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The most widely used zinc fertilizer is zinc sulphate. Generally, zinc sulphate is applied at a rate providing 5 to 20 kg Zn ha1. Actual rates would depend on the crops to be fertilized, the type of soil and the method of application. Metallic zinc (as zinc dust) is also used as a soil amendment. The efficiency of zinc fertilizers is influenced by several environmental and biological factors. Morgan (1980) described large variations in flux of zinc (and phosphorus) fertilizers with changes in...

Nadp

The oxidative pentose phosphate pathway In boron-deficient plants, the activities of both glucose 6 phosphate dehydrogenase and 6-phosphogluconate dehydrogenase increase (Lee and Aronoff, 1967 Gomez-Rodriguez et al. 1987b). Lee and Aronoff (1967) attributed the increase in 6-phosphogluconate dehydrogenase activity in boron-deficient plants to the property of borate to form complex with 6-phosphogluconate (B-6-phosphogluconate), rendering it inactive to...

Uptake transport translocation

While most soils contain chlorine predominantly as CI ions, it is also reported to occur as natural organochlorine compounds (Fleming, 1995 Oberg, 1998). Chlorine is taken up by plant roots either as free anion (CI) or in association with a monovalent cation. Salts of chlorine are highly soluble and mobile in the rhizosphere. Besides absorption by roots, chlorine is also absorbed by aerial parts of plants, either as an anion (CI) or as gas (Johnson et al. 1957). Rainwater and environmental...

Crop Response

Crop response forms the ultimate measure of micronutrient deficiency and a dependable method for control of the deficiencies. Response of a crop to a nutrient amendment is a function of crop nutrient status, which in turn is determined by the bioavailability of the nutrient in soil. Crop yields obtained with different quantities of fertilizer nutrient amendment offers an easy-to-follow and dependable method for evaluation of the nutrient status, absorbing the soil, plant and environmental...

Uptake transport distribution

Plants show a taxonomic distinction in the way they mobilize iron from the rhizosphere and transport it across the plasmalemma (Brown and Jolley, 1989 Romheld and Marschner 1986a,b Marschner et al. 1986a). Iron deficiency induces two distinct and mutually exclusive mechanisms or strategies for iron acquisition (Bienfait, 1988 Marschner and Romheld, 1994) one by the dicotyledons and monocotyledons except the graminaceae (Strategy I) and the other by the members of the graminaceae (Strategy II)....

Use Of Micronutrient Efficient Genotypes

In general, the traditional method of applying micronutrients to plants subjected to their deficiency provides effective control of their deficiencies but this method involves high-energy inputs. Costs on both labour and fertilizers are high. Continuous fertilizer usage also contributes to resource depletion and, at times, soil pollution. The alternative approach of 'tailoring the plant to fit the soil' Foy, 1983 circumvents these problems. Growing plant genotypes that can produce reasonably...