Fe,Mn and the grey effect in hydroponically-cultured flue-cured tobacco

A study of the influence of Fe or Mn (supplied as 5, 20, 35, 50 or 65 ppm) on the grey disorder in flue-cured tobacco (Nicotiana tabacum L.) was conducted with mater-cultured plants grown under greenhouse conditions and fertilized with Hoagland's nutrient solution. The solution was highly unbuffered as is the podzolic soil in which grey tobacco plants grow. When plants were treated with 5 to 35 ppm Fe, the trend in grey index (a measure of grey tobacco symptoms) in top and middle leaves was similar to the trend in Fe content of tobacco leaves. The highest grey index was found in these leaf positions with the 35 ppm Fe treatment. When Fe in solution was increased from 35 to 65 ppm grey index in top leaves decreased but was unchanged in middle leaves. Leaf Fe content for these leaf positions changed little. No apparent relationship between grey index and Fe in bottom leaves was observed. Initially, pH of the nutrient solution increased from a mean of 4.75 to 6.50 (indicating preferential anionic absorption) followed by an abrupt decrease in pH to 4.2 (suggesting preferential cationic absorption which included the Fe treatment in solution). The grey effect identical to that found in field-grown plants developed in the cured leaf of plants treated with high levels of Fe and was considered to be one of the major causal agents in grey flue-cured tobacco. None of the levels of Mn induced the grey effect.     

Effect of silicon on manganese tolerance of bean plants (Phaseolus vulgaris L.)

Summary The effect of silicon on manganese tolerance of bean plants (Phaseolus vulgaris L. var. ‘Red Kidney’) grown in water culture was studied at different levels of manganese supply. Without silicon, growth depression and toxicity symptoms occurred already at 5 × 10⁻⁴ mM Mn in the nutrient solution. After addition of Aerosil (0.75 ppm Si), the plants tolerated 5 × 10⁻³ mM Mn and, at a higher silicon supply of 40 ppm, as much as 10⁻² mM Mn in the nutrient solution without any growth depression. This increase in manganese tolerance was not caused by a depressing effect of silicon on uptake or translocation of manganese but rather by an increase in the manganese tolerance of the leaf tissue. In absence of silicon, 100 ppm Mn was already toxic for the leaf tissue, whereas with a supply of 40 ppm Si, this ‘critical level’ in the leaves was increased to more than 1000 ppm Mn. At lower manganese levels in the leaf tissue, a molar ratio Si/Mn of 6 within the tissue was sufficient to prevent manganese toxicity. Above 1000 ppm Mn, however, even a much wider Si/Mn ratio (> 20) could not prevent growth depression by manganese toxicity. With⁵⁴Mn and autoradiographic studies, it could be demonstrated that, in absence of silicon, even at optimal manganese supply (10⁻⁴ mM), the distribution of manganese within the leaf blades was inhomogeneous and characterized by spot-like accumulations. In presence of silicon, however, the manganese distribution was homogeneous in the lower concentration range of manganese and still fairly homogeneous in the high concentration range. This effect of silicon on manganese distribution on the tissue level was also reflected on the cellular level. In the presence of silicon, a higher proportion of the leaf manganese could be found in the press sap,i.e., had been transported into the vacuoles, than in the absence of silicon. The increase in manganese tolerance of bean leaves by silicon therefore seems to be primarily caused by the prevention of local manganese accumulation within the leaf tissue which leads to local disorders of the metabolism and, correspondingly, growth depression.     

Litterfall and nutrient returns in red alder stands in western Washington

Summary Litterfall was collected over 1 year from eight natural stands of red alder growing on different sites in western Washington. The stands occurred at various elevations and on different soils, and differed in age, basal area, and site index. Most litterfall was leaf litter (average 86 percent). Amounts of litterfall and leaf litter varied significantly (P<0.05) among the sites. Average weights of litterfall and leaf litter in kg ha^–1 yr^–1, were 5150 and 4440, respectively. Weight of leaf litter was not significantly (P<0.05) related to site index, stand age, or basal area. The sites varied significantly (P<0.05) in concentrations of all elements determined in the leaf litter, except Zn. Average chemical concentrations were: N, 1.98 percent; P, 0.09 percent; K, 0.44 percent; Ca, 1.01 percent; Mg, 0.21 percent; S, 0.17 percent; SO₄–S, nil; Fe, 324 ppm; Mn, 311 ppm; Zn, 53 ppm; Cu, 13 ppm; and Al, 281 ppm. There were significant correlations between some stand characteristics and concentrations of some elements, and among the different chemical components of the leaf litter. Important correlations were found between stand age and P concentration (r=–0.84,P<0.01); weight of leaf litter and P concentration (r=0.74,P<0.05); weight of leaf litter and K concentration (r=0.71,P<0.05); concentrations of N and S (r=0.81,P<0.05); and concentrations of Fe and Al (r=0.98,P<0.01). Returns of the different elements to the soil by leaf litter varied among the different sites. Average nutrient and Al returns, in kg ha^–1 yr^–1, were: N, 82; Ca, 41; K, 19; Mg, 8; S, 7; P, 4; Fe, 1; Mn, 1; Al, 1; Zn, 0.2, and Cu, <0.1.     

Influence of temperature on the expression of manganese toxicity by two soybean varieties

Summary Two soybean varieties (Glycine max) were grown in nutrient solution to investigate their response to manganese toxicity at two different temperature regimes. Dry matter yields of both varieties were markedly reduced by lower temperature (21°C day/18°C night). At these temperatures leaf crinkle symptoms of Mn toxicity were very severe on Bragg and moderate on Lee at high levels of Mn in solution (15 ppm). However increasing the temperature to 33°C day/28°C night completely eliminated symptoms on both varieties. High levels (15 ppm) of Mn in nutrient solution decreased yields of both varieties at low temperature with Bragg showing the greater reduction. At high temperature neither variety showed yield reductions at 15 ppm Mn. Higher concentrations of Mn in shoots and roots were obtained at higher temperature, indicating that increased tolerance was not associated with lower plant Mn levels. Lee consistantly contained higher levels of Mn in the shoots than Bragg in the 15 ppm Mn solution at both temperatures although appearing to be more tolerant at low temperatures. The implications of these results for environmental effects on the expression of Mn toxicity in the field are discussed. re]19751202     

Chemical composition of five deciduous tree species in four-year-old,closely spaced plantations

Summary Contents of N, P, K, Ca, Mg, and Mn in aboveground tree components of five deciduous species were determined in closely-spaced (0.9×0.6 m) 4-year-old plantations growing on a river terrace site in the Ohio Valley region of western Kentucky (USA). Species evaluated were: a hybrid poplar, American sycamore, European alder, river birch and green ash. The only significant difference in dry weight of tree components was greater bolebark biomass of the hybrid poplar. Total aboveground elemental content of N, K, Ca, and Mn varied significantly for some species. N content of green ash was significantly lower and K content of the hybrid poplar and Mn content of European alder were significantly greater compared with the other species. Ca contents of the hybrid poplar, American sycamore and European alder were significantly greater than those of other species. Based on the relationship between biomass production and nutrient content of the harvested biomass, it seems that on this and comparable sites, river birch is a preferred species in view of the lower potential nutrient removals in the harvested biomass.The investigation reported in this paper (79-8-129) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with approval of the Director.     

Growth and ion uptake by maize seedlings on solutions variable in calcium and flow rate

Summary Growth and ion uptake by maize seedlings was studied as functions of calcium concentration and rate of flow of nutrient solutions. With calcium concentrations established at 1, 10, and 100 ppm Ca, all other nutrients being kept at constant concentration, the solutions passed through narrow culture trays at velocities of 2, 8, and 24 liter/day.Fresh and dry weights of seedlings increased as the concentration of calcium increased from 1 to 10 or 100 ppm for any value ofV.Positive response in the plant calcium content was particularly noticed when Ca increased to 100 ppm in the nutrient solution. Phosphorus content of tops decreased with increasing (Ca) in the nutrient solution, while the other elements were more or less unaffected. In the case of roots, phosphorus was generally increased, iron decreased and potassium showed inconsistent trends.Estimates of the uptake efficiency relative to calcium were made by calculating the ratio of the amount of calcium taken up by the entire seedling to the product of calcium concentration and daily flow rate of the solution. It appears that the uptake efficiency diminishes with increasing flow rate. Other instances points to the maintenance of the same uptake efficiency as (Ca) increased with the decreasingV or vice versa. These observations point to the critical nature of environmental factors on the effective contacts between supply and uptake belts that have been adopted as model in this study.     

甜橙叶片营养元素适宜含量的研究

本研究探讨闽南甜橙主栽品种(印子柑、改良橙、伏令夏橙)叶片营养元素含量的适宜范围。结果表明,各品种不同地点、年份的叶片元素含量存在明显差异,而三个甜橙品种间叶片元素含量未见稳定的差异,因此,作者认为,可建立三个甜橙品种通用的叶片营养元素含量适宜标准。统计分析表明:其叶片毛素含量的变异系数,大量元素以氮、磷较小,镁、钾、钙较大;微量元素多高于大量元素。本文初步提出甜橙于片元素的适宜含量:氮2.50％～3.30％,磷0.12％～0.18％,钾1.00％～2.00％,钙2.00％～3.50％,镁0.22％～0.40％,铜4.0～18.0ppm,锌25.0～70.0ppm,锰20.0～100.0ppm,铁90.0～160.0ppm,硼25.0～100.0ppm。大量元素含量的适宜比值为氮:磷:钾:钙:镁=1:0.05:0.5:2:0.95:0.11。上列指标可供甜橙营养诊断指导合理施肥之参考。     

Distribution of selected elements within flax plants as affected by FeEDDHA

Summary Flax growing on a calcareous soil in the greenhouse developed Mn toxicity symptoms. The toxicity was eliminated by application of 2 ppm FeEDDHA-Fe. FeEDDHA had major effects on distribution of Mn, Zn, Fe and P among selected plant parts. Application of the chelate reduced Mn concentration in older leaves, the tissue most susceptible to Mn toxicity, associated stem tissue, plant tops, and roots from 2295 to 133 ppm, 62 to 7 ppm, 550 to 34 ppm, and 42 to 34 ppm, respectively. Analysis of older leaves is recommended for diagnosing Mn toxicity in flax.FeEDDHA reduced Zn concentration in plant tops and this was chiefly reflected in greatly reduced leaf concentrations, especially in older leaves. FeEDDHA increased plant Fe concentration and the effect was greatest in root and older leaf tissues. The overall effect of FeEDDHA on P concentration was small but large increases occurred in younger leaf tissue due to application of the chelate. Relative distributions of K, Na, Ca, and Mg among plant parts were only slightly affected by FeEDDHA.     

Influence of iron and pH on the yield and iron,manganese, zinc,and sulfur concentrations of carrots grown on sphagnum peat soil

Summary In two greenhouse experiments, sphagnum peat, adjusted to various pH levels, was used to study the effect of various levels of Fe on the growth of carrots (Daucus carota L., var. sativa D.C.). The Fe was added to the medium as sequesterine 330 chelate. Maximum carrot root and top tissue yields were obtained at soil pH 6.6 and 7.1. At soil pH 5.2 and 7.8 the yields were in the intermediate range. The yields were low at pH 4.3, 4.5 and 8.1 and at pH 8.4 the carrots did not grow. The chlorotic symptoms on carrot leaves, accom-panied by reduced yields, were associated with 39 to 82 ppm Fe and > 332 ppm Mn in the leaf and were likely due to Mn toxicity. Toxic levels of Mn in tissue were found even at soil pH 8.1 and were associated with reduced carrot yields. The leaf tissue concentrations of Fe and Mn decreased as the pH of soil increased; however, at pH 5.2, 7.8, and 8.1 the tissue Mn concentration increased. The added Fe had no effect on the Fe concentration but decreased the Mn and Zn concentration of leaf tissue and increased carrot root yields. There was a significant interaction between added lime and Fe, whereby the decrease in leaf tissue Mn concentration and increases in root yields with added Fe were much greater at pH 4.5 and 5.2 than at pH values of 6.6 and 7.8. The S concentration in the leaf tissue decreased with added Fe and lime. The leaf tissue Zn concentrations of 184 to 490 ppm and S concentrations of 0.32 to 0.63%, as found here, are considered to be high but not in the toxic range.Contribution No. 321, Research Station, Charlottetown, P.E.I. and No. 1534, Research Station, Kentville, N.S.Contribution No. 321, Research Station, Charlottetown, P.E.I. and No. 1534, Research Station, Kentville, N.S.     

Macronutrient content in leaves of bean plants (Phaseolus vulgaris,L.) grown with differents rates of N/S as fertilizers

Summary The effect of increasing rates of nitrogen (N) and sulphur (S) as fertilizers on the yield, leaf area and N, P, S, Ca, Mg, NO₃ ⁻ and SO₄ ⁼ content in leaves of bean (Phaseolus vulgaris, L.) were studied in a hydroponic culture experiment under greenhouse conditions. Bean plants responded significantly to all treatments with differents N/S ratios. When plants grew with high N/S ratios, the leaf content of N, Ca and NO₃ ⁻ increased while the content of K, P and SO₄ ⁼ decreased. However, optimal yield and leaf area were not obtained. Optimal leaf and fruit dry matter was obtained at N/S ratio value of 1.41. When lower N/S rates were used, optimal leaf and fruit dry matter was only observed when the leaf N/S ratio was between 15 and 16. At high sulphate levels in the nutrient solution there is no interaction with nitrate which is easily observed, resulting in an increase in yield. An interaction between nitrate and sulphate in the nutrient solution was found at a N/S ratio of 0.81 which produced in leaves a synergic effect between P-K, an antagonistic effect between N-P and N-K and a lower yield. This research was supported by Fundacion ‘Ramon Areces’.     

Allometry of Salsola collina in response to soil nutrients,water supply and population density

The allometry of greenhouse‐grown Salsola collina Pall. in response to variation in soil nutrient content, water supply and population density has been compared. The results showed that the biomass allocation was size‐dependent. Root, stem, leaf and reproductive allocation showed a ‘true’ plasticity in response to soil nutrient variation. At low soil nutrient content, plants tended to allocate more biomass to the development of reproductive organs than to stem and leaf, but root allocation was consistent due to a tradeoff between the effects of plant size and soil nutrient content. The plasticity of stem allocation and reproductive effort was ‘true’, while the plasticity of root allocation was ‘apparent’, but there was no plasticity for leaf allocation in response to soil water variation. At lower soil water content, plants tended to allocate more biomass to the stem than to development of reproductive organs. With the exception of ‘apparent’ plasticity of root allocation, no plasticity was detected in biomass allocation when population density was varied.     

Effect of typhoon disturbance on fine litterfall and related nutrient input in a subtropical forest on Okinawa Island, Japan

Typhoons are frequent on Okinawa Island, southwestern Japan. The effects of typhoon disturbance on the patterns of fine litterfall and related nutrient inputs in a subtropical evergreen broad-leaved forest were studied over 5 years from May 1996 to April 2001. Annual fine litterfall averaged 7558 kg ha⁻¹ (range from 6188 to 9439 kg ha⁻¹) for six sampling plots over 5 years, which differed significantly among years (p<0.001) but not among plots (p=0.122). A seasonal maximum was most evident for leaf litter component. Woody litter fell more irregularly through the year, and peak fall varied with typhoon and windstorm. The mean ratio of annual litterfall mass of sexual organs to leaves was 0.06, much lower than that in other tropical and subtropical rain forests. Nutrient concentrations varied in litterfall components, but were not significantly different among plots. The lowest concentrations of N and P in leaf litter were observed in March, which is also the month with the greatest leaf fall. However, the highest concentrations were recorded in typhoon season. Nitrogen and P concentrations were 34% and 106% greater in the green leaves that fell during typhoons than in senescent leaves. Mean nutrient inputs by litterfall were: N 83, P 3.2, K 25, Ca 71, Mg 19, Al 12, Na 10, Fe 0.86 and Mn 3.9 kg ha⁻¹ yr⁻¹, and differed significantly among years for all elements (p<0.0005) and among plots only for K (p<0.05) and Mn (p<0.0001). Typhoon disturbance strongly affected annual fine litterfall and related nutrient inputs, which contributed an average of 30% of the annual litterfall mass, and from 30% to 39% (for different nutrient elements) of annual total nutrient inputs. The results from this study suggest that typhoon-driven maintenance of rapid cycling of P and N and their high availability in soil appears to be an important mechanism to maintain productivity in the subtropical forest on Okinawa Island.     

元谋干热河谷燥红土和变性土上植物叶片的元素含量及其重吸收效率

采用盆栽试验,研究元谋干热河谷燥红土和变性土上生长的植物叶片以及凋落叶营养元素含量,并分析养分重吸收效率对土壤类型与物种互作的响应.结果表明: 土壤类型对叶片N、P、Ca、Mg、Cu、Zn、Fe、N∶P以及凋落叶N、P、Mn、N∶P均有显著影响;燥红土植物叶片与凋落叶N、Mn含量和N∶P显著高于变性土,而燥红土植物叶片P、Ca、Mg、Fe、Cu、Zn和凋落叶P含量显著低于变性土.燥红土植物叶片N含量较变性土高34.8%,而P含量低40.0%;在叶片凋落时,N、P、K表现为重吸收,而其他元素呈富集状态.燥红土凋落叶Ca、Mg、Mn富集系数显著高于变性土.物种仅对叶片N含量有显著影响,物种与土壤交互作用对植物叶片和凋落叶元素含量影响不显著,表明各土壤类型对不同物种元素含量的影响方式较为一致.土壤类型对植物元素含量的影响可进一步作用于干热河谷植物凋落物分解、植物-土壤的养分反馈以及生物地球化学循环.     

不同竹龄雷竹中硅及其他营养元素吸收和积累特征

在浙江省临安市的雷竹主产区,分别采集不同竹龄(1～4 a)和不同器官(叶、枝、秆)的雷竹样品,分析了Si和其他营养元素含量、吸收和积累特征,以及Si和其他营养元素之间的相互关系.结果表明： 雷竹各器官中C含量的大小顺序为竹秆>竹枝>竹叶,Si、N、P、K、Ca、Mg、Al、Fe和Mn含量的大小顺序为竹叶>竹枝>竹秆.除Mn主要积累在竹叶中外,其他9种营养元素主要积累在1年生雷竹的秆中.3～4年生雷竹竹叶的Si平均含量为13.66 g · kg^-1. 雷竹属于Si积累植物.随竹龄的增加,雷竹叶中的N、P、K和Mg含量减少,C、Al和Mn含量增加.雷竹对Si的吸收主要集中在第2年(57.1%),对N和K的吸收主要集中在前两年(67.7%～93.7%),此后N和K从植株体内流出,其流失量分别占总积累量的19.1%～39.1%.雷竹中Si与Ca、Al、Mn呈显著正相关,与N、P、K、Mg呈显著负相关.     

Effects of pH and bicarbonate on the nutrient status and growth of three Lupinus species

Aims

High pH, and high bicarbonate (HCO₃⁻) and calcium (Ca) availability characterise calcareous soils. High [Ca] only partially explains why some Lupinus species are calcifuge, so we explored high [HCO₃⁻] and high pH.

Methods

We grew six Lupinus genotypes in hydroponics with pH 5, 6.5 and 8^a (adjusted by KOH), and 8^b (adjusted by KHCO₃). Leaf symptoms and areas, root appearance and biomass were recorded; whole leaf and root nutrient concentrations, and leaf cellular phosphorus (P), Ca and potassium (K) concentrations were determined using elemental X-ray microanalysis.

Results

Chlorosis was observed in young leaves at high pH for L. angustifolius and L. cosentinii, and P deficiency at high pH for all genotypes. High pH decreased iron (Fe) and zinc (Zn) uptake in all genotypes. It also decreased lateral root growth, the uptake of P, K, Ca, and manganese (Mn) by all sensitive species; and translocation of P, Fe, Zn, Mn, and Ca to leaves in most sensitive species. However, leaf [Ca], leaf [K], [K] within each measured cell type, and translocation of K and Ca to leaves of L. pilosus and L. cosentinii at pH 8 were greater than at pH 5 and 6.5. Compared with pH 8^a, all L. angustifolius genotypes translocated more P, Fe, Zn, Mn and K from roots to leaves at pH 8^b. High pH did not affect the leaf cell types that accumulated P and Ca, but decreased the leaf cellular [P].

Conclusions

Lupinus angustifolius and L. cosentinii were sensitive to high [HCO₃⁻] and/or high pH; L. pilosus was relatively tolerant. High pH decreased lateral root growth and nutrient uptake, inhibiting growth of sensitive species. High [HCO₃⁻] diminished the negative effect of pH 8 on nutrient translocation to leaves in most L. angustifolius genotypes. This knowledge provides critical insights into the habits of Lupinus species to guide breeding of calcicole plants.

     

The effects of water and multi-nutrient stress on xylem sap chemistry,photosynthesis and transpiration of seedlings of two Eucalypts

Summary Ten seedlings each of Eucalyptus kitsoniana Maiden and Eucalyptus globulus Labill. were subjected to two levels of water stress and two levels of nutrient stress (macro and micro-nutrients) in a greenhouse for 3 weeks. The objectives were to determine the degree to which seedlings show differences in sap chemistry, photosynthesis and transpiration that relate to the environments in which these two species live. Whole plants were then extracted for xylem sap using a pressure chamber and the sap was analyzed for 14 elements using an inductively coupled plasma spectrometer and a nitrometer. For E. kitsoniana water and nutrient stress, applied separately or in combination, significantly reduced leaf conductance, transpiration, photosynthesis and midday water potential. Nutrient stress alone had less effect than water stress on most functions measured. Water stress alone reduced the root/shoot ratio; the combination of water and nutrient stress increased the root/shoot ratio, primarily because of reduced shoot weight. In E. kitsoniana, water stress alone or in combination with nutrient stress increased the xylem sap concentrations of B and Si. Multi-nutrient stress alone, or in combination with water stress, significantly decreased sap Zn and K. For this species, sap N was decreased by nutrient stress, but increased by water stress. E. globulus had significantly lower transpiration rates and less root mass than E. kitsoniana. Slightly lower leaf conductance and photosynthesis were not significant in E. globulus compared to E. kitsoniana. Water and nutrient stress reduced conductance, transpiration (except for nutrient stress) and photosynthesis, and the effects of water stress on E. globulus were greater than the effects of nutrient stress. Midday water potential was reduced by water stress. Water or nutrient stress alone did not alter seedling root/shoot ratio, but the combination of water and nutrient stress significantly increased the root/shoot ratio for both species. For E. globulus, sap concentrations of Mn, Na, Si and K were increased by water stress (alone or in combination with nutrient stress). Sap N increased with water stress or combined stresses, but decreased under nutrient stress alone. When the two species were compared, E. globulus generally had lower or similar nutrient concentrations in the sap, with Ca, Mg, Mn and P significantly lower than in E. kitsoniana. Seedlings of these two species show strong site adaptations to water and nutrient availability.     

VARIATION IN THE NUTRIENT CONTENT OF LEAVES OF QUERCUS ALBA,QUERCUS COCCINEA,AND PINUS RIGIDA IN THE BROOKHAVEN FOREST FROM BUD-BREAK TO ABSCISSION

Leaves of Quercus coccinea, Q. alba, and Pinus rigida were collected at six dates during the growing season and analyzed for N, P, K, Ca, Mg, Fe, S, and Na. Leaf weights per unit of leaf area (or length) were determined for the same period. Quercus coccinea and Q. alba leaves increased in weight per unit area by about 30 % and 50 %, respectively. First-year pine leaves increased in weight per unit length by about 65 %. During the second year the weight of pine leaves changed little. Two broad patterns in the nutrient content of leaves were apparent when nutrient content was expressed on the basis of leaf area rather than leaf weight. N, P, and K concentrations increased to a peak in mid- or late summer and declined abruptly just prior to abscission. Concentrations of other elements tended to rise slowly throughout the life of the leaves in all three species. The differences among nutrients and among species support the hypothesis that differential partitioning of the nutrient pool occurs as a result of evolutionary adaptation. The changes in weight of leaves per unit area and in nutrient content during the growing season are important for studies of net primary production and in appraisals of the cycling of nutrients. Least distortion of nutrient relationships occurs when area or length of leaf is used as the basis for expression of nutrient content.     

Variation in Nickel Content in the Nickel-Hyperaccumulating Shrub Psychotria douarrei (Rubiaceae) from New Caledonia1

Plants that hyperaccumulate Ni contain > 1000 ppm (dry wt.) in their tissues. Variation of Ni content within hyperaccumulating plant species is poorly explored. Using the Ni-hyperaccumulating shrub Psychotria douarrei, we documented variation of leaf Ni levels within individual shrubs, and variation with respect to plant size and leaf age. Plant size did not correlate significantly with leaf Ni content, and leaf Ni content did not correlate significantly with soil Ni content. Older leaves contained twice as much Ni as younger leaves. Older leaves also contained greater concentrations of Ca, Fe, and Cr but less K, P, and Cu. Five elements (Zn, Pb, Co, Mn, Mg) showed no significant variation due to leaf age. We also examined the effect of leaf age on epiphyll cover, finding increased epiphyll cover on the upper surface of older leaves. The dominant leafy liverwort epiphyll had a relatively high Ni content (400 ppm), suggesting that epiphylls of Ni hyperaccumulators obtain some Ni from host leaves. Individual shrubs differed in mean leaf Ni content almost two-fold (14,900-27,700 ppm). Variation among branches within individuals also ranged widely; however, this intraplant variability was not strongly correlated with the mean leaf Ni content of an individual shrub. We concluded that Ni contents in leaves of P. douarrei vary considerably due to leaf age, among individual shrubs, and among branches within a shrub.     

Calcium deficiency in potato (Solanum tuberosum ssp. tuberosum) leaves and its effects on the pectic composition of the apoplastic fluid

Potato plants (Solanum tuberosum ssp. tuberosum cv. Adelheid), multiplied in vitro, were cultivated in growth chambers on nutrient solution at calcium regimes of 1000, 90, 60 or 30 μM Ca. An absolute Ca deficiency, particularly at the low Ca‐supply levels of 30 and 60 μM Ca, manifested itself initially in the form of marginal necrosis in younger, but not in the youngest, leaves of the potato plants. Further symptoms were rolling of the leaf lamina, browning of veins and roots, and finally necrosis also of the youngest leaves. Only in an advanced stage of Ca deficiency, the meristem of the shoots died. Ca‐deficiency symptoms could be expected at a Ca content in the leaves of less than 5 mg Ca (g dry weight)^?1. However, there was no close negative correlation between the extent of leaf damage and the total Ca content of the leaves. In order to obtain information about the Ca concentration in the apoplast fluid of the leaves, apoplastic washing fluid was extracted by an infiltration‐centrifugation technique. A low Ca supply reduced the Ca concentration both in the apoplast fluid of the leaves and in the cell walls. Up to 60% more diffusible pectin fragments were then found in the apoplast of younger leaves, as compared to the control supplied with an optimum Ca level of 1000 μM. The amount of diffusible pectins accounted for 1–2% of the total pectin content of younger potato leaves. The size of the existing pectin fragments varied depending on the Ca supply. Compared with an optimum Ca supply of 1000 μM, fewer monomers and up to 7 times more diffusible pectin fragments with a degree of polymerization 9–20 were present at the low Ca‐supply level (30 μM). In addition, polygalacturonase activity in tissue homogenates increased remarkably with Ca deficiency. Thus it appears that one major effect of Ca deficiency was a stimulation of the activity of polygalacturonase, which could control the breakdown of pectic polysaccharides in the cell wall. Whether the release of potentially biologically active pectic fragments in cell walls might be involved in the occurrence of Ca‐deficiency symptoms is discussed.     

Plant Seeds as Mineral Nutrient Resource for Seedlings--A Comparison of Plants from Calcareous and Silicate Soils

Mineral nutrients of seeds constitute a significant source ofessential elements to seedlings and developing individuals ofvascular plants. In spite of their potential ecological significance,seed nutrient pools have attracted little attention with respectto calcifuge–calcicole behaviour of plants. The objectivesof this study were, therefore, to compare concentrations of13 macro- and micronutrients (K, Rb, Mg, Ca, Mn, Fe, Co, Cu,Zn, Mo, B, P and S) in seeds and leaves of 35 mainly herbaceousvascular plant species growing on both limestone (calcareous)and silicate (non-calcareous) soils. Concentrations of Rb andCo in seeds of plants originating from limestone soils were,on average, about half of those from silicate soils. Concentrationsof Mn, Mg, Zn and P of seeds were, or tended to be, lower orslightly lower in limestone-soil plants, whereas mean Ca andMo concentrations were higher. Comparing seed and leaf concentrationsof the same species from limestone and silicate soils generallydemonstrated a high P enrichment ratio, but a particularly lowK enrichment ratio in seeds, valid for both types of soil. Itwas also apparent that Fe and Mn, micronutrients which are lessreadily solubilized and taken up by plants on limestone soils,had significantly higher seed:leaf concentration ratios in plantsfrom limestone than from silicate soils, whereas the oppositewas true for Ca. This indicates a ‘strategy’ tosatisfy the demand of seedlings for elements which are lessreadily available in the soil.Copyright 1998 Annals of BotanyCompany Seed, leaf, plant, nutrient, content, calcareous, silicate, acid, soil.