Zn Nutritional Status Research Articles

Uptake and transport of foliar applied zinc (65Zn) in bread and durum wheat cultivars differing in zinc efficiency

Using two bread wheat (Triticum aestivum) and two durum wheat (Triticum durum) cultivars differing in zinc (Zn) efficiency, uptake and translocation of foliar-applied 65Zn were studied to characterize the role of Zn nutritional status of plants on the extent of phloem mobility of Zn and to determine the relationship between phloem mobility of Zn and Zn efficiency of the used wheat cultivars. Irrespective of leaf age and Zn nutritional status of plants, all cultivars showed similar Zn uptake rates with application of 65ZnSO4 to leaf strips in a short-term experiment. Also with supply of 65ZnSO4 by immersing the tip (3 cm) of the oldest leaf of intact plants, no differences in Zn uptake were observed among and within both wheat species. Further, Zn nutritional status did not affect total uptake of foliar applied Zn. However, Zn-deficient plants translocated more 65Zn from the treated leaf to the roots and remainder parts of shoots. In Zn-deficient plants about 40% of the total absorbed 65Zn was translocated from the treated leaf to the roots and remainder parts of shoots within 8 days while in Zn-sufficient plants the proportion of the translocated 65Zn of the total absorbed 65Zn was about 25%. Although differences in Zn efficiency existed between the cultivars did not affect the translocation and distribution of 65Zn between roots and shoots. Bread wheats compared to durum wheats, tended to accumulate more 65Zn in shoots and less 65Zn in roots, particularly under Zn-deficient conditions. The results indicate that differences in expression of Zn efficiency between and within durum and bread wheats are not related to translocation or distribution of foliar-applied 65Zn within plants. Differential compartementation of Zn at the cellular levels is discussed as a possible factor determining genotypic variation in Zn efficiency within wheat.

Zinc nutritional status in obese children and adolescents.

Studies in animals and humans have corroborated that zinc (Zn) metabolism is altered in obesity. The present work intends to evaluate the Zn nutritional status in obese children and adolescents by the determination of some biochemical parameters and analyses of the diets. The investigation was carried out in a group of obese children and adolescents (n = 23) and compared to a control group (n = 21), both between 7 and 14 yr of age. A software analyzed diet information from 3-d food records. Body composition was evaluated by body mass index, bioelectrical impedance, and skinfold measurements. Zinc nutritional status was evaluated by Zn determination in plasma, erythrocyte, and 24-h urine, by atomic absorption spectrophotometry (lambda = 213.9 nm). Diets consumed by both groups had marginal concentrations of zinc. Zinc concentrations in plasma and erythrocytes were significantly lower in the obese group. Urinary zinc excretion was significantly higher in the same group. The results allowed one to conclude that zinc nutritional status in obese individuals is altered.

INTER-RELATIONSHIPS BETWEEN ZINC NUTRITION, GROWTH PARAMETERS, AND NUTRIENT PHYSIOLOGY IN A HYDROPONICALLY GROWN TOMATO CULTIVAR

An experiment was carried out to investigate the role of zinc (Zn) in physiological and nutritional development of the tomato (Lycopersicon esculentum Mill.) cultivar Moneymaker grown hydroponically in a controlled temperature room. The experiment was a 2 × 3 factorial arrangement with two levels of nutrient solution Zn concentrations, 0.01 or 0.10 mg L−1, and three levels of foliar applied Zn, 0, 23, or 230 mg L−1. Low (0.01 mg L−1) nutrient solution Zn seems to be inadequate for optimum plant growth; in this treatment plants showed Zn deficiency symptoms. Foliar application of Zn at 23 mg L−1 alleviated Zn deficiency by enhancing Zn concentration in the leaves, dry weight, and chlorophyll content. However, foliar application of Zn at 230 mg L−1 Zn caused adverse effects on both dry weight and chlorophyll content. Phosphorus (P) reached a detrimental level in the leaves of plants grown at 0.01 mg L−1 Zn in nutrient solution, but 23 mg L−1 Zn applied via the leaves reduced P concentrations from toxic to adequate levels. Concentration of iron (Fe) was also higher but not detrimental in the leaves of plants grown at 0.01 mg L−1 Zn. Foliar application of both concentrations of Zn slightly reduced Fe concentration in the leaves. Membrane permeability was impaired both in the plants grown at low Zn and in those receiving the high (230 mg L−1) foliar application. Foliar Zn at 23 mg L−1 maintained membrane permeability by decreasing electrolyte leakage from leaves of Zn-deficient plants. Low (0.01 mg L−1) Zn in the nutrient solution resulted in plants with very leaky root systems as measured by high potassium (K) efflux; this leakiness was ameliorated by foliar application of Zn at 23 mg L−1. Cumulative potassium release from intact roots was higher in both the Zn-deficient plants (0.01 mg L−1) and those receiving high (230 mg L−1) foliar Zn. These data show that Zn nutritional status affects root membrane integrity.

Tansley Review No. 111: Possible roles of zinc in protecting plant cells from damage by reactive oxygen species.

Zinc deficiency is one of the most widespread micronutrient deficiencies in plants and causes severe reductions in crop production. There are a number of physiological impairments in Zn-deficient cells causing inhibition of the growth, differentiation and development of plants. Increasing evidence indicates that oxidative damage to critical cell compounds resulting from attack by reactive O2 species (ROS) is the basis of disturbances in plant growth caused by Zn deficiency. Zinc interferes with membrane-bound NADPH oxidase producing ROS. In Zn-deficient plants the iron concentration increases, which potentiates the production of free radicals. The Zn nutritional status of plants influences photooxidative damage to chloroplasts, catalysed by ROS. Zinc-deficient leaves are highly light-sensitive, rapidly becoming chlorotic and necrotic when exposed to high light intensity. Zinc plays critical roles in the defence system of cells against ROS, and thus represents an excellent protective agent against the oxidation of several vital cell components such as membrane lipids and proteins, chlorophyll, SH-containing enzymes and DNA. The cysteine, histidine and glutamate or aspartate residues represent the most critical Zn- binding sites in enzymes, DNA-binding proteins (Zn-finger proteins) and membrane proteins. In addition, animal studies have shown that Zn is involved in inhibition of apoptosis (programmed cell death) which is preceded by DNA and membrane damage through reactions with ROS. contents Summary 185 I. introduction 186 II. effect of zinc on production of reactive oxygen species 186 III. membrane damage by reactive oxygen species 193 III. membrane damage by reactive oxygen species 193 V. involvement of zinc in plant stress tolerance 199 VI. conclusions 199 Acknowledgements 200 References 200.

Zinc deficiency as a practical problem in plant and human nutrition in Turkey: A NATO-science for stability project

Zinc (Zn) deficiency is a critical nutritional problem for plants and humans in Turkey. About 14 Mha of cropped land in Turkey are known to be Zn deficient, particularly cereal growing areas of Anatolia. In 1993, a joint research project was started in Turkey with the financial support of the NATO-Science for Stability Programme to select and characterize cereal genotypes with high yield and/or high Zn accumulation in grain under deficient supply of Zn. Field, greenhouse and growth chamber experiments were carried to study morphological, physiological and genetic factors determining the bases of genotypical differences in Zn efficiency among cereal species and within cultivars of wheat. Among the cereals, rye had particularly high Zn efficiency (high yield under Zn deficiency). There were large genotypical differences among wheat lines. High Zn efficiency was closely associated with enhanced capacity of some lines to take up Zn from soils, but not with increased Zn accumulation per unit dry weight of shoot or grain. Measurement of Zn-containing superoxide dismutase activity in leaves revealed that an efficient utilization of Zn at the tissue or cellular level is an additional major factor involved in Zn efficiency of cereals. Zinc present in grains from Anatolia seems to be not bioavailable. Phytate : Zn molar ratios in grains, a widely accepted predictor of Zn bioavailability, were extremely high and ranged between 95 and 216 for crops grown severely on Zn-deficient soils of Central Anatolia. In the studies concerning determination of Zn nutritional status of school children in Southeastern Anatolia, most children were found to be of shorter stature and had very low levels of Zn (<100 mg kg −1) in hair.

Zinc-phosphorus interactions in two cultivars of tomato (Lycopersicon esculentum L.) grown in chelator-buffered nutrient solutions

Zinc-phosphorus interactions have been frequently studied using a diverse number of crop species, but attainment of reproducible Zn deficiencies, especially severe ones, has been hampered by the use of conventional hydroponic solutions wherein contaminating levels of Zn are often near-adequate for normal growth. We utilized novel, chelator-buffered nutrient solutions for precise imposition of Zn deficiencies. Tomato (Lycopersicon esculentum L. cv. Jackpot or Celebrity) seedlings were grown for 15 to 18 d in nutrient solutions containing 200, 600, or 1200 μM P, and 0 to 91 μM total Zn. Computed free Zn2+ activities were buffered at ≤10-10.3M by inclusion of a 100-μM excess (above the sum of the micronutrient metal concentrations) of the chelator DTPA. At total added Zn=0, acute Zn deficiency resulted in zero growth after seedling transfer, and plant death prior to termination. Free Zn2+ activities ≤10-10.6M resulted in Zn deficiencies ranging from mild to severe, but activities ≤10-11.2 were required to cause hyperaccumulation of shoot P to potentially toxic levels. Despite severe Zn deficiency (i.e. ca. 20% of control growth), tissue Zn levels were usually much higher than the widely reported critical value of 20 mg kg-1, which may be an artifact of the selection of DTPA for buffering free Zn2+. Across Zn treatments, increasing solution P depressed growth slightly, especially in Celebrity, but corresponding increases in tissue P (indicative of enhanced P toxicity) or decreases in tissue Zn (P-induced Zn deficiency) were not observed. The depressive effect of P was also not explained by reductions in the water-soluble Zn fraction. Within 40 h, restoration of Zn supply did not ameliorate high leakage rates (as measured by K+ efflux) of Zn-deficient roots. Similarly, transfer of Zn-sufficient plants to deficient solutions did not induce leakiness within 40 h. Foliar sprays of ZnSO4 almost completely corrected both Zn deficiency and membrane leakiness of plants grown in low-Zn solutions. Hence, maintenance of root membrane integrity appears to depend on the overall Zn nutritional status of the plant, and not on the presence of certain free Zn2+ levels in the root apoplasm.

Decrease in nitrate uptake and increase in proton release in zinc deficient cotton, sunflower and buckwheat plants

The effect of varied Zn supply on the pH of the nutrient solution and uptake of cations and anions was studied in cotton (Gossypium hirsutum L.), sunflower (Helianthus annuus L.) and buckwheat (Fagopyrum esculentum Moench) plants grown under controlled environmental conditions in nutrient solutions with nitrate as source of nitrogen. With the appearance of visual Zn deficiency symtoms, the pH of the nutrient solutions decreased from 6 to about 5 whereas the pH increased to about 7 when the plants were adequately supplied with Zn. In Zn deficient plants the pH decrease was associated with a shift in the cation-anion uptake ratio in favour of cation uptake. Of the major ions, uptake of Ca2+ and K+ was either not affected or only slightly lowered whereas NO3 - uptake was drastically decreased in Zn deficient plants. Although the Zn nutritional status of plants hardly affected the NO3 - concentrations in the plants, the leakage of NO3 - from roots of Zn deficient plants into a diluted CaCl2 solution was nearly 10 times higher than that of plants adequately supplied with Zn. In contrast to Zn deficiency, Mn deficiency in cotton plants neither affected NO3 - uptake nor the pH of the nutrient solution. The results indicate that, probably as a consequence of the role of Zn in plasma membrane integrity and nitrogen metabolism, when Zn is deficient in dicotyledonous species net uptake of NO3 - is particularly depressed which in turn results in an increase in cation-anion uptake ratio and a corresponding decrease in external pH. The ecological relevance of this rhizosphere acidification is discussed.

Breeding-Hen and Progeny Performance When Hens Are Fed Excessive Dietary Zinc

Short-term (12 wk) and long-term (44 wk) studies were conducted to observe the effects of excessive Zn supplementation on the performance of breeding hens and their progeny. Zinc sulfate was added to a corn-soybean meal diet containing 28 mg of Zn/kg in order to provide Zn supplementation at 0, 20, 200, and 2,000 mg/kg. Each dietary treatment was fed to two groups of 20, Single Comb White Leghorn hens and one New Hampshire rooster. The hens were 56-wk old at the start of the short-term study and 24-wk old when the long-term study began. Determinations were made for: fertility, hatchability, progeny growth to 3 wk of age, Zn-related feather-fraying among the progeny as well as Zn, Cu, and Fe in the liver, pancreas, and right tibiotarsus. The Zn treatments had no effect on hen performance or on reproductive performance. Even though Zn was considerably elevated and Cu was reduced in the eggs collected from hens fed the highest level of Zn, chick performance and the tissue content of Zn, Cu, and Fe were not influenced by the maternal Zn nutritional status.

Effect of Zinc Nutritional Status on Growth, Protein Metabolism and Levels of Indole-3-acetic Acid and other Phytohormones in Bean (Phaseolus vulgarisL.)

Bean (Phaseolus vulgaris L. var. Prelude) plants were grown for 17 d under controlled environmental conditions with varied Zn supply in the nutrient solution. The concentrations of amino acids; indole-3-acetic acid, IAA; abscisic acid, ABA; isopentenyl adenine, I-Ade; isopentenyl adenosine, I-Ado; zeatin, Z; and zeatin riboside, ZR were determined in various shoot fractions. The growth of plants, especially shoot growth, was severely depressed under conditions of Zn deficiency. Simultaneously, concentrations of soluble protein and chlorophyll decreased, whereas amino acid concentrations increased several-fold. In the Zn deficient plants, the level of IAA in the shoot tips and young leaves decreased to about 50% of that in Zn-suflicient plants. A similar decrease occurred in the ABA levels of shoot tips. In contrast, Zn deficiency was without effect on cytokinin levels in the leaves. Re-supply of Zn to the deficient plants for up to 96 h significantly increased shoot growth, soluble protein, and IAA levels up to the values of Zn-sufficient plants. Simultaneously, the concentration of amino acids dropped to low levels. The effect of Zn nutritional status on the tryptophan level was parallel to that of most of the other amino acids. The results confirm the role of Zn in protein synthesis and demonstrate that the decrease in IAA level in Zn-deficient plants is not brought about by impaired synthesis of tryptophan. It is also unlikely that in Zn-deficient plants the conversion of tryptophan to IAA is specifically inhibited.

Mechanism of phosphorus‐induced zinc deficiency in cotton. III. Changes in physiological availability of zinc in plants Is mail

The effect of varied supply of P (2.5× 10−5 to 6× 10−4 M) and Zn (0 to 10−6 M) on uptake and concentrations of P and Zn was studied in cotton (Gossypium hirsutum L. cv. Deltapine 15/21) grown in nutrient solution under controlled environmental conditions. At a given Zn supply, increasing levels of P had no significant effect on the concentrations of total Zn in plants. However, increasing levels of P induced or enhanced visual Zn deficiency symptoms when the Zn concentration in the nutrient solution was low. The concentrations of water‐soluble Zn in roots and shoots constituted 60% of the total Zn concentrations for plants grown with low P and 30% for plants grown with high P. The concentration of water‐soluble Zn in leaves, but not total Zn, was closely correlated with visual Zn deficiency symptoms, levels of chlorophyll, super oxide dismutase and membrane permeability. The critical deficiency concentration of water‐soluble Zn in cotton leaves was in the range of 6 to 7 μg (g dry weight)−1 or about 1.0 μg (g fresh weight)−1. The results show that high P concentrations in plant tissue decrease the physiological availability of Zn. Water‐soluble Zn in the tissue appears to be a suitable indicator for Zn nutritional status in general and phosphorus‐induced Zn deficiency in particular. Also in field‐grown orange trees (Citrus sinensis) visual Zn deficiency symptoms in leaves were closely related to the concentration of water‐soluble Zn.

Mechanism of phosphorus‐induced zinc deficiency in cotton. II. Evidence for impaired shoot control of phosphorus uptake and translocation under zinc deficiency

Cotton (Gossypium hirsutum L. cv. Deltapine 15/21) plants were precultured for 19 to 25 days under controlled climatic conditions in nutrient solutions with different levels of Zn. With the onset of visual Zn‐deficiency symptoms the pH of the nutrient solution decreased from 6.0 to about 5.0. In contrast, Zn‐sufficient plants raised the pH of the nutrient solution to about 7.0. In short‐term studies it could be demonstrated that the Zn nutritional status of the plants remarkably influenced the uptake and translocation rates of mineral nutrients. Compared to Zn‐sufficient plants, P uptake rate in severely Zn‐deficient plants was increased by a factor of 2 to 3, whereas the uptake rates of K, Ca and particularly NO3 decreased. The accumulation of P in the roots of Zn‐deficient plants was either not affected or even lower than in Zn‐sufficient plants. Thus, Zn deficiency had a specific enhancement effect on root to shoot transport of P. This enhancement effect of Zn deficiency on uptake and transport of P was similar at nutrient solution pH values of 7.0 and 5.8; i.e. it was not the result of acidification of the nutrient solution. After application of 36CI, 86Rb and 32P to plant stems, basipetal transport of 36CI and 86Rb was not affected by the Zn nutritional status of the plants. However, in Zn‐deficient plants, only 7.8% of the 32P was translocated basipetally compared to 34% in the Zn‐sufficient plants. A resupply of Zn for 19 h to Zn‐deficient plants enhanced basipetal 32P transport. The results indicate that a feedback mechanism in the shoots is impaired in Zn‐deficient plants which controls the P uptake by roots and especially the P transport from roots to shoots. As a result of this impairment toxic concentrations of P accumulate in the leaves. The mechanism responsible is likely the retranslocation of P in the phloem from shoots to roots.

Responses to Fe deficiency in roots of “Fe‐efficient” plant species

Abstract Under Fe deficiency (Fe stress) the roots of so‐called “Fe‐efficient” plant species (mainly dicots and some monocots) show typical responses, such as increased formation of root hairs, development of rhizoder‐mal transfer cells, and increased capacity to reduce Fe‐III in the rhizodermis: simultaneously the uptake rate of Fe increases rapidly. Fe deficiency also enhances the uptake rates of Mn and Zn, although to lower levels than for Fe uptake. Thus, these responses to Fe deficiency also have a favourable effect on the Mn and Zn nutritional status of those plant species grown on substrates with low Fe availability. In contrast to “Fe‐efficient” species, in the so‐called “Fe‐inefficient” species (mainly grasses) these responses for the fine regulation of Fe uptake are absent. Bicarbonate severly inhibits the reducing capacity of roots in “Fe‐efficient” species under Fe deficiency. Furthermore, with low Fe availability in the substrate, Fe uptake and chlorophyll formation are both more inhibited ...

427 IMPROVING GROWTH HORMONE RESPONSE WITH ORAL ZING THERAPY IN RUSSELL-SILVER DWARFISM

Growth hormone deficiency has been reported in 10-20% of Russell-Silver dwarfs. Two siblings with all the classical features of Russell-Silver Syndrome were low in growth hormone (insulinarginine stimulation test), and blood and hair zinc (Zn). They received 50 mg elemental Zn orally each day for 2 months and 50 mg weekly for 4 more months. Growth hormone and Zn determinations were repeated at 6 months: It appears there is a direct relationship between the growth hormone response and Zn nutritional status. We have data indicating that growth hormone therapy increases hair Zn and decreases urinary Zn in children with growth hormone deficiency. These two children provide new data indicating that there are patients whose growth hormone production is affected by their Zn nutritional status.

450 ZINC (Zn) AND BIRTH DEFECTS (BD)

Zn deficiency has been reported in infants with BD and in children born with achondroplasia. 304 families were studied comparing parental age, Zn nutritional status and infant weight at the time of birth. There is a statistically significant correlation (p < .01) between infant hair Zn and maternal age at time of birth. The decrease in infant hair Zn seen with teenage (14-20) and elder mothers (31-40) may be related to the incidence of increased BD which occurs in these groups. Infant hair Zn was lowest in the heaviest infants and in a group with BD made up of porencephaly, anencephaly and microcephaly as the presenting sign (N=4; Zn=134±10). The heavier children may represent the infants of potential diabetic mothers (who have more BD). Placental Zn was 18-19 ug/g and did not correlate well with maternal or infant hair Zn. Finally, diet did not explain parental Zn status since paired deficiencies did not occur. Therefore, an association between Zn levels, high-risk age groups and those children with BD is apparent.

1153 OBESITY IN CHILDREN. RELATIONSHIP BETWEEN ZINC (ZN) TRIGLYCERIDE (TG) AND TESTOSTERONE (T)

Childhood obesity is caused by a variety of genetic and environmental factors which have been difficult to identify. We have recently found that some obese children have reduced levels of hair ZN. Our studies in rats and in adults with coronary artery disease have confirmed an inverse relationship between nutritional ZN status and serum TG levels. We have also reported a direct relationship between serum T and Zn nutritional status. We are here reporting data indicating that obese children can be divided into two groups. In Group 1 the serum TG level and hair ZN concentrations are significantly higher than in Group 2, and only in Group 1 is there a direct correlation between serum T and hair ZN. The cause of the lack of a direct relationship between ZN and T in Group 2 obese children is not known. Thus, obese children also had an inverse relationship between serum TG and hair ZN (*p<0.005).

Further Evidence for a P‐Zn Imbalance in Plants

AbstractBeans (Phaseolus vulgarus) and potatoes (Solanum tuberosum) were grown using a split‐medium technique that permitted Zn to be supplied to the plants from a soil medium while variable levels of P were supplied from a solution. A balance between P and Zn levels was attained through trial and error so that only the highest level of P induced interveinal chlorosis and stunting.In both crops, P induced the deficiency without causing a decrease in the Zn nutritional status of the plants. Increasing the soil Zn level at a given P level resulted in plants with normal growth. The results are interpreted to support the hypothesis that normal metabolism is dependent upon a physiological balance between P and Zn.