石灰菌代谢产物的化学研究(Ⅰ)

从石灰菌(Lactarius hysginus Fr.)提取物的中性部分,分离得到六个化合物,经物理常数和光谱分析,鉴定为麦角甾醇(A)、硬脂酸甲脂(B)、N-苯基-2-萘胺(C)、24E-麦角甾7,22-二烯-6-酮一3β,5α-二醇(D)、庚酰胺(E)、24E-麦角甾-7.22-二烯-3β,5α,6β-三醇(F),其中化合物D作为天然产物尚未见文献报道。     

In vitro activity of 15-azasterol (A25822B) against chalkbrood pathogen Ascosphaera apis in the honey bee

The antifungal agent 15-azasterol A25822B was examined for effects on the growth and development of Ascosphaera apis. The minimum inhibition concentration (MIC) of azasterol against A. apis was 1 m. Growth and development of A. apis was completely controlled at this concentration. At a concentration of 0.01 m growth of A. apis was retarded and although sporocysts were formed developing spores were not be able to reach maturation. A major effect of azasterol at this low concentration was the accumulation of lipid in the hyphae, sporocysts and immature spores. In addition it caused a conformational change in mitochondria and damage to the spore membrane structure. On the basis of these results, further investigations of azasterol for the treatment of chalkbrood disease in the honey bee are warranted.Work was performed during sabbatical leave at the University of California, Davis.     

Formation and role of glycine betaine in the moderate halophile Vibrio costicola

The moderate halophile Vibrio costicola, growing on a chemically-defined medium, transformed choline into glycine betaine (betaine) by the membrane-bound enzyme choline dehydrogenase and the cytoplasmic enzyme betainal (betaine aldehyde) dehydrogenase. Choline dehydrogenase was strongly induced and betainal dehydrogenase less strongly induced by choline. The formation of these enzymes was also regulated by the NaCl concentration of the growth medium, increasing with increasing NaCl concentrations. Intracellular betaine concentrations also increased with increasing choline and NaCl concentrations in the medium. This increase was almost completely blocked by chloramphenicol, which does not block the increase in salt-tolerant active transport on transfer from a low to a high salt concentration.Choline dehydrogenase was inhibited by chloride salts of Na⁺, K⁺, and NH _inf4 ^su+ , the inhibition being due to the Cl^- ions. Betainal dehydrogenase was stimulated by 0.5 M salts and could function in up to 2.0 M salts.Cells grew as well in the presence as in the absence of choline in 0.5 M and 1.0 M NaCl, but formed no intracellular betaine. Choline stimulated growth in 2.0 M NaCl and was essential for growth in 3.0 M NaCl. Thus, while betaine is important for some of the adaptations to high salt concentration by V. costicola, it by no means accounts for all of them.Abbreviations CDMM chemically-defined minimal medium - PPT proteose-peptone tryptone medium - SDS sodium dodecyl sulfate Deceased, 1987     

Soybean Yield as Related to Rates of 1,3-Dichloropropene Applied at Planting for Management of Root-Knot Disease

1,3-Dichloropropene (1,3-D) at rates of 17.2 to 51.6 liters/ha applied 3 days preplant or at planting significantly (P < 0.05) reduced the amount of galling on roots of soybean grown in sites infested with Meloidogyne incognita or M. arenaria. Populations of M. incognita second-stage juveniles at harvest were significantly (P < 0.05) reduced by all treatments. Only the 51.6-liters/ ha treatments and a 3-day preplant 34.4-liters/ha application significantly reduced at-harvest juvenile infestations of M. arenaria. Equations (P < 0.001) relating soybean yield and 1,3-D dosage indicated soybean phytotoxicity at the upper range of the nematicide rates. The maximum yield response was predicted at 40 liters/ha applied 3 days preplant at both infestation sites. Maximum yield response was predicted with 30 liters/ha applied at planting to M. incognita-infested soil and from 25 liters/ha applied at planting to M. arenaria-infested soil. Application of economic factors suggested that management of M. incognita may be cost effective with at-plant treatments of low rates of 1,3-D. Yield responses of M. arenaria-infected soybean exposed to similar treatments were insufficient to justify their use at prevailing prices.     

Relative Virulence of Meloidogyne incognita Host Races on Soybean

Sensitivity and host efficiency of susceptible (''Lee 68'', ''Coker 156'') and resistant (''Bragg'', ''Centennial'', ''Forrest'', ''Lee 74'') soybean (Glycine max (L.) Merr.) cultivars for races of Meloidogyne incognita (Mi) were determined in greenhouse experiments. Eight Mi populations collected from the southeastern United States were utilized. All Mi races reproduced readily on Lee 68 and Lee 74 and moderately on Forrest and Bragg. Coker 156 exhibited resistance to races 1 and 2, and some race 3 populations, but was very susceptible to certain race 3 and 4 populations. Reproduction of all races was lowest on Centennial. Forrest and Centennial shoot growth was not significantly suppressed by any race. There were no distinct differences in virulence between races except for a race 3 population which reproduced readily on all cultivars, stunting their growth. Considerable variation in reproduction existed within races 1 and 3.     

Nitrate and ammonium absorption by plants growing at a sufficient or insufficient level of phosphorus in nutrient solutions

Summary Absorption of nitrate and ammonium was studied in water culture experiments with 4 to 6 weeks old plants of barley (Hordeum vulgare L.), buckwheat (Fagopyrum esculentum L. Moench) and rape (Brassica napus L.). The plants were grown in a complete nutrient solution with nitrate (5.7±0.2 mM) or nitrate (5.6±0.2 mM) + ammonium (0.04±0.02 mM). The pH of the nutrient solution was kept at 5.0 using a pH-stat. It was found that phosphorus deficiency reduced the rate of nitrate uptake by 58±3% when nitrate was the sole N source and by 83±1% when both nitrate and ammonium were present. The reduction occurred even before growth was significantly impeded by P deficiency. The inhibition of the uptake of ammonium was less,i.e. ammonium constituted 10±1% of the total N uptake in the P sufficient plants and 30±5% in the P deficient plants. The reduction of nitrate absorption greatly decreased the difference between the uptake of anions and cations. It is suggested that P deficiency reduced the assimilation of NO ₃ ^– into the proteins, which might cause a negative feedback on NO ₃ ^– influx and/or stimulate NO ₃ ^– efflux.     

Root contribution to nitrate reduction in barley seedlings (Hordeum vulgare L.)

Summary The leaf and root nitrate reductase activities were measured in 7 day-old barley seedlings by anoxic nitrite accumulation in darkness, during 48h after the transfer from a N-starved medium to a 1.5 mM K¹⁵NO₃ medium. Thisin situ nitrate reduction was compared with the¹⁵N incorporation in the reduced N fraction of the whole seedlings.The nitrate reduction integrated fromin situ measurements was lower than the reduced¹⁵N accumulation. The rootin situ nitrate reductase activity seemed to account for only the third of the real root nitrate reduction, which may have been responsible for the overall underestimation. This discrepancy was partly explained by the ability of the root to reduce nitrite in an anoxic environment.These results suggest that, after correction of thein situ estimation of the nitrate reduction. the roots contribute to about 50% of the total assimilation.     

Influence of partial defoliation of green pepper on the senescence,growth, and nitrate reductase of the remaining leaf

Summary Removal of all but one leaf from pepper plants prevented the senescence of the remaining leaf and caused increases of approximately 140, 200, and 200%, respectively in leaf area, weight, and nitrate reductase activity. Development of the fruit (fresh and dry weight increases) was only approximately 65% of that of fruit on control plants.     

Cadmium and zinc influx characteristics by intact corn (Zea mays L.) seedlings

Summary Cadmium and zinc uptake parameters were determined for intact corn (Zea mays L.) seedlings grown for 15 and 22 in nutrient solutions containing levels of Cd and Zn that were similar to those found in soil solutions. Uptake of both elements was assumed to follow Michaelis-Menten kinetics. Calculations were based on the concentrations of free ionic Cd (Cd²⁺) and Zn (Zn²⁺) rather than the total solution concentration. Rates of Zn uptake were measured by determining depletion of Zn for periods of up to 30 h from solutions containing initial concentrations of 1.5 and 10μmol Zn 1⁻¹. Depletion curves suggested that Zn uptake characteristics were similar at both levels of Zn in solution. The Imax for Zn uptake decreased from 550 to 400 pmol m⁻² root surface s⁻¹ between 16 and 22 d of growth while Km decreased from 2.2 to 1.5 μmol Zn²⁺ 1⁻¹. Cadmium uptake parameters were measured by controlling Cd²⁺ activities in nutrient solution betwen 6.3 to 164 nmol l⁻¹ by continuous circulation of nutrient solution through a mixed-resin system. Imax for Cd uptake was 400 pmol m⁻² root surface s⁻¹ at 15 and 22 d of growth. The magnitude of Km increased from 30 to 100 nmol Cd²⁺ 1⁻¹ during this time period. The Km value suggests that corn is efficient for Cd uptake. The results of these uptake studies are consistent with the observed uptake of Zn and Cd by corn seedlings in soils.