Long-term effect of superphosphate on accumulation of soil phosphorus and exchangeable cations on a grazed,irrigated pasture site

The annual herbage dry matter yield, herbage P concentrations and quantities of P, K, Mg and Ca cycled by grazing sheep were calculated for a 37 year-old grazed pasture supplied with superphosphate at rates of 0, 188 and 376 kg ha^-1 annually. The amount and distribution of inorganic and organic P and exchangeable K, Mg and Ca in the soil below the three grazed treatments was also measured and compared with that below a wilderness area which had not been used for agriculture. Increasing rates of superphosphate increased herbage dry matter yield, herbage P concentrations and thus the amounts of P ingested and, in turn, excreted by the grazing sheep. Annual quantities of K, Mg and Ca cycled back to the pasture in the form of excreta were also increased. The increased cycling of K by animals induced by increasing superphosphate applications resulted in greater losses of K and consequently concentrations of exchangeable and non-exchangeable ‘fixed’ K in soil decreased in the order wilderness > control > 188 > 376. Differences were evident to a depth of 20 cm. Some losses of Mg during cycling also occurred and concentrations of exchangeable Mg followed the order: wilderness > control >188=376. Concentrations of exchangeable Ca increased with pasture development due to additions of Ca in lime and superphosphate. Concentrations of total soil organic P (0–4 cm) increased in the order: wilderness < control <188<376 but for inorganic P and total P the control had a lower content than wilderness indicating losses of P during cycling in the grazed control treatment. Phosphorus fractionation suggested that with increasing superphosphate rates inorganic P primarily accumulated in a form adsorbed to Al hydrous oxides and as calcium phosphate compounds whilst organic P accumulated in both labile forms and forms associated with humic compounds. In the fertilised sites both inorganic and organic P accumulated in the soil profile to a depth of 20 cm.     

Genetic (co)variances between milk mineral concentration and chemical composition in lactating Holstein-Friesian dairy cows

Milk mineral concentration is important from both the perspective of processing milk into dairy products and its nutritive value for human consumption. Precise estimates of genetic parameters for milk mineral concentration are lacking because of the considerable resources required to collect vast phenotypes quantities. The milk concentration of calcium (Ca), potassium (K), magnesium (Mg), sodium (Na) and phosphorus (P) in the present study was quantified from mid-IR spectroscopy on 12 223 test-day records from 1717 Holstein-Friesian cows. (Co)variance components were estimated using random regressions to model both the additive genetic and within-lactation permanent environmental variances of each trait. The coefficient of genetic variation averaged across days-in-milk (DIM) was 6.93%, 3.46%, 6.55%, 5.20% and 6.68% for Ca, K, Mg, Na and P concentration, respectively; heritability estimates varied across lactation from 0.31±0.05 (5 DIM) to 0.67±0.04 (181 DIM) for Ca, from 0.18±0.03 (60 DIM) to 0.24±0.05 (305 DIM) for K, from 0.08±0.03 (15 DIM) to 0.37±0.03 (223 DIM) for Mg, from 0.16±0.03 (30 DIM) to 0.37±0.04 (305 DIM) for Na and from 0.21±0.04 (12 DIM) to 0.57±0.04 (211 DIM) for P. Genetic correlations within the same trait across different DIM were almost unity between adjacent DIM but weakened as the time interval between pairwise compared DIM lengthened; genetic correlations were weaker than 0.80 only when comparing both peripheries of the lactation. The analysis of the geometry of the additive genetic covariance matrix revealed that almost 90% of the additive genetic variation was accounted by the intercept term of the covariance functions for each trait. Milk protein concentration and mineral concentration were, in general, positively genetically correlated with each other across DIM, whereas milk fat concentration was positively genetically correlated throughout the entire lactation with Ca, K and Mg; the genetic correlation with fat concentration changed from negative to positive with Na and P at 243 DIM and 50 DIM, respectively. Genetic correlations between somatic cell score and Na ranged from 0.38±0.21 (5 DIM) to 0.79±0.18 (305 DIM). Exploitable genetic variation existed for all milk minerals, although many national breeding objectives are probably contributing to an indirect positive response to selection in milk mineral concentration.     

Combining ability analysis over environments in diallel crosses of linseed (Linum usitatissimum L.)

Summary This paper reports on combining ability studies for yield and its component traits in diallel crosses involving ten ecogeographically and genetically diverse linseed (Linum usitatissimum L.) cultivars in the F₂ generation over three locations. The general combining ability (GCA) and specific combining ability (SCA) mean squares were significant at all three locations for all traits. Combined analysis over locations showed the same trend of significance. The ratio of GCA to SCA mean squares was significant for all the traits in individual location analysis as well as in combined analysis. This indicated the predominant role of additive gene effects in the inheritance of these characters. The GCA mean squares were several times larger than SCA mean squares for all the traits, indicating the presence of considerable magnitude of additive genetic variance and the additive x additive components of the epistatic variance. Consequently, effective selection should be possible within these F₂ populations for all characters. Significant genotype-location and GCA-location interactions indicated that more than one test location is required to obtain reliable information. The inexpensive and reliable procedure used for making the choice of parents was the determination of breeding values of the parents on the relative performance of their F₂ progeny bulks.Part of the thesis submitted by the senior author in partial fulfillment of the requirements for the Ph. D. degree of the Marathwada Agricultural University, Parbhani, 431 402, India     

Genetic analysis of the effect of zinc deficiency on Arabidopsis growth and mineral concentrations

Aims

Zinc deficiency is a common micronutrient deficiency in plants growing in many different regions of the world and is associated with disturbances in uptake and accumulation of mineral nutrients. Despite many published data on physiological factors affecting ion accumulation in Zn deficient plants, there is very little information about the genetic factors underlying this. We aim to identify genetic loci involved in mineral accumulation and plant performance under Zn deficiency.

Methods

Genetic loci were identified using the genetically segregating Ler × Cvi recombinant inbred line (RIL) population grown under Zn deficient conditions. Lines were analysed for the concentrations of Zn, Fe, Mn, K, Ca, Mg, P, Cu, S and Al in shoot dry matter. The same was done for the same lines grown under Zn sufficient conditions.

Results

We found considerable heritable variation for most mineral concentrations. In general, there was a positive correlation between mineral concentrations. For Zn only condition-dependent QTLs were identified, while for most other mineral concentrations both condition-dependent and -independent QTLs were identified. Several QTLs co-localize, including co-localization to loci controlling shoot biomass and to mineral concentration loci found previously in this and other RIL populations.

Conclusions

There are different genetic loci controlling Zn accumulation under deficient and sufficient Zn supply. Only for few minerals, their accumulation is controlled by Zn-supply-specific loci.     

Inheritance of S-methyl-L-cysteine sulphoxide and thiocyanate contents in forage rape (Brassica napus L.)

Summary Inheritance of thiocyanate and (+)S-methyl-L-cysteine sulphoxide (SMCO) contents were studied in a diallel cross involving five varieties of forage rape. Although both additive and dominance components were significant for the two characters, the greater mean squares of the additive gene effect indicated its greater importance. Non-allelic gene interaction was detected for thiocyanate only. Narrow sense heritability was relatively high for both characters. The general and specific combining ability effects and heterosis of the individual crosses, identified the potential of the cross Nevin × Akela for production of varieties with low thiocyanate content. Thiocyanate and SMCO contents were positively correlated, and they were not correlated with dry matter yield and its components.     

Seasonal Dynamics of the Accumulation, Distribution and Redistribution of Dry Matter and Mineral Nutrients in a Weedy Species of Gladiolus (Gladiolus caryophyllaceus)

The seasonal dynamics of the accumulation, distribution andredistribution of dry matter and 12 mineral nutrients by a weedyspecies of gladiolus (Gladiolus caryophyllaceus) were studiedat Perth, Western Australia, where it has colonized the nutrient-poorsandy soils. Parent corms sprouted in autumn, and the plantshad completed their growth cycle by early summer. The maturereplacement corm had 15-25% of the plant's P, Ca, Na, Zn andCu, 5-15% of its K, N, Cl, Mg, S and dry matter, and < 5%of its Fe and Mn. Seeds had 26% of the plant's dry matter, 60%of its N and P, 21-33% of its S, Mg, Cu and K, 5-20% of itsFe, Mn and Zn, and < 5% of its Ca and Na. The mature vegetativeshoot had 47% of the plant's dry matter and over 40% of eachnutrient, except for N, P and Cu. Phosphorus, K and N were redistributedfrom the parent corm with over 85% efficiency, S, Mg, Zn andCu with 60-70% efficiency, but there was < 10% redistributionof Ca, Na, Cl, Fe and Mn. The efficiency of redistribution fromthe leafy shoot was over 70% for N and P, 29-52% for K, Mg andCu, 16-20% for S, Zn and Cl, but negligible for Ca, Na, Fe andMn. Redistribution from the shoot could have provided the replacementcorm and seeds with 53-98% of their Cu, Mg, N, P and K, and29-38% of their S, Zn and dry matter. Seeds contained over 60%of each nutrient in a capsule, except for Ca, Na and Fe. Redistributionfrom the capsule walls could have provided 13-19% of the P,Cu and Zn, and 3-7% of the N, K, Mg and dry matter accumulatedby seeds. Each plant produced an average of 520 seeds. Removalof flowers and buds at first anthesis resulted in a larger replacementcorm containing a greater quantity of most nutrients, indicatingcompetition between the replacement corm and seeds for nutrients.Redistribution from parent to replacement cormlets in the absenceof shoot and root development was high, with over 50% of thedry matter and each nutrient, except for Ca, being transferred.Concentration of nutrients were low in all organs of G. caryophyllaceus,especially the replacement corm. It was concluded that the effectiveredistribution of key nutrients, such as N and P, to reproductivestructures and tolerance of low internal concentrations of nutrientscontribute to the capacity of G. caryophyllaceus to colonizeand persist on infertile soils.Copyright 1993, 1999 AcademicPress Gladiolus caryophyllaceus, corm, distribution, dry matter, gladiolus, mineral nutrients, nutrient accumulation, nutrient redistribution, seasonal growth, weed     

Varietal differences in uptake and utilization of nitrogen and other macro-elements in seedlings of barley, Hordeum vulgare

Growth and uptake of N, P, S, K, Ca and Mg in barley ( Hordeum vulgare L.) were studied in water culture using young plants of 17 cultivars. Large varietal differences were obtained in dry weight production and mineral accumulation. The differences were not the same for plants grown in high- and low-salt media. For plants grown under both conditions there was a good correlation between dry weight production and total N content. Total shoot contents of K and Ca were closely correlated with shoot dry weight. Utilization of P and S in high- and low-salt plants and Mg in low-salt plants was variable in relation to dry weight production in both types of nutrient conditions. The correlation between dry weight and total content of Mg in high-salt plants was good. These differences in mineral economy between young barley plants were partly caused by varietal differences in relative growth rate, and in high-salt seedlings also by differences in seed content of N. The significance of root size, and of uptake, root-shoot partitioning and use-efficiency of specific elements differed; all four factors were important for P and S, but had varying impact on K, Mg and Ca. For N, differences in root size and ion accumulation were the most important factors causing varietal variation in mineral nutrition. – In a special experiment seedlings of barley were transferred to N-free nutrient solution after six days of adequate N supply. There was no significant varietal differences in use-efficiency ratio of N. Root/shoot partitioning of N was unaffected.     

Accumulation, Partitioning and Redistribution of Dry Matter and Mineral Nutrients in Ixia flexuosa L., with Special Reference to its Cormaceous Habit

The seasonal dynamics of uptake, partitioning and redistributionof dry matter, N, P, K, S, Ca, Mg, Na, Cl, Fe, Zn, Mn and Cuby the cormaceous plant Ixia flexuosa were studied in pot cultureat Perth, Western Australia. Dry matter and P, N, K, Zn andCu were redistributed from the mother corm with about 90 percent net efficiency: there was no net redistribution of Ca,Na, Fe or Mn. The efficiency of redistribution from the leafyshoot to fruits and the new season's corm was 80 per cent forN and P, 24–49 per cent for K, Cu and Zn, and 0–15per cent for Na, Fe, Ca, Mn, Cl, Mg, S and dry matter. Redistributionfrom the mother corm and vegetative organs could have suppliedthe replacement corm, cormlets and fruits with 32–53 percent of their S, K, P, N, Cu and Zn, and 11–25 per centof their Ca, Cl, Mn, Mg and dry matter. The mature replacementcorm had over 60 per cent of the plant's N and P, 25–50per cent of its dry matter, Zn, Cu, Mg, K and Cl, but less than20 per cent of its Ca, Na, Fe and Mn. Each plant produced anaverage of 12 cormlets; these had 35 per cent of the dry matterand 23–47 per cent of the amount of a particular nutrientin the new season's corms. Fruits had less than 16 per centof the dry matter and each mineral in the mature plant. Ratesof mineral intake by Ixia were much lower than reported forcrop plants, and may be related to the long growing season ofthe species. Ixia polystachya L., corm, nutrition, mineral nutrients, nutrient redistribution     

Foliar macronutrient concentrations of forest understorey species in relation to Ellenberg's indices and potential relative growth rate

In order to investigate broad patterns of variation of the foliar mineral nutrient concentrations of herbaceous plant communities in the ground layer of W Europe forests, correlations were examined between Ellenberg's indices (N-index: mineral nitrogen availability, R-index: pH, F-index: soil moisture and L-index: light intensity) and literature values of macronutrient concentrations for 84 forbs and 39 graminoid species. Significant, positive correlations were found between the R-index and the plants' concentration of Ca and K (forbs only) and between the N-index and the plants' concentration of K, P (forbs only) and N (forbs and graminoids). Multiple regressions showed that the N-index was the best predictor of the plants' concentration of N (forbs and graminoids), P (forbs) and Ca (graminoids) and the R-index of the plants' concentration of Ca and K (forbs). The mineral nutrient concentrations of graminoids were lower and less strongly correlated with Ellenberg's indices than those of forbs. It is argued that the mineral nutrient concentrations in the plants match the availability of mineral nutrients in the soil for N, P (N-index) and Ca (R-index), but not for K and Mg. Significant, positive correlations were found between potential relative growth rate and the concentration of some elements (N, P, K and Ca in forbs, Ca and Mg in graminoids). This suggests that the increase in the concentration of these elements in plants along fertility gradients is due, at least partly, to genetically controlled alterations of leaf anatomy associated with increasing potential relative growth rate.     

Genetic variation in Solanum tuberosum group Andigena haploids

Summary A random sample of haploids, derived from 28 parental introductions from Solarium tuberosum Gp. Andigena, was used to estimate the quantitative genetic variation for six traits within this group. The six traits analyzed on a plot mean basis were: total tuber weight, fresh vine weight, total fresh weight (tuber+vine), dry vine weight, total dry matter (tuber+vine) and specific gravity. Progenies were obtained following the North Carolina mating Design I and were evaluated along with the female parental clones at two locations. Components of variance and narrow sense heritabilities were calculated by two methods: Design I and female parent-offspring regression. Heritability estimates calculated by the two procedures were in close agreement for most traits. The estimates for total tuber weight from the Design I procedure were twice that from parent offspring regression. The genetic coefficient of variation for these traits indicated a large amount of total genetic variance in this population. Genetic variability for total tuber weight was mostly additive, while both additive and dominant genetic variances were equally important for the remaining traits.     

Bioconcentration of some macrominerals in soil,forage and buffalo hair continuum: A case study on pasture irrigated with sewage water

The present study aimed to evaluate the bioaccumulation of some macrominerals in grazing buffaloes fed forage irrigated with sewage water or canal water. In particular, the transfer of sodium (Na), magnesium (Mg), potassium (K) and calcium (Ca) from soil to plant and in turn to animals was evaluated under sub-tropical environmental conditions. Samples of soil, forage and buffalo hair were collected and digested by wet method. Sodium and K concentrations were significantly higher in the soil but lower in the forages; however, Mg and Ca concentrations in both soil and forages were higher. The correlation between soil, forage and hair showed an imbalanced flow of Na, Mg and K and a balanced flow of Ca from soil to forage and then to animals. Based on the findings, the highest rates of transfer of minerals were found for sewage water treatment, whereas lowest rates were found for canal water treatment, except for Na. As the transfer of minerals depends on their bioavailability, the highest values may be due to the high rates of mineral uptake by plants. Thus, the high transfer rate of some elements by plants could become toxic in future causing detrimental effect to grazing livestock.     

Taxonomic effect on plant base concentrations and stoichiometry at the tips of the phylogeny prevails over environmental effect along a large scale gradient

Despite the well‐known importance of all elements to plant growth and nutrient fluxes in ecosystems, most studies to date have been restricted to the roles of foliar nitrogen (N) and phosphorus (P). Much less is known about cycling and pools of base cations in ecosystems and the drivers of variation in cation concentrations among plant species, even though these cations are paramount for plant and ecosystem function. In particular, little is known about the contributions of taxonomic position and environmental variation on base cation concentrations. The extent to which concentrations of elements in plants are determined by phenotypic response to their availability in current environments versus by inherent species‐specific uptake and processing adaptations, should be most directly evident at the tips of the phylogeny, where inherent variation among species should reflect relatively recent adaptation to environmental variation since their common ancestry. To test this hypothesis, we explored the geographic pattern and the effects of taxonomy, climate and soil on concentrations and stoichiometry of the base cations potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg) across a lineage of Artemisia species and their close relatives across northern China. We found that species identity explained the largest proportion of the total variance for all four base cations (38.3–53.8%) and their stoichiometry (35.2–59.6%). K, Na and Ca concentrations increased significantly with climate seasonality, while Ca concentration decreased with annual temperature and precipitation. Plant K concentration, K:Ca and K:Mg were negatively correlated with soil organic carbon concentrations, but positively with soil pH. Our results suggest that taxonomy still needs to be fully considered for interpreting variation in vegetation nutrition and stoichiometry along broad geographical gradients even for species at the tips of the phylogeny.     

锐齿栎林个体光合器官生长与营养季节动态

锐齿栎林单叶面积和干重的季节生长呈不同的S型曲线,叶面积叶干重比的季节变化呈不完全S型.叶从萌动到落叶持续约160d,展叶第1周,叶重量绝对增长快于叶面积的增加,之后相反.叶季节变化表现为叶面积增长迅速且持续时间较短,叶重量增加相对缓慢且持续时间较长.刚展叶时N、P、K含量很高,展叶期明显下降,落叶前最低,Ca含量季节变化则相反;Mg含量展叶期较高,之后逐渐下降且趋于稳定.叶N、P、K、Mg间呈显著的正相关,前者与Ca间呈显著的负相关.叶在生长期内具有较高的N/P、N/K,且其季节变化比单个元素含量更稳定;展叶初期K/Ca很高,之后变化逐渐稳定;叶K/Mg的季节变化趋于降低.展叶第1周叶N、P、K和Mg积累量迅速增加,继而缓慢增加,第45～50天达峰值,之后逐渐降低;Ca积累随叶龄的增加一直处于上升的趋势.叶内N、P、K、Mg和Ca积累量与叶的生长发育期有密切的关系.     

Epistasis in the expression of relevant traits in cassava (Manihot esculenta Crantz) for subhumid conditions

There is limited knowledge on the inheritance of agronomic traits in cassava and the importance of epistasis for most crops. A nine-parent diallel study was conducted in subhumid environments. Thirty clones were obtained from each F1 cross. Each clone was represented by six plants, which were distributed in three replications at two locations. Therefore the same 30 genotypes of each F1 cross were planted in the three replications at the two locations. Analysis of variance suggested significant genetic effects for all variables analyzed (reaction to thrips, fresh root and foliage yields, harvest index, dry matter content, and root dry matter yield). Significant epistatic effects were observed for all variables, except harvest index. Dominance variance was always significant, except for dry matter content and dry matter yield. Additive variance was significant only for reaction to thrips. Results suggested that dominance plays an important role in complex traits such as root yield. The significance of epistasis can help us understand the difficulties of quantitative genetics models and QTLs in satisfactorily explaining phenotypic variation in traits with complex inheritance. Significant epistasis would justify the production of inbred parental lines to fix favorable allele combinations in the production of hybrid cassava cultivars.     

Potassium and magnesium relationship in cowpea (Vigna unguiculata (L.) Walp.)

Summary The effects of K and Mg application on dry matter yield and uptake of K, Mg and Ca in cowpea were studied in greenhouse at Haryana Agricultural University, Hissar (india). Dry matter yields of leaves, stems and roots increased by 17, 30 and 27 per cent over control due to application of 150 ppm K and 17, 16 and 26 per cent by 40 ppm Mg respectively. Potassium application has antagonistic effect on Ca concentration of leaves, stems and roots and synergistic on root Mg concentrations upto 25 ppm K. However, Mg had a synergistic effect on concentration of K upto 20 ppm Mg and antagonistic at 40 ppm Mg in all plant parts. Uptake of K, Mg and Ca increased by Mg application, but K increased only K uptake.     

Minerals and dry matter in coastal scrub and grassland at Sydney,Australia

Summary Two adjacent coastal ecosystems, dry sclerophyll scrub and introduced grassland, were sampled two (grassland) or three (scrub) times throughout one year to estimate total and component dry matter and mineral contents. The soil was the major mineral pool in both ecosystems and contained at least 60% of all minerals except potassium. The scrub live plus dead biomass amounted to 150 t ha^-1 of which half was below ground. The distribution of minerals was similar to that of biomass. In the grassland 70% of the biomass was below ground but only half the biotic minerals were located here. Although the grassland total live plus dead biomass was one-sixth that of the scrub, mineral amounts in the biomass ranged between one-third (N) and one-twentieth (Ca) of the amounts in the scrub. Leaf concentrations of N, P, and K were lower in most scrub species than in the grass while leaf Ca and Mg were generally higher in the scrub than in the grass.     

Shoot calcium and magnesium concentrations differ between subtaxa, are highly heritable, and associate with potentially pleiotropic loci in Brassica oleracea

Calcium (Ca) and magnesium (Mg) are the most abundant group II elements in both plants and animals. Genetic variation in shoot Ca and shoot Mg concentration (shoot Ca and Mg) in plants can be exploited to biofortify food crops and thereby increase dietary Ca and Mg intake for humans and livestock. We present a comprehensive analysis of within-species genetic variation for shoot Ca and Mg, demonstrating that shoot mineral concentration differs significantly between subtaxa (varietas). We established a structured diversity foundation set of 376 accessions to capture a high proportion of species-wide allelic diversity within domesticated Brassica oleracea, including representation of wild relatives (C genome, 1n = 9) from natural populations. These accessions and 74 modern F(1) hybrid cultivars were grown in glasshouse and field environments. Shoot Ca and Mg varied 2- and 2.3-fold, respectively, and was typically not inversely correlated with shoot biomass, within most subtaxa. The closely related capitata (cabbage) and sabauda (Savoy cabbage) subtaxa consistently had the highest mean shoot Ca and Mg. Shoot Ca and Mg in glasshouse-grown plants was highly correlated with data from the field. To understand and dissect the genetic basis of variation in shoot Ca and Mg, we studied homozygous lines from a segregating B. oleracea mapping population. Shoot Ca and Mg was highly heritable (up to 40%). Quantitative trait loci (QTL) for shoot Ca and Mg were detected on chromosomes C2, C6, C7, C8, and, in particular, C9, where QTL accounted for 14% to 55% of the total genetic variance. The presence of QTL on C9 was substantiated by scoring recurrent backcross substitution lines, derived from the same parents. This also greatly increased the map resolution, with strong evidence that a 4-cM region on C9 influences shoot Ca. This region corresponds to a 0.41-Mb region on Arabidopsis (Arabidopsis thaliana) chromosome 5 that includes 106 genes. There is also evidence that pleiotropic loci on C8 and C9 affect shoot Ca and Mg. Map-based cloning of these loci will reveal how shoot-level phenotypes relate to Ca(2+) and Mg(2+) uptake and homeostasis at the molecular level.     

Comparative mapping of fiber,protein, and mineral content QTLs in two interspecific <Emphasis Type="Italic">Leymus</Emphasis> wildrye full-sib families

Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral content are important components of forage quality in grasses. Elevated [K]/([Ca] + [Mg]) ratios (KRAT) substantially increase the risk of grass tetany (hypomagnesemia) in grazing animals, which is a serious problem associated with some cool-season grasses. The objectives of this study were to map and compare QTLs controlling concentrations of CP, NDF, ADF, Al, B, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, P, S, Si, Zn, and KRAT in two full-sib Leymus triticoides × (L. triticoides × L. cinereus) TTC1 and TTC2 families. Significant genetic variation and QTLs were detected for all traits, with evidence of conserved QTLs for ADF (LG1a, LG5Xm, LG7a), NDF (LG7a), Ca (LG1b), CP, (LG5Xm), KRAT (LG3b, LG6b, LG7a, LG7b), Mn (LG2b, LG3b, LG4Xm), and S (LG3a) content in both TTC1 and TTC2 families. Moreover, the direction of QTL effects was the same for 13 of the 14 homologous QTLs in both families. The TTC1 and TTC2 KRAT QTLs on LG7a and LG7b were located near markers defining homoeologous relationships between the sub-genomes of allotetraploid Leymus, suggesting possible QTL homoeology. Another 88 QTLs were unique to one family or the other, but many of these clustered in genome regions common between the two families. These results will support development of new Leymus wildrye forages and help characterize genes controlling mineral uptake and fiber synthesis.     

Nutrient content and dynamics in north Swedish shrub tundra areas

Forbs and leaves of deciduous shrubs had high concentrations of Ca, Mg, K, P, and N. Deciduous dwarf shrubs had intermediate concentrations but higher than evergreen dwarf shrubs. Monocots, cryptogams, woody and belowground tissues had low concentrations.
Plant nutrient concentrations and nutrient content in soil organic matter increased from dry towards moist tundra areas.
The residence time of nutrients was considerably less than ten years in surface litter, but several decades or centuries in total organic matter. The longest residence time was found in the moist part of the tundra.
N, K, and P in Betula nana leaves were translocated to a great extent prior to leaf fall, whereas Mg and particularly Ca were only slightly translocated. As on other tundra areas shortage of nutrients probably limits plant growth. In that case short supply of N and F seems most probable due to retention in litter and soil organic matter.     

Mg content of healthy and chronically diseased human cancellous bone in relation to age and some physical and chemical factors

The magnesium (Mg) content of human cancellous bone was studied in relation to its elemental composition and mineral density. The material was collected from 138 cadavers consisting men and women of different ages. Duplicate specimens from anterior iliac crest (one macerated and one fixed with alcohol) were obtained from individuals who had died suddenly or whose deaths were due to chronic immobilizing diseases. The cation concentrations were analyzed with an atomic absorption spectrophotometer, fluoride with the ion specific electrode, from macerated samples. The samples fixed in alcohol were used for determination of the mineral density with gamma rat attenuation. The mean Mg concentration (+/- SD) was 2.84 +/- 0.29 mg/g in the samples obtained from individuals who had died suddenly with no correlation with age. In the group with chronic diseases the mean Mg levels decreased slightly with increasing age. There was a significant, positive correlation between the Mg and Ca concentrations. In the linear regression analysis 16.4% of the variance of Mg concentration was accounted for by Ca. This relationship was more evident in men than in women. Only the postmenopausal women suffering from chronic diseases and having bone loss showed correlation between the bone Mg and Ca contents. The Mg/Ca ratio in men was quite constant and did not change significantly with age. In women the Mg/Ca ratio versus age showed no statistically significant relationship. The correlation between Mg and other elements was weak. The weak relationships between F and Zn to Mg clearly have no significant effect on the contents of these elements in bone.