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

WOS: 000176778900009Using two bread wheat (Triticum aestivum) and two durum wheat (Triticum durum) cultivars differing in zinc (Zn) efficiency, uptake and translocation of foliar-applied Zn-65 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 (ZnSO4)-Zn-65 to leaf strips in a short-term experiment. Also with supply of (ZnSO4)-Zn-65 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 Zn-65 from the treated leaf to the roots and remainder parts of shoots. In Zn-deficient plants about 40% of the total absorbed Zn-65 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 Zn-65 of the total absorbed Zn-65 was about 25%. Although differences in Zn efficiency existed between the cultivars did not affect the translocation and distribution of Zn-65 between roots and shoots. Bread wheats compared to durum wheats, tended to accumulate more Zn-65 in shoots and less Zn-65 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 Zn-65 within plants. Differential compartementation of Zn at the cellular levels is discussed as a possible factor determining genotypic variation in Zn efficiency within wheat

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.Deutsche ForschungsgemeinschaftThis study was supported by German Research Council (DFG)

Increasing the efficacy of the tests for outliers for geodetic networks

Outliers in geodetic networks badly affect all parameters and their variances estimated by least-squares. Tests for outliers (e.g. Baarda’s and Pope’s tests) are frequently used to detect outliers in geodetic networks. To measure the ability of these tests, the mean success rate (MSR) is proposed. Studies have shown that the MSRs of these tests in geodetic networks are low due to the smearing effect of the least-squares estimation even if there is only one outlier in the data set. In this paper, a new approach, for small outliers, is presented to increase the MSRs of the tests for outliers in geodetic networks. The main idea is that if the weight of one observation is increased, the corresponding studentized or normalized residuals are increased, too. This thesis is proved. Hence, the ability of the tests to detect outliers can be increased by appropriately increasing the weight of one observation at a time and repeating this for all observations. This approach is applied to three simulated geodetic networks. We show that the MSRs of the outlier tests are improved by approximately 5% if there is one small outlier in the data set. However, the improvements in the MSRs for more than one outlier are low

Phytosiderophore release in Aegilops tauschii and Triticum species under zinc and iron deficiencies

PubMedID: 11432925Using three diploid (Triticum monococcum, AA), three tetraploid (Triticum turgidum, BBAA), two hexaploid (Triticum aestivum and Triticum compactum, BBAADD) wheats and two Aegilops tauschii (DD) genotypes, experiments were carried out under controlled environmental conditions in nutrient solution (i) to study the relationships between the rates of phytosiderophore (PS) release from the roots and the tolerance of diploid, tetraploid, and hexaploid wheats and Ae. tauschii to zinc (Zn) and iron (Fe) deficiencies, and (ii) to assess the role of different genomes in PS release from roots under different regimes of Zn and Fe supply. Phytosiderophores released from roots were determined both by measurement of Cu mobilized from a Cu-loaded resin and identification by using HPLC analysis. Compared to tetraploid wheats, diploid and hexaploid wheats were less affected by Zn deficiency as judged from the severity of leaf symptoms. Aegilops tauschii showed very slight Zn deficiency symptoms possibly due to its slower growth rate. Under Fe-deficient conditions, all wheat genotypes used were similarly chlorotic; however, development of chlorosis was first observed in tetraploid wheats. Correlation between PS release rate determined by Cu-mobilization test and HPLC analysis was highly significant. According to HPLC analysis, all genotypes of Triticum and Ae. tauschii species released only one PS, 2'-deoxymugineic acid, both under Fe and Zn deficiency. Under Zn deficiency, rates of PS release in tetraploid wheats averaged 1 µmol (30 plants)-1 (3 h)-1, while in hexaploid wheats rate of PS release was around 14 µmol (30 plants)-1 (3 h)-1. Diploid wheats and Ae. tauschii accessions behaved similarly in their capacity to release PS and intermediate between tetraploid and hexaploid wheats regarding the PS release capacity. All Triticum and Aegilops species released more PS under Fe than Zn deficiency, particularly when the rate of PS release was expressed per unit dry weight of roots. On average, the rates of PS release under Fe deficiency were 3.0, 5.7, 8.4, and 16 µmol (30 plants)-1 (3 h)-1 for Ae. tauschii, diploid, tetraploid and hexaploid wheats, respectively. The results of the present study show that the PS release mechanism in wheat is expressed effectively when three genomes, A, B and D, come together, indicating complementary action of the corresponding genes from A, B and D genomes to activate biosynthesis and release of PS.Deutsche ForschungsgemeinschaftThis work was supported by the TUBITAK (Scientific and Technical Research Council of Turkey) and DFG (Deutsche Forschungsgemeinschaft)

Light-mediated release of phytosiderophores in wheat and barley under iron or zinc deficiency

The effect of varied light intensity (50 - 600 µmol m-2 s-1) on the rate of phytosiderophore release was studied under zinc (Zn) deficiency using a bread (Triticum aestivum L. cv. Aroona) and a durum wheat cultivar (Triticum durum Desf. cv. Durati) differing in zinc (Zn) efficiency and under iron (Fe) deficiency using a barley cultivar (Hordeum vulgare L. Europe). Plants were grown under controlled environmental conditions in nutrient solution for 15 days (wheat plants) or 11 days (barley plants). Phytosiderophore release was determined by measuring capacity of root exudates to mobilize copper (Cu) from a Cu-loaded resin. With increasing light intensity visual Zn deficiency symptoms such as whitish-brown lesions on leaf blade developed rapidly and severely in wheat, particularly in the durum cultivar Durati. In wheat plants supplied well with Zn, increases in light intensity from 100 to 600 µmol m-2 s-1 did not clearly affect the rate of phytosiderophore release. However, under Zn deficiency increases in light intensity markedly enhanced release of phytosiderophores in Zn-deficient Aroona, but not in Zn-inefficient Durati. When Fe-deficient barley cultivar Europe was grown first at 220 µmol m-2 s-1 and then exposed to 600µmol m-2 s-1 for 24 and 48 h, the rate of release of phytosiderophores was enhanced about 4-fold and 7-fold, respectively. Transfer of Fe-deficient plants from 600 to 50 µmol m-2 s-1 for 48 h reduced the rate of release of phytosiderophores by a factor of 7. The effect of light on phytosiderophore release was similar regardless of whether the rate of phytosiderophore release was expressed per plant or per unit dry weight of roots. The results demonstrate a particular role of light intensity in phytosiderophore release from roots under both Zn and Fe deficiency. It is suggested that in the studies concerning the role of phytosiderophore release in expression of Zn or Fe efficiency among and within cereals, a special attention should be given to the light conditions.California Department of Fish and GameThis study was supported by NATO’s Scientific Affairs Division in the framework of the Science for Stability Programme and by DFG (Deutsche Forschungs-gemeinschaft)

Effect of iron end zinc deficiency on release of phytosiderophores in barley cultivars differing in zinc efficiency

Using two barley (Hordeum vulgate L.) cultivars differing in Zn efficiency (Tarm-92: Zn-efficient; Hamidiye-79: Zn-inefficient), the effect of varied zinc (Zn) and iron (Fe) supply on the rate of phytosiderophore release was studied under controlled environmental conditions in nutrient solution during the 20 days of growth. Visual Zn deficiency symptoms such as inhibition in shoot length and development of necrosis and reddish-brown lesions on leaves, mainly along the leaf edges and tips, were first and more distinctly observed in Hamidiye-79 than in Tarm-92. However, in both cultivars shoot and root growth was similarly affected by Zn deficiency. Under Fe deficiency, Tarm-92 and Hamidiye-79 did not differ in severity and development time of leaf chlorosis as well as decreases in shoot and root growth. In plants supplied adequately with Zn and Fe, the release rate of phytosiderophores was very low and could not exceed 1 µmol 42 plants-1. 3h-1. However, under Zn deficiency and especially Fe deficiency the plants showed marked increases in rate of phytosiderophore release. Under Fe deficiency, Tarm-92 and Hamidiye-79 were more or less similar in their capacity to release phytosiderophores. The maximal rate of phytosiderophore release under Fe deficiency was, on average, 20 µmol per 42 plants and 3h for both cultivars. In the case of Zn deficiency, Zn-efficient Tarm-92 released higher amounts of phytosiderophores than Zn-inefficient Hamidiye-79. The rate of phytosiderophore release under Zn deficiency reached maximal values of 7 µmol for Tarm-92 and 3 µmol for Hamidiye-79, expressed per 42 plants and 3h. The presented results indicate a possible role of phytosiderophores in Zn efficiency in barley. The role of phytosidrophores was discussed in terms of enhancements in solubility and mobility of Zn both in the rhizosphere and within the plants. The results also demonstrate that the release of phytosiderophores from roots of graminaceous species is not solely a specific response to Fe deficiency; It is also an adaptive response occurring under Zn deficiency