Uptake of phosphorus by plants in relation to carbon dioxide production and organic phosphorus mineralization in soils

Summary In previous work, the yield of phosphorus in plants grown in the greenhouse on 36 alkaline soils was correlated significantly with the organic phosphorus mineralized during incubation of the soils in the laboratory, independently of the labile inorganic phosphorus. In this investigation, the same soils were used to test the hypothesis that the apparent organic-phosphorus effect observed previously was an indirect effect of CO₂ evolved from soil organic matter in increasing the susceptibility of the inorganic phosphorus to uptake by plants. The hypothesis was tested on the basis of measurements of CO₂ evolved and organic phosphorus mineralized concurrently during incubation of the soils in the laboratory. Statistical tests showed that the yield of phosphorus in the plants was correlated significantly with the organic phosphorus mineralized, independently of correlations with CO₂ evolved and labile inorganic phosphorus; the yield of phosphorus in plants, however, was not correlated significantly with CO₂ evolved, independently of correlations with organic phosphorus mineralized and labile inorganic phosphorus. The results thus provide no justification for discarding the organic-phosphorus theory and for substituting the CO₂ theory in its place.Journal Paper No. J-5691 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.Rockefeller Foundation Fellow and Professor of Soils.     

Changes in extractable organic phosphorus in soil in the presence and absence of plants

Summary The effect of cropping on soil organic phosphorus was investigated in laboratory and greenhouse work with six soils. Successively lower contents of extractable organic phosphorus were found in samples that had been (a) airdried initially and stored in that condition, (b) incubated in a moist condition but without a crop, and (c) planted to four successive crops, the roots of the crops being removed before analysis of the soil. These differences were statistically significant. Samples of rhizosphere soil taken after the fourth crop did not yield significantly different amounts of extractable organic phosphorus than did bulk samples of cropped soil taken at the same time. Extractable organic and inorganic phosphorus in the soils were not significantly affected by drying the soil before each crop.Journal Paper No. J-5916 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.Former Rockefeller Fellow and Professor, respectively. The senior author is now Associate Professor, Department of Soils, Punjab Agricultural University, Ludhiana, Punjab.     

Characterization of soil phosphorus by anion exchange resin adsorption and P32-equilibration

Summary Adsorption of phosphate by the anion-exchange resin Dowex-2 was investigated. The resin adsorbed small quantities of P from solution quantitatively. The rate of P-adsorption by resin agitated in solution was proportional to the P-concentration in solution, and was independent of the rate of diffusion of adsorbed P in the resin. When 1 g of soil was shaken continuously with 1 g of resin in 100 ml of water, the rate of P-adsorption by the resin was controlled by the rate of P-release from the soil. Quantities of P adsorbed from soil by resin after different lengths of time were less than those equilibrated with P³² during the same time intervals. The curves showing quantity of P adsorbed vs. time could be satisfactorily described by the hypothesis that there were three simultaneous reactions differing in rate, each reaction being first-order with respect to P. The same was true of the P³²-equilibration data, except that the rate of the slowest reaction was apparently independent of time. In a group of 16 soils, the correlation between P adsorbed by the resin in 2 hours and P-availability to plants in the greenhouse, measured by the isotope-dilution method of Fried and Dean, was 0.95. The corresponding correlation between P extracted by the 0.25N HCl — 0.03N NH₄F extractant of Bray and Kurtz was 0.91.Joint contribution from the Iowa Agricultural Experiment Station and the Eastern Soil and Water Management Section, U.S. Department of Agriculture. Journal Paper No. J-2639 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 1183.Graduate Assistants, Professor of Soils, and Associate Professor of Chemistry, respectively.     

Changes in extractable organic phosphorus in soil in the presence and absence of plants

Summary No significant phosphatase activity was demonstrated in solutions in which mycorrhizal or nonmycorrhizal white-pine seedlings had been grown, but considerable activity was found in solutions in which corn and tomato had been grown. Phosphatase preparations from solutions in which corn had been grown and from purchased, dry, acid- and alkaline-phosphatase sources were incubated with soil, and organic-phosphorus analyses were made at the end of the incubation to determine the effect of the phosphatase. In general, the organic phosphorus found at the end of the incubation increased with the quantity of phosphatase added, with or without toluene. These results do not support the view that enhanced phosphatase activity in the soil around the roots is responsible for the plant-induced decrease in soil organic phosphorus now observed in three investigations. Journal Paper No. J-6014 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1183.     

Plastids of sieve tube members in the stamen vascular bundle ofSorghum bicolor (Gramineae)

Summary The plastids in sieve tube members of the stamen vascular bundles ofSorghum bicolor, fixed in glutaraldehyde with postfixation in osmium tetroxide, are of the P-type containing cuneate crystalloids of a proteinaceous nature surrounded by a double envelope. Secondary inclusions are present in these P-type plastids. P-type plastids inSorghum often remain intact in the mature sieve tube members.This work was supported by a grant from the Iowa Agricultural and Home Economics Experiment Station, Ames, U.S.A. Project No. 1740 toHarry T.Horner, Jr., andNels R.Lersten and Project No. 1914 toHarry T.Horner, Jr. of the Department of Botany and Plant Pathology, Iowa State University, Ames, U.S.A. This work was completed by the author as part of the Ph. D. dissertation research.     

Patulin effects on wheat plants in field treatments

Summary Fall field patulin applications (500 µg/g of soil) to Cheyenne winter wheat seedlings at growth stages 0, 1, and 2, decreased germination, plant growth, winter survival, and tillering. Decreased tillering decreased the number of heads and grain yield. Spring patulin application of 250 and 500 µg/g of soil to wheat at growth stages 6, 7, 8, 9, and 10 decreased yields by decreasing the number of heads, kernels per head, and kernel weight. With fall patulin applications, yields were decreased more when patulin was applied near seeding. Spring patulin applications to wheat during sensitive heading stages decreased yield the most.Stages of wheat growth especially susceptible to patulin are the germination, stem-elongation, and flowering, which occur during the fall and spring when soil Penicillium urticae Bainier numbers are maximun and patulin has been extracted from the soil.Contribution from the Soil, Water, and Animal Waste Management Research Unit, North Central Region, Agricultural Research Service, U.S. Department of Agriculture, in cooperation with the Nebraska Agricultural Experiment Station, Lincoln. Published as Paper No. 4071, Journal Series, Nebraska Agricultural Experiment Station.Microbiologist, USDA, A.R.S. University of Nebraska, Lincoln; Soil Scientist, USDA, A.R.S. Fort Collins, Colorado; and Microbiologist, USDA, A.R.S. University of Nebraska, Lincoln, respectively.     

Penicillium urticae Bainier enumeration in soils

Summary A dilution plating method estimatedPenicillium urticae Bainier numbers in soil. This method, which used an agar layering technique and a cyclic incubation of 8 hours at room temperature (about 25°C) and 16 hours at 5°C, permitted the differential growth and sporulation in favor ofP. urticae B. over other common soil fungi.Procedures of extraction, paper chromatography, infrared analysis, and bioassay assayed for accumulated patulin. A combination of these methods routinely estimatedP. urticae B. numbers in soils and authenticated patulin production by selected isolates.Contribution from the Northern Plains Branch, Soil and Water Conservation Research Division, Agricultural Research Service, USDA, in cooperation with the Nebraska Agricultural Experiment Station, Lincoln. Published as Paper No. 2275, Journal Series, Nebraska Agricultural Experiment Station.Soil Scientist, USDA, Grand Junction, Colorado (formerly Chemist, USDA, Lincoln, Nebraska); and Microbiologist, USDA, Lincoln, Nebraska, respectively.     

Variation in polychlorinated biphenyl levels in common carp from a primarily agricultural drainage

Concentrations of polychlorinated biphenyls (PCBs) in common carp, Cyprinus carpio, from the Des Moines River, Iowa, were assessed for variability related to sampling location, sampling period, fish age, and fat content. Concentrations were highest at a location near the City of Des Moines; they were substantially lower in 1981 than in 1980. Age and fat content had little influence on PCB concentrations in carp. Overall concentrations were some of the lowest recorded in the United States and Canada in recent times.The Unit is jointly supported by Iowa State University, the Iowa State Conservation Commission, and the U.S. Fish and Wildlife Service.Journal Paper No. 10754 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2465. Financed by a grant from the U.S. Department of Defense Army Corps of Engineers and made available through the Engineering Research Institute, Iowa State University.     

Combined S2 and crossbred family selection in full-sib reciprocal recurrent selection

Summary A method (CRRS) that combines S₂ and crossbred family selection in full-sib reciprocal recurrent selection (FSRRS) is proposed. The method requires four generations per cycle in single-eared maize populations. Selection is based on performance of S₂ and full-sib families by applying selection index theory. Equations to estimate the coefficients included in the index are given. These estimates are functions of the genetic and phenotypic variances and covariances among and between the two kinds of families. Comparisons of FSRRS and CRRS under equivalent amount of effort show that CRRS has some advantage over FSRRS for low heritability of the trait being selected (e.g., maize yield) and when only one or two locations with two replications are involved in the selection experiment.Joint contribution: Institute Nacional de Investigaciones Agrarias, La Coruna, Spain; and Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-10118 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project 2194     

Electrophoretic analysis of genetic variability in the house fly (Musca domestica L.)

Methods are described for the resolution of house fly, Musca domestica L., enzymes by vertical polyacrylamide gel electrophoresis. An electrophoretic survey in Ames, Iowa, of 51 loci distributed among 26 enzyme systems revealed that 40% of the loci are polymorphic. Observed and expected heterozygosities measured at 33 loci were 0.0981 and 0.1148, respectively. A significant deficiency of heterozygotes was noted at certain loci.Journal Paper No. J-11423 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 2411.     

Characterizing soil fertility by ion diffusive flux measurements

Summary The general acceptance of diffusion as a rate-limiting step in transferring ions to plant roots was considered in characterizing soil fertility. Soil ion diffusive flux measurements to an exchange resin were measured with two soil: resin cells, one with untreated soil, the other with the same soil fertilized with P, K, and Cl. The P, K, and Cl that diffused to the resin of each cell was extracted and determined. Using only these measurements and some simplifying assumptions of diffusion theory, calculations were made of the soil's P and K solution concentration, adsorbed concentration, a capacity factor, transmission factor, and quantity of fertilizer needed to attain any desired flux. Excellent to fair correlations existed between these calculated values and traditionally measured chemical quantities. Plant uptake of P and K was generally well correlated with diffusive flux measurements as well as traditional chemical measurements.Contribution from the Western Region, Agricultural Research Service, U.S. Department of Agriculture; and the Montana Agricultural Experiment Station, Bozeman, Montana, submitted as Station Paper No. 654, Journal Series.Soil Scientist, Snake River Conservation Research Center, Kimberly, Idaho; Professor of Chemistry, and Professor of Soils, Montana State University, Bozeman, respectively.     

The inhibition of seedling growth by crop residues in soil inoculated withPenicillium urticae Bainer

Summary Laboratory experiments were conducted to determine the effects of crop residues, without and withPenicillium urticae Bainer inoculation, on growth of wheat seedlings in soil. Fifty grams of Sharpsburg silty clay loam soil, containing 1% by weight of incorporated alfalfa, sorghum and corn stover residue, were placed in petri dishes, autoclaved, wetted to 40% moisture, and incubated at 24°C. for periods of 2, 3, and 4 weeks. One-half of the petri dishes were inoculated withP. urticae. Germination and seedling-shoot measurements were taken after 7 days of growth.The results of this study showed that (1) inoculation of soil generally reduced seedling height regardless of the residue treatment; (2) inoculation of soil containing corn and sorghum residues resulted in greater tissue production but reduced height of seedlings as compared to non-inoculated soils; and (3) in the absence of residues, the inoculated control soils were a better growth medium for wheat seedlings than were the non-inoculated control soils. In addition, alfalfa residues, especially in the presence ofP. urticae, were strongly inhibitory to the wheat seedlings, causing curling and reduced wheat-seedling root growth.Joint contribution from University of Nebraska and Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Department of Agriculture, and Nebraska Agricultural Experiment Station, Lincoln, Nebraska, cooperating. Published with the approval of the Director as Paper No. 1242, Journal Series, Nebraska Agricultural Experiment Station.     

Evaluation of laboratory indexes of absorption of soil phosphorus by plants: I

Summary The yield of phosphorus in sorghum plants grown on samples of 22 different soils from the United States was determined in the greenhouse. Analyses of variance of the regressions of these values on the measurements of soil phosphorus by various laboratory methods were calculated as an aid in evaluating the methods.No general advantage was found from incubating the samples in moist condition for a week before analysis versus making the analysis on the initially-dry samples. In the order of decreasing precision of predicting the yields of phosphorus the methods are as follows: (1) anion-exchange resin method of Amer and coworkers, (2) 0.5M NaHCO₃ method of Olsen and coworkers, (3) phosphate potential method of Schofield and Aslyng, (4) phosphorus concentration in the 0.01M CaCl₂ extract of Schofield and Aslyng, and (5) 0.1N HCl, 0.03N NH₄F method of Bray and Kurtz.After taking into account the additional variables, little or no improvement in precision of prediction was obtained when the phosphorussorbedvs. time curves for the anion-exchange-resin method were (a) divided into four segments on the basis of time, the quantities of phosphorus in the four segments being used as independent variables in a multiple-regression equation, or (b) broken down into a maximum of four components on the assumption that the overall curve represents the summation of a group of simultaneous first-order reactions, the quantities of phosphorus in the several components being used as independent variables in a multiple-regression equation.The precision of prediction was improved by using as the soil-phosphorus measurement the sum of the products of the rate of phosphorus extraction by the anion-exchange-resin method and the quantities of phosphorus extracted within individual time intervals. A logarithmic expression was used to fit the relationship, however, and it appeared that the greater precision of prediction resulted from the logarithmic transformation rather than the superiority of the method as such.The precision of prediction was improved also by using the H₂PO ₄ ^– concentration instead of the total-inorganic-phosphorus concentration as the independent variable in the 0.01M CaCl₂ extracts of Schofield and Aslyng and by using the H₂PO ₄ ^– instead of the total inorganic phosphorus sorbed by the anion-exchange resin. This modification made the anion-exchange-resin method considerably better than the others tested.Journal Paper No. J-3452 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1183. Contribution from the Department of Agronomy.Graduate Students and Professor of Soils, respectively.     

Transfer aleurone cells inSetaria lutescens (Gramineae)

Summary Typical aleurone cells occur around the periphery of the caryopsis. These cells are tabular with moderately thick walls and lack cell wall ingrowths. Transfer aleurone cells only occur adjacent to the placental vascular bundle, which supplies the developing embryo and endosperm. These specialized aleurone cells are approximately columnar, with thick walls bearing ingrowths on the outer radial and outer tangential walls. The wall ingrowths of transfer aleurone cells appear similar to those of transfer cells previously described and quite likely also function in short-distance transport of substances.Journal paper No. J-6737 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1685.     

Genetic control of immunoglobulin allotypes in the fowl

Eight immunoglobulin allotypic specificities have been identified in the fowl by isoimmunization. Aa1 and Aa2 are controlled as codominants at the a locus, Ab1 and Ab2 at the b locus, and Ac1, Ac2, Ac3, and Ac4 at the c locus. Column chromatography and ultracentrifugation indicate that the specificities at the a locus are located on molecules corresponding to IgG with sedimentation coefficients 7 S. Immunoelectrophoresis results also indicate that we are dealing with an immunoglobulin G molecule. Further tests are underway to resolve this beyond doubt.Journal Paper No. 5405 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project 1039. Supported in part by National Science Foundation Grants GB 318 and GB 4450.     

Soil moisture influence on micronutrient cation availability under aerobic conditions

Summary The three major soil series comprising the Gezira scheme (Sudan) are Hosh, Suleimi, and Laota. Surface soil samples from each soil series were employed to study the effect of soil moisture on the DTPA-extractable micronutrient cation under aerobic conditions. The study continued for 8 weeks using an incubation technique at two levels of soil moisture (continuously moist and moist/dry cycles). The DTPA-extractable Cu, Fe, Mn and Zn from air-dry soil samples were much higher compared to values from their incubated counterparts. For the three soils the CO₂ production (microbial activity) reached the maximum in 5 weeks and then levelled off while the lowest values of micronutrient cation from the incubated soils were obtained between 2 to 8 weeks.Generally, the study suggests that the hot dry months preceding crop growth should increase clay surface acidity and hence availability of mironutrient cations.Contribution from the Texas Agricultural Experiment Station, Texas A&M University, College Station. TX 77843, U.S.A.     

A method for determining the in vivo stability of Drosophila alcohol dehydrogenase (E.C.1.1.1.1.)

A rapid and accurate method of measuring the relative in vivo stability of Drosophila alcohol dehydrogenase is presented. The potential of this technique for examining posttranslational control of in vivo enzyme concentrations is discussed.This work was supported by NSF grant #DEB 7815466 to J.M.Journal Paper No. J-9977 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2272.     

A FORTRAN program for the calculation and analysis of two-locus linkage disequilibrium coefficients

Summary A FORTRAN program was written that calculates composite linkage disequilibrium coefficients from genotypic data. Chi-square tests determine whether coefficients calculated for allele and locus pairs are significantly greater than zero. A subroutine is provided that partitions the variance in linkage disequilibrium into within- and between-subpopulation components. Output obtained from analysis of allozyme data collected from natural subpopulations of the house fly (Musca domestica L.) are included to illustrate features of the program.Journal Paper No. J-11345 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2411     

Glucosyltransferase activity in a water extract of maize pollen

Summary Glucosyltransferase activity was extracted from maize pollen in distilled water. The enzymatic reaction required UDP-glucose, mercaptoethanol and Ca⁺⁺, and had a pH optimum at 8.2. Either kampferol or quercetin served as a substrate. Michaelis-Menten constants obtained were 0.6×10^-4 M for quercetin and 0.74×10^-3M for UDP-glucose. Ammonium-sulfate precipitation of the enzyme gave a 4fold purification.Cooperative investigations, Plant Science Research Division, Agricultural Research Service, U. S. Department of Agriculture, and Missouri Agricultural Experiment Station, Columbia. Journal Series No. 6224.     

Vegetative growth and sporulation ofBipolaris sorokiniana on sequentially older infected leaves ofPoa pratensis exposed to postemergence herbicides

Poa pratensis was exposed to the postemergence herbicides 2,4-D, MCPP, and dicamba at concentrations of 10^–6 M applied to the soil surface. Sequentially older leaf blades were inoculated withBipolaris sorokiniana and detached to determine the effect of the herbicides on saprophytic hyphal growth and sporulation on the tissue of each older leaf. 2,4-D and dicamba stimulated hyphal growth in vitro from leaf tissue of all ages; MCPP had no effect on hyphal growth. All herbicides increased sporulation byB. sorokiniana on leaf tissue of all ages. Both hyphal growth and sporulation increased progressively on tissue from sequentially older leaves ofP. pratensis exposed to dicamba.Journal Paper No. J-14985 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, USA, Project No. 2616.