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Micronutrients-role and deficiency symptoms Dr. Javed, Department of Botany Govt. Degree College Pulwama j&k Email: [email protected] ZINC Zinc (Zn) is taken up by plants as the zinc ion (Zn ++) and is an essential constituent of several important enzyme systems in plants. It controls the synthesis of indoleacetic acid, an important plant growth regulator. Terminal growth areas are affected first when zinc is deficient. Deficiency is most common on soils with neutral or alkaline pH that are sandy or have low organic matter content (including cut areas) and are very high in available phosphorus. Symptoms of Zn Deficiency: Decrease in stem length and rosetteing of terminal leaves. Reduced fruit bud formation. Mottled young leaves (interveinal chlorosis). Dieback of twigs after first year. IRON Iron (Fe) is taken up by plants as ferrous ions (Fe++) and is required for the formation of chlorophyll in plant cells. It serves as an activator for biochemical processes, such as respiration, photosynthesis, and symbiotic nitrogen fixation. Iron deficiency can be induced by high levels of manganese or high lime content in soils. Deficiencies are common in high pH soils, in situations with poor aeration, or when high levels of zinc or manganese are present. Symptoms of Fe Deficiency: Interveinal chlorosis of young leaves. Veins remain green except in severe cases. Twig dieback. In severe cases, death of entire limbs or plants. MANGANESE Manganese (Mn) uptake is in the form of the ion Mn++. Manganese serves as an activator for enzymes in plant growth processes. It assists iron in chlorophyll formation. High concentrations of manganese in plants may induce iron deficiency. Manganese is generally required with zinc in foliar spraying of commercial citrus. Other tree crops may show deficiencies. Symptoms of Mn Deficiency: Interveinal chlorosis of young leaves. Gradation of pale-green leaf coloration, with darker color next to veins. No sharp color distinction between veins and interveinal areas as with iron deficiency. COPPER Plant uptake of copper is in the ionic form (Cu++). Copper serves as an activator of numerous plant enzymes and plays a role in the development of plant pigments that influence color. A copper deficiency interferes with protein synthesis. Copper deficiency has been observed on trees and vines growing on organic soils and sands. Symptoms of Cu Deficiency: Stunted growth. Dieback of terminal shoots in trees. Poor pigmentation. Wilting and eventual death of leaf tips. Formation of gum pockets around central pith in oranges. BORON Boron (B) is predominately in solution as boric acid, H3BO3, and is taken up by plants in this form. It functions in the differentiation of meristematic cells. Boron is also involved in regulating metabolism of carbohydrates in plants. Nearly all fruiting crops have a high demand for boron in the early fruiting stage. Foliar applications are an effective way to meet this demand at this critical growth state. Recent research has shown that boron is effective in increasing pollen viability, thus contributing to increased fruit set. When boron is deficient, cells may continue to divide, but structural components are not differentiated. Symptoms of B Deficiency: Death of terminal growth, causing lateral buds to develop, producing a “witch’s broom” effect. Thickened, curled, wilted and chlorotic leaves. Soft or necrotic spots in fruit or tubers. Reduced flowering or improper pollination. MOLYBDENUM Molybdenum (Mo) is taken up by plants as the molybdate ion (MoO4 =). It is required by plants for the utilization of nitrogen. Nitrate nitrogen is converted to amino acids by the nitrate reductase enzyme; this enzyme requires molybdenum. In addition, molybdenum is required for the symbiotic fixation of nitrogen by legumes. Symptoms of Mo Deficiency: Stunting and lack of vigor. This is similar to nitrogen deficiency, because of the key role of molybdenum in nitrogen utilization. Marginal scorching and cupping or rolling of leaves. “Whiptail” of cauliflower. Yellow spotting of citrus.