Iron Presented to you by Karl, Carl, Rebecca and Rose.
Iron is an essential micronutrient, meaning that it is used in small quantities by plants. It is one of the most abundant elements on Earth (which is why there was an Iron Age). Iron in Plants
Functions of Iron in Plants needed for chlorophyll formation assists in photosynthesis and respiration assists in oxidation process of extracting energy from starch and enzymes assists in converting nitrate to ammonia helps form proteins
Iron deficiency: Chlorosis
Iron deficiency: chlorosis - Details lime-induced (not that kind of lime) o add HCl, see if it fizzes bright yellow leaves, green veins severe cases: entire leaf turns yellow/white, scorching may occur lack of chlorophyll for photosynthesis attacks younger leaves first acid-loving plants: blueberries, azaleas, rhododendron, maple
How Plants Access Iron Iron is acquired by plants from the soil through the roots It is fourth most abundant element in Earth s crust Despite its abundance, it is often limiting for plants Forms insoluble complexes at neutral and basic ph Two mechanisms evolved to acquire iron from the soil
Iron Access: Reduction based strategy Release of Protons o o Lowers acidity Utilized by all plants except grasses Three enzymatic activities o o o H+ ATPase Pumps out protons Solubilizes ferric iron Ferric chelate reductase Reduces ferric iron to more soluble Ferrous form Ferrous iron transporter
Iron Access: Chelation-Based Strategy Chelation Mechanism o Utilized by grasses Synthesis of Phytosiderophores o High affinity for ferric iron o Secreted into rhizosphere o Phytosiderophores bind to ferric iron PS-ferric iron complex transported into root cells o Via PS-Fe(III) transporters
Iron Access: Microorganisms Soil-level microorganisms Mycorrhizae o Increasing surface area of the roots (less useful for iron) Produce byproducts that increase iron availability o Lowering ph of rhizosphere o Enzymes unlocking bound iron in soil
Iron Access: Microorganisms Arbuscular mycorrhizal fungi (AMF or VAM) Ectomycorrhizal fungi (EcM) o Form mantle around outside of root, Hartig net o Enzyme production, transport of nutrients Bonfante, P. & Genre, A. Mechanisms underlying beneficial plantfungus interactions in mycorrhizal symbiosis. Nature communications.
Iron deficiency: chlorosis - Causes not dependent on iron levels dependent on availability of iron to plants alkaline soil, cool soil temperatures o 1 ph unit increase = 1000x lower iron solubility non-water-soluble iron compounds cannot be absorbed by plant roots salt conditions light intensity restricted air movement into soil erosion / lack of topsoil
Iron deficiency: Chlorosis - Treatments sulfur + iron sulfate o simple, cheap o slow, labor-intensive iron chelates o simple, fast o < 1 season, expensive ferrous sulfate / iron chelate sprays o quick, simple, practical o expensive, leaf burning, spotty control, < 1 season trunk injection of iron compounds (trees) o lasts years o injury to trunk, variable results
Sources 1. Koenig, R. and M. Kuhns (June 2010). Control of Iron Chlorosis in Ornamental and Crop Plants. Utah State University, Salt Lake City, UT. http://extension.usu.edu/files/publications/publication/ag-so-01.pdf 2. Pestana, Maribela, et al. (2003). Diagnosis and correction of iron chlorosis in fruit trees: a review. Food, Agriculture, and Environment, 1(1), 46-51. 3. Morgan, J., & Connolly, E. (2013). Plant-Soil Interaction: Nutrient Uptake. Nature.com. Retrieved May 6, 2014, from http://www.nature.com/scitable/knowledge/library/plant-soil-interactions-nutrient-uptake-105289112 4. Morrissey, J., & Guerinot, M. (2009). Iron uptake and transport in plants: the good, the bad, and the ionome. Retrieved May 6, 2014, from http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2764373/ 5. "The Plant Nutrients." North Eastern Oklahoma A&M College, Web. 29 Apr. 2014. http://neo.edu/portals/4/faculty%20staff/web%20pages/fent,%20roger/nutrients.pdf 6. Hochmuth, George. "Iron (Fe) Nutrition of Plants SL353." : pag. ifas.ufl.edu. http://edis.ifas.ufl.edu/pdffiles/ss/ss55500.pdf Web. 1 May 2014. 7. Bonfante P., Genre A. Mechanisms underlying beneficial plant-fungus interactions in mycorrhizal symbiosis. Nature Communications. 2010 Jul 27;1:48. 8. Campbell, N. A., & Reece, J. B. (2011). Biology (9th ed.). Boston: Benjamin Cummings.