Movement and metabolic fate of [14C]ethephon in flue-cured tobacco

The absorption, distribution, and metabolic fate of [¹⁴C]ethephon in flue-cured tobacco (Nicotiana tabacum L.) was studied using autoradiography, thin-layer chromatography, high-voltage paper electrophoresis, and liquid scintillation spectrometry. Labeled ethephon penetrated mature leaf tissue easily and was translocated primarily in an acropetal direction. No ¹⁴C activity was detected in any other plant part except the treated leaf. The first day after treatment, most of the translocated ¹⁴C was detected in the midrib, and after 2 days radioactivity was noticed in veinal areas distal to the point of application. Four days later, however, ¹⁴C was detected in slight amounts only in the midrib, indicating that [¹⁴C]ethephon was rapidly degraded by the leaf tissue. Depending on leaf position on the stalk, as much as 92% of the radioactivity had disappeared from the leaf tissue during the first day after treatment, and as little as 5% of the applied radioactivity was recovered 4 days later. Methanol-extracted plant residues contained insignificant amounts of ¹⁴C. All of the ¹⁴C in methanol extracts was present in the form of a labeled compound with an R_f value corresponding to that of ethephon, indicating the absence of any detectable metabolites of the parent compound. Smoke analysis of cigarettes showed that more [¹⁴C]ethylene than ¹⁴CO₂ was recovered in the main stream, whereas the trend was reversed in the case of side stream smoke.     

Quinone accumulation in S-ethyl dipropylthiocarbamate-treated wheat

Wheat (Triticum aestivum L. cv Holley) was grown for 15 days in sand into which S-ethyl dipropylthiocarbamate (EPTC) (0, 15.6, 31.25, 62.5, or 125.0 μg/kg) had been incorporated. Growth was decreased more by EPTC under high light intensity (270 μein/m²/sec) than under low light (20 μein/m²/sec) intensity. Wheat grown in the dark did not respond to EPTC at these concentrations. In high light intensity, plastoquinone-9, plastohydroquinone-9, α-tocopheroquinone, and α-tocopherol contents (nanomoles per gram fresh weight) increased as EPTC concentration increased. Similar but less marked results occurred at the low light intensity. Plastohydroquinone-9/plastoquinone and α-tocopherol/α-tocopheroquinone ratios increased at both light intensities as EPTC concentration increased. This indicated an EPTC-induced inhibition of plastohydroquinone and α-tocopherol epoxidation. Chlorophyll a and b and total carotenoid contents increased as EPTC concentration increased in plants grown at high light intensities. Changes in the membrane electron carriers contents per unit of chlorophyll or carotenoid (micrograms per milligram of pigment) occurred. As a tentative hypothesis, it is suggested that transmembrane electron transport systems were inhibited, but growth in size (fresh weight per pot) was inhibited more than was synthesis of the various pigments and quinones. Thus, a separation of growth and metabolic response to EPTC was demonstrated.     

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.     

A leaf spot disease of Nymphaea alba in the Netherlands

A destructive leaf spot disease was found onNymphaea alba in the lakes near Kortenhoef, Netherlands. After comparison of fresh material and herbarium specimens the causal agent is namedColletotrichum nymphaeae (Pass.) van der Aa, comb. nov. Synonymy, morphology and cultural characters of the fungus are described and discussed. Some remarks on the relationship with several host plants are given and the provisional conclusion is that the species is a widespread parasite, but that the destructive attack in the Kortenhoef region is probably caused by a combination of various factors.     

L‐aspartic acid and urea supplementation of low‐protein layer diets1

1. Urea supplementation of low‐protein (125 g/kg) conventional‐type diets for layers, whether containing fish meal or not, did not appear advantageous.

2. Supplementation of the low‐protein diet with aspartic acid did not affect egg production rate or efficiency.

3. Soyabean meal supplementation of the low‐protein diet increased egg weight significantly whereas aspartic acid did not.     

Factors affecting the variability in cracked and dirty eggs and egg production profitability on an integrated poultry operation

1. A number of factors causing variability in the percentages of cracked, and dirty eggs and weekly standard margin (WSM) of returns from eggs over production costs were examined on an integrated commercial poultry plant in Scotland.

2. As the bird aged, the percentage of cracked eggs increased (P <0.01) and the percentage of grade A eggs and WSM decreased (P <0.01). Cracks in dirty eggs (10.1%) were more than double those in all eggs laid (4.9%).

3. Seasonal effects on percentage cracked eggs and percentage grade A eggs were one‐third the magnitude of those due to age but were significant (P <0.05).

4. Variability in percentage cracked eggs, dirty eggs and WSM accounted for by the factors measured, were 72, 64 and 92% respectively.

5. The variability in WSM was significantly affected by percentage lay, food consumption and age but not by percentage cracked eggs, originally dirty and grade A eggs.

6. Flock management and climate inside the laying house each increased the amount of variability accounted for in the percentage cracked eggs and dirty eggs by at least 10%.     

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.     

Broiler growth and feeding behaviour in three different lighting regimes

1. Female broiler chicks reared in a 12‐h photoperiod which included a simulated “dawn” and “dusk” grew slightly faster than those reared in a 12‐h photoperiod of uniform light and others kept in continuous light.

2. This was apparently because the chicks subjected to dawn and dusk ate more food than those subjected to 12‐h uniform light and converted food more efficiently than those in continuous light.