When it is thought simply, it comes that aerobic rice has susceptibility to Fe deficiency. That it is, it has no good capacity taking Fe from soil.

Rice is a typical/ideal plant to show the Fe deficiency though exact mechanism underlying physiology is not known.

Iron is available when the chemically reduced ionic forms are in solution of a water medium. This is facilitated by an aqueous slightly acidic condition and the alkaline oxidized environment is not favorable for solubilization of iron. The addition of sulfur as planting treatment would probably allow the rice to have optimized iron at the seedling stage as it would acidify the soil near the seedling root zone. Some rice varieties have superior ability to acidify alkaline soil environment and to produce siderophores which are substances which promote iron solubilization. The foliar spraying of iron chelate can be employed to outcome iron yellowing in rice and other crops.

((The reason why young rice plant is highly susceptible to Fe-deficiency was clarified as follows: Among Gramineae plants rice secreted a very low amount of deoxy-MA as a phytosiderophore even under Fe-deficiency, and the secretion by rice ceased within 10 days under Fe-deficiency although barley secreted MAs during a period of more than one month. When iron depletion continued, the rice root tips become chimeric and epidermal cells became necrotic. The mitochondrial membrane systems in the cortex cells were also severely damaged. Iron starvation occurred even in the mitochondria, and energy charge in the root decreased. This reduced energy charge has firstly diminished the secretion activity of deoxy-MA from the roots, secondly reduced the activity of the transporter which absorb deoxy-MAFeIII chelate and finally reduced the synthesis of deoxy-MA from methionine. Consequently, the depletion of FeII in the shoot was induced and severe chlorosis rapidly developed in the young rice plant under Fe-deficiency.))

In addition, Iron deficiency can increase by

High pH

Water logged soils

Calcareous soils

High copper, manganese or zinc soils

Iron deficiency is particularly problematic a pH of over 7.8 and a high carbonate value. Ammoniated fertilizer and sulfur can be used to lower alkaline soil issues which can be common in semi arid and arid environments. Humic materials can be effective chelators for some low mobility elements. Iron EDTA is the iron source which allows mobility of iron when applied as a foliar remedy. Classic iron chlorosis deficiency is found in the apical growing points which show the immobility of the element in plants. The veins can retain green ness and chlorosis is highly interveinal.

Iron deficiency (plant disorder)

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Figure 1. Lemon tree showing foliar Iron deficiency. The youngest new leaves turn yellow while veins can retain green known interveinal chlorosis.

Plant iron (Fe) deficiency is also known as "lime-induced chlorosis" as it commonly not an absolute deficiency of iron in soil but the action of carbonate and alkali which immobilizes the iron not allowing its absorption nor translocation to all plant parts. It can be confused with manganese deficiency. A deficiency in the soil is rare rather iron becomes unavailable for absorption when the soil pH is not between about 5 and 6.5 especially when soils are over pH 7.3 and particularly when over 7.8.[1] A common problem is excessive alkalinity of the soil (the pH is above 6.5). Also, iron deficiency can develop if the soil is too waterlogged or has been over fertilized. Elements like calcium, zinc, manganese, phosphorus, or copper can tie up iron if they are present in high amounts.[1]

Iron is needed to produce chlorophyll, hence its deficiency causes chlorosis. For example, iron is used in the active site of glutamyl-tRNA reductase, an enzyme needed for the formation of 5-Aminolevulinic acid which is a precursor of heme and chlorophyll.[2]

Symptoms

Symptoms include leaves turning yellow or brown in the margins between the veins which may remain green interveinal chlorosis, while young leaves may appear to be bleached. The terminal apices as symptom sites shows the immobility of the iron in the plants. Yield and quality is reduced because of interference with normal photosynthesis. Any plant may be affected, but raspberries and pears are particularly susceptible, as well as most acid-loving plants such as azaleas and camellias.

Treatment

Iron deficiency can be avoided by choosing appropriate soil for the growing conditions (e.g., avoid growing acid loving plants on lime soils), or by adding well-rotted manure or compost. Check the pH of the soil with an appropriate test kit or instrument when iron deficit chlorosis is suspected then take plant tissue samples. Take a soil sample at surface and at depth. If the pH is over seven then consider soil remediation that will lower the pH toward the 6.5 - 7 range. Remediation includes: i) adding compost, manure, peat or similar organic matter (warning. Some retail blends of manure and compost have pH in the range 7 - 8 because of added lime. Read the MSDS if available. Beware of herbicide residues in manure. Source manure from a certified organic source.) ii) applying Ammonium Sulphate as a Nitrogen fertilizer (acidifying fertilizer due to decomposition of ammonium ion to nitrate in the soil and root zone) iii) applying elemental Sulfur to the soil (oxidizes over the course of months to produce sulphate/sulphite and lower pH). Note: adding acid directly e.g. sulfuric/hydrochloric/citric acid is dangerous as you may mobilize metal ions in the soil that are toxic and otherwise bound. Iron can be made available immediately to the plant by the use of iron sulfate or iron chelate compounds. Two common iron chelates are Fe EDTA and Fe EDDHA. Iron sulphate (Iron(II)_sulfate) and iron EDTA are only useful in soil up to PH 7.1 but they can be used as a foliar spray (Foliar_feeding). Iron EDDHA is useful up to PH 9 (highly alkaline) but must be applied to the soil and in the evening to avoid photo degradation. EDTA in the soil may mobilize Lead, EDDHA does not appear to.

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