Symptoms of Deficiency In Essential Minerals -part 4

May 8, 2008

Cobalt - (Co) (immobile in plant/immobile in soil)

Cobalt Deficiency

Deficiencies are rare, but express themselves as chlorosis of younger leaves.

Cobalt is a chelation “bridge” that assists uptake of other metals and nitrogen fixation. It assists enzymes related to manufacture of aromatic compounds. It is also required for a few bacteria and algae.

Cobalt is essential to proper use of nitrogen Three enzyme systems of Rhizobium bacteria are known to contain cobalamin. There’s correlation between cobalt concentration, nitrogen fixation and root nodule development.

Cobalt is required for methionine synthesis, ribonucleotide synthesis and synthesis of methylmalonyl-coenzyme A mutase. The latter is necessary for the synthesis of leghemoglobin, which plays a major role in protection of nitrogenase against oxygen, which is able to irreversibly damage the enzyme.

Copper - (Cu) (immobile in plants/mobile in soil)

Copper Deficiency

Deficiencies show up first on youngest leaves, young tips, buds and shoots. Older leaves develop chlorosis, growing tips die and bud development is small. Copper deficiencies cause irregular growth and pale green leaves that wither at leaf margins.

Leaves at top of the plant wilt first, followed by chlorotic and necrotic areas on leaves, and necrosis of the apical meristem (the center stem of the plant).

Leaves on top half of plant show unusual puckering with veinal chlorosis. Copper deficiencies also show on the leaf, where the petiole joins the main stem of the plant beginning about 10 or more leaves below the growing point.

Excess copper is extremely dangerous to plants. Plants can develop iron chlorosis, stunted growth and stunted root development. Toxic buildup of copper occurs quicker in acidic soils.

Copper activates several enzymes, is needed for photosynthesis, and assists metabolism of carbohydrates and proteins. It intensifies color and flavor. It is essential in several enzyme systems and in plant respiration.

Copper is a divalent cation and is taken up by the plant as Cu+ or as a copper chelate complex and transported via xylem and phloem.

Copper deficiency immediately harms activity of copper-containing enzymes, but remember, an excess of copper is toxic to plant cells.

Chlorine - (CL) (immobile in plants, mobile in soil)

Chlorine Deficiency

Believe it or not, chlorine is essential for plant growth. It’s needed for photosynthesis. It’s an enzyme activator that assists production of oxygen from water and in water transport regulation.

Plants use chlorine as chloride ion. Chlorine is useful as a charge balancing ion and for turgidity regulation, keeping plant cells free of infection by disease. It helps open and close stomata by increasing osmotic pressure in cells.

Excess chlorine causes burnt tips and margins on young leaves. If chlorine levels are too high, cuttings will not root well, and seeds may not germinate.

High chlorine levels also cause leaves to take on a yellowish bronze color, and they are slow to develop. Chlorine is commonly used to treat drinking water, so you are far more likely to see an excess of chlorine in your garden rather than a deficiency.

If you determine that chlorine is at toxic levels in your garden, get a reverse osmosis unit or distiller to remove chlorine from the water you use for your plants.

Molybdenum - (Mb) (mobile in plant, immobile in low pH soils)

Molybdenum Deficiency

Deficiencies show up in older and middle-aged leaves first, and then show up in younger leaves.

Molybdenum is rarely deficient in most plants, but chlorosis symptoms similar to nitrogen deficiency are typical of molybdenum deficiency, along with scorching and strapping of leaf margins.

Molybdenum deficiency often occurs when sulfur and phosphorus are deficient. It can reveal itself as interveinal yellow spotting and mottling of older leaves. Deficiency also shows as pale leaves (similar to nitrogen deficiency), with some marginal leaf chlorosis. New leaves may twist and leaves may cup and thicken.

Excessive molybdenum looks like iron or copper deficiency.

Molybdenum is needed for the reduction of absorbed nitrates into ammonia prior to incorporation into amino acids. It performs this function as part of the enzyme nitrate reductase.

In addition to direct plant functions, molybdenum is used for nitrogen fixation by nitrogen-fixing bacteria.

Molybdenum is primarily present in the form of MoO4. Depending on the environmental conditions a molybdate ion can accept one or two protons. Polyanions such as tri- and hexamolybdate can be formed under certain physiological conditions. Molybdenum (Mo) has limited mobility in plants and is apparently transported through the xylem and phloem.

Several enzymes are known to use Mo as a co-factor. The two most important molybdenum-containing enzymes are nitrogenase and nitrate reductase.

Molybdenum is directly involved in the reduction of nitrogen. Nitrogen molecules bind to molybdenum atoms in the nitrogenase complex. After activation of the nitrogenase complex, the iron-molybdenum complex changes its structure and as a result reduction of nitrogen occurs. The electrons required for this reduction are supplied by an iron-sulfur protein which is part of the nitrogenase complex. This is an energy-intensive reaction.

Nitrate reductase reduces nitrate into nitrite in the nitrogen assimilation process of the plant. Nitrate reductase contains a heme-iron molecule and two molybdenum atoms. FAD, cytochromes [Fe2/Fe3] and molybdenum [Mo(V)/(VI)] are functional parts of the nitrate reductase complex and the electron transport chain. Electrons derived from NADPH are used to reduce nitrate to nitrite. The activity of nitrate reductase is reduced during molybdenum deficiency but can be restored by adding molybdenum.

As you can see, this hard to pronounce micronutrient is important to plant functions.

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