Zinc Deficiency in Plants

Zinc Deficiency in Plants The role of zinc in plants has been summarized by the NRC (1979). Because zinc is not readily translocated within the plant, deficiency symptoms first appear on younger leaves. Plant tissues containing < 20 mg Zn kg dry weight are often zinc-deficient (Kabata-Pendias and Pendias 1994, Vitosh etal. 1994). Due to impaired internode growth, disorders caused by zinc deficiency (Sauchelli 1969) result in a rosette condition... 

The sensitivity of plants to zinc deficiency is variable among species. For example, oats, wheat, barley, and rye are not very sensitive, whereas potatoes, tomatoes, lucerne, and red clover have a medium sensitivity. By contrast, maize, hops, flax, and soybeans require a high level of zinc supply (Viets 1966 see also Table 3.29-3, p. 612 in Henkin 1984). Soils associated with zinc deficiency in plant are usually low in organic matter content and neutral to alkaline in reaction (Pais and Jones 1997). In Asia, zinc deficiency has been identified as the most widespread micronutritional disorder of wetland rice which occurs on sodic, calcareous, and poorly drained soils. 

Zinc deficiency in plants varies from year to year, though wet, cool, cloudy weather during the early growth season increases the deficiency (Vitosh et al. 1994). 

Forno DA, Asher CJ, Yoshida S. 1975. Zinc deficiency in rice. n. Studies on two varieties differing in susceptibility to zinc deficiency. Plant and Soil 42 551-563. 

When zinc fertilizers are used on soils deficient in zinc, crop production may be increased even though the zinc concentration in the plant tissues and especially in the seed show no increase. With higher levels of zinc fertilization, the zinc concentration in plants may increase. Some evidence shows that the value of food and feed crops as sources of dietary zinc can be improved by using zinc fertilizers at rates exceeding those required for optimal plant growth. However, very high rates of zinc fertilization can depress crop yields. 

The relative order of efficiency of accumulation of the thpee radionuclides into edible tissues was Zn>Fe>Se. Most of the Zn transported to the above ground plant parts was accumulated by the seeds, however, much of the dose of each of the radionuclides remained in the roots and nutrient solution. The calculated percent of the applied dose taken up by soybean leaves is underestimated since some of the leaves abscised as the plants senesced and they were discarded. Zinc and iron have been classified as partially mobile in the phloem (8). Translocation of iron within plants is poor since new growth of plants require a continuous supply of iron via the xylem or from external applications ( ). Zinc deficiencies of plants can be corrected by applying ZnSO. in a dilute spray. However, iron deficiences of plants are usually difficult to correct which implies a lesser mobility within the plant. 

Mohamed AA, Khalil I, Varanini Z and Pinton R (2000) Increase in NAD(P)H-dependent generation of active oxygen species and changes in lipid composition of microsomes isolated from roots of zinc-deficient bean plants. J Plant Nutr 23 285-295. 

ViETS EG Jr. (1966) Zinc deficiency in the soil plant system. In Prasad AS, ed. Zinc Metabolism, pp. 90—128. CC Thomas, Springfield, Illinois. 

Bozhenko, V. P., and Belyaeva, V. N. (1977). Content of 5-methyl cytosine in total DNA of plants under conditions of molybdenum and zinc deficiency. Sov. Plant Physiol. 24 281-6. 

Conversely, an excess soil P may effect the uptake of some micronutrient elements. A high P content can induce a zinc deficiency in the plant, even if sufficient zinc is present in the soil. On the other hand, the uptake of manganese from alkaline manganese-deficient soils can be increased by the presence of phosphatic fertilisers. There is also some evidence that excessive and prolonged buildup of phosphatic fertilisers in the soil might lead to toxic effects due to the trace quantities of certain metals (e.g. Cd above) in the fertilisers [38,59-61]. 

Zinc is essential to the function of more than 100 enzymes. It is also important in growth and development, immune function, learning, wound healing, and sperm production. Vegetarians are most at risk for zinc deficiency since plant sources contain only small amounts of zinc. Overconsumption of zinc is toxic. Animal products are excellent sources of zinc these include meat, shellfish, and poultry. 

Zinc is an essential element and thus can exist in both the deficient or toxic state in plants and animals. Deficiency occurs in some plants when the tissue content drops below 20 ppm. The normal range is 25—150 ppm. The toxic effect of zinc has been seen at 400 ppm, although plants vary widely in their tolerance. 

Cakmak and H. Marschner, Increase in membrane permeability and exudation in roots of zinc deficient plants. J. Plant Physiol. 132 356 (1988). 

I. Cakmak, B. Erenoglu, K. Y. Giiliit, R. Derici, and V. Romheld, Light-mediated release of phytosiderophores in wheat and barley under iron or zinc deficiency. Plant Soil 202 309 (1998). 

D. Gries, S. Brunn, D. E. Crowley, and D. Parker, Phytosiderophore production in relation to metal micronutrient deficiencies in barley. PIcmi Soil 772 299 (1995). B. Erenoglu, I. Cakmak, H. Marschner, V. Romheld, S. Eker, H. Daghan, M. Ka-layci. and H. Ekiz, Phytosiderophore release does not relate well zinc efficiency in different bread wheat genotypes. J. Plant Niiir. 79 1569 (1996). 

Zinc fertilizer is used to supply plants to correct for Zn deficiency. In 1987, Zn fertilizers were used in an area of more than 2,670,000 ha in China (Zhu, 1996). Zinc inorganic salts, chelate forms, and biosolids such as sewage sludge have been applied to arid and semi-arid soils to correct for Zn deficiency. 

The balance between excess and insufficient zinc is important. Zinc deficiency occurs in many species of plants and animals, with severe adverse effects on all stages of growth, development, reproduction, and survival. In humans, zinc deficiency is associated with delayed sexual maturation in adolescent males poor growth in children impaired growth of hair, skin, and bones disrupted Vitamin A metabolism and abnormal taste acuity, hormone metabolism, and immune function. Severe zinc deficiency effects in mammals are usually prevented by diets containing >30 mg Zn/kg DW ration. Zinc deficiency effects are reported in aquatic organisms at nominal concentrations between 0.65 and 6.5 pg Zn/L of medium, and in piscine diets at <15 mg Zn/kg FW ration. Avian diets should contain >25 mg Zn/kg DW ration for prevention of zinc deficiency effects, and <178 mg Zn/kg DW for prevention of marginal sublethal effects. 

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