Effect of sowing date on the temperature response of leaf emergence and leaf size in barley

Abstract Rate of leaf emergence of barley grown in the field in each of 2 years was affected by sowing date and, where direct comparisons were possible, it was found that leaves on late-sown plants emerged more quickly. Rate of leaf emergence fluctuated throughout the season, slowing almost to zero in the winter. Much of this variation in rate was removed when the number of leaves was plotted against accumulated temperature rather than time. When emergence rates for each sowing were calculated using a common base temperature they were found to be well correlated with rate of change of daylength. However, it was (bund that base temperature as well as temperature response was affected by date of sowing. The pattern of change of size of leaves was also affected by date of sowing. It appeared that in low temperatures and short days, there was no increase in leaf size from leaf position to leaf position. The responses of leaf emergence, extension and final size to date of sowing appear to adapt the plant to grow quickly when sown early but to cease growth and possibly frost-harden at low temperatures.     

Induction of sporulation of fungi isolated from Dactylis glomerata seed by exposure to near-ultraviolet radiation*

Pure cultures of fifty-two species of plant pathogenic and saprophytic fungi isolated from orchard (cock's-foot) grass seed (Dactylis glomerata L.) were incubated either in total darkness or exposed to a diurnal cycle of near-ultraviolet (NUV) radiation (12 h NUV/12 h darkness). Twenty-four species sporulated only after exposure to NUV including seven species of Drechslera, five species of Fusarium, as well as species olAscochyta, Photna, Septoria, Pyrenochaeta, Rhynchophoma and Stagonospora; six species sporulated moderately in darkness but more profusely following exposure to NUV; twenty species sporulated whether they were irradiated or not; and only two species failed to sporulate. To assess the pathogenic fungal microflora of orchard grass seed accurately, seeds should be incubated under a daily regime that includes NUV to induce sporulation.     

Critical Sensitivity of the Ovary of <Emphasis Type="Italic">Aedes aegypti</Emphasis> Adults to Sterilization by Juvenile Hormone Mimics

STERILIZATION of adult insects with juvenile hormone mimics has been reported several times^1–5, but only once for adult mosquitoes and no details were given². I report here on the sterilizing effect of three juvenile hormone mimics on female Aedes aegypti. They were (i) mixed geometric isomers of methyl 10,11-epoxy-3,7,11-trimethyl-2,6-tridecadienoate (CJH2), one of two substances with high juvenile hormone activity isolated from Cecropia oil⁶; (ii) mixed geometric isomers of farnesyl methyl ether (FME) and (iii) 2 cis/trans, 6 trans farnesenic acid ethyl ester (FAE). All three compounds were first tested on fifth instar Rhodnius prolixus using Wiggles-worth's method⁷. The doses to give a score of ten were as follows: CJH2 1.3µg; FME 1.4 µg; FAE 31.7 µg.     

Insights into the evolution of heliozoa (Protozoa, Sarcodina) as provided by ultrastructural studies on a new species of flagellate from the genus Pteridomonas

The fine structure of Pteridomonas danica , a new species of helioflagellate (protozoa), is described. The organism has a single apical flagellum which bears two rows of tripartite tubular hairs. There are two kinetosomes which are bound to each other and to the surface of the single nucleus by amorphous electron-dense material. The flagellum is surrounded by a wreath of fine arms, which are supported internally by triads of microtubules. The triads terminate on the nucleus. The mitochondria have tubular cristae which contain wisps of intracristal material. The dictyosomes are located in the posterior part of the cell, being clustered around the internal element of the contractile stalk. Extrusomes are present. Pteridomonas has substantial similarities with the colourless flagellate Ciliophrys and with the pedinellid algal flagellates. As Ciliophrys resembles the actinophryid heliozoa in several important respects, the evidence supports the contention that these heliozoa have a common ancestry with the heterokont algae and have evolved along a line involving the pedinellids and some colourless helioflagellates. If the perceived relationships are to be reflected in their taxonomy, then a substantial reclassification of these organisms is required.     

A dissolved oxygen budget model for Lake Erie in summer

SUMMARY.

• 1 In this paper we extend a vertical mixing model of Lake Erie with an oxygen budget model. The model was tested against data gathered in the summers of 1979 and 1980 with good results, showing that it is capable of simulating vertical distributions of temperature and dissolved oxygen over relatively short time periods.
• 2 The results underline the importance of turbulent mixing in distributing oxygen throughout the water column in the Central Basin of the lake. In addition, the results indicate that production and respiration processes dominate the budget under the influence of low wind speeds, while surface fluxes dominate during periods of high wind.
• 3 Bottom mixing delays the onset of anoxic conditions at the sediment/water interface by distributing the sediment demand over the 5–6 m depth of the bottom mixed layer.

     

Host ranges, symptoms and amino acid compositions of eight potexviruses

The host ranges, symptom expression and coat protein compositions of eight definitive potexviruses are described and compared. Only limited host range similarity was observed: clover yellow mosaic virus and white clover mosaic virus shared 11 of the 28 host species tested; foxtail mosaic virus and narcissus mosaic virus infected monocotyledons; barrel cactus virus and viola mottle virus had narrow host ranges but had eight of the host species in common. Amino acid analyses of coat proteins showed some similarity among the viruses tested, but little correlation with the different host range types. There was more variation of structurally important amino acids such as lysine, arginine, leucine and proline than might have been expected, but high alanine and low tyrosine, tryptophan, cysteine and methionine were typical of plant virus coat proteins.     

The Ultrastructure of Vampyrellidium perforans Surek & Melkonian and Its Taxonomic Position Among the Naked Filose Amoebae1

An account of the fine structure of Vampyrellidium perforans is given. The organism has filose pseudopodia, mitochondria with flattened cristae, and cytoplasmic microtubules, some of which arise from a perinuclear cytoplasmic sheath. Microtubules were observed within nuclei presumed to be at an early stage of division. Relatively massive (non-filose) pseudopodia are formed by cells feeding by engulfment. The cytoplasm of these pseudopodia has a fibrillar consistency with local aggregations of material. Despite sharing aspects of feeding behavior with vampyrellid filose amoebae, Vampyrellidium perforans is ultrastructurally more similar to Nuclearia , and it is here assigned to nucleariid filose amoebae.     

Fimbriae and Haemagglutinins in Erwinias of the Carotovora Group

1. Thirteen Erwinia carotovora strains produced mannose-sensitive haemagglutinins associated with the presence of type-1 fimbriae.
2. Three fimbriate Er. rhapontici strains produced haemagglutinins of the mannose-resistant and eluting (MRE) type.
3. There were 12 Er. carotovora , 12 Er. atroseptica and 2 Er. chrysanthemi strains that produced no detectable haemagglutinins and were non-fimbriate.