Short-term physiological indicators of N deficiency in phytoplankton: a unifying model

Nitrogen resupply to N-limited microalgae elicits several rapid physiological responses which have been used as indicators of N deficiency. These include a stimulation of dark respiration and dark carbon fixation. In addition, N resupply to some microalgae results in a transient suppression of photosynthetic carbon fixation. Long term, N enrichment results in an increase in the rate of photosynthesis and ultimately in the rate of growth. In this report these physiological indicators of N deficiency are documented as a function of steady-state growth rate in Selenastrum minutum Naeg. Collins (Chlorophyta). Based on previous biochemical and physiological studies, we suggest that these short-term responses are a reflection of redirection of photosynthetic carbon flow to the process of N assimilation. A unifying model is proposed that interrelates these responses to N resupply.     

Iodine deficiency status in the WHO Eastern Mediterranean Region: a systematic review

Iodine deficiency is a global public health issue because iodine plays a major role in the thyroid hormone synthesis and is essential for normal neurological development. This review summarizes the publications on iodine status in the WHO Eastern Mediterranean Region (EMR) countries. All related studies available in main national and international databases were systematically searched using some specific keywords to find article published between 1909 and 2015. The prevention of iodine deficiency disorders (IDDs) in the WHO EMR countries is currently under control without significant side effects. Mild to severe IDDs exist in some countries of the Middle East, due to lack of effective iodine supplementation program, but the Islamic Republic of Iran, Jordan, Bahrain and Tunisia have achieved the goal of universal salt iodization. Overall, despite enormous efforts to control IDDs, still IDD remains a serious public health problem in some countries of the region, requiring urgent control and prevention measures.     

植物对硼素不足的反应及其成因探讨

硼是植物生长过程中必不可少的微量元素之一,缺硼将严重影响植物的正常生长与发育。文章综述了植物对硼素不足的反应,包括细胞壁和生物膜的结构与功能变化、糖类运输、酶活性的改变以及植物根、茎、叶和生殖生长的变化等,探讨了植物缺硼的可能原因,并提出了防止植物缺硼的对策。     

Soil factors associated with zinc deficiency in crops and humans

Zinc deficiency is the most ubiquitous micronutrient deficiency problem in world crops. Zinc is essential for both plants and animals because it is a structural constituent and regulatory co-factor in enzymes and proteins involved in many biochemical pathways. Millions of hectares of cropland are affected by Zn deficiency and approximately one-third of the human population suffers from an inadequate intake of Zn. The main soil factors affecting the availability of Zn to plants are low total Zn contents, high pH, high calcite and organic matter contents and high concentrations of Na, Ca, Mg, bicarbonate and phosphate in the soil solution or in labile forms. Maize is the most susceptible cereal crop, but wheat grown on calcareous soils and lowland rice on flooded soils are also highly prone to Zn deficiency. Zinc fertilizers are used in the prevention of Zn deficiency and in the biofortification of cereal grains.     

Sauerstoffmangelresistenz mariner Bodenvertebraten aus der Westlichen Ostsee

Among the macrobenthos fauna of the Western Baltic Sea, lamellibranchs occurring in poorly oxygenated soft sediments exhibit especially high tolerances to temporary oxygen deficiency. Such tolerance is less well developed in mobile species of various systematic groups than in more or less immobile forms. Commonly, tolerance to oxygen deficiency tends to increase with decreasing temperature. Different qualitative relations between tolerance to oxygen deficiency and temperature may be correlated with the distributional range of the species.     

镉和铁及其交互作用对植物生长的影响

镉是植物的非必需元素，而铁是植物生长发育过程中必不可少的元素。虽然这两种元素对植物的作用是截然相反的，但是它们在植物体内存在着交互作用关系，相互影响着对方功能的发挥。供给植物足够的铁可极大地缓解植物的镉污染毒害，利于植物合成更多的叶绿素，促进光合作用进行，降低镉对氨基酸、蛋白质合成以及酶活性的影响。相反，镉污染将诱导植物的铁营养缺乏。渍水植物根表形成的铁氧化物胶膜可促进植物对镉的吸收。     

Excessive fluoride consumption increases haematological alteration in subjects with iron deficiency,thalassaemia, and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency

Excessive fluoride consumption leads to accelerated red blood cell death and anaemia. Whether that increases the haematological alteration in subjects with haematological disorders (iron deficiency, thalassaemia, and G-6-PD deficiency) is still unclear. The fluoride in serum and urine and haematological parameters of students at Mae Tuen School (fluoride endemic area) were analysed and compared to those of students at Baan Yang Poa and Baan Mai Schools (control areas). Iron deficiency, thalassaemia, and G-6-PD deficiency were also diagnosed in these students. The students at Mae Tuen School had significantly (P < 0.001) higher levels of mean fluoride in the serum and urine than those in control areas. In both control and fluoride endemic areas, students with haematological disorders had significantly lower levels of Hb, Hct, MCV, MCH, and MCHC than those without haematological disorders. Moreover, the lowest levels of Hb, MCH, and MCHC were observed in the students with haematological disorders who live in the fluoride endemic area. Thus, the excessive fluoride consumption increased haematological alteration in subjects with iron deficiency, thalassaemia, and G-6-PD deficiency and that may increase the risk of anaemia in these subjects.     

Multiple-locus heterozygosity,mortality, and growth in a cohort of Mytilus edulis

A positive correlation between the degree of individual heterozygosity (H) at five polymorphic enzyme loci and shell length was reported for a cohort of Mytilus edulis L. sampled in September, 1983, two months after settlement (Koehn and Gaffney, 1984). In the present study, the same cohort was resampled four and eight months after settlement in November, 1983, and April, 1984, respectively. Among individuals four months of age, there was a small, but statistically significant, negative correlation between H and shell length. In this sample, heterozygote deficiency in the cohort was less than that of any size group in the September sample. The reversal of the H-size relationship between September and November suggests that differential mortality, particularly among small, homozygous individuals, occurred in this period. For individuals eight months of age, there was no correlation between H and shell length, there was no heterozygote deficiency in the cohort and the average heterozygosity was the same as that of the largest individuals in September. At the youngest age, there was a positive relationship, between H and growth rate; as aging occurred, differential mortality altered the relationship between H and growth rate. viability differences among heterozygosity classes obscured the original effect of H on growth rate. If there is a positive relationship between heterozygosity and size, it can most likely be detected from sampling a large outbreeding population before differential mortality occurs and before energy is allocated to reproduction.     

Soils and geomedicine

Geomedicine is the science dealing with the influence of natural factors on the geographical distribution of problems in human and veterinary medicine. Discussions on potential harmful impacts on human and animal health related to soil chemistry are frequently focused on soil pollution. However, problems related to natural excess or deficiency of chemical substances may be even more important in a global perspective. Particularly problems related to trace element deficiencies in soils have been frequently reported in agricultural crops as well as in livestock. Deficiencies in plants are often observed for boron, copper, manganese, molybdenum, and zinc. In animals deficiency problems related to cobalt, copper, iodine, manganese, and selenium are well known. Toxicity problems in animals exposed to excess intake have also been reported, e.g., for copper, fluorine, and selenium. Humans are similar to mammals in their relations to trace elements and thus likely to develop corresponding problems as observed in domestic animals if their supply of food is local and dependent on soils providing trace element imbalances in food crops. In large parts of Africa, Asia, and Latin America, people depend on locally grown food, and geomedical problems are common in these parts of the world. Well-known examples are Keshan disease in China associated with selenium deficiency, large-scale arsenic poisoning in Bangladesh and adjacent parts of India, and iodine deficiency disorders in many countries. Not all essential elements are derived only from the soil minerals. Some trace elements such as boron, iodine, and selenium are supplied in significant amounts to soils by atmospheric transport from the marine environment, and deficiency problems associated with these elements are therefore generally less common in coastal areas than farther inland. For example, iodine deficiency disorders in humans are most common in areas situated far from the ocean. There is still a great need for further research on geomedical problems.     

Growth of plankton algae as a function of N-concentration,measured by means of batch technique

Employing a special batch technique which involves extremely low concentrations of the alga Selenastrum capricornutum, it is shown that a growth rate of ca. 75% of optimum growth occurs at a concentration of 0.02 g-at N(NH₄ ⁺) l^-1. The low concentrations of this N-source in the oligotrophic parts of the oceans (ca. 0.06 g-at l^-1) thus give rise to a borderline deficiency. As the half-saturation constant (K _S) for growth was recorded at 0.05 g-at N(NO₃ ^-), this ion can hardly be of much importance at the low concentrations present in these parts of the oceans. It is wrong to assert that N is the primary limiting nutrient. Phosphate also is found at concentrations giving rise to a borderline deficiency.     

土壤-植物系统中的碘与碘缺乏病防治

碘是人和动物必需的微量元素之一。碘缺乏将导致甲状腺肿、克汀病等疾病的发生。文章综述了土壤中碘的来源，碘质量分数和形态，影响土壤碘有效性的因素，植物体内碘的质量分数和分布，不同形态的碘对植物生长的影响，碘毒害等方面的研究进展；最后提出防治碘缺乏病的有效措施。     

Dietary selenium fortification: a potential solution to chronic arsenic toxicity

Selenium (Se), an important micronutrient and antioxidant, also acts as an antagonist of arsenic (As). Se supplementation of diet was investigated in mitigating chronic As toxicity in mammals. Experiments were conducted to determine whether Se supplementation in As-exposed rats might (i) decrease As-induced lipid peroxidation in liver, (ii) increase blood antioxidant status, and (iii) reverse suppression of the secondary antibody response. Male Wistar rats were exposed to As (40 and 80?ppm) in drinking water and received challenge diets with three different levels of Se (deficient: <0.01?ppm, adequate: 0.15 ppm, and fortified: 0.6?ppm) for 16 weeks. Clinical variables including behavior, body weight, and food and water consumption were recorded weekly, and blood sample was collected monthly. Antioxidant status was assessed through glutathione sulfhydryl (GSH) levels in whole blood. Lipid peroxidation in the liver was evaluated using the malondialdehyde (MDA) assay. The antibody response was measured using keyhole limpet hemocyanin as an immunogen. Se deficiency significantly increased hepatic lipid peroxidation and suppressed antibody production relative to the Se-adequate and -fortified groups, confirming that Se deficiency exacerbates the damage produced by As exposure. Se fortification markedly elevated the blood GSH level in both As-exposed groups, indicating protective effects. At adequate Se levels, rats showed signs of counteracting As-mediated toxicity. However, Se fortification produced more pronounced benefits against As-induced toxicity, a pattern that was particularly notable in the 40?ppm As group.     

Improving human micronutrient nutrition through biofortification in the soil–plant system: China as a case study

Micronutrient malnutrition is a major health problem in China. According to a national nutritional survey, approximately 24% of all Chinese children suffer from a serious deficiency of iron (Fe) (anemia), while over 50% show a sub-clinical level of zinc (Zn) deficiency. More than 374 million people in China suffer from goiter disease, which is related to iodine (I) deficiency, and approximately 20% of the Chinese population are affected by selenium (Se) deficiency. Micronutrient malnutrition in humans is derived from deficiencies of these elements in soils and foods. In China, approximately 40% of the total land area is deficient in Fe and Zn. Keshan and Kaschin-Beck diseases always appear in regions where the soil content of Se in low. The soil–plant system is instrumental to human nutrition and forms the basis of the “food chain” in which there is micronutrient cycling, resulting in an ecologically sound and sustainable flow of micronutrients. Soil-plant system strategies that have been adopted to improve human micronutrient nutrition mainly include: (1) exploiting micronutrient-dense crop genotypes by studying the physiology and genetics of micronutrient flow from soils to the edible parts of crops; (2) improving micronutrient bioavailability through a better knowledge of the mechanisms of the enhancers’ production and accumulation in edible parts and its regulation through soil-plant system; (3) improving our knowledge of the relationship between the content and bioavailability of micronutrients in soils and those in edible crop products for better human nutrition; (4) developing special micronutrient fertilizers and integrated nutrient management technologies for increasing both the density of the micronutrients in the edible parts of plants and their bioavailability to humans.     

Nutrient deficiency in dune slack pioneer vegetation: a review

A review of results of fertilization experiments in wet dune slacks is presented. In most cases the above-ground biomass appeared to be limited by nitrogen availability. Primary phosphorus limitation was assessed only once in a dune slack where sod cutting had been applied very recently. In most other case studies phosphorus limits biomass production after nitrogen deficiency was lifted. Potassium availability is of minor importance for biomass production in this type of ecosystem. Singular nitrogen additions led to increased dominance ofCarex andJuncus species as well as perennial grasses, such asAgrostis stolonifera andCalamagrostis epigejos. A combined addition of nitrogen and phosphorus led to total dominance of grasses, while the characteristic basiphilous pioneer species (including mosses) decreased or even disappeared. Certain mechanisms are considered which may maintain nutrient availability in slacks with basiphilous pioneer vegetation at a low level, despite of the accumulation of nutrients in the developing organic soil layer. Some implications for management and further research are discussed.     

磷肥施用量对缺锌土壤上水稻生长的影响

磷肥施用量对缺锌土壤上水稻生长的影响李延，潘伟彬（福建农业大学土化系，福州３５０００２）（闽西职业大学，龙岩３６４０２１）ＥｆｆｅｃｔｏｆＰｈｏｓｐｈａｔｉｃＦｅｒｔｉｌｉｚｅｒｏｎＧｒｏｗｔｈｏｆＲｉｃｅｏｎＺｉｎｃＤｅｆｉｃｉｅｎｔＳｏｉｌ￥Ｌｉ...     

Food-grade nanoencapsulation of vitamins

Environmental Chemistry Letters - Vitamin deficiency arises when the dietary intake of essential vitamins is too low. Insufficient levels of vitamin weaken the body and induce diseases. Although...     

Selenium deficiency in subtropical littoral pampas: environmental and dietary aspects

Environmental Geochemistry and Health - Se deficiency has a critical effect on human health. The littoral near Patos Lagoon in the south of Brazil is composed of Quaternary sandy deposits and...     

Biogeochemistry and cycling of zinc and copper in a dyked seasonally flooded savanna

There is very little information on the cycling of heavy metals in natural savannas. Venezuelan flooded savannas are characterised by acid soils with redox conditions which might induce Zn and Cu solubilisation. In those flooded savannas a network of small dykes has been constructed to control floods. The biomass accretion after dyking and the abundance of clay particles in the vertisols, dominant in the overflow plains, might be responsible for an increase in nutrient uptake and immobilisation. Due to the redox and pH conditions prevailing during flooding, some questions arise on the fate of the heavy metals. Are they significantly lost as soluble and particulate forms, which in turn, can induce a potential risk of microelement deficiency? Or, on the contrary, are heavy metal inputs in precipitation waters retained somewhere in the terrestrial pools of the watershed allowing for an adequate micronutrient economy? By using input-output budgets, which consider the total atmospheric input and total output in stream runoff (soluble and particulate) for zinc and copper we concluded that in Mantecal flooded savannas, a net accumulation of micronutrient in soils is actually occurring through organic and inorganic complexes, a process that is counterbalanced by the losses of particulates through erosion.     

Simultaneous nitrogen and silicate deficiency of a phytoplankton community in a coastal jet-front

The nutritional status of a phytoplankton community was investigated in a coastal jet-front located in the Gulf of St. Lawrence, Canada, in 1987. During the sampling period, the frontal community was mainly composed of the diatomsChaetoceros debilis, Skeletonema costatum, Thalassiosira gravida andC. pelagicus. As previously reported for the St. Lawrence, some frontal stations were depleted both in nitrate and silicate. At stations impoverished in nitrate, internal nitrate pool concentrations were low or undetectable, suggesting that cells had not, recently, been exposed to a nitrate flux which exceeded the nitrate assimilation rate. At these impoverished stations, however, ambient and intracellular concentrations of ammonium and urea were high, suggesting that the community was not nitrogen-deficient. The comparison between the ambient silicate concentrations and the silicate requirement (K _s ) of the dominant diatoms suggests thatC. debilis andS. costatum were Si-deficient. This is further supported by the low silicate uptake rates and intracellular concentrations measured at the silicate impoverished stations. The silicate deficiency also resulted in a decrease in the seston and phytoplankton N:C ratios.Please address all correspondence and requests for reprints to Dr Levasseur at his new address: Maurice Lamontagne Institute, 850 Route de la Mer, Mont-Joli, Québec G5H 3Z4, Canada