温度、丙烯和1-MCP对西洋梨果实乙烯合成和乙烯受体ETR1同源基因表达的影响

研究了贮藏温度、丙烯和 1 MCP (1-甲基环丙烯 )处理对帕斯—卡桑 (Passe -Crassane)西洋梨果实成熟的影响。结果表明 :低温可促进果实的乙烯合成 ,未经低温处理的果实 ,用丙烯处理 ,不能正常合成乙烯。丙烯促进乙烯合成的效应随冷藏时间延长而增强。1 MCP处理可抑制冷藏果实的乙烯合成。定量PCR分析结果表明 ,果实中乙烯受体ETR1同源基因的表达不受低温的调节 ;但冷藏后升温或升温后用丙烯处理时 ,mRNA含量降低     

Amyloodinium ocellatum (Brown, 1931) (Dinoflagellida) infestations in cultured marine fish at Eilat, Red Sea: epizootiology and pathology

Abstract. Since 1977, repeated outbreaks of infestation by Amyloodinium ocellatum (Dinoflagellida) in cultured gilthead bream Sparus aurata L. and seabass Dicen-trarchus labrax (L.) resulted in sporadic and mass mortalities. Fingerlings and yearlings as well as breeders were affected and, since 1978, larval and post-larval S. aurata in the hatchery. Infestations in juvenile and breeder fish were located predominantly on the gills and mucosal integument but in larval fish only the skin rather than the gills was infested. Histopathological changes of the infested gills are described. Vacuolar degeneration of the cells penetrated by the parasites' rhizoids was evident at the site of attachment and cloudy swelling was apparent in the surrounding epithelial cells. In heavy infestations the entire epithelium of the gill filaments underwent hyperplasia with consequent fusion of the lamellae. Where hyperplasia was extensive the cells gradually degenerated while the inner epithelial layer showed distinct spongiosis and in some cases completely disintegrated. All heavily infested gills lacked mucous cells.     

Regrowth of ryegrass swards subject to different cutting regimes and stocking densities

A cutting experiment was carried out on a sward of S23 perennial ryegrass to study the effect of different defoliation regimes on regrowth and the factors affecting regrowth. The defoliation frequencies and intensities encompassed the range commonly found on continuously stocked pastures. The defoliation regimes produced swards of contrasting growth form with regrowth characteristics which differed in respect of senescence loss, fall in water-soluble carbohydrate concentration, residual leaf area index, photosynthesis per unit leaf area index and photosynthesis per unit area of land. Regrowth was most closely related to the latter. These results were used to interpret data for net canopy photosynthesis of continuously grazed pastures.     

Charcoal column/thin layer chromatographic method for high fructose corn sirup and spectrophotometric method for hydroxymethylfurfural in honey: collaborative studies.

A new spectrophotometric method is described for determining hydroxymethylfurfural in honey in which interfering background absorption of honey is corrected for by use of a bisulfite-treated sample as blank. Two procedures for detecting high-fructose corn sirup (HFCS) in honey were also tested. In one, charcoal column pretreatment is used to concentrate trace oligosaccharides, followed by thin layer chromatography to differentiate those of HFCS from those of honey. The other method depends on measurement of the isomaltose/maltose ratio by gas-liquid chromatography. The charcoal/thin layer chromatographic method for HFCS has been adopted official first action. The bisulfite method for hydroxymethylfurfural has been adopted interim first action.     

The effect of propionic acid on the storage losses of hay

Storage losses in moist hay treated with propionic acid were compared with those occurring in untreated moist hay in two experiments and with field-cured hay in three experiments. Dry matter losses in treated hays ranged from 41 to 8.6% and from 1.7 to 12.6% in untreated hays. Digestible organic matter losses in both treated and untreated hays were generally greater than dry matter losses. Only in one experiment did propionic acid application significantly reduce nutrient losses in moist hays. Nutrient losses, and water-soluble carbohydrate losses in particular, were shown to be correlated with maximum and cumulative bale temperatures during storage in two of the experiments. The rise in hale temperatures during storage was reduced in all three experiments, to a greater or lesser extent, by application of the additive. Loss of propionic acid from the hay during and after application was very large. In the three experiments 86.2, 85.3 and 85.6% of the acid applied was lost by the end of the storage period. Acid distribution studies indicated that variation in acid concentration within bales was as great as between bales. It was concluded that more research is needed into applicator design and position on the baler and into alternative application methods if the benefits of propionic acid as a moist hay preservative are to be fully exploited.     

Production and persistence of urease activity in soils

Addition of urea to Iowa soils did not induce urease activity, but production of urease activity was observed on addition of glucose and other organic materials that promote microbial activity. The persistence of the urease activity produced on addition of these materials varied with the soil, but, with each soil studied, the urease activity after addition of organic materials eventually was identical to that of the unamended soil. No increase or decrease in urease activity was observed when unamended or urea-treated soils were incubated under aerobic conditions for several months. It is concluded that soil constituents protect urease against microbial degradation and other processes leading to inactivation of enzymes and that every soil has a stable level of urease activity determined by the ability of its constituents to provide this protection.     

The effect of delayed autumn harvest on the survival of varieties of perennial ryegrass

The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable.     

Removal of mineral nutrients by red clover varieties

K, P, Ca and Mg contents and uptakes are reported from total herbage of plots sown with six varieties of red clover harvested three times a year for 3 years. K, P and Mg contents were above those reported as critical for growth; values for Ca were lower than quoted ranges which suggested that growth might have been affected by either deficiency of Ca or low pH. Hungaropoly was characterized by relatively low K and P and high Ca contents. Maximum uptakes in red clover total herbages over 3 years were 1198 kg ha^?1 K (Hera), 112 kg ha^?1 P (Hera), 494 kg ha^?1 Ca (Hungaropoly) and 104 kg ha^?1 Mg (Mars). Results were compared with those found for S101 perennial ryegrass, harvested on a similar system and receiving similar fertilization with uptakes of 759 kg ha^?1 K, 100 kg ha^?1 P, 200 kg ha^?1 Ca and 46 kg ha^?1 Mg, by expressing accumulating uptakes and inputs as linear regression equations. The better varieties of red clover, Hera, Hungaropoly, Mars and S123 show rates of DM accumulation similar to S101 perennial ryegrass and similar uptake rates of K and P but higher rates of uptake of Ca and Mg. The levels of application of K and P used in the experiment seem to be more than adequate but attention to the Ca status may be required to sustain high-yielding red clover swards.     

Cherry leaf roll virus causing a disease of Betula spp. in the United Kingdom

A virus, serologically related to isolates of cherry leaf rollvirus (CLRV) from Prunus avium (L.) L. and Sambucus nigra L.was transmitted to a range of herbaceous plants from leavesor roots of thirty-one of forty-seven trees of Betula spp. growingat two heathland sites in Berkshire. Ageing leaves of virus-infectedindividuals which had mild chiorotic blotches or ring and linepatterns in July showed bright yellow ring and line patternsin October. In the season after B. verrucosa seedlings wereinoculated with CLRV isolates, leaves developed chlorotic ringand blotch patterns; the symptoms being similar whether theinocula were originally isolated from S. nigra, P. avium orB. verrucosa. Palisade and mesophyll cells of naturally infectedleaves of B. verrucosa contained chloroplasts in which granalorganization was appreciably less distinct than that of chloroplastsfrom virus-free leaves. In many instances, virus-infected leafcells had spherical virus-like particles about 30 mn in diametercontained within tubular structures in cell wall projections;these structures were not seen in virus-free material. An isolate of CLRV from B. verrucosa, purified from systemicallyinfected leaves of Nicotiana clevelandii Gray by ammonium sulphateprecipitation and differential centrifugation, contained twomajor components having sedimentation coefficients of 118s and130s. Each component was composed of spherical particles withdiameters in the range 26–30 nm and having buoyant densitiesin caesium chloride of 1·460 and 1·493 gm/cm³.Polyacrylamide gel electrophoresis of preparations from bothbuoyant components indicated that they each contained a singlespecies of protein whose molecular weight was in the range 53,000–54,000daltons.