Deficiency symptoms in plants

Selenium deficiency in soils occurs in some parts of the world [56] and it is standard practice in such areas to dose animals with selenium in order to correct this deficiency. Selenium-responsive diseases can appear when the level of selenium is lower than 0.03 xg/g in the blood [57]. Levels of selenium in pasture plants associated with deficiency symptoms in animals are in the range 0.01-0.03 xg/g [58]. 

Iron distribution in plants and animals is tightly regulated to counteract deficiency symptoms in situations of scarce supply (see Chapter 13.1.5). An iron-replete adult male organism contains about 4 g of iron, approximately 60% of which is used in... 

Peterson, N. K., and Purvis, E. R. (1961). Development of molybdenum deficiency symptoms in certain crop plants. Soil Sci. Soc. Am. Proc. 25 111-17. 

Plant (1956) described the development of whiptail in cauliflower, which was severe when S was applied to low-Mo soils. He also described Mo deficiency symptoms in other brassicas and lettuce that increased in severity when S was applied to low-Mo soils. 

Cobalt is one of twenty-seven known elements essential to humans (28) (see Mineral NUTRIENTS). It is an integral part of the cyanocobalamin [68-19-9] molecule, ie, vitamin B 2> only documented biochemically active cobalt component in humans (29,30) (see Vitamins, VITAMIN Vitamin B 2 is not synthesized by animals or higher plants, rather the primary source is bacterial flora in the digestive system of sheep and cattle (8). Except for humans, nonmminants do not appear to requite cobalt. Humans have between 2 and 5 mg of vitamin B22, and deficiency results in the development of pernicious anemia. The wasting disease in sheep and cattle is known as bush sickness in New Zealand, salt sickness in Florida, pine sickness in Scotland, and coast disease in AustraUa. These are essentially the same symptomatically, and are caused by cobalt deficiency. Symptoms include initial lack of appetite followed by scaliness of skin, lack of coordination, loss of flesh, pale mucous membranes, and retarded growth. The total laboratory synthesis of vitamin B 2 was completed in 65—70 steps over a period of eleven years (31). The complex stmcture was reported by Dorothy Crowfoot-Hodgkin in 1961 (32) for which she was awarded a Nobel prize in 1964. 

The general recommendations on energy and fat intake are similar to those for the avoidance of heart disease. However, the recommendation to consume a variety of fruits and vegetables is based partly on the putative presence of diverse protective factors in plant foods. This concept does provide, at least in principle, a rationale for the functional health benefits of plant foods beyond the simple provision of nutrients at a level that prevents symptoms of deficiency. 

Mineral deficiencies can cause plants to fail and show symptoms of "disease" (technically disorder), but in a well-ordered organic... 

Excess selenium intake can occur in both animals and humans living in areas with elevated selenium in the soil. Most grass and grains do not accumulate selenium, but when an animal consumes plants that do accumulate selenium (some up to 10,000 mg/kg) they can develop a condition called the blind staggers . Symptoms include depressed appetite, impaired vision, and staggering in circles and can ultimately lead to paralysis and death. Humans are susceptible to similar effects as well as additional neurological effects. Selenium deficiency results in heart disorders, skeletal muscle effects, and liver damage. 

Phenolic accumulation in B-deficient tissues can activate a group of enzymes that use these compounds as substrates. In B-deficient sunflower leaves, PPO activity progressively augments as symptoms characteristic of this deficiency appear. Plants with sensitivity to B deficiency differ in PPO activity. The accumulation of phenolics and PPO activity are reportedly greater in more sensitive plants, such as sunflower, than in less deficiency-sensitive plants, such as com (Zea mays) [125]. 

In agriculture, excesses or deficiencies of essential and beneficial elements (Epstein, 1972 Hewitt and Smith, 1975 Webber, 1981) have profound effects on the health and hence the yields of plants. Chlorosis is often the visible deficiency symptom (Kabata-Pendias and Pendias, 1984). However, disturbances of metabolic processes and consequent losses of biomass production may occur before deficiency symptoms are recognised. Thus the analysis of plants for mineral and nutrient status is particularly important in agriculture. The agricultural agencies of many countries publish recommended analytical methods (for example, HMSO, 1986). 

Prevention and Control Phosphorus deficiency symptoms develop fairly frequently in transplants set out in early spring. Unlike some other nutrients, phosphorus does not move through the soil roots must grow to reach it. Until the soil warms sufficiently to stimulate root growth, plants may not be able to take up enough phosphorus. 

Magnesium is a constituent of chlorophyll and acts as an activator of numerous plant enzymes. Thus, chlorosis in plants is an early symptom of Mg deficiency, as well as weak stalks and premature leaf and fruit drop. 

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