Influence of environmental conditions on spore dispersal and infection by Septoria nodorum

In field experiments using healthy trap plants it was found that pycniospores of S. nodorum were dispersed from diseased wheat plants whenever rain fell and occasionally in the absence of rain. Of two spring wheats tested, cv. Kolibri seemed a better ‘source’ plant and cv. Maris Butler a better ‘receptor’ when rainfall was light, but this difference was not apparent when rainfall was heavy. On 44 occasions, plants of Kolibri and M. Butler were also exposed to natural conditions immediately following artificial inoculation with S. nodorum. Infection of plants occurred on 10 occasions and was associated with the following minimum conditions: r.h, at inoculation >63%; and in the following 24 h, minimum temperature <6°C, at least 4 h with r.h. >90% and not more than 4 h with r.h. >60%.     

Local population differences in emergence of cabbage root flies from south-west Lancashire: implications for pest forecasting and population divergence

ABSTRACT.

• 1 Emergence of cabbage root fly, Delia radicum (L.), from overwintering populations of puparia collected from twenty-one sites in south-west Lancashire, was extremely variable.
• 2 The patterns of emergence indicated that there were two extreme biotypes, one with early- and the other with late-emerging flies. There was also evidence of an intermediate biotype, tending more to early than to late emergence.
• 3 This gradient of biotypes, or clinal divergence, was maintained by populations breeding at different times and by females mating close to their sites of emergence. Non-dispersive females then perpetuated their genotype within their own locality.
• 4 The time of emergence was not obviously associated with the type of host-crop on which larvae had developed.
• 5 The late-emerging biotype was most prevalent around Halsall. The minimum distance between populations of the late- and the early-emerging biotypes was 16 km. 20 km south-east from Halsall only half of the fly population was early-emerging, possibly a result of a displacement of the Halsall biotype by the prevailing NW wind.
• 6 Regional-based forecasts will need to take into account the emergence characteristics of the populations to predict the peak periods of cabbage root fly activity adequately in south-west Lancashire and other areas where emergence patterns differ.

     

THE MANTLE AND SHELL OF SOLEMYA PARKINSONI (PROTOBRANCHIA: BIVALVIA)

The shell of Solemya exhibits considerable flexibility which is further enhanced by the marked extension of the periostracum beyond the calcareous portions of the valves. This fcature, more than any other, has made possible the habit, unique among bivalves, of burrowing deep within the substrate without direct contact with the water above. The inner calcareous layer of tho valves is restricted to a small area near the umbones while the outer calcareous layer is thin and contains a high proportion of organic material. The shell conchiolin consists mainly of protein, varying in composition, but much of it strengthcned by quinone-tanning, and in ccrtain regions probably by the presence of appreciable quantities of chitin. The ligament, although superficially resembling an amphidetic structure, is opisthodetic, the extcnsion anterior to the umbones consisting of anterior outer layer only.
The mantle is characterized by an extension of the outer fold of the mantle margin which has effected equally both the inner and outer surfaces of this fold. The secretory epithelium and the modified pallial musculature, contraction of which results in the intucking and plaiting of the periostracum, is dcscribed. Simple tubular oil glands open at the mantlo margin and are responsible for the water-repellent nature of the periostracum.
The form of the mantlelshell and that of the enclosed body are discussed and compared with those of other bivalves in which elongation of the mantle/shell is achieved in a different way. It is concluded that the mantlelshell of Solemya is of little value in determining its relationships, and that the greatly elongatod ligament, the edentulous hinge and the flexible shell are all adaptations to a specialized mode of life.     

Aluminium Effects on ATPase Activity and Lipid Composition of Plasma Membranes in Sugar Beet Roots

The effect of aluminium (Al) in vivo and in vitro on root plasmamembranes has been studied in two sugar beet (Beta vulgarisL.) cultivars, Monohill (Al-sensitive) and Regina (relativelyAl-tolerant). Although Al in vitro inhibited the MgATPase inan uncompetitive way for both cultivars raised in the absenceof Al, the specific K⁺-activation of the MgATPase was only inhibitedby Al in cv. Monohill. Arrhenius analysis of the MgATPase activity showed that theeffect of Al in vitro depended on whether or not the plantswere exposed to Al in vivo. Al treatment in vitro of the MgATPasefrom control plants cultivated at a low pH (5·4) causedan increase in the phase transition temperature from 17 to 22°C. Only at a higher pH range (pH 6·1) could a secondtransition temperature be induced (at 9 °C). By additionof Al in vitro to plants cultivated with Al at pH 5·4,the slopes of the activity plots did not change. Aluminium changedthe K_m of the ATPase for MgATP in an opposite way by treatmentin vivo and in vitro. Lipid analyses of the plasma membranes showed that the acylcomposition differed little following Al treatment in vivo,but that the ratio of phosphatidylcholine: phosphatidylethanolamineincreased. The changes correlated with the observed change inthe K_m for the MgATPase. We conclude that the main effect ofAl on the MgATPase is not due to the formation of an Al-ATPcomplex. Instead, Al may bind to the membrane-bound enzyme(s)and/or modify the lipid environment. Key words: Aluminium, ATPase, Beta vulgaris, lipids     

The effect of pH on host plant 'preference' for strains of Rhizobium trifolii using fluorescent ELIS A for strain identification

The effect of pH on host plant ‘preference’ for strains of R. trifolii was studied using the fluorescent ELISA technique. Four white clover cultivars were compared growing at pH 5, 6 and 7 inoculated with 1:1 mixtures of two strains of R. trifolii, CP3B and R4. The growth of these two bacterial strains was also studied at the same pH levels in pure culture. At pH 5, in pure culture, CP3B grew very well but R4 failed to reach the log phase. CP3B also produced the majority of nodules at this pH (86%). At pH 7, in pure culture, R4 grew better than CP3B and also produced 66% of the nodules in the nodulation experiment. However, there was good evidence of host cultivar ‘preference’ with cv. Milkanova having no nodules inhabited by CP3B at pH 7 but cv. S100 having 32%. The results are discussed from the point of view of the establishment of white clover in acid soils and the usefulness of the fluorescent ELISA technique for Rhizobium strain identification is also emphasised.     

IDENTIFICATION OF BRITISH BAT SPECIES BY MULTIVARIATE ANALYSIS OF ECHOLOCATION CALL PARAMETERS

ABSTRACT

Previous studies have found variability and individual distinctiveness in the echolocation calls of bats. We consider two implications of individually distinct echolocation calls: 1) whether bats may be able to use such variation to recognise familiar conspecifics, and 2) whether investigators could use such variation to identify known individuals or to census populations. We compared the discriminability of the echolocation calls of big brown bats (Eptesicus fuscus) recorded in three situations: (a) while held in the hand, (b) while perched on a platform, and (c) while flying in an anechoic chamber. Using variables describing each sonar call, we employed discriminant function analysis (DFA) to assign calls to recording situation or to bat. Discrimination of calls by recording situation was largely unsuccessful, although flying calls could be distinguished from platform calls. Assignment of calls to individual bat across recording situations yielded 72% success, and, within a given recording situation, yielded 87% success. Stepwise DFA reduced the number of variables needed to discriminate between individuals with only a slight decrease in correct classification. These results suggest that bats (or researchers) may be able to use the information contained in the echolocation calls for individual recognition. Individual distinctiveness raises the possibility of censusing bats by sound. We used cluster analysis in an attempt to determine whether, given a sample of calls from an unknown number of bats, a reasonable estimate of the number of bats could be obtained. Results were unsatisfactory, suggesting that cluster analysis probably will not permit acoustic censusing of bats in the field.     

A well‐preserved ‘charadriiform‐like’ fossil bird from the Early Eocene Fur Formation of Denmark

Abstract: We describe a new, exceptionally well‐preserved fossil bird recovered from marine deposits of the Early Eocene Fur Formation of Denmark. Morsoravis sedilis gen. et sp. nov. is known by a single specimen that consists of a three‐dimensional skull, vertebral column, ribs, pelvis, and left hindlimb and associated parts of the right hindlimb. Comparisons based on overall morphology and particularly characters of the skull, vertebrae and pelvis indicate that the new specimen is morphologically similar to charadriiform birds (the shorebirds and relatives). This similarity is also expressed by a phylogenetic analysis of higher neornithine (modern birds) taxa, which supports a close relationship between the new fossil and modern charadriiforms. The morphology of the hindlimbs, in particular, shows that the new fossil corresponds to a new taxon that is distinguishable from modern charadriiform clades. One interesting aspect of its morphology is the presence of hindlimb specializations that are most commonly found among perching birds – these suggest that ecologically the new Danish fossil bird may have differed from the wading habits typical of most charadriiforms.     

Disease progress of non-specialised fungal pathogens in intraspecific mixed stands of cereal cultivars. I. Models

Two mathematical models are presented which describe progress of disease, caused by an unspecialised pathogen, in pure and mixed stands of cereal cultivars. One is a simple, discrete model utilising the parameters infection frequency (lesions/spore) and sporulation rate (spores/lesion/event) on each cultivar. The model predicts that, in most circumstances, the amount of disease in mixtures will be equal to or less than the arithmetic mean of the component pure stands. An increase in disease is only predicted in situations where the ranking of cultivars with respect to infection frequency and sporulation rate is opposed. In the other model differential equations are proposed. Solutions of these equations indicate that disease amelioration can usually be expected in such mixtures, confirming the conclusions of the discrete model and that disease levels will deviate around the geometric, rather than arithmetic, mean of the pure stands. However the advantages of this model lie in wider generality and conceptual, rather than practical, utility.