Herbicidal interference with the photochemical activities of chloroplasts (in vivo and in vitro) of certain crop and weed species

The independent modes of action of diuron and atrazine on the photochemical activities of chloroplasts (In vivo and in vitro) from the leaves of crop plants Pisum sativum and Pennisetum typhoides and the weeds Amaranthus viridis and Cyperus rotundus were investigated. Hill reaction activity (DCPIP photoreduction) of in vivo chloroplasts (chloroplasts isolated from herbicide-sprayed plants) was unaffected by treatment at sublethal or intermediate levels of diuron or atrazine while that of in vitro chloroplasts (chloroplasts incubated in the required herbicidal concentration) was severely inhibited. The ferricyanide catalyzed noncyclic photophosphorylation was markedly reduced in both the in vivo and in vitro chloroplast systems. N-Methyl phenozonium sulfate (PMS)-mediated cyclic photophosphorylation was inhibited in the in vivo system while a pronounced enhancement of activity was noticed in the in vitro chloroplasts. The rate of NADP⁺ photoreduction was severely inhibited in the in vitro chloroplasts. The unaffected in the in vivo system. The herbicidal effects on the photoreactions of isolated chloroplasts were compared with chloroplasts isolated from herbicide-sprayed plants.     

Effect of tricyclazole on growth and secondary metabolism in Pyricularia oryzae

Tricyclazole [5-methyl-1,2,4-triazolo (3,4-b)-benzothiazole] controls rice blast disease caused by Pyricularia oryzae at concentrations (5–10 μg/ml) which do not inhibit growth of the pathogen in vitro. However, concentrations of 1 μg/ml or less inhibit melanin formation in the fungus. Production of pyriculol by the pathogen is usually enhanced by 10 μg/ml of tricyclazole, whereas production of 3,4-dihydro-4,8-dihydroxy-1(2H)-naphthalenone is strongly inhibited or markedly reduced and delayed. Evidence suggests that tricyclazole blocks aspects of polyketide metabolism in P. oryzae which may have a role in pathogenicity.     

Components of the electron transport system in the microsomal mixed-function oxidase system in wild birds

Notable differences were found among six species of wild-caught birds in the levels of cytochrome P-450, cytochrome b₅, NADPH-cytochrome c reductase, and NADH-cytochrome c reductase. Ethyl isocyanide difference spectra showed significant variations among the species in peak height and in the ratios of the $\text{430}\text{455}\text{-}\text{nm}$ peaks. Substantial aldrin epoxidase activity was found in all species, and the amounts of dieldrin produced compared favorably with pigeon and rat liver microsomes. Higher content of cytochrome P-450 was not always accompanied by a similar rise in specific catalytic activity. Thus, no correlation could be established between these two parameters. Aldrin epoxidase activity with NADH as the sole electron donor was 25–49% as effective as with the NADPH-generating system. Addition of both NADH and NADPH-generating systems to the incubation mixture produced a synergistic effect with liver microsomes of two species but not with two other species. DDE and polychlorinated biphenyls residues were found in the heart tissue of all species examined, and this might indicate a possible inductive effect on the microsomal mixed-function oxidase system by environmental contaminants.     

Inhibition of chitin synthesis by two 1-(2,6-disubstituted benzoyl)-3-phenylurea insecticides. II

The knowledge of the biochemical mode of action of 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea (diflubenzuron) is presented, explaining the insecticidal effect. Like its structural analog, 1-(2,6-dichlorobenzyl)-3-(3,4-dichlorophenyl)urea (Du 19111), it inhibits chitin synthesis in the cuticle of larvae. Virtually complete inhibition was demonstrable 15 min after the application of diflubenzuron. Neither diflubenzuron nor Du 19111 has any effect upon chitinase activity either in vivo or in vitro. The insecticidal effect upon the cuticle, therefore, must be explained as an inhibition of chitin synthesis and not as an activation of chitin degradation. In contrast to the action of Du 19111, no accumulation of N-acetylglucosamine occurs upon treatment of larvae with diflubenzuron. Similarities and differences in the mode of action of both compounds are discussed, together with other effects reported in the literature.     

On estimating non‐additive genetic parameters in chickens 1

1. Several economically important traits in two Leghorn populations (over 9000 birds) were examined for additive and non‐additive components of genetic variance and sex‐linked effects. Data were analysed by two different statistical models based on least‐squares procedures.

2. Six different covariances were first calculated between relatives; i.e., full‐sibs, 3/4‐sisters, half‐sisters, dam‐daughters, grandam‐granddaughters and aunt‐nieces.

3. From the covariances, weighted least‐squares equations were used to obtain estimates of variance components for additive genetic, dominance, maternal and sex‐linkage effects.

4. The estimates of non‐additive components were highly variable but generally small compared with the additive genetic estimates.

5. In general this study suggests that for most traits, with the possible exception of rate of egg production, there is relatively little non‐additive genetic variation.

6. The consequences of possible negative correlations between additive effects and maternal effects are considered as they might apply to egg production in poultry.     

Etiology of the stomatitis pneumoenteritis complex in Nigerian dwarf goats.

The causative agent of stomatitis pneumoenteritis complex was isolated in domesticated goats and Vero cell culture. It was identified immunologically and morphologically as identical with the "Peste des Petits Ruminants" virus. There were cross reactions between stomatitis pneumoenteritis complex virus isolate and rinderpest virus by immunodiffusion and complement fixation tests but no cross neutralization. Goats recovered from stomatitis pneumoenteritis complex were protected against a challenge with rinderpest virus that was lethal to control goats. Ultrastructural morphology revealed intracytoplasmic and intranuclear inclusions made up of random arrays of fibrillar strands. Pleomorphic particles budded from the plasma membrane of infected cells and enveloped virions were seen extracellularly. Specific ferritin tagging was demonstrated in the stomatitis pneumoenteritis complex virus infected cells treated with homologous and peste des petits ruminants viral antibody systems but little, if any, tagging in the heterologous rinderpest system.     

The selectivity of methabenzthiazuron between barley, perennial ryegrass and Poa trivialis

In field experiments methabenzthiazuron at 1.1 kg ai/ha applied pre-emergence gave good control of Poa trivialis L. in perennial ryegrass S23 which was undersown in spring barley (Zephyr); no significant damage to barley or perennial ryegrass resulted from 2.2 kg ai/ha. However this dose applied when barley had three to four leaves decreased the subsequent barley yield. In pot experiments in the glasshouse methabenzthiazuron was active mainly due to uptake through the soil. Much greater damage to barley and perennial ryegrass resulted when herbicide-treated soil was placed below seed level than above the seed. The difference was less marked with P. trivialis. The latter started to develop secondary roots near the soil surface earlier than either perennial ryegrass or spring barley.     

Weed competition in spring-planted strawberries

Annual weeds germinating after planting strawberry (Fragaria chiloensis (L.) Duch. cv. Cambridge Favourite) in late March had no effect on crop growth if removed by late May. Dense weed cover thereafter severely inhibited stolon growth, virtually eliminating it if allowed to remain beyond mid-August. Shading by weeds inhibited leaf production and caused etiolation of existing leaves. New leaves appeared shortly after weed removal and few plants died unless weed cover persisted for most of the growing season. Further weed germination was allowed on some plots. Although not removed until late autumn, these weeds only had adverse effects on crop growth where initial weeding had occurred before mid-June. In one experiment, delaying weed removal until 6 July, 31 August or 2 November in the first year reduced fruit yield in the second (weed-free) year by 34%, 54% and 67% respectively. In a later experiment, competition from weeds until July or later in the first growing season gave fruit yields similar to those in the first experiment, but totally weed-free plots and those kept clean after weeding in mid-June produced less fruit than plots which remained weedy between mid-June and mid-August. It is suggested that competition from uncontrolled stolon growth in this experiment severely inhibited crown and hence truss production on plots which did not suffer weed competition. Unless left untouched until early September, weeds had less adverse effect on truss production than the stolons which they displaced. The results are interpreted in relation to improving the efficiency of weed control techniques.     

Studies on viremia and antibody formation in ducklings and goslings after experimental infection with Lednice (Yaba 1) virus.

A very low virus level was found for a short time in the blood of ducklings and goslings after experimental Lednice (Yaba 1) virus infection by subcutaneous (scut) and intranasal (inas) route and in blood of ducklings also after infection by intracerebral (icer) route. Subsequently virus neutralizing antibody formation was examined. Antibody formation was found in most of animals. In goslings onset of antibody formation seems to be slower than in ducklings after the same virus infection dose; vice versa, in ducklings antibody titer decreased after 6 weeks. Using low infection virus dose, neutralizing antibody level in ducklings was lower than in the former case. On examining the blood and the organs, the virus was detected in a very low amount and for a very short time in blood and spleen of goslings and only in blood of ducklings.     

Chemotaxonomy of Compositae related to their host suitability for Pratylenchus penetrans

Experimental work and a survey of literature gave data on the effects of 175 Compositate on populations ofPratylenchus penetrans in the soil. Nearly 70 Compositae effectively suppress populations ofP. penetrans. It is shown that a close relationship exists between this suppressing feature and the chemotaxonomy of the Compositae.Samenvatting Eigen onderzoek aangevuld met gegevens uit de literatuur gaf informatie over de invloed van 175 Composieten op populaties vanPratylenchus penetrans in de grond. Bijna 70 soorten verlaagden deze dichtheden (Tabel 1). Het betreft soorten van de geslachtenGrindelia, Solidago, Coreopsis, Eclipta, Rudbeckia, Verbesina, Melampodium, Parthenium, Iva, Ambrosia, Milleria, Baeria, Schkuhria, Eriophyllum, Chaenactis, Helenium, Gaillardia, Tagetes, Arctotis, Gazania, Berkheya, Didelta, Echinops enUrospermum. Er is een duidelijk verband tussen de taxonomische indeling van Composieten en deze eigenschap. Bijna alle getoetste soorten van de subtribus Ambrosiinae, Heleniinae, Arctotinae, Gorteriinae en Echinopinae reduceerden populaties vanP. penetrans. In sommige geslachten zoalsSolidago, Coreopsis, Rudbeckia enMelampodium veroorzaakten slechts een of enkele getoetste soorten dit effect.Van de 16 Composieten, waarvan bekend is dat zij -terthienyl in hun wortels bevatten, verlaagden er 15 dichtheden vanPratylenchus. Vrijwel hetzelfde geldt voor Composieten met 5-(3-buteen-1-ynyl)-2,2-bithienyl in hun wortels (Tabel 1). Ook de aanwezigheid in een aantal andere Composieten van een groep rode dithio-acetyleen-verbindingen met waarschijnlijk nematicide eigenschappen in vitro, komt goed overeen met de eigenschap om dichtheden vanP. penetrans in de grond te verminderen.