Role of water stress in differential aluminum tolerance of two barley cultivars grown in an acid soil

Two cultivars of barley (Hordeum vulgare L.), Al‐sensitive ‘Dayton’ and Al‐tolerant ‘Kearney’, were grown under controlled environmental conditions to determine the influence of Al stress and water stress imposed separately and in combination with one another. Plants were grown for 4 weeks in polyethylene‐lined, waxed cartons containing 1 kg of acid, Al‐toxic, Tatum subsoil (clayey, mixed, thermic, Typic Hapludult) at high (pH 4.7) or low (pH 6.6) Al stress. During the final 2 weeks they were also subjected to low (‐20 to ‐40 kPa) or high (‐60 to ‐80 kPa) water stress. Under low water stress, little difference in the growth or appearance of the two cultivars was found, even in the presence of low Al stress (pH 6.6). When high water stress treatment was superimposed on low Al stress treatment, however, significant differences between the two cultivars in biomass production, leaf enlargement, and tillering resulted. When high water stress was combined with high Al stress (pH 4.7), these differences in vegetative growth were further magnified. Thus, drought exacerbates the stress effects of Al toxicity in plants and may account for a significant portion of the reduction in yield commonly observed in acid soils under field conditions and formerly attributed to Al toxicity alone. By increasing soil moisture level, the growth suppressive effect of Al toxicity was significantly reduced.     

Role of water stress in differential aluminum tolerance of six sunflower cultivars grown in an acid soil

Six cultivars of sunflower (Helianthus annuus L.), were screened under controlled environmental conditions for tolerance to Al stress and water stress imposed separately and in combination with one another. Plants were grown for 4 weeks in waxed cartons containing 1 kg of acid, Al‐toxic Tatum, subsoil (clayey, mixed, thermic, Typic Hapludult) at high (pH 4.3) or low (pH 6.3) Al stress. During the final 2 weeks they were also subjected to low (‐20 to ‐40 kPa) or high (‐60 to ‐80 kPa) water stress. Plant growth responses and symptoms of Al toxicity suggested that a wide range of cultivar sensitivity existed. ‘Manchurian’, ‘S‐212’, ‘S‐254’, and ‘S‐265’ were relatively tolerant to Al toxicity while cultlvars ‘Romania HS‐52’ and ‘RM‐52’ were extremely sensitive. Under high Al stress and high water stress, chloroplasts in cells from the Al‐sensitive cultivar ‘Romania HS‐52’ were smaller and contained less starch than chloroplasts from the Al‐tolerant cultivar ‘Manchurian’. Furthermore, the smaller chloroplasts tended to have fewer grana stacks per unit area than did the chloroplasts from tolerant plants. These differences were not apparent when the Al‐sensitive cultivar was grown either in the absence of Al or water stress. In general, Al‐sensitive cultivars of sunflower were more tolerant to water stress than were Al‐tolerant cultivars. Increasing the soil moisture level reduced Al toxicity in Al‐sensitive cultivars. Similarly, decreasing Al stress partially overcame the detrimental effects of high water stress. Hence, Al stress and water stress are interrelated factors which must be considered in the characterization and breeding of plants for better adaptation to acid soils.     

Effect of saline irrigation water composition on selenium accumulation by wheat

Abstract

Trace amounts of selenium (Se) are essential for animal and human nutrition. However, the optimum concentration range is very narrow and outside of this range deficiencies or toxicities can occur. Potentially harmful levels of Se in soils and irrigation waters have been reported in regions where salinity is also a hazard. This study was conducted to determine the effects of irrigation water composition and salinity level on Se accumulation in leaves and grain of spring wheat (Triticum aestivum L. cv. ‘Yecora Rojo'). Plants were grown in greenhouse sand cultures and irrigated with complete nutrient solution. Salinity treatments were initiated 4 days after planting by irrigating the seedlings with either chloride‐dominated waters or with waters containing both chloride and sulfate salts. Compositions of the mixed salt waters were designed to simulate saline drainage waters commonly present in the San Joaquin Valley of California. The experimental design was a randomized complete block with two salinity types (Cl^? or mixed salts), eight salinity levels (osmotic potentials=0.07, 0.16, 0.21,0.30.0.36, 0.44, 0.52, and 0.63 MPa), and three replications. Four weeks after planting, Se (1 mg L^?1 as sodium selenate) was added to all irrigation waters. In the chloride system, the molar ratio of SO₄ ^2‐:SeO₄ ^2‐ was approximately 110 across all salinity levels, whereas in the mixed salt system, the SO₄ ^2‐ SeO₄ ^2‐ratio in solution increased from about 300 to 4,700 as salinity increased. Selenium concentration was determined in fully‐expanded flag leaf blades and grain. Salinity type, and to a lesser extent, salinity affected Se accumulation. In the Cl‐system, wheat accumulated Se to levels that may be potentially harmful to livestock and humans, e.g., blade‐Se ranged from 435 to 295 mg kg^?1 dry wt; grain‐Se ranged from 81 to 54 mg kg^?1 dry wt. Under the saline conditions of the mixed salt system, the inhibition of selenium uptake by sulfate reduced both blade‐ and grain‐Se to levels that would minimize the health risk to consumers.     

Effect of rate and source of nitrogen fertilizers on mineral composition of d'Anjou pears

Abstract

Thirteen‐year‐old ‘d'Anjou’ pear trees, Pyrus communis L., were fertilized with 3 rates of ammonium nitrate or 2 rates of calcium nitrate in late autumn from 1978 to 1980. In 1981, mid‐terminal and fruiting‐spur leaves and fruit peel and flesh were sampled for mineral analysis of N, P, K, Ca, Mg, B, Cu, Fe, Mn, and Zn. The level of N increased in the above tissues as rate of N fertilizer was increased. In most cases, the levels of N, P, K, Mg, Cu, and Mn in the fruiting spur leaves and fruit were greater in the ammonium nitrate‐treated trees than with calcium nitrate fertilizer. Calcium was higher in the fruit peel and flesh of trees treated with the low rate of calcium nitrate than with the highest rate of ammonium nitrate fertilizer while Ca in the fruiting spur leaves was lower in the calcium nitrate‐fertilized trees.     

GROWTH,YIELD, AND ION RELATIONS OF STRAWBERRY IN RESPONSE TO IRRIGATION WITH CHLORIDE-DOMINATED WATERS

Strawberry is listed as the most salt sensitive fruit crop in comprehensive salt tolerance data bases. Recently, concerns have arisen regarding declining quality of irrigation waters available to coastal strawberry growers in southern and central California. Over time, the waters have become more saline, with increasing sodium (Na⁺) and chloride (Cl^?). Due to the apparent extreme Cl^? sensitivity of strawberry, the rising Cl^? levels in the irrigation waters are of particular importance. In order to establish the specific ion causing yield reduction in strawberry, cultivars ‘Ventana’ and ‘Camarosa’ were grown in twenty-four outdoor sand tanks at the ARS-USDA U. S. Salinity Laboratory in Riverside, CA and irrigated with waters containing a complete nutrient solution plus Cl^? salts of calcium (Ca²⁺), magnesium (Mg²⁺), Na⁺, and potassium (K⁺). Six salinity treatments were imposed with electric conductivities (EC) = 0.835, 1.05, 1.28, 1.48, 1.71, and 2.24 dS m^?1, and were replicated four times. Fresh and dry weights of ‘Camarosa’ shoots and roots were significantly higher than those of ‘Ventana’ at all salinity levels. Marketable yield of ‘Camarosa’ fruit decreased from 770 to 360 g/plant as salinity increased and was lower at all salinity levels than the yield from the less vigorous ‘Ventana’ plants. ‘Ventana’ berry yield decreased from 925 to 705 g/plant as salinity increased from 0.835 to 2.24 dS m^?1. Relative yield of ‘Camarosa’ decreased 43% for each unit increase in salinity once irrigation water salinity exceeded 0.80 dS m^?1. Relative ‘Ventana’ yield was unaffected by irrigation water salinity up to 1.71 dS m^?1, and thereafter, for each additional unit increase in salinity, yield was reduced 61%. Both cultivars appeared to possess an exclusion mechanism whereby Na⁺ was sequestered in the roots, and Na⁺ transport to blade, petiole and fruit tissues was limited. Chloride content of the plant organs increased as salinity increased to 2.24 dS m^?1 and substrate Cl increased from 0.1 to13 mmol_cL^?1. Chloride was highest in the roots, followed by the leaves, petioles and fruit. Based on plant ion relations and relative fruit yield, we determined that, over the range of salinity levels studied, specific ion toxicity exists with respect to Cl^?, rather than to Na⁺ ions, and, further, that the salt tolerance threshold is lower for ‘Camarosa’ than for ‘Ventana’.     

Immunochemical cross-reactivity ofβ-naphthoflavone-inducible cytochrome P450 (P450IA) in liver microsomes from different fish species and rat

Antibodies prepared against the major -naphthoflavone (BNF)-inducible cytochrome P450 (P450) forms from three species of fish (rainbow trout, Atlantic cod, and scup) well separated in teleost phylogeny, were used to investigate the immunochemical relatedness of liver microsomal P450 in different species of BNF-treated fish and rat. Rabbit polyclonal IgG against all three P450s and mouse monoclonal antibodies prepared against scup P450E were employed in this study. Liver microsomes were prepared from BNF-treated specimens of hagfish, herring, rainbow trout, cod, scup, perch, plaice and rat. With Western blotting it was shown that the various antibodies cross-reacted with a protein band in liver microsomes in the P450-region of each of the BNF-treated fish species. The apparent molecular weight of the cross-reacting proteins showed differences within the range 54,000–59,000 daltons. The effects of the different antibodies on the microsomal BNF-inducible 7-ethoxyresorufin O-deethylase (EROD) activity gave inhibition patterns that reflected to a certain extent the phylogenetic relationship of the species investigated. In rat microsomes a protein band of relative molecular mass similar to rat P450c (Mr=54,000) was recognized by all antibodies. In addition, a second band of lower molecular mass was strongly recognized by anti-cod P450c antibodies, and faintly stained with anti-rainbow trout P450LM4b IgG and anti-scup P450E MAb 1-12-3. This band could correspond to rat P450d, the isosafrole-inducible rat isoenzyme. Considering the long separate evolutionary history of some of these fishes (50–200 million years), the results demonstrate that certain antigenic epitopes in the BNF-inducible P450 isoenzymes have been strongly conserved during the evolution of fish species. These conserved epitopes seem however not to be directly involved in the measured EROD activities. Furthermore, the results suggest that the BNF-inducible P450s in fish contain regions with structural similarity to the homologous counterpart that has evolved through gene duplication into a P450 family in mammals containing at least two gene products (the P450IA gene family).     

Estimation of the Dietary Lipid Requirement Level of the White Crayfish Procambarus acutus acutus

Six isonitrogenous and isoenergetic diets containing graded levels of lipid (menhaden fish oil) were fed to juvenile white crayfish ( Procambarus acutus acutus ) over a 10 week period. A significant depression in weight gain was observed in crayfish fed diets containing 9% or more lipid. There were no significant differences in growth of crayfish fed diets containing 0 to 6% lipid. Whole-body percentages of lipid and dry matter decreased, and protein increased in crayfish fed high-lipid diets. Dietary lipid did not appear to influence survival or molting frequency. Whole-body lipids generally reflected dietary fatty acid composition.     

Interactions of temperature,size and photoperiod on growth and smoltification of chinook salmon (Oncorhynchus tshawytscha)

Underyearling fall chinook salmon (Oncorhynchus tshawytscha) were reared at two temperatures (9 and 15°C) and three photoperiods simulating winter (WIN), spring—summer (SS), and natural (NAT) conditions. The two artificial photoperiods were adjusted according to fish size so that an equinoctial photoperiod was synchronized with a hypothesized optimum size range for smolting (8–14 cm fork length). Fish exposed to a winter (WIN) photoperiod had the slowest growth rate. Fish under the SS photoperiod at both temperatures and under the WIN photoperiod at 9°C displayed hypoosmoregulatory capability near the equinoctial daylength. Thyroxine concentrations in fish reared under a natural photoperiod remained at basal levels during the period of early saltwater adaptiveness and throughout the remainder of the experiment. Thyroxine titers showed significant increases under all experimental photoperiod—temperature combinations near the equinoctial daylength with the exception of the 15°C/SS treatment.     

Pond production of the mud crabs Scylla paramamosain (Estampador) and S. olivacea (Herbst) in the Mekong Delta, Vietnam, using two different supplementary diets

The production performance of Scylla paramamosain and S. olivacea reared together in ponds and provided with different supplementary diets (crustaceans or trash fish) were evaluated with that of an unfed control group relying only on natural food available within the pond. Each treatment was conducted in triplicate. The aim was to evaluate two production strategies over a 130‐day grow‐out trial: (1) production to 200 g crab^?1, which is the minimum preferred marketable size in the Lower Mekong Delta (LMD) and (2) production to 300 g crab^?1, the size that fetches the highest market price. Growth production models were estimated which revealed that the rearing period required to produce crabs of 200 g was 102 days with supplementary feeding, compared with 120 days for the unfed control group. The rearing period needed to produce 300‐g‐sized crabs was estimated to be 144 days and 186 days for the supplementary fed and unfed groups respectively. The additional risk involved in rearing mud crabs to 300 g is not considered worthwhile, under similar culture conditions as observed in this trial, as a decrease in pond water quality and higher mortality rates were observed in the final month of culture needed to achieve this larger size.