Showing papers in "Plant and Soil in 1985"

The use of sigmoidal dose response curves in soil ecotoxicological research

Abstract: The advantages of a generalised logistic sose response model as compared to a linear model were demonstrated while following the inhibitory effect of Ni on soil respiration rates in a sandy loam. The biological meaning of the parameters to describe the logistic model was indicated. An Ecological Dose Range to describe the increased rate of inhibition upon increasing concentrations of a pollutant was proposed. Remarks were made about the way this model must be used together with applications in other fields of soil biological research.

Critical tissue concentrations of potentially toxic elements

Abstract: Tissue concentrations of young plants, or of young leaves, of crop plants or species used as test plants offer some promise as simple and approximate indicators of toxic levels of elemental pollution of the soil environment.

The effect of air-borne ammonium sulphate on Pinus nigra var. maritima in the Netherlands

Abstract: As a result of air pollution, considerable deposition of ammonium sulphate occurs on vegetation and soil in the vicinity of chicken farms and fields dressed with animal slurry. A clear relation exists between this ammonium sulphate deposition and the distance to certain agricultural activities. Field investigations and ecophysiological experiments both show that the needles ofPinus nigra var.maritima (Ait.) Melville take up ammonium and excrete potassium, magnesium and calcium. This often results in potassium and/or magnesium deficiencies and may lead to premature shedding of needles. The high levels of nitrogen in the needles are strongly correlated to fungal diseases. Whether the observed cation leaching will result in disturbed nutrient budgets depends mainly on soil conditions. Leaching of K, Mg and Ca from the soil, caused by ammonium sulphate, may further inhibit nutrient uptake. Field investigations show a clear correlation between increased ratios of NH4 to K, Mg and Ca in the soil solution and the damage to pine forests.

Kinetic parameters of nitrogen mineralization rates of leguminous crops incorporated into soil

Abstract: Fresh leguminous plant residues were incorporated into soil columns and incubated at 23°C for up to 20 weeks. The N released from specific fractions (foliage, stems, and roots) of each residue were monitored at specific time intervals. Relationships between organic carbon, total nitrogen, C∶N ratio, lipids, and lignin content of the plant materials and the cumulative amount of N mineralized in soil were investigated. Statistical analyses indicated that the rates of N mineralized were not significantly correlated with the organic C nor lipid content of the residues. However, the cumulative amount of N released was significantly correlated with the total N content of the plant material (r=0.93***). The percentage of organic N of the legumes mineralized in soil ranged from 15.9 to 76.0%. The relationship between the percentage of N released and the C∶N ratio of the plant material showed an inverse cuvilinear response (r= 0.88***). It was also evident that the composition of lignin in the residue influenced N mine-ralization rates of the leguminous organs incorporated into soil. There was a curvilinear relationship between the cumulative amount of N released from the residues and time of incubation. Nitrogen mineralization rates were described by first-order kinetics to estimate the N mineralization potential (N0), mineralization rate constant (k), and the time of incubation required to mineralize one-half of N0 (t1/2). The kinetic parameters were calculated by both the linear least squares (LLS) and nonlinear least squares (NLLS) transformations. The N0 values among the crop residues varied from −35 to 510 μg Ng−1 soil. Statistical analyses revealed that the N0 values obtained by both LLS and NLLS methods were significantly correlated (r=0.93***). The mineralization rate constants (k) of the residues ranged from 0.045 to 0.325 week−1. The time of incubation required to mineralize one-half the nitrogen mineralization potential (t1/2) of the legumes incorporated into soil ranged from 2.1 to 15.4 weeks.

Some mechanisms of salt tolerance in crop plants

Abstract: In the first part of this review the main features of salt tolerance in higher plants are discussed. The hypothesis of intracellular compartmentation of solutes is used as a basis for models of tolerance mechanisms operating in roots and in leaves. Consideration is given to the implications of the various mechanisms for the yield potential of salt-tolerant crop plants.

Physiology of halophytes

Abstract: The cellular basis of salt tolerance in halophytes depends upon the compartmentation of ions necessary for osmoregulation in vacuoles and upon osmotic adjustment of the cytoplasm by compatible solutes. The central role played by Na+ and Cl− in osmotic adjustment suggests that the transport of these ions and its regulation must be of primary importance in the physiology of the plant as a whole. There have been few investigations into the regulation of leaf ion concentrations, but such data as are in the literature suggest that limiting xylem Na+ (and Cl−) concentrations, together with continued leaf expansion, are particularly important. The role of phloem in retranslocation is uncertain due to lack of data. Decreases in transpiration rate per unit area of leaf help to lower the ion input into leaves. Any linked reductions in photosynthesis appear to be due to decreases in stomatal frequency.

Principles and strategies in breeding for higher salt tolerance

Abstract: Salinity is an environmental component that usually reduces yield. Recent advances in the understanding of salt effects on plants have not revealed a reliable physiological or biochemical marker that can be used to rapidly screen for salt tolerance. The necessity of measuring salt tolerance based upon growth in saline relative to non-saline environments makes salt tolerance measurements and selection for tolerance difficult. Additionally, high variability in soil salinity and environmental interactions makes it questionable whether breeding should be conducted for tolerance or for high yield. Genetic techniques can be used to identify the components of variation attributable to genotype and environment, and the extent of genetic variation in saline and nonsaline environments can be used to estimate the potential for improving salt tolerance. Absolute salt tolerance can be improved best by increasing both absolute yield and relative salt tolerance.

Alley cropping sequentially cropped maize and cowpea with leucaena on a sandy soil in Southern Nigeria.

Abstract: The potential of alley cropping maize and cowpea with the giant Leucaena (Leucaena leucocephala (Lam) de Wit) cultivar K-28 was studied on an Entisol (Psammentic Ustorthent) in Southern Nigeria. In this trial the crops were grown in 4 m wide alleys formed by periodically pruned leucaena hedgerows. The effect of application of leucaena prunings, nitrogen fertilizer and tillage was studied. Despite the very intensive pruning regime (five prunings/year) for a six-year period, the leucaena hedgerows continue to produce substantial amounts of prunings, nitrogen yield and stakes. Application of nitrogen to the maize crop increased dry matter and nitrogen yield from the leucaena prunings. Although high nitrogen yield was obtained from the prunings, the application of low nitrogen rates was still needed for obtaining a high maize yield. Maize grain yield can be sustained at about 2.0 t/ha with continuous application of leucacna prunings only. Without application of leucaena prunings and nitrogen maize yield continued to decline with subsequent croppings. Cowpea grain yield was not affected either by leucaena prunings or by residual nitrogen. Tillage (rototilling) resulted in either higher or the same maize and cowpea yields as compared with no-tillage. Application of leucaena prunings resulted in higher soil moisture retention, organic matter, exchangeable K, Ca, Mg, and also nitrate levels in the soil solution. Leucaena and maize appear to extract soil moisture from different zones in the soil. Timely pruning of hedgerows is necessary to minimize shading.

Fertilization management of crops irrigated with saline water

Abstract: Available data concerning nutrition and fertilization effects on crops irrigated with saline water are presented and discussed. Published data on the salinity-fertility relationship are, at least to some extent, contradictory; both positive and negative effects as well as no effect of fertilization on salinity tolerance have been recorded. However, a great deal of the experimental work supports the view that standard fertilization recommendations for non- saline conditions are also suitable for saline conditions. In addition, available data indicate that the apparent salt tolerance of agricultural crops varies with soil fertility level. Consequently, crops showing exceptionally high apparent salt tolerance at a low fertility level become more sensitive when adequately fertilized, although the absolute yield may be greatly increased. On the other hand, some data seem to show a real increase in salinity tolerance under improved fertility conditions.

Crop tolerance to saline sprinkling water

Abstract: Crops sprinkled with saline irrigation water are subject to foliar salt absorption and injury as well as to injury from soil salinity. Yield reductions caused by soil salinity alone are well documented, and data are presented here for 71 agricultural crops. Factors affecting these data and their applicability to sprinkler-irrigated crops are discussed. Although foliar injury has been observed with many sprinkled crops, particularly tree crops, essentially no information is available to predict yield losses as a function of the salt concentration of the irrigation water. Salinity thresholds for sprinkling-induced foliar injury are estimated for some crops; however, climatic conditions greatly affect the onset and degree of injury. Management strategies that minimize sprinkling injury are mentioned.

Genotype dependent variation in mycorrhizal colonization and response to inoculation of pearl millet

Abstract: Genotypes of pearl millet (Pennisetum americanum L. Leeke) were examined for differences in vesicular-arbuscular mycorrhizal (VAM) colonization and response to inoculation. For thirty genotypes tested across three field locations there was a range of mycorrhizal colonization intensity between 25 and 56%. In another experiment with two male-sterile lines, restorer lines and their derived crosses, grown in pots filled with non-sterilized soil there were significant differences between genotypes for colonization by mycorrhiza. This showed hostgenotype dependence for mycorrhizal colonization. Root growth rates, mycorrhizal root length, percentage root colonization and plant growth and P uptake were studied in ten genotypes. A set of 3 genotypes with similar root lengths varied significantly with regard to mycorrhizal root length and the percentage colonization. This supports the suggestion that VAM colonization and spread is dependent on the host genotype. The growth responses differed significantly between the genotypes and they also differed in their responses to P uptake and VAM inoculation. The utility of host-genotype dependent differences in VAM symbiosis in plant breeding is discussed.

Halophytic crops for cultivation at seawater salinity

Abstract: Several hundred halophytes from salt marshes and salt deserts of the world have been evaluated in our laboratory at various degrees of intensity, and a few have been selected for development as crops. The development of the cultivars and the basic biology of the plants is being studied in Delaware in the United States. Agronomic testing, feeding trials, and development of the best agronomic practices are taking place in the saline desert at the American University in Cairo research station in Sadat City. Our present efforts focus primarily on three forages, one grain, and one vegetable. Sporobolus virginicus cultivars for both hay and pasture are being tested. A Distichlis spicata cultivar for hay has been identified, and Spartina patens is being evaluated as a hay as well. Although we do not yet have the data for a full year’s growth in Egypt, forage yields of these various cultivars, when harvested as hay crops, range to 6.9 or more tons per acre, depending on the salinity and other environmental conditions, and the crude protein content as indicated by the nitrogen content ranges from 6 to 10%. Cultivars having the most useful agronomic qualities have been identified and are being increased in quantity. The grain crop Kosteletzkya virginica is a perennial, producing a seed which resembles millet; its whole seeds contain approximately 25% protein and 15% oil. The yields of one of our better cultivars are about 1460 kg/ha (1300 lb/acre) when grown under 25‰ salinity. The vegetable Atriplex triangularis (similar to spinach) has been under mass selection for four years; a cultivar has been identified and seed is now being increased for this species.

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Abstract: Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg−1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m−1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low (≤ 0.2 mmol kg−1 NaHCO3-extractable P) at soil saturation extract salinities from 1.1 dS m−1 to 8.8 dS m−1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m−1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.

Transformations in soil and availability to plants of15N applied as inorganic fertilizer and legume residues

Abstract: A pot experiment was conducted to study the transformations of organic and inorganic N in soil and its availability to maize plants. Inorganic N was in the form of15N labelled ammonium sulphate (As) and15N labelledSesbania aculeata (Sa), a legume, was used as organic N source. Plants utilized 20% of the N applied as As; presence of Sa reduced the uptake to 14%. Only 5% of the Sa-N was taken up by the plants and As had no effect on the availability of N from Sa. Losses of N from As were found to be 40% which were reduced to 20% in presence of Sa. Losses of N were also observed from Sa which increased in the presence of As. Application of As had no effect on the availability of soil or Sa-N. However, more As-N was transported into microbial biomass and humus components in the presence of Sa.

Incubation experiments on nitrogen mineralization in loess and sandy soils

Abstract: In aerobic incubation experiments, nitrogen mineralization was investigated in agricultural loess and sandy soils. Fresh, fieldmoist samples were used for incubation. Using an optimization procedure the N-mineralization was split into two nitrogen fractions: A resistant, slowly decomposable organic N-fraction (index rpm) and a fast decomposable N-fraction (index dpm). Loess- and sandy soils showed similar mean reaction coefficients for N-mineralization. The results also indicated that the amount of mineralizable nitrogen in the resistant N-fraction depended directly on clay content. Soil sampling at different times during crop growing period gave different mineralization amounts and courses. Effect of added plant residues on N-mineralization, was also studied by incubation. Variation of type and quantity of added residues changed the net N-mineralization in a characteristic way: Sugar beet leaves, added in minced form, caused an increase in mineralization; while straw caused a temporary immobilization, followed by remineralization. Incubation experiments on undisturbed soil columns showed nearly linear mineralization with time.

Drought resistance of wheat plants inoculated with vesicular-arbuscular mycorrhizae

Abstract: Drought resistance of wheat (Triticum aestivum L.) as influenced by two vesiculararbuscular mycorrhizal (VAM) fungi,Glomus fasciculatum 10 andGlomus deserticola 19, was evaluated. Soil columns 0.15 m diam. by 1.20 m length were used to reduce the influence of limited rooting space. With initial soil water at 0.5 MPa (0.145 kg kg−1), plants were subjected to low-level water stress throughout the experiment and severe water stress for 24 h at one (55 days after transplanting, Feekes scale 10.1) two (55 and 63 days, Feekes 10.1 and 10.2), or three (55, 63, and 70 days, Feekes 10.1, 10.1, and 10.2) periods. After each stress period, one set of plants was watered and grown to maturity without subsequent water stress. A second set of plants was harvested 1 week after stress.G. fasciculatum-inoculated plants harvested 7 days after stress at 55 days had greater leaf area and leaf, total plant, and root weight than non-VAM plants.G. deserticola-inoculated plants had greater leaf area and leaf weight than non-VAM plants. After stress at 55 and 63 days, leaf area, and leaf and total dry weight were again greater for VAM than for non-VAM plants. However, after stress at 55, 63, and 70 days, differences in aboveground biomass between VAM and non-VAM plants were not significant at P=0.05. Aboveground biomass was not affected by VAM species in plants stressed at 55 or 55 and 63 days, butG. fasciculatum-inoculated plants produced more tillers atter stress at 55 days. When grown to maturity, VAM plants which had undergone three stress periods had twice the biomass and grain yield as non-VAM plants subjected to the same stress. The three stress periods reduced number of heads and kernel numbers of weight of non-VAM plants compared to VAM plants.G. fasciculatum-inoculated plants consistently had increased root weight and rooting depth.

Salt-tolerant crops: origins, development, and prospects of the concept

Abstract: The genetic approach to the problems posed by salt-affected soils and water, i.e., breeding crops resistant to salinity stress, is traced to two principal origins: the European ecological interest in halophytes, and the exigencies of growing crops in the arid and semi-arid lands of the American West. The point is made that breeding for resistance to salinity stress cannot be divorced from breeding for various other desirable traits of mineral plant nutrition and metabolism. A survey is conducted of the existing body of information on breeding for desiderata of mineral nutrition in general and salt tolerance in particular. The prospects of breeding crops for salt tolerance are discussed, with emphasis on a) its relation to breeding for resistance to other mineral stresses; b) field trials; c) collaboration between plant physiologists and geneticist-breeders; and d) extensive exploration of germplasm.

Effects on winter wheat seedling growth by toxin-producing rhizobacteria

Abstract: Root-colonizing pseudomonads capable of inhibiting seedling winter wheat (Triticum aestivum L.) root growth in an agar seedling bioassay also significantly inhibited wheat root growth in vermiculite; however, the inhibitory trait is quite labile in laboratory culturing. The extent of inhibition in both the agar and vermiculite medium depended on inoculum level. These pseudomonads were found to produce a toxin capable of inhibiting growth ofEscherichia coli C-la andBacillus subtilis. Field isolates that strongly inhibit growth of indicator bacteria also inhibited root growth. Toxin production by the bacteria appeared necessary for inhibition of root growth and indicator bacteria as toxin-negative (TOX−) mutants no longer inhibited either. Antibiosis towardsE. coli as well as wheat seedling root inhibition in agar was reversed by L-methionine, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.

Pesticidal effect on soybean-rhizobia symbiosis

Abstract: Relative compatibility of selected pesticides at two levels of application (recommended rate and 5× or 10 ×) with soybean-rhizobia symbiosis was tested in pot culture experiments using a prepared peat inoculant. PCNB, carboxin and carboxin+captan at recommended level were innocuous to growth, nodulation, N2-fixation and total N content of shoot. Carboxin and carboxin+captan but not PCNB at 10 times recommended level proved detrimental to nodulation and N2-fixation. Carbaryl and malathion at recommended level had no adverse effect but at 10 times recommended level severely reduced N2-fixation but not other parameters. Acephate, diazinon and toxaphene at both levels reduced N2-fixation and total N content but not growth and nodulation. All five herbicides used at recommended and 5 times recommended level adversely affected nodulation and N2-fixation. Glyphosate proved least toxic to all parameters. 2,4-DB at recommended level was less harmful to nodulation and N2-fixation than trifluralin, alachlor and metribuzin.

Plant uptake and phytotoxicity of boron in Australian fly ashes

Abstract: French bean (Phaseolus vulgaris cv. Redland Pioneer) and Rhodes grass (Chloris gayana cv. Pioneer) were grown in glasshouse experiments to examine the potential for phytotoxicity of B in a range of Australian fly ashes. In each experiment, the ashes used were either untreated, leached or adjusted to pH 6.5 and subsequently leached. In the first eperiment, the yield and B status of plants grown on five fly ashes mixed (5 and 10% by weight) with an acid-washed sand were measured and, with the exception of one ash, yield differences among ash sources and among ash treatments were attributed to differences in the degree of B toxicity. In a subsequent experiment, a fly ash with properties representative of most Australian ashes was mixed (0, 15, 30, 70 and 100% by weight) with a sandy loam, and the yield and mineral composition of plants grown on these mixtures determined. Although the available water capacity of the soil was substantially increased by fly ash addition, incorporating large proportions of untreated fly ash resulted in poor plant growth primarily due to B toxicity. In both experiments, leaching the ash reduced the potential for B toxicity, whereas adjustment of the pH to 6.5 and subsequent leaching of the fly ash resulted in plants with normal levels of B. There were marked differences in both the tissue levels of B and the extent of B toxicity symptoms between the two species. Rhodes grass appeared to be able to tolerate higher B contents in the growing medium by taking up much less of the element than French bean. The results indicate that phytotoxicity of B would be a major problem in establishing vegetation on ash dams and in the agronomic utilization of unweathered fly ashes in Australia.

Quantitative estimation of root exudation of maize plants

Abstract: The rate of root exudation of maize plants was estimated by measuring the rate of denitrification in a hermetically sealed root system. While CO2 production measured in the rhizosphere results both from root respiration and microbial respiration N2O production during nitrate respiration is solely related to the amount of root exudates available for bacterial degradation. With 4 week old plants growing in quartz sand or soil root exudation amounted to 7% of the net photosynthates. Calculations revealed that about 25% of the organic matter flowing into the root system was excreted into the rhizosphere.

Response of potatoes to N fertilizer: dynamic model

Abstract: A simulation model is described to interpret N fertilizer experiments on potatoes. It calculates the total growth of dry matter, the N uptake, the partition of dry matter and of N between tuber and foliage and the distribution of inorganic N down the profile for each day during the growing season. The validity of the model was tested against measurements of these parameters made at approximately fortnightly intervals on plots that received N fertilizer and those that received none in 4 experiments on a sand, 4 on a sandy loam and 3 on a clay soil. Simulated values were in reasonably good agreement with the measured values in all experiments. Overall the sums of squares of the differences between the simulated and measured values of the %N in the total plant, and the total amount of inorganic N in the top metre of soil and the logarithms of the total weight of dry matter, tuber dry weight, N uptake in the entire plant and N uptake in the tubers were each less than 25% of the sum of squares of the measured values about the mean. Only 9 inputs were required for the model. It was found essential to take account of differences in spring and summer leaching but not of inter-site differences in mineralization rate.

Net mineralization and nitrification rates in a clay soil measured and predicted in permanent grassland from soil temperature and moisture content

Abstract: Net mineralization of N and net nitrification in field-moist clay soils (Evesham-Kingston series) from arable and grassland sites were measured in laboratory incubation experiments at 4, 10 and 20°C. Three depth fractions to 30 cm were used. Nitrate accumulated at all temperatures except when the soil was very dry (θ=0.13 cm3 cm−3). Exchangeable NH4-ions declined during the first 24 h and thereafter remained low. Net mineralization and net nitrification approximated to zero-order reactions after 24 h, with Q10 values generally <1.6. The effect of temperature on both processes was linear although some results conformed to an Arrhenius-type relationship. The dependence of net mineralization and net nitrification in the field soil on soil temperature (10 cm depth) and moisture (0–15, 15–25, 25–35 cm depths) was modelled using the laboratory incubation data. An annual net mineralization of 350 kg N ha−1 and net nitrification of 346 kg N ha−1 were predicted between September 1980 and August 1981. The model probably overstressed the effect of soil moisture relative to soil temperature.

Effect of soil moisture and phosphate level on root hair growth of corn roots

Abstract: Root hairs have been shown to enhance P uptake by plants growing in low P soil. Little is known of the factors controlling root hair growth. The objective of this study was to investigate the influence of soil moisture and P level on root hair growth of corn (Zea mays L.). The effect of volumetric soil moistures of 22% (M0), 27% (M1), and 32% (M2) and soil (Raub silt loam, Aquic Argiudoll) P levels of, 0.81 (P0), 12.1 (P1), 21.6 (P2), 48.7 (P3), and 203.3 (P4) μmol P L−1 initially in the soil solution, on shoot and root growth, P uptake, and root hair growth of corn was studied in a series of pot experiments in a controlled climate chamber. Root hair growth was affected more by soil moisture than soil P. The percentage of total root length with root hairs and the density and length of root hairs on the root sections having root hairs all increased as soil moisture was reduced from M2 to M0. No relationship was found between root hair length and soil P. Density of root hairs, however, was found to decrease with an increase in soil P. No correlation was found between root hair growth parameters and plant P content, further suggesting P plays a secondary role to moisture in regulating root hair growth in soils. The increase in root hair growth appears to be a response by the plant to stress as yield and P uptake by corn grown at M0 were only 0.47 to 0.82, and 0.34 to 0.74, respectively, of that measured at M1 across the five soil P levels. The increase in root hair growth at M0, which represents an increase of 2.76 to 4.03 in root surface area, could offset, in part, the reduced rate of root growth, which was the primary reason for reduced P uptake under limited soil moisture conditions.

Effect of salinity on quality of various agricultural crops

Abstract: The effect of salinity on the quality of various agricultural crops has not yet been explored much. This information is very important to Israel due to the increasing use of saline water for irrigation. This paper reports the effect of saline irrigation water on the quality, especially the taste, of several crops. Fruits from a processing tomato cultivar exposed to various degrees of salinity had higher values for total soluble solids (TSS) and acidity than their controls. The yield of fruit after saline water irrigation is lower, but this is offset by the higher fruit quality and its consequent higher value. Melon fruits from plants subjected to saline water scored higher in taste than their controls when the fruits were analyzed fresh. After 3–4 weeks of storage at room temperature, there was no longer any difference in taste. Even though salinity slightly increased the TSS content, this did not correlate with the taste scores. Iceberg lettuce grown with saline water did not significantly differ in taste from its control, even when the sensitive triangle taste test was used. The same was true for peanuts. Thus, for these two crops no advantage of better quality would compensate for possible lower yields. Salinity had little effect on the yield of two varieties of Chinese cabbage, but increased the frequency of tipburn.

Restriction enzyme digestion patterns of Frankia plasmids

Abstract: After the initial screening of more than 200 Frankia strains, the plasmid DNA observed in eight Frankiae was analyzed. In situ lysis was performed to obtain an estimate of their copy number and molecular weight. Four plasmid classes were distinguished, 7–9, 18–20, 30–35 and 50–55 kb. Twelve plasmids were thus analysed with restriction enzymes to determine their plasmid restriction patterns.

Agricultural production of halophytes irrigated with seawater

Abstract: Growing agricultural crops with direct seawater irrigation has progressed within the past few years from the conceptual to the experimental phase. This has been accomplished by selecting halophytes with inherently high salinity tolerance for use as crop plants rather than by increasing the ability of traditional crop plants to tolerate seawater. Some of the halophytes being investigated for use as crops in seawater irrigation scenarios have high nutritional value as forage or fodder crops. Most of them also have high digestibility. The limiting factor in such use is their high salt content, but this limitation can be moderated. However, since seeds of halophytes do not accumulate salt any more than do those of glycophytes, the greatest promise for seawater-irrigated halophytes probably will be as seed crops. The seeds of many halophytes have high protein and oil contents and compare favorably with traditional oilseed crops. Sustained high yields of seed and biomass already have been obtained from some halophytes irrigated with seawater, and within the next few years seawater agriculture should proceed from the experimental to the operational phase.

Major and trace element concentrations in needles of Picea abies: levels, distribution functions, correlations and environmental influences

Abstract: Eighteen major and trace elements (Al, As, Ba, Br, Ca, Cl, Co, Cu, Fe, K, Mg, Mn, Na, Sb, Sc, Sr, V, Zn) have been determined in needles ofPicea abies by neutron activation analysis. Trees from 31 sites with different characteristics were investigated. The sampled area was 140 km2 and centered around the city of Winterthur, Switzerland. The effect of washing the needles before analysis was investigated. Washing was found to be essential for a meaningful determination of most elements. The values of the individual elements could be approximated by normal or by lognormal distributions. The width of these distributions varies greatly, being 14% for Cu and a factor of 5 for Mn. Many elements show highly significant positive or negative correlations. Whereas the levels of the major elements as determined here are in the generally accepted range, the values for most of the minor elements show very poor correspondence with published values. For some elements the present data seem to be the only available values. Distinct environmental influences were only manifest for Na, Cl, Br, and these elements show very high values at sites bordering highways.

Macroalgae (seaweeds): industrial resources and their utilization

Abstract: Seaweeds are distributed widely in all oceans of the world, but exploited in limited areas These plants have been used for food and as soil conditioners for centuries, with industrial application of extractives a relatively recent innovation generally limited to the more developed areas of the world There are relatively few species of industrial importance, and these occur in both the red (Rhodophyta)and brown (Phaeophyta) algal divisions

Genetics of salt tolerance in higher plants: theoretical and practical considerations

Abstract: An interdisciplinary approach to breeding for stress tolerance in plants has gained considerable recognition in the past few years. Accordingly, this article presents a synthesis of the genetic, physiological, and ecological aspects of salt tolerance in plants. An understanding of these aspects and the interrelationships between them is essential for an efficient breeding program.