Ethylene formation by germinating,Drechslera graminea — Infected barley (Hordeum sativum) grains: A simple test for fungicides

Grains of barley (Hordeum sativum L.); infected with the parasitic, systemic fungus Drechslera graminea, produce more ethylen than uninfected controls. Treatment of infected grains with mercury-free fungicides yields a differentiated suppression of the ethylene evolution 7 d after the beginning of germination. Suppression of visible symptoms (chlorotic stripes on leaves) appearing six to eight weeks after germination of infected, untreated seeds correlates with the decrease in ethylene formation after treatment with fungicides. The gaschromatographic ethylene determination thus allows for an early and reliable (significance higher than 99.9%) differentiation of fungicidal activities against the barley stripe disease.Abbreviations ACC I-aminocyclopropane-1-carbonic acid - CD critical difference     

Relative addition rate and external concentration; Driving variables used in plant nutrition research

Abstract An increasing literature accounting for various types of experiments indicates that far lower external nutrient concentrations are required by plants than is usually thought to be the case. It is concluded that the ion uptake capacity of the roots, as described by the carrier concept, is high compared to that required for maintenance of the internal concentration. Serious errors in experimental conclusions are associated with insufficient and constant nutrient addition rates. The main errors are caused by non-steady states of the plants both with regard to the internal nutrient concentrations and the relative growth rate. A dynamic concept has been proposed for direct use as the treatment variable within the range of sub-optimum nutrition. The nutritional factor is expressed as a flow, the relative nutrient addition rate in laboratory studies and the nutrient flux density in the field. The experimental use of the relative addition rate has led to steady-state nutrient status and relative growth rate and the interpretation of plant responses which differ fundamentally from accepted views. Thus, for instance, deficiency symptoms disappear, as in natural conditions, when the internal nitrogen concentration is stable, independent of level. The nutrition/growth relationships are very different from those observed when external concentration is varied. The regression line of relative growth rate on relative addition rate passes near to the origin at an angle close to 45 to the axes, which implies that the obtained relative growth rate approximates closely the treatment variable. A striking example of observed differences is the positive effect on nitrogen fixation exerted by high relative nitrogen addition rates compared to the well-known negative effect of increasing external nitrogen concentration. The application of fertilizer on the basis of the nutrient flux density concept provides the possibility of supplying fertilizers corresponding to the consumption potential of the vegetation and to the natural flux density resulting from mineralization in the soil. Nitrogen utilization is high under such conditions and the resulting feedback of nutrition on the mineralization rate suggests that there will be a long-term increase in fertility.     

Preferred conformations and flexibility of aminoacyl side chain of penicillins

Possible conformations of penicillin G; d and l isomers of ampicillin; α-amino-α-methyl-benzyl penicillins and 3- pyridyl methyl penicillin have been studied by an energy minimization procedure using empirical potential functions. The preferred conformations of these antibiotics have been correlated with their biological activity. The conformational requirement of the antibiotic to be active against Gram-positive and Gram-negative (β-lactamase-negative) bacterial strains seems to be the same. The reduced activity of penicillin G against Gram-negative bacteria has been attributed to its lower ability to permeate the outer membrane. The flexibility of the sidechains of these antibiotics is also shown to be important for the desired biological activity.     

Population dynamics of daphnia pulex and utilization by the rainbow trout (salmo gairdneri)

The effect of rainbow trout (Salmo gairdneri) predation on the population dynamics of the water flea,Daphnia pulex, was examined during 1976 and 1977 in Becker Lake, a small, shallow, productive reservoir in northeastern Arizona.Rainbow trout were size-biased feeders, utilizing daphnids which were 1.3 mm in size or larger. Trout predation uponDaphnia pulex occurred mainly during winter and early spring when their numbers were relatively low but their clutch size high, suggesting that trout selectedDaphnia on the basis of brood pigmentation. By far the greatest proportion ofDaphnia mortality was due to nonpredatory sources, since generally less than 6% could be attributed to trout predation.TheD. pulex population exhibited a bimodal seasonal abundance curve which was attributed to ephippial egg production and trout predation during the winter and poor food quality/quantity during the summer.This work was supported in part by the Arizona Department of Game and Fish. The authors wish to thank Jim Novy and Joe Stone of that department for their invaluable assistance in the field collecting segment of this study.     

Ornithodiplostomum ptychocheilus: migration to the brain of the fish intermediate host, Pimephales promelas.

Migration of cercariae of the diplostomatid trematode, Ornithodiplostomum ptychocheilus, to the brain of the fathead minnow, Pimephales promelas, takes place via directed, nonrandom movement. Penetration of the fish epidermis is rapid and is essentially complete by 2 hr postinfection. Migration to the central nervous system occurs almost exclusively via the general body musculature and connective tissue, although a few cercariae gain direct access to the nervous system via the eyes. Cercariae enter either the neural canal and spinal cord, or the brain via the spinal or cranial nerves and their associated foramina, although cercariae appear to remain in (on) these peripheral nerves for only a short time. Cercariae associated with cranial nerves continue to the brain. Those becoming associated with spinal nerves travel up the neural canal and (or) spinal cord to the brain. Data suggest that most arrive at the brain via the neural canal and spinal cord. Within the brain, most developing metacercariae (neascus-type) occur in the optic lobes and cerebellum. Whether this is “selective localization” or merely the result of the larger space afforded by these brain regions could not be determined.     

Schistosomatium douthitti: effects of Lymnaea catascopium age on susceptibility to infection

Laboratory-reared Lymnaea catascopium snails (1–269 days old) were exposed individually to different numbers of Schistosomatium douthitti miracidia. Increasing the exposure dosage from 3 to 10 miracidia generally increased infection rates, in some age classes up to 100%. Successful re-exposure of snails not infected after a primary exposure was possible. Neonatal snails were least likely to become infected, primarily because miracidia were not attracted to them. Snails 12–55 days old were most susceptible to infection. Miracidia were readily attracted to these snails, and many were ingested and subsequently penetrated the host esophageal wall. Miracidial penetration of external snail surfaces was rare. Susceptibility of older snails (65–269 days) progressively declined with age. Many miracidia were entangled and immobilized in mucus produced by these snails, and fewer were ingested. No conspicuous host cellular responses to mother sporocysts were observed in any of the snails sectioned. A comparison of susceptibility of deliberately stunted snails and comparably aged controls of normal size indicated that the former were more susceptible.     

A comparative study of the temporal bone in three populations of man

A comparative study was made to determine race and sex differences in the temporal bone, to investigate growth relationships, and to establish a basis for phylogenetic studies of the temporal bone and the temporal lobe of the brain. Data on Eskimo, Indian, and white crania were collected from radiographs and directly from the skulls. Of the 25 variables studied, only the minimum diameter of porus failed to demonstrate some difference among the races. Variation between sexes was found for all measurements except the cranial base angle (of deflection) and three angles related to the petrous pyramids. Correlation coefficients indicated that none of the angles are related in any consistent manner to the other variables studied. This is interpreted as further evidence of cranial base stability. The Indians have the lowest, longest squamae, differing most from the whites. The position of squama is more anterior in the Eskimos. Females of each race possess more anteriorly positioned squamae than males. When the squama is more anteriorly located, the porus is in a more posterior position within the squama itself. Strong race variation exists in the shape of porus. In order to establish a basis for phylogenetic studies of the temporal lobe of the brain better reference points for reflecting its size and shape must be found.     

Aldolases of the lactic acid bacteria

Reciprocal qualitative and quantitative immunological experiments employing an anti-Pediococcus cerevisiae aldolase serum confirmed many of the interspecific relationships demonstrated previously among lactic acid bacteria with antisera prepared against the Streptococcus faecalis fructose diphosphate aldolase. The extent of immunological relatedness observed between the Lactobacillus and Pediococcus aldolases was markedly greater than that noted between Pediococcus and Streptococcus aldolases indicating that the pediococci share closer phylogenetic ties with the rod-shaped lactobacilli than with their spherical counterparts in the streptococci. In addition to confirming the existence of definitive, but distant, relationships between the lactic acid bacteria and certain gram positive nonsporeforming anaerobes, immunological cross-reactivity was also demonstrated between the pediococcal aldolases and those of Aerococcus viridans.This paper is dedicated with deepest appreciation to Prof. Roger Y. Stanier on the occasion of his 60th birthday in token of what his friendship and guidance have meant to me. — J. L.     

The influence of ants on patterns of colonization and establishment within a set of coexisting lycaenid butterflies in a south-east Asian tropical rain forest

In Peninsular Malaysia ten species of lycaenid butterflies use leaf flushes or inflorescences of the legume tree Saraca thaipingensis as larval hostplant. Resource partitioning among these species is regulated by a complex mixture of patterns of interaction with ants. Females of obligately myrmecophilous species lay their eggs exclusively on trees colonized by their specific host ants. On trees colonized by weaver ants, only specialist mutualists adapted to these territorial ants are able to survive, while larvae of other species are killed. The formicine ant Cladomyrma petalae, which inhabits hollow twigs of the myrmecophytic hostplant, likewise precludes oviposition by female butterflies. Lycaenid larvae confronted with this ant species never survive, but one concealed feeding species (Jamides caeruleus) escapes removal due to the cryptic life-habits of the larvae. Two facultative myrmecophiles associate in a mutualistic way with a wide and largely overlapping range of ant genera which forage at the extrafloral nectaries of leaf flushes. One species (Cheritra freja) is not myrmecophilous, but is tolerated by all but the most territorial ants. Ant-dependent hostplant selection and egg-clustering characterize the obligate mutualists, whereas facultative myrmecophiles and the non-myrmecophile distribute their eggs singly over appropriate hostplants. Signals mediating caterpillar-ant communication are highly specialized in one obligate myrmecophile (Drupadia theda), but rather unspecific in four other species tested. Altogether our observations indicate that colonization and establishment of lycaenid butterflies on S. thaipingensis trees are governed by specializations as well as opportunistic use of resources (ants and hostplant parts). Therefore, the diversity of this species assemblage is maintained by deterministic as well as stochastic factors.     

Origin of the cultivated passion fruit Passiflora edulis f. flavicarpa and genomic relationships among species of the subgenera Decaloba and Passiflora

• Passiflora edulis f. flavicarpa is the most economically important species in the genus Passiflora. However, the origin of this yellow form of passion fruit remains unclear, being suggested as a hybrid (P. edulis f. edulis × P. ligularis) or wild mutant.
• Here, the origin and genomic relationships of P. edulis f. flavicarpa with some related species in the genus Passiflora (subgenera Decaloba and Passiflora) were investigated using genomic in situ hybridization (GISH). Genomic DNA of 18 species was used as probe, which was hybridized onto chromosomes of P. edulis f. flavicarpa.
• Of all genomic DNA probes tested, none allowed us to identify a specific chromosome set in P. edulis f. flavicarpa. Conversely, probes from the subgenus Passiflora, P. edulis f. edulis, P. alata, P. cincinnata, P. coccinea, P. nitida and P. vitifolia, produced intense and uniform hybridizations on all chromosomes of P. edulis f. flavicarpa. Moreover, probes from P. ligularis, P. foetida and P. sublanceolata produced more intense hybridizations in the terminal region of four chromosomes, corresponding to the DNAr 45S locus, and also dispersed, less intense, hybridization across all chromosomes. Probes from the subgenus Decaloba, P. biflora, P. capsularis, P. cervii, P. coriacea, P. micropetala, P. morifolia, P. rubra and P. suberosa, produced hybridizations restricted to the DNAr 45S sites.
• The hybrid origin of P. edulis f. flavicarpa could not be supported based on the GISH results, and it is suggested that this species is conspecific with P. edulis f. edulis, because the probe with DNA of this form hybridized strongly throughout the target genome. The other putative parent species, P. ligularis, showed only a distant relationship with the target genome. The results also suggest that species of the subgenus Passiflora share many repetitive sequences and that the relationship between subgenera Decaloba and Passiflora is very distant.