Ronald W. McNew

Influence of fruit development on seasonal elemental concentrations and distribution in fruit and leaves of pecan

Abstract The elemental concentrations of leaves and fruits were monitored during one season on fruiting and vegetative pecan shoots. Pecan fruit and leaves of fruiting and vegetative shoots on 31‐year‐old ‘Western’ pecan trees were collected biweekly from May 15 through October 15, 1982 and analyzed for N, P, K, Ca, Mg, Fe, Zn and Mn. The concentrations of Ca, Mg, Zn, Fe and Mn were greater in leaves of fruiting shoots. The N concentration was higher in leaves of fruiting shoots the first ten weeks, then was significantly less in leaves on fruiting shoots the latter part of the season. K concentration was lower in leaves of fruiting shoots than vegetative shoots from June 25 through Oct. 15. Leaf P concentration did not appear to be influenced by fruiting. Content of N,K,P, and Zn in the fruit increased slowly until the tenth week after full bloom, then rapidly until fruit maturity. Ca, Mg and Mn accumulation in the fruit was linear throughout fruit development. Fe increased rapidly during early kernel de...

Evaluation of a Maximum‐Likelihood Estimator for Analysis of Length‐Frequency Distributions

Abstract The maximum-likelihood estimation procedure described by Hasselblad is a statistical method applicable to estimates of population parameters in a mixture of normal distributions of component age-groups. The method was used to estimate mean length-at-age and percentage composition of the component age-groups in 10 collections of largemouth bass (Micropterus salmoides) for which age was determined by the scale method. Compared to fish aged by the scale method, the error of the estimates of mean length-at-age averaged 3.2%. About one-third of the 31 frequency distributions, and six of seven distributions with more than 100 fish, deviated significantly from that of a normal distribution; many distributions exhibited skewness and kurtosis. However, the general failure of the samples to fit characteristics of the normal curve did not greatly influence accuracy in estimating mean length. The average error of the estimates of percentage composition by age was 28%; the magnitude of this error was related ...

Changes in dopamine-sensitive adenylate cyclase activity in salivary glands of female lone star ticks, Amblyomma americanum (L.), during feeding

Abstract The activity of dopamine-sensitive adenylate cyclase in feeding female ixodid tick salivary glands was dependent on the state of tick feeding. Activity was significantly greater than the “basal” activity in salivary glands from ticks at all stages of tick feeding. Enzyme activity was not detected in the glands of unfed females. Enzyme activity reached a peak in glands of ticks weighing approx. 200 mg then declined as ticks increased in weight beyond 200 mg to repletion. Replete ticks (detached from the host for 12–24 hr) had similar levels of basal and dopamine-stimulated adenylate cyclase activity as that measured in salivary glands of high weight (>200 mg) ticks. Enzyme activity was 19–62% less in glands from ticks feeding on hosts that had been parasitized 2–4 months earlier by lone star ticks.

Adenosine-3',5'-monophosphate in salivary glands of unfed and feeding female lone star ticks, Amblyomma americanum (L.)

Basal levels of cAMP in salivary glands of female lone star ticks were found to be about 5 pmoles/mg protein during all stages of feeding. Glands stimulated with 10(-5)M dopamine and 10(-5)M dopamine plus theophylline exhibited significant increases in cAMP/mg protein. After stimulation by 10(-5)M dopamine was removed, cAMP decreased faster in glands from slowly feeding ticks (less than 200 mg) than in glands of rapidly feeding ticks (greater than 200 mg).

Soil potassium effects on nitrogenase activity with associated nodule components of hairy vetch at anthesis

Abstract Acetylene reduction techniques are frequently utilized to estimate legume nodule nitrogenase activity levels. However, the known symbiotic nitrogen fixation reactions have no equivalent for the rapid permeastic transport of C2H4 reduced by nitrogenase of rhyzobial cells through the cortex tissues with the subsequent volatile excretion that is essential for GC quantitation procedures. The objective of this study was to determine interrelationships of nitrogenase (C2H2 reduction) with associated cytosol enzyme components from morphologically homologous nodules of Madison hairy vetch (Vicia villosa, Roth) at anthesis as influenced by soil potassium levels. The vetch plants were grown in a siliceous thermic Psammentic Paleustalf, Eufaula, and inoculated with Rhizobium leguminosarum Frank, ATCC 10314. Highly significant enhancement of nitrogenase activity progressed from quadratic to linear with increased soil K levels in time‐course samplings at 30, 60, 90 and 120 min. incubations at 27C. Means as C2...

Inoculation effects on growth, nodulation, cytosol components and nitrogen fixation of narrowleaf and hairy vetch

Abstract Underutilized indigenous legumes have potential for enhanced nitrogen fixation when properly managed. Many species have unusual tolerance and adaptive capabilities to survive when intensively grazed, and to continue vigorous regrowth on sites with very low soil productivity under extremes of climatic stress. The objective of these studies was to determine effects of specific inoculation compared to intrinsic soil Rhizobium on growth, nodulation, nitrogenase (C2H2 red.) and associated nodule components of narrowleaf vetch (Vicia angustifolia L.). Responses were determined for soil fertility treatments and evaluated with comparative responses of hairy vetch (Vicia villosa, Roth). Field evaluations for availability of fixed nitrogen by these vetch species was determined as fertilizer nitrogen equivalence (NH4NO3) with Maton rye (Secale cereale L.). Top growth of both vetch species at anthesis significantly increased with inoculation. Narrowleaf growth was approximately one third or less of hairy vet...