Effets de divers herbicides sur la croissance mycélienne de souches de Botrytis cinerea pers et de Penicillium expansum Link, sensibles ou résistantes à certains fongicides

Effects of various herbicides on mycelial growth of strains of Botrytis cinerea. Pers. and Pénicillium expansum Link, sensitive or resistant to certain fungicides Of seventy herbicides tested, thirty-eight were slightly toxic to B. cinerea (CI50, concentration giving 50% inhibition of the speed of mycelial growth, exceeding or equal to 100g of herbicide/ml of nutrient solution) and, of those, ten had no effect even at 1000 g/ml. The most active products (CI50 less than 10 g/ml) were Chlorthiamid, dichlobénil, nitrofen, propyzamide and phenolic derivatives (DNOC, ioxynil, PCP). In most cases P. expansum was less sensitive than B. cinerea except to endothal, propachlor, prynachlor and certain substituted ureas. Strains resistant to the benzimidazole fungicides (carbendazim, thiabendazole etc.) show increased sensitivity to certain carbamade herbicides (barban, chlorbufam etc.), this indicates the existence of a negative cross resistance between these groups of antimitotic pesticides. Strains resistant to the cyclic-imide fungicides (iprodionc, procymidone, vinclozolin) and to various aromatic compounds (biphenyl. chloroneb, dicloran etc.) may also be resistant to bipyridilium, dinitroanilinc and diphenylethcr herbicides, to chlorthamid. dichlobénil and oxadiazon. This cross resistance between pesticides with different biochemical modes of action has yet to be explained.     

Changes in surface reactivity and organic matter composition of clay subfractions with duration of fertilizer deprivation

Preservation of organic matter in soils depends on the chemical structure of organic compounds and on the surface properties of the mineral matrix. We tested the effect of mineral surface reactivity on organic matter decomposition by (i) investigating changes of organic matter composition in clay subfractions of an illitic Haplic Chernozem along a time series of fertilizer deprivation and (ii) simultaneously characterizing the reactivity of mineral surfaces. The soil was subjected to fertilizer deprivation for 18, 44 and 98 years, respectively. Mineral surface properties were characterized by selective dissolution of pedogenic oxides. The number of hydroxyls released after exposure to sodium fluoride was taken as an index for mineral surface reactivity. Organic soil constituents were determined by ¹³C cross‐polarization magic‐angle spinning nuclear magnetic resonance (¹³C CPMAS NMR). Clay subfractions had different mineral surface properties. The coarse fractions have more reactive surfaces and contain more organic carbon than the fine clay fractions. Mineral surface properties are constant over time and are not affected by fertilizer deprivation. Surface reactivity is a function of iron oxide density and controls carbon concentrations in the clay subfractions. Within the time frame of our investigation, alkyl C and aromatic C responded to the duration of fertilizer deprivation, but were indifferent to mineral surface reactivity. O–alkyl C seems to be protected by interactions with pedogenic oxides.     

Endosperm protein synthesis in maize mutants with increased lysine content

The endosperm proteins of the maize mutants, opaque-2, opaque-7, floury-2, brittle-2, and the double mutant of opaque-2 and brittle-2, were separated into five soluble fractions by the Landry-Moureaux method. As compared to their isogenic normal counterparts, the mutant endosperms had higher concentrations of albumins, globulins, and glutelin-3, and lower concentrations of prolamines. The combination of the opaque-2 and brittle-2 genes enhanced this difference. Although the four mutant genes are located on three different chromosomes, they exert a similar effect on endosperm protein composition. Five other starchmodifying mutants with high lysine content resemble the brittle-2 mutant in endosperm protein composition, when the gene is present either singly or combined with opaque-2. Therefore, the pattern of protein synthesis in all maize mutants with high lysine concentrations may be either identical or very similar. Because no synergistic effect on lysine concentration is obtained when floury-2 is combined with opaque-2, different pathways leading to reduced zein synthesis may exist in the floury and starch-modifying mutants with high lysine concentrations.     

Ethically chosen studies with early-weaned piglets during their raising in pens with different applications of straw. 1. The effects of different applications of straw and different floor conditions in areas of uniform size

In extension of earlier experiments in housing systems with perforated floors, utilization rates of solid floor with litter, straw in a rack and deep litter, as well as the behaviour and physical condition, especially of claws, were investigated. Each pen had an area of 0.45 m2/piglet. In further experiments the influences of race (DL instead of DL x Piétrain), kind of rearing (without straw instead of rearing with straw), lowering temperature and the effect of a preferred perforated floor in comparison with solid floor were investigated. Deep litter was preferred for activity and lying behaviour only in the case of low temperature (14-18 degrees C) whereas solid floor with litter was preferred in the case of higher temperature (19-25 degrees C). The perforated floor was equivalent to solid floor on the condition that the area dimension was sufficient, temperature 3 degrees C higher than in the other experiments and straw in a rack was offered. However, the utilization rates of solid floor increased in the case of lowering temperature by 4 degrees C. There was no significant influences of the different race or kind of rearing. In the experiments there were significant signs of a more harmonious condition of the animals and a shorter, respectively no period where the animals had to adapt to the housing conditions. These findings were in contrast to those of earlier investigations. The possibility of acting with straw led to an undisturbed circadian rhythm and to a higher rate of standing within the total activity which was as high as in earlier studies. Further social companions and environmental objects lost attractiveness.(ABSTRACT TRUNCATED AT 250 WORDS)