membranes that conduct large volumes of water rapidly.

5 Taiz. P-lipid is a remarkable barrier to ions 6-7. Proteins catalyze transport. Channel, carrier pump Active Fig Taiz. Protein catalyze transport just like enzymes catalyze chemical reactions. Specific, fast 3. Transport can be active or passive. Passive transport is movement down an electrochemical gradient. Active transport is movement against an electrochemical gradient. What is an electrochemical gradient? µ = conc gradient + electrical gradient Chemical gradient Electrical gradient: unequal distribution of charges across a membrane. Passive or active transport of ions result in electric potential difference across membranes. How do you know if an ion is moving uphill or downhill? Nernst equation It predicts passive ion distribution for a given electrical potential. Diffusion of uncharged species depend only on the concentration gradient Taiz. A diffusion potential develops when + & - ions diffuse across a membrane at different rates. Diffusion of charged species is dependent on the concentration and the electrical gradient. More K+

6 Pump potential is generated when there is an active ion pump. F 6-3 Taiz. Microelectrodes are used to measure membrane potentials across cell membrane Pump potential H + ATP Proton transport is a major determinant of the membrane potential. Diffusion potential K+ What is the driving force for uphill movement? ATP and a H + electrochemical gradient 6-5. Evidence for a Pump potential and diffusion potential. Nernst equation states that at equilibrium the difference in concentration of an ion between two compartments is balanced by the voltage difference. Thus it can predict the ion conc at equilibrium at a certain E. Very useful to predict active or passive transport of an ion.