SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/605094
www.stma.org December 2015 | SportsTurf 27 thesis. The green-up connection with iron is fairly direct in that iron is required for the synthesis of chlorophyll. While iron is not a component of the chlorophyll molecule, it is required as a cofactor in three reactions leading to chlorophyll synthesis. There is also ongoing research that iron may have some fungi- cidal properties in helping protect turf from disease pathogens; however, this research is still relatively new and is too early to make any conclusions as of yet. MEANS OF ENTRY The most commonly available iron foliar sources are ferrous sulfate, mono- or hepta-hydrate (FeSO 4 H 2 0) ferric sulfate Fe 2 (SO 4 ) 4 H 2 0, and iron chelate (NaFeEDTA, NaFeHEDTA, or NaFeDTPA. To be effective, these foliar iron sources have to enter the turf through the stomata, cuticular layer, or through aqueous pores. Stomata. The upper (adaxial) and lower (abdaxial) surface of turf leaves consists of numerous stomata, an opening for gas- eous exchange (CO2 and O2) between the internal and external atmosphere of leaf blades. The stomatal density is usually higher on the lower surface while a few may be present on the upper turf leaf surface. One problem with stomatal openings as a means of entry is that they are often more closed than they are open. Transcuticular pores. Turf cuticles are lipid-rich protec- tive layers mainly composed of a biopolymer matrix of cutin, waxes, and some amount of polysaccharides and phenolics. Transcuticular pores have a diameter of less than a billionth of a meter, but are abundant. The molecules of the foliar iron have to be small enough to pass through these very small pores, and they have to be neutral or negatively charged to get through the electro-chemical gradients of the turf leaf and to translocate within the leaf tissue and throughout the leaf plant. Aqueous pores. Aqueous pores are the openings localized in cuticular ledges, preferentially at the basal cells of guard cells. These pores arise due to hydration of permanent dipoles and functional ionic groups. As the name suggests, aqueous pores are formed only in the presence of water, and are dynamic in nature. Since the atomic radius of ionized iron is 0.126 nm (nanometers) it is very likely that they can penetrate easily through the aqueous pores and reach the epidermal cell walls of the turf leaf. Biochemical pathway. Once iron enters into the turf leaf and is absorbed, the iron diffuses across the cell wall against a concentration gradient and reaches the apoplast. The ion relation in apoplast varies temporally as a result of changes in metabolic activity caused by day/night transition. Immediately after onset of light, the process of photosynthesis leads to an increase in apoplastic pH (alkalization) as protons are removed from the cytoplasm and apoplast. The change in apoplastic pH Name Formula Abbreviation N-2 (-hydroxyethyl)ethylenediaminetriacetic acid C10 H18N2O7 HEDTA Ethylenediaminetetraacetic Acid C10H16O8N2 EDTA Diethylenetriaminepentaacetic Acid C14H23O10N3 DTPA Ethlyenediaminedi-o-hydroxyphenlyacetic Acid C18H20O6N2 EDDHA Citric Acid C6H8O7 CIT