Difference in selenium accumulation in shoots of two rice cultivars

Two japonica rice （Oryza sativa L.） cultivars, Xiushui 48 and S. Andrea, differing in their ability to accumulate Se in the grain （as high as a three-fold difference）, were compared for selenium （Se） accumulation in their shoots when their growth media was supplied with different forms of Se. Results indicated that when treated with 0.25μmol L^-1 Na2SeO3, Xiushui 48 accumulation of Se in the shoots was significantly more rapid （P〈0.05） than S. Andrea, probably because of greater Se uptake and transport in Xiushui 48. Xiushui 48 rice seedlings had a higher shoot-Se accumulation rate and absorbed selenocysteine （Se-Cys） more rapidly than S. Andrea seedlings. However, when treated with Se as 0.25μmol L^-1 selenomethionine （Se-Met）, the S. Andrea seedlings＇ accumulation rate was significantly greater （P〈0.05） than that of Xiushui 48. Possibly, the high Se accumulation rate of Xiushui 48 seedling shoots compared to S. Andrea shoots was the result of a higher capacity of Xiushui 48 to transform selenite to organic Se compounds and a higher selenite uptake rate.     

Effect of PCMBS on calcium‐ or aluminum‐induced curvature in roots of two watermelon cultivars

Unilateral application of calcium (Ca) or aluminum (Al) in agar to the primary roots of watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] cultivars ‘Dixielee’ and ‘Mirage’ induced root curvature. Root curvature induced by Al was greater than that induced by Ca in both cultivars. PCMBS inhibited Al‐induced root curvature in both cultivars, but had no effect on Ca‐induced curvature. The inhibition of curvature indicated that PCMBS reduced Al uptake. ‘Dixielee’ was more responsive to PCMBS than was ‘Mirage’.     

Soil‐boron affects straw quality and other agronomic traits in two cultivars of barley

Abstract

Boron (B) toxicity in crops occurs in many dry areas. However, the effect of high external B levels on straw quality is not known. In this greenhouse study, the responses of straw yield, straw quality, and other characters to high soil B levels were investigated in barley. Two cultivars, Galleon and Harmal, were tested. In Experiment I, three B levels were prepared by mixing 0, 25, and 50 mg B kg^‐1 soil‐mix (designated as B0, B25, and B50, respectively). Straw yield, straw quality (nutritional value), and other characters were measured. In Experiment II, an additional soil B level, prepared by adding 12.5 mg B kg^‐1 soil‐mix (designated as B12), was used. Shoots and roots were harvested at tillering and after heading. In Experiment 1, the B50 treatment improved straw quality, had no effect on straw yield, but decreased grain yield, and harvest index. Considering the shoot B concentrations and B uptake at the tillering stage at moderate to high levels of soil B in both experiments, Galleon was able to restrict B uptake better than Harmal. However, Harmal, unlike Galleon, had a better growth and more tillers at moderate levels of soil‐B than at BO. Since Harmal had higher or similar B concentrations as Galleon, Harmal appeared to tolerate higher tissue B concentrations than Galleon. The limitation of selecting genotypes tolerant to high‐B soil was pointed out, and the need to study adult performance after the initial selection was suggested. The finding on straw quality and yield would be a positive finding for sheep owners in dry areas, where barley straw and stubble are a valuable ruminant feed.     

Plant residue decomposition and nitrogen dynamics in an alley cropping and an annual legume‐based cropping system

Abstract

Field experiments were conducted to compare plant residue decomposition and nitrogen (N) dynamics in an alley cropping system (AC) and an annual legume‐based cropping system (NA) in the Piedmont region of Georgia, USA. The hedgerows of the alley cropping system consisted of Albizia julibrissin (albizia) established in January 1990. Hedges were four meters apart with a spacing within rows of one‐half meter. A rotation beginning with Mucuna deeringiana (velvet bean) followed by a winter annual crop of Trifolium incarnatum L. (crimson clover), a summer crop of Sorghum bicolor (L.) Moench (grain sorghum) and a winter crop of Triticum aestivum L. (wheat) was established in the alley cropping system and a control annual cropping system. All crops were grown using no‐tillage systems. Plant residue decomposition and N dynamics were measured using litterbag technologies on crimson clover, albizia, and grain sorghum. Soil and plant total N, decay rate constants (k) for dry matter, soil potentially mineralizable N, and nitrification rates were determined. Decay rate constants for N were best correlated with the lignin content of the plant residues. No residue quality parameter was significantly correlated with decay rate for dry matter. There was no significant difference between AC and NA systems in soil inorganic N and potentially mineralizable N; however, nitrification rates were greater in the AC. Grain sorghum N uptake and biomass production were not different for AC and NA. This was thought to be due to large inputs of organic N prior to the start of the experiment.     

Differentiation and geographical distribution of β-amylase isozyme in barley

This study reports on the investigation of the polymorphism and geographical distribution of -amylase isozymes by isoelectric-focusing (IEF) analysis in samples of world barley. The isozyme pattern of high thermostability type A and low thermostability type C varieties was restricted in isozyme type II. However, the isozyme pattern of the middle thermostability type B varieties was polymorphic. The -amylase isozyme of 1,554 lines of the middle thermostability group was investigated next. Besides types I and II, new isozyme types III and IV were observed. Most lines were grouped into type II in all growing areas, except for Europe where type I and type II were even in number. Types III and IV were observed in only one line in India and Afghanistan, respectively. In Northern Europe, especially in Denmark, type I was major. It was concluded that a mutant IEF isozyme type I originated from the type II prototype of the thermostability B group in Northern Europe.     

Effects of bioenergy crop cultivation on earthworm communities—A comparative study of perennial (Miscanthus) and annual crops with consideration of graded land-use intensity

Energy crops are of growing importance in agriculture worldwide. This field study aimed to investigate earthworm communities of different intensively cultivated soils during a 2-year period, with special emphasis on annual and perennial energy crops like rapeseed, maize, and Miscanthus. These were compared with cereals, grassland, and fallow sites. Distribution patterns of earthworm abundance, species, and ecological categories were analysed by constrained ordination procedures (redundancy analysis; CANOCO) using a set of environmental variables as predictors, such as CN value of harvest residues, SOC and N_t content, soil pH, soil texture, and land-use intensity. The latter was determined by principal component analysis using average soil coverage and intensity of tillage, weed control, and fertilisation as input variables. It was clearly found that land-use intensity was the dominant regressor for earthworm abundance and total number of species. The diversity of earthworm communities was especially enhanced and showed a more balanced species composition in extensively managed soils under grassland, fallow, and Miscanthus. For the total number of species, Miscanthus (5.1 ± 0.9) took a medium position and neither differed significantly from intensively managed rapeseed (4.0 ± 0.9), cereals (3.7 ± 1.1), and maize sites (3.0 ± 1.4), nor from grassland (6.8 ± 1.5) and fallow (6.4 ± 1.0) sites. Total earthworm abundance ranged between 355 (±132) and 62 (±49) individuals m⁻² in fallow and maize sites, respectively.Interestingly, Miscanthus had quite positive effects on earthworm communities although the CN value of harvest residues was very high. It is recommended that Miscanthus may facilitate a diverse earthworm community even in intensive agricultural landscapes.     

Enhancement of nitrate efflux and the plasma membrane hydrogen ion‐transport activity of barley roots by nitrate treatment

The effect of nitrate (NO₃) on the activities of hydrogen (H⁺)‐ATPase and H⁺‐transport in the plasma membrane vesicles isolated from barley (Hordeum vulgare L. cv. Kikaihadaka) roots was investigated. After treatment with 10 mM NO₃ for longer than 24 h, both activities of H⁺‐ATPase and H⁺‐transport assayed in the presence of chloride (Cl) were stimulated less than 20%. While H⁺‐transport activity was approximately two times higher in NO₃‐grown roots than in control roots when assayed in the presence of NO₃ instead of Cl. This result suggests that NO₃ is permeable in the plasma membrane vesicles isolated from NO₃‐grown roots rather than that of the control, and thereby stimulate H⁺‐transport activity through the collapse of positive potentials established by H⁺‐ATPase. Furthermore, NO₃ efflux from roots was markedly enhanced after 48 h of the exposure to NO₃. Taken together, NO₃ efflux may be mediated by the permeability to NO₃ which is induced by NO₃.     

Tolerance of barley cultivars to an acid,aluminum‐toxic subsoil related to mineral element concentrations in their shoots

Abstract

Barley, Hordeum vulgare L., is extremely sensitive to excess soluble or exchangeable aluminum (Al) in acid soils having pH values below about 5.5. Aluminum tolerant cultivars are needed for use in rotations with potatoes which require a soil pH below 5.5 for control of scab disease. They are also potentially useful in the currently popular “low input, sustainable agriculture (LISA)”; in which liming even the plow layer of soil is not always possible or cost effective, or in situations where surface soils are limed but subsoils are acidic and Al toxic to roots. Ten barley cultivars were screened for Al tolerance by growing them for 25 days in greenhouse pots of acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic, typic Hapludult) treated with either 750 or 4000 μg?g^‐1 CaCO₃ to produce final soil pH values of 4.4 and 5.7, respectively. Based on relative shoot dry weight (weight at pH 4.4/weight at pH 5.7 X 100), Tennessee Winter 52, Volla (England), Dayton and Herta (Denmark) were significantly more tolerant to the acid soil than Herta (Hungary), Kearney, Nebar, Dicktoo, Kenbar and Dundy cultivars. Relative shoot dry weights averaged 28.6% for tolerant and 14.1% for sensitive cultivar groups. Comparable relative root dry weights were 41.7% and 13.7% for tolerant and sensitive cultivars, respectively. At pH 4.4, Al concentrations were nearly three times as high in shoots of sensitive cultivars as in those of the tolerant group (646 vs. 175 μg?g^‐1), but these differences were reduced or absent at pH 5.7. At pH 4.4, acid soil sensitive cultivars also accumulated phosphorus concentrations that were twice as high as those in tolerant cultivars (1.2% vs. 0.64%). At pH 5.7, these P differences were equalized at about 0.7% for both tolerant and sensitive groups. At pH 4.4, shoots of the Al‐sensitive cultivar Nebar contained 1067 μg?g^‐1 Al and 1.5% P. Concentrations of Al and P in the shoots of acid soil sensitive cultivars grown at pH 4.4 exceeded levels reported to produce toxicity in barley. The observed accumulation of such concentrations of Al and P in the shoots of plants grown under Al stress is unusual and deserves further study.     

H+‐atpase and H+‐transport activities in tonoplast vesicles from barley roots under salt stress and influence of calcium and abscisic acid 1

Seedlings of two barley cultivars differing in NaCl sensitivity were treated with low (100 mM) or high (400 mM) concentration of NaCl for 6 days. Tonoplast vesicles were prepared from roots, and H⁺‐ATPase and H⁺‐transport activities associated with tonoplast were assayed. Both H⁺‐ATPase and H⁺‐transport activities in the two cultivars were increased at 100 mM NaCl. These activities also increased in the salt‐tolerant cultivar at 400 mM NaCl, but in salt‐sensitive cultivar were decreased. In vivo treatment with 10 mM Ca²⁺ stimulated H⁺‐ATPase and H⁺‐transport activities at two levels of NaCl, however, treatment with 10⁵M (±) abscisic acid (ABA) inhibited these activities. From these results we propose that the increase of the vacuolar H⁺ pumps in barley roots reflects an adaptation to salt stress. The stimulation of HVATPase and H⁺‐transport activities by calcium (Ca) depends mainly on its effect in maintaining stability of membrane under salt stress.     

Evidence of depleted uranium‐induced hormesis and differential plant response in three grasses

General plant response to depleted uranium (DU) was tested using three widespread range‐grass species, Aristida purpurea Nutt. (purple threeawn), Buchloe dactyloides (Nutt.) Engelm. (buffalograss), and Schizachyrium scoparium (Michx.) Nash (little bluestem). Aboveground, belowground, and total biomass measures of these grasses were analyzed over the five different DU soil concentrations of 0, 50, 500, 5,000, and 25,000 mg kg^‐1. Differential plant response to DU was observed between the three grasses, wiith A. purpurea and B. dactyloides exhibiting a threshold‐type response in which no changes in biomass occurred until the highest treatment level of 25,000 mg kg^‐1 was reached. Schizachyrium scoparium, however, demonstrated a large degree of growth stimulation, or hormesis, at the 50 and 500 mg kg^‐1 DU concentrations. Several possible mechanisms of this hormetic response are offered.     

Effects of vesicular arbuscular mycorrhizal inoculation on growth and phosphorus nutrition of barley in natural or methyl bromide‐treated soil

The growth and phosphorus (P) nutrition of barley (Hordeum vulgare L.) in a soil, methyl bromide fumigated or untreated and supplied with or without mycorrhizal inoculum, was studied in pots placed under a field environment. Inoculation significantly raised the overall levels of vesicular arbuscular mycorrhizal (VAM) infection. The relative increase was significantly greater in sterile than nonsterile soil. Soil sterilization produced significantly higher dry matter throughout the experiment. Inoculation resulted in a significant growth depression earlier in the season which could not be offset by the following mycorrhizal enhancement in P absorption rates. The primary reasons for this yield depression were most probably the root density and available P status of the soil which might have been over the threshold limit for positive mycorrhizal yield response in barley. In this experiment, the result of inoculation could be regarded beneficial considering 17 and 30% higher P concentrations in grain and straw, respectively, but detrimental with respect to 20% loss in grain plus straw yield.     

Copper availability in two soils amended with eleven annual applications of copper‐enriched hog manure

Abstract

Relatively high amounts of Cu are found in manure of hogs (Sus scrofa domesticus) maintained on diets containing growth‐stimulating levels of Cu. While disposal of Cu‐enriched hog manure through repeated long‐term application to agricultural land is commonly practiced, concern exists regarding Cu availability in these soils. Field studies were conducted on a Bertie fine sandy loam (Aquic Hapludults) and a Starr‐Dyke clay loam (Fluventic Dystochrepts‐Typic Rhodudults), located in the Coastal Plain and Piedmont regions of Virginia. The objective was to examine the effects of long‐term Cu application on corn (Zea mays L.) growth and to ascertain the Cu sorption capacity of these soils. Field plots were treated with Cu‐enriched hog manure or CUSO₄ (on an equivalent Cu basis) annually. Manure amendments totaled about 240 t ha^‐1 (dry weight) over an 11 yr period (1978 through 1989). The manure averaged 1300 mg Cu kg^‐1 (dry weight) over this time period totaling 340 kg Cu ha^‐1. Sorption isotherms were determined for sorption of Cu by the Bertie and Starr‐Dyke soils. In comparison with unamended control plots, studies conducted in 1989 showed an early season stunting effect for corn grown on the CUSO₄ treated Bertie soil. No differences in plant heights were observed for corn grown in CuSO₄ treated Starr‐Dyke soil or control plots. Plant growth rates were increased on plots amended with Cu‐enriched hog manure. Copper sorption capacity of Bertie and Starr‐Dyke soils increased following several annual applications of manure.     

Simulation of heat and moisture transfer through a surface residue—soil system

A simulation model suitable for describing the dynamic aspects of mass and energy transfer in a soil—residue—atmosphere system has been developed and used to determine soil heat and water budgets. The model has been programmed in BASIC and uses numerical methods suitable for microcomputer applications. It displays a fundamental coupling of the surface residue to the soil—atmosphere system, and uses network analysis to describe heat and moisture transfer. Short-wave and long-wave radiative transfer, changes in energy status, rainfall interception by the residue, infiltration, redistribution, evaporation, and drainage are all accounted for. Daily input requirements include global short-wave radiation, maximum and minimum air temperatures, average wind speed, precipitation, and temperature and water content deep within the soil. General site, residue, and soil characteristics are also needed.Surface residues are treated as a thin layer with uniform horizontal distribution and residue loading rate is 3000 kg ha⁻¹. Application of the model to energy and water budget studies using environmental data recorded at Pullman, WA during 1981/82 is discussed. Simulation results indicate that for the Pullman conditions surface residues decreased evaporation by roughly 36% when compared with simulations of bare soil evaporation. Monthly trends, however, indicate that the effectiveness of residues in conserving soil moisture decreases as the length of rain-free periods increases.     

Zinc nutrition and levels of endogenous lndole‐3‐acetic acid in radish shoots

Radish (Raphanus sativus cv. Akamaru‐Hatsukadaikon) was grown for several experiments in a glasshouse with zinc (Zn) supply in the nutrient solution. Lack of Zn resulted in stunted growth and reduced leaf of radish shoots were observed. Two‐dimensional thin layer chromatography (TLC) and gas chromatography‐mass spectrometry (GC‐MS) analysis revealed the presence of endogenous indole‐3‐acetic acid (IAA) in Zn‐deficient radish shoots. An estimate has been made of alkali‐labile (1 and 7N NaOH) IAA in Zn‐deficient radish shoots with the use of gas chromatography (GC). The level of 7N NaOH‐labile IAA (peptidic + ester + free) and IN NaOH‐labile IAA (ester + free) in Zn‐deficient radish shoots was almost the same as that of control radish shoots. These results suggest that Zn nutrition did not affect the level of endogenous IAA in radish shoots.     

Effects of iron nutritional status and time of day on concentrations of phytosiderophores and nico‐tianamine in different root and shoot zones of barley

The diurnal pattern in concentrations of phytosiderophores (PS) and its precursor nicotianamine (NA) was studied in different root and shoot zones of iron (Fe)‐sufficient and Fe‐deficient barley (Hordeum vulgare L. cv. Europa) grown in nutrient solution. Roots were separated into apical (0–3 cm) and basal zones (>3 cm) and shoots into young (3 cm basal zones of youngest two leaves) and old (remaining zones of youngest two leaves and oldest leaf) parts. The main PS in barley was identified as epi‐hydroxymugineic acid (epi‐HMA). Regardless of the sampling zone and time of day, epi‐HMA concentrations were several times higher in Fe‐deficient than in Fe‐sufficient plants and several times higher in the roots than in the shoots. In roots and shoots, epi‐HMA concentrations were always higher in the younger compared with the older zones. In both root zones of Fe‐deficient plants, an inverse diurnal rhythm occurred in epi‐HMA concentrations and in its release by the roots. In contrast, such a rhythm was absent in roots of Fe‐sufficient plants and in the shoots regardless of the Fe nutritional status. Nicotianamine concentrations in roots were not affected by the Fe nutritional status in apical zones but slightly enhanced under Fe deficiency in basal zones. In contrast to roots, NA concentrations in both shoot parts were lower in Fe‐deficient than in Fe‐sufficient plants. Regardless of the Fe nutritional status in roots and shoots, NA concentrations were higher in young than in old parts and no consistent diurnal variations were observed. The results suggest that PS are also synthesized in the shoot, although at much lower rates than in roots. As with roots, PS synthesis in the shoot is enhanced under Fe deficiency and is mainly localized in young growing tissue. The distinct diurnal rhythm in PS release in roots is apparently not regulated by variation in the rate of PS synthesis during the day.     

Importance of acid‐insoluble residue in plant analysis for total macro and micro elements

Abstract

Insoluble siliceous residues remaining after HNO₃/HClO₄ decomposition of the plant tissues National Bureau of Standards, standard reference materials spinach (Spinacea oleracea), orchard leaves and tomato leaves (Lycopersicon escuientum), contained varying quantities of the macro and micro elements Na, K, Mg, Ca, Mn, Fe, Cu and Zn. For the different samples with total element concentrations ranging from 11 μg/g (Cu in orchard leaves) to 45,000 μg/g (K in tomato leaves), residues contained element concentrations ranging from 0.05 to 88 times the respective concentrations in the samples. Contributions of residues to element concentrations in the plant tissues varied from 0.04 to 42% of the total concentrations. Overall, these constituted negligible (ca 0.1% for Mg and Ca), small (0.5% for Zn, Mn, K and 1% for Cu), and large (6% for Fe, 28% for Na) contributions depending on sample and analyte. Residue contributions to total element concentrations of plant tissues must be considered for reliable estimations of macro and micro elements.     

Decomposition of cattle manure and colonization by macroinvertebrates in sediment of a wetland of the Middle Paraná River

Purpose

The study was carried out in a wetland of the Middle Paraná River system, Argentina, in order to evaluate the processes associated with the decomposition of manure, which includes changes in chemical composition, nutrient release of manure, and colonization of invertebrates. We also compared the invertebrate assemblage that colonized manure with that present in the benthos of the wetland.

Materials and methods

Nylon bags were filled with fresh cattle manure and anchored to the littoral zone of the wetland. Six bags were collected after 1, 2, 6, 14, 21, 28, 33, 55, and 79 days: three for invertebrate determination and the other three bags for determination of dry mass and chemical analyses. The nutrient content, cellulose, lignin, and total phenolic compounds of manure were determined. In addition, the leachate of manure was collected for nutrient analyses. Samples of the wetland benthic sediment were collected for benthic invertebrate determination and particle size analyses. Spearman rank correlation was used to evaluate the relationship between chemical compounds of manure and breakdown rate. Principal component analysis was used to explore invertebrate assemblage composition of manure and sediment during the experiment.

Results and discussion

Limnodrilus, Dero, and Chironomus were dominant in the manure. Gatherer-collector was the dominant group in the manure, comprising almost 95 % of the total density of invertebrates. Breakdown rate was significantly related with nutrients, cellulose and total phenolics of manure. An ordination plot showed changes in invertebrate assemblages of manure and sediment samples over time.

Conclusions

This study provides new insight on the importance of manure as a substrate for macroinvertebrate colonization. Cattle manure needs to be considered as a potential source of nutrients for aquatic systems and a substrate for invertebrate assemblages.

     

Influence of fusicoccin and gramicidin‐D on Rb+ transport in intact barley seedlings

The influence of the fungal toxin fusicoccin or the quasi‐ionophore gramicidin‐D on Rb⁺ transport in intact barley seedlings (Hordeum vulgare cv Morex) was studied. Fusicoccin (1 μM) or gramlcidin‐D (3.2 μM) were added to absorption solutions which contained 0.1 mM RbCl and 0.5 mM CaSO₄, and the Rb⁺ content of roots and shoots determined over a 24 hour period. Roots of fusicoccin‐treated seedlings contained greater amounts of Rb⁺ throughout the entire course of the experiment, and roots of gramlcidin‐D treated seedlings contained greater amounts of Rb⁺ for the first 10 hours but contained smaller amounts of Rb⁺ for the rest of the experiment when compared with control seedlings. However, shoots of seedlings treated with fusicoccin or gramicidin‐D contained smaller amounts of Rb⁺ than the control seedlings throughout the entire course of the experiment. These results are discussed in terms of the interrelationships of the ion transport mechanisms which mediate the vectorial movement of ions from the absorption solution to the stelar apoplasm of the root.