Showing papers in "Plant and Soil in 1979"
TL;DR: In this article, the authors studied the influence of vegetation burning (ash and heat) on the soil environment and their relation to nutrient availability, and the relationship between ash deposition and soil fertility.
Abstract: 2.3 Changes in soil temperatures after fire 3. Influence of the products of vegetation burning (ash and heat), on the soil environment, and their relation to nutrient availability 3. 1 The soil as an environment for biological activities and nutrient transformations 3.2 The ash component 3.2.1 Relationship between ash deposition and soil fertility 3.2.2 Effects of ash on nutrient cycling and soil chemical and biological processes 3.2.2.1 Ash formation 3.2.2.2 Ash return and properties 3.2.2.3 Nutrient return in ash, and the effect of ash on soil chemical properties 3.2.2.4 Influence of ash on soil biological processes 3.3 The heat component 3.3.1 General introduction 3.3.2 Plant growth in heated and sterilized soils 3.3.3 Effect on soil physical properties 3.3.4 Influence of heat on soil chemical properties 3.3.4.1 Changes in properties other than N compounds 3.3.4.2 Non-biological changes in soil N fractions 3.3.5 Biological changes in heated soils 3.3.6 Non-biological gas exchange in heated soils
709 citations
TL;DR: The amount of mineral nitrogen in the root zone at the beginning of the growing season (Nmin content, kg N/ha) and the amount of nitrogen mineralized during growing season are the two main components of nitrogen supply in soil.
Abstract: Nitrogen supply in soil is divided into two components: the amount of mineral nitrogen in the root zone at the beginning of the growing season (Nmin content, kg N/ha) and the amount of nitrogen mineralized during the growing season.
158 citations
TL;DR: The use of variations in natural abundance of15N between nitrogen fixing and non nitrogen fixing soybeans was investigated for quantitative estimate of symbiotic nitrogen fixation and it was found that inoculated soybeans had a significantly lower15N content than non-inoculated ones.
Abstract: The use of variations in natural abundance of15N between nitrogen fixing and non nitrogen fixing soybeans was investigated for quantitative estimate of symbiotic nitrogen fixation
138 citations
TL;DR: In this paper, the authors established that mycorrhiza increased the availability of phosphate at a level of about 0.5-2 μm P (60-70% coverage of the goethite surface).
Abstract: Pot trials using phosphated-goethite (bridging complex) as the source of P for ryegrass were established. No P was readily available to ryegrass until the surface was >40% covered with phosphate ions. Availability increased as the P level in solution increased up to 2 μM. Maximum availability was attained when the initial concentration of P in solution was 2 μM which occurred at about 75% coverage on geothite. Mycorrhiza increased the availability of phosphate at a level of about 0.5–2 μM P (60–70% coverage of the goethite surface).
133 citations
TL;DR: Low concentrations of ethylene, comparable with those known to occur in anaerobic soil, inhibited extension of pea roots to a similar extent to that previously reported for barley, and pea appeared to be less sensitive to ethylene than some non-leguminous dicotyledons.
Abstract: Low concentrations of ethylene, comparable with those known to occur in anaerobic soil, inhibited extension of pea roots to a similar extent to that previously reported for barley. Thus pea appeared to be less sensitive to ethylene than some non-leguminous dicotyledons. Perfusion of 10ppm of ethylene through the soil around the roots of pea and white clover resulted in reduced shoot dry weight. Nodulation, and the nitrogenase activity of those nodules which did form, was also greatly reduced. The ecological consequences of the sensitivity of nodulation and nitrogen fixation to ethylene, and the possible significance for quantitative studies involving the acetylene-reduction assay, are discussed.
117 citations
TL;DR: There is a great variation in the competitive ability of the Rhizobium strains and this is not related to the ability to form root nodules, and the critical period of competition is restricted to ca.
Abstract: Nodulation of pea cv. Afghanistan and cv. Iran by a nodulating Rhizobium strain is suppressed by the presence of a non-nodulating strain. The degree of suppression varies, dependent on the Rhizobium strains used. There is a great variation in the competitive ability of the Rhizobium strains and this is not related to the ability to form root nodules. The critical period of competition is restricted to ca. 24 hours after inoculation.
104 citations
TL;DR: In this article, the influence of NaCl-salinization (80 mM) and KCl addition (5 and 10 mM) on the uptake and turnover of labelled nitrogen (15NH415NO3) was studied.
Abstract: In a solution culture experiment with 31 days old barley plants (var. Miura) the influence of NaCl-salinization (80 mM) and KCl addition (5 and 10 mM) on the uptake and turnover of labelled nitrogen (15NH415NO3) was studied. Labelled N was applied for 24 h at the end of a 20 days' salinization period. Salinization impaired growth and incorporation of labelled N into the protein fraction paralleled by accumulation of labelle dinorganic N. All salt effects were much more pronounced in the shoots than in the roots.
103 citations
TL;DR: In this article, the effect of Humic acid on nutrient uptake and growth of corn plants was investigated by growing corn in plastic growth pouches containing a Hoagland nutrient solution to which were added 0, 320, 640, 1,600 or 3,200 ppm HA, pH 7.0.
Abstract: The effect of humic acids on nutrient uptake and growth of corn plants (Zea mays L.) was investigated by growing corn in plastic growth pouches containing a Hoagland nutrient solution to which were added 0, 320, 640, 1,600 or 3,200 ppm HA, pH 7.0. The experiments were carried out in three replicates for a growing period of 16 days after germination. Humic acid was in general beneficial to shoot and root growth of corn plants. Dry matter yield in corn shoots was stimulated by HA, especially by treatments with 640 ppm HA. Nutrient uptake showed a number of differences as a result of treatments with HA. Moderate applications with HA resulted in a significant increase in N content of corn shoots, while large amounts of HA had a tendency to reduce the N concentration in corn shoots. As a result of the HA treatments, P concentrations in corn shoots were decreased, but differences in K contents were statistically nonsignificant and Mn contents in shoots were also nonsignificantly different among the treatments. However, Zn content showed a tendency to increase with increasing applications of HA.
91 citations
TL;DR: In this paper, soil cores extracted at 5 day intervals from 3 May to 6 August from a Sitka spruce plantation, 14 years old, fluctuated with maxima in late May and mid July and the earlier peak coincides with increasing soil temperatures during a period of high incident precipitation and the latter developed when the soil profile was rewetted.
Abstract: From soil cores extracted at 5 day intervals from 3 May to 6 August it was found that the biomass of fine roots in a Sitka spruce plantation, 14 years old, fluctuated with maxima in late May and mid July. The earlier peak coincides with increasing soil temperatures during a period of high incident precipitation and the latter developed when the soil profile was rewetted. Fine root biomass and soil moisture tension (SMT) were significantly and negatively correlated in three of four soil horizons. Root mortality occurred whenever incident precipitation failed to maintain soil moisture tension near zero. In the very open pored horizons the critical SMT for root death was unexpected small, <0.1 bars; in the peat horizons it wasc 0.2 bars.
88 citations
TL;DR: The relative efficiencies of calcined aluminum phosphate and hyperphosphate for the various plant species were closely related to the ratio of total cations and total anions absorbed by these plants.
Abstract: Six plant species, wheat, paspalum grass (Paspalum plicatulum), maize, molasses grass (Melinis minutiflora), soybean and buckwheat (Fagopyrum esculentum) were compared for their abilities to utilize phosphate from superphosphate, a calcined aluminum phosphate and four rock phosphates. Buckwheat showed an exceptional behaviour in that it could utilize all phosphates. For the other plants, only the calcined aluminum phosphate and one rock phosphate (hyperphosphate) had significant fertilizing values. Their efficiencies, relative to superphosphate, were 0.45 and 0.11 for wheat, 0.73 and 0.43 for paspalum grass, 0.50 and 0.37 for maize, 0.46 and 0.42 for molasses grass, 0.28 and 0.38 for soybean, and 0.72 and 1.08 for buckwheat, respectively. For three P sources, superphosphate, calcined aluminum phosphate and hyperphosphate, a relationship between soil acidity and P uptake was found. Soil pH in its turn was negatively related to the ratio of total equivalents of cations and those of anions absorbed. Consequenly, P uptake was positively related to the ratio of total equivalents of cations to those of anions absorbed. The same effect of plant species on soil pH could also explain the difference in uptake of P from sparingly soluble phosphates. The relative efficiencies of calcined aluminum phosphate and hyperphosphate for the various plant species were closely related to the ratio of total cations and total anions absorbed by these plants.
82 citations
TL;DR: Growth toxins are released to the soil through leaching and during decay from the air-dried parts of Parthenium hysterophorus to inhibit nodulation and growth in legumes and ragi, but have stimulatory effect on bajra.
Abstract: Growth toxins are released to the soil through leaching and during decay from the air-dried parts ofParthenium hysterophorus L. The dry leaves mixed to the soil inhibit nodulation and growth in legumes, branching in tomato (Lycopersicum esculentum L. cv. ‘Pusa Ruby’), plant height and tillering in ragi (Eleusine coracana Gaertn. cv. ‘Poorna’), and yield in bean (Phaseolus vulgaris. L. cv. ‘Burpees Stringless’), cowpea (Vigna sinensis L.), tomato and ragi, but have stimulatory effect on bajra (Pennisetum typhoideum Rich cv. ‘H.B.1’). The inhibitors released to the substratum remain active for about thirty days.
TL;DR: The root: shoot ratio increased as the soil water content decreased, and the plants in the soil at low water contents had significantly lower leaf water potentials than those in soil at high water contents.
Abstract: Cotton (Gossypium hirsutum L. cv. H14) seedlings were raised in soil of differing soil water content in specially designed pots in which the roots had access to freely available water and nutrients located 2.5 cm below the base of the soil core. The time for root emergence from the soil core and the rate of root growth were measured daily from sowing to harvest. The root and shoot dry weight and leaf water potential were measured at the final harvest 16 days after sowing. As soil water content decreased, the root emerged from the soil earlier and the initial rate of root elongation was faster. In spite of the availability of freely available water, the plants in the soil at low water contents had significantly lower leaf water potentials than those in soil at high water contents. The root: shoot ratio increased as the soil water content decreased. This arose from an absolute increase in root weight, with shoot weight not being significantly affected.
TL;DR: In this paper, a comparison of the plant growth and chemical analysis revealed that Cr(VI), Cu, Cd, and Hg(II) in the solution are most toxic to the cabbage growth and Mn, Fe, and Zn are less toxic than other heavy metals.
Abstract: Cabbage plants were grown for 55 days with a nutrient solution containing 1 and 10 ppm of V, Cr(III), Cr(VI), Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg(I), orHg(II). A comparison of the plant growth and chemical analysis revealed that Cr(VI), Cu, Cd, and Hg(II) in the solution are most toxic to the plant growth (hence detrimental to the cabbage-head formation) and Mn, Fe, and Zn are less toxic than other heavy metals, and that Mn, Zn, Co, Ni, and Cd and translocated into all the plant organs while V, Cr(III), Cr(VI), Fe, Cu, Hg(I), and Hg(II) are accumulated in the roots.
TL;DR: The interaction between the VA mycorrhizal fungus, Glomus fasciculatus and the root-knot nematodes, Meloidogyne incognita andM.
Abstract: The interaction between the VA mycorrhizal fungus,Glomus fasciculatus and the root-knot nematodes,Meloidogyne incognita andM. javanica, and their effects on the growth and phosphorus nutrition of tomato was studied in a red sandy loam soil of pH 6.0. Inoculation of tomato roots with root-knot nematodes enhanced infection and spore production byG. fasciculatus. Inoculation of tomato plants withG. fasciculatus significantly reduced the number and size of the root-knot galls produced byM. incognita andM. javanica. Inoculation withG. fasciculatus although improved plant growth and its total phosphorus content compared to the uninoculated plants, the difference were not statistically significant.
TL;DR: The inhibitory nature of the root exudate was confirmed under sterile cultural conditions by its effect on wheat seedling growth and on Parthenium hysterophorus L. caused retarded growth and nodulation in bean.
Abstract: Association with Parthenium hysterophorus L. caused retarded growth and nodulation in bean (Phaseolus vulgaris var. 'Burpees Stringless') the inhibition decreasing with increasing distance from the weed. Leachate collected from Parthenium grown pots also caused similar inhibition in bean growth. The inhibitory nature of the root exudate was confirmed under sterile cultural conditions by its effect on wheat (Triticum aestivum var. 'UP301') seedling growth. At the rosette and flowering stage of the weed there was maximum exudation of inhibitors which remained active for about thirty days. © 1979 Martinus Nijhoff Publishers.
TL;DR: In this article, tomato plants were grown in water culture under two different humidity regimes (50% R.H. and 95% RH.) were harvested at intervals over the growth period and cation uptake and calcium distribution investigated.
Abstract: Tomato plants grown in water culture under two different humidity regimes (50% R.H. and 95% R.H.) were harvested at intervals over the growth period and cation uptake and calcium distribution investigated. The following results were obtained:
1.
Plants in the high humidity regime initially grew faster but at the final harvest after 22 days, dry matter yields were the same.
2.
In the high humidity treatment particularly towards the end of the experiment, the growth of the young leaves was disturbed and the plants showed symptoms resembling Ca or B deficiency. Analysis revealed that these tissues were lower in Ca than comparative tissues of the low humidity plants. The converse was true for B.
3.
Cation uptake was little affected by the humidity treatment. However, the distribution of calcium within the plant was markedly influenced by humidity. In the high humidity treatment the level of Ca in the young leaves was very low and Ca accumulated in the stems. A high proportion of both Ca and Mg in these younger Ca deficient leaves was found to be associated with pectate. The same trend was observed in the stems, more of the Ca and Mg in this case being bound to oxalate as well as pectate. These results further indicate the possible significance of exchange movement of Ca particularly under low transpiration conditions when Ca transport by mass flow is restricted.
4.
Xylem sap analysis showed a close cation-anion balance in all samples. NO3-ion was the predominant anion and the two major cations were K and Ca. This provides further evidence that the upper plant parts provide the major site of NO3-reduction in the tomato plant.
TL;DR: Supply of boron improved the pollen vitality of rice flowers and increased the yield of rice grains in the same order, linked with greater availability of sugars, increased enzymatic activity and respiration which favoured better growth of pollen.
Abstract: Rice plants were grown in sand cultures with nutrient solution including boron at 0, 1, 2.5 and 5 ppm concentrations.
TL;DR: This report describes inoculation of soils in pots, containing radish or tomato plants, with algal suspensions or exudates, which resulted in increased growth rates of both plants and increased their overall yield.
Abstract: Biologically active compounds may be liberated from blue-green algae growing on the surface of moist soils. Such compounds may also be released as exudates from algae grown in liquid culture.
TL;DR: In this paper, two experiments were carried out with two nodulating and non-nodulating soybean isolines, with three different levels of N as (15NH4)2SO4 at the equivalent of 0, 25 and 50 kg N/ha.
Abstract: Two experiments were carried out with two nodulating and non-nodulating soybean isolines, with three different levels of N as (15NH4)2SO4 at the equivalent of 0, 25 and 50 kg N/ha. In the first experiment three seeds were sown in each pot and the plants harvested at 35, 55 and 75 days. In the second experiment only one seed was sown per pot and harvested at 75 days.
TL;DR: In this article, the soil moisture distribution at different distances from the water source in a high-yielding apple orchard planted on a 60 cm-deep heavy basalt soil underlined with gravel was studied.
Abstract: The soil moisture distribution at different distances from the water source in a high-yielding apple orchard planted on a 60-cm-deep heavy basalt soil underlined with gravel was studied. The soil water content was determined in three irrigation treatments which differed in discharge rates, distances between the tricklers on the lateral, and frequencyof application of an equal amount of water. The determinations were made several times during the wetting and drying processes in one irrigation cycle of each treatment. The roots of the trees perpendicular to and along the trickler line were counted in the soil profile. The results showed that the soil moisture and root system distribution covered a wider area when irrigated twice a week with 8 1/h tricklers rather than by irrigating every day or once a week with 4 1/h tricklers. Every day compared with once a week irrigation caused an appreciably narrower soil moisture distribution but a quite similar root distribution pattern. The soil-moisture-saturated level in the soil profile in all treatments, in the area under the trickler, caused water loss by drainage while irrigation continued. The loss was estimated to be 17% of the water applied. A pulsed irrigation was assumed to decrease this drainage loss by trying to supply the water in pace of the plant consumption.
TL;DR: In this paper, a machine for determining the root length of a sample is described, where root segments are cut and placed in water on a glass plate (375×375 mm) and the interruption of a light beam moving across the root sample is detected by a photo-diode and the total root length computed.
Abstract: A machine for determining the root length of a sample is described. The machine is basically an opto-electronic scanner. Root segments are cut and placed in water on a glass plate (375×375 mm). The interruption of a light beam moving across the root sample is detected by a photo-diode and the total root length computed. Using this machine a root sample can be measured in less than 3 minutes. Detailed calibration was only conducted up to 50 m although samples as large as several hundred metres can be measured using this machine.
TL;DR: Seed inoculation with a broth culture of Azospirillum brasilense alone alone significantly increased nodulation and grain yield of soybean grown in pots in unsterilized soil with different levels of urea.
Abstract: Azospirillum was associated with nodules of soybean. In general, seed inoculation with a broth culture ofAzospirillum brasilense alone significantly increased nodulation and grain yield of soybean grown in pots in unsterilized soil with different levels of urea ranging from 0 to 80 kg N/ha. This trend was significantly reproducible in a second experiment when a carrier based inoculant of the bacterium was used for seed inoculation. Inoculation withRhizobium japonicum andA. brasilense in combination generally increased grain yield in both the experiments, although the data were not significant.
TL;DR: In this article, a laboratory incubation experiment was conducted to study the influence of three moisture regimes, viz (i) waterlogged (W1), (ii) alternate Waterlogged and saturated (W2), and (iii) continuous Saturated (W3), on the extractable zinc and copper content.
Abstract: A laboratory incubation experiment was conducted to study the influence of three moisture regimes,viz (i) waterlogged (W1), (ii) alternate waterlogged and saturated (W2) and (iii) continuous saturated (W3) and two levels of organic matter application,viz (i) 0 (T1) and (ii) 0.5% of the soil (T2) in their all possible combinations on the extractable (N NH4OAC, pH 7.0) zinc and copper in three lowland alluvial rice-growing soils of West Bengal (India). The results showed that the extractable zinc and copper content in soils recorded marked decrease on incubation under all the moisture regimes, but the same was most prominent under the continuous saturated moisture regime (W3), followed by waterlogged (W1) and alternate waterlogged and saturated (W2) moisture regimes. Application of organic matter brought about further decrease in the content of these elements. Organic matter application combined with saturated moisture regime brought about the greatest decrease both in zinc and copper content. The microbiological immobilisation and the antagonistic effect of increased concentration of extractable iron, manganese and phosphorus have been suggested as the possible reasons for the observed decrease of the content of extractable zinc and copper.
TL;DR: In a 3-year field study, the effect of two rotations, paddy (Oryza sativa L), wheat (Triticum aestivum L.), mung (Phaseolus aureus L.) and corn (Zea mays L.), wheat ( Triticum aureivum), mung and phaseolus anaphora on wheat yield and chemical, physical and biological properties of soil was evaluated as mentioned in this paper.
Abstract: In a 3 year field study, the effect of two rotations, paddy (Oryza sativa L.), wheat (Triticum aestivum L.), mung (Phaseolus aureus L.) and corn (Zea mays L.), wheat (Triticum aestivum L.), mung (Phaseolus aureus L.) on wheat yield and chemical, physical and biological properties of soil was evaluated. Grain yield of the wheat sown after paddy during 1972–73, 1973–74 and 1974–75 was lesser by 0,300 and 390 kg/ha respectively than that of the wheat following corn. The reduction in the yield of wheat was attributed to relatively higher NPK removal by paddy, greater immobilization of N applied to wheat and deterioration of soil physical conditions in the paddy field. Total NPK removal by paddy average 131 kg/ha more than that by corn. Sharp increase in bacterial population of soil during early growth of wheat that followed paddy and the concurrent less available N in soil and low N content in wheat plants suggested that the N applied to wheat was immobilised to organic form. The increase in soil bulk density and particle dispersion ratio and decrease in water storage in deeper soil layers in the paddy field probably restricted the root proliferation and growth of wheat.
TL;DR: Herbarium specimens of 17 species of Geissois were analysed for nickel, cobalt, chromium and iron with a view to discovering further hyperaccumulators of nickel, including G. pruinosa.
Abstract: Herbarium specimens of 17 species of Geissois were analysed for nickel, cobalt, chromium and iron with a view to discovering further hyperaccumulators of nickel (>1000 μg/g on a dry mass basis) in addition to the previously recordedG. pruinosa. A further six hyperaccumulators were discovered, all from New Caledonia. Unlike 90% of hyperaccumulators, Geissois is in Subclass Rosidae of the Magnioliate which it shares with three other hyperaccumulators (two species ofArgophyllum andPearsonia metallifera. The work highlights the remarkable concentration of hyperaccumulators in New Caledonia.
TL;DR: In the standard methods of washing and storage of root samples of wheat, losses of dry weight from 20 to 40% may occur.
Abstract: In the standard methods of washing and storage of root samples of wheat, losses of dry weight from 20 to 40% may occur.
TL;DR: The plants of Hawkeye showed no iron deficiency symptoms whereas all the plants of the Fe-inefficient cultivar T-203 developed Fe deficiency after about one week following emergence.
Abstract: The effects of increasing amount of nitrate nitrogen on the growth, dry matter production, ionic balance and the appearance of iron chlorosis in two soybean cultivars were studied. More nitrogen increased the dry matter production of the Fe-efficient cultivar Hawkeye and decreased that of the Fe-inefficient cultivar T-203. The plants of Hawkeye showed no iron deficiency symptoms whereas all the plants of the Fe-inefficient cultivar T-203 developed Fe deficiency after about one week following emergence. The degree of chlorosis in the cultivar T-203 was more pronounced as the amount of nitrate applied increased.
TL;DR: The tolerance of each species was determined and for cobalt was highest inH. robertii (4000 μg/g) and for copper was highest for Haumaniastrum biformifolius (9000 μg /g) as discussed by the authors.
Abstract: Pot trials were carried out on plants ofHaumaniastrum katangense, Haumaniastrum robertii andAeolanthus biformifolius. These metallophytes from Zaire were grown in substrates containing from 0–10,000 μg/g (0–1%) copper or cobalt. The tolerance of each species was determined and for cobalt was highest inH. robertii (4000 μg/g) and for copper was highest inAeolanthus biformifolius (9000 μg/g). Discontinuities in the plant-soil curves for each element indicate an exclusion mechanism operating for all three species at lower concentrations of the element in the soil. All species would grow in soils containing only traces of cobalt or copper and this indicated that uptake of heavy metals was not linked to a physiological requirement for either element. The plant-soil relationship for cobalt (P<0.001) was sufficiently good for all three species for them to be useful in biogeochemical prospecting for this element.
TL;DR: Soybean (Glycine max {L.} Merr.) cultivars were inoculated with Gigaspora gigantea and Glomus mosseae to determine mycorrhizal: cultivar relationships as affected by soil pH.
Abstract: Soybean (Glycine max {L.} Merr.) cultivars were inoculated withGigaspora gigantea andGlomus mosseae to determine mycorrhizal: cultivar relationships as affected by soil pH. The specific cultivarfungal response was dependent on soil pH. Overall cultivar responses in unlimed soil (pH 5.1) were greater forG. gigantea thanG. mosseae. The ‘Bossier’ —G. gigantea combination was particularly responsive in unlimed soil and showed an increase of 10% in shoot length, 35% in shoot dry weight. 75% in root dry weight, and 397% in nodule dry weight over uninoculated controls. Little cultivar response was observed withG. mosseae inoculation in unlimed soil. In limed soil (pH 6.2), the larger responses were obtained withG. mosseae inoculated plants, although inoculation with eitherG. mosseae orG. gigantea appeared effective. In general, nodulation was greater on mycorrhizal roots than on control roots.
TL;DR: Lactic acid was the most dominant organic acid through whole growing stages and could be positive factors for the growth of Spirillum lipoferum which can fix nitrogen non-symbiotically at the rhizosphere of maize.
Abstract: Excretion products of maize roots (Zea mays cv. Koshu) were estimated. All excreted products were the highest by fresh weight basis at the young seedling stage. In amino acids excreted, glutamic acid accounting for 60% of the total was the highest and followed by alanine. These two amino acids showed the diverse fluctuation according to the growing age, that is, glutamic acid increased while alanine decreased. Stachyose was a main soluble sugar excepting the stage prior to the heading. At this stages, glucose and fructose together with stachyose were observed. Lactic acid was the most dominant organic acid through whole growing stages. These excreted materials could be positive factors for the growth ofSpirillum lipoferum which can fix nitrogen non-symbiotically at the rhizosphere of maize.