Purification of cell wall fragments by sucrose gradient centrifugation

Summary A procedure for purification of cell wall fragments was developed. The method utilizes sucrose density gradients to efficiently remove soluble enzyme and membrane contaminants from the cell wall. Purification at each stage was monitored biochemically by the removal of cytoplasmic associated markers and ultrastructurally by thorough electron microscopic examination of the isolated cell wall fractions. Cell walls purified by the procedure were compared to those purified by the more conventional multiple washing procedure.     

防护林网内玉米田生物量和生产力格局的研究

 本文报道了松嫩平原防护林网内玉米(Zea mays)田的生物量和生物生产力的时空格局及其与生态、生理因子的关系。研究结果表明：林网东西两条主林带间不同位置玉米的生物量和生产力在生长季各时期均有显著差异。生物量在距西侧主林带5—10倍树高(H)处最高,距离为1树高处最低,25倍树高处亦较高。在大部分时间里生产力的水平格局为“N”形。两个峰分别为10H和25H。南北两条副林带间的生物量和生产力无明显差异。林网内生物量和生产力的分布格局受林网内温、湿因子分布的制约,不同时期的限制因子不同。叶面积和同化速率对生产力格局也有重要影响。林网内玉米穗生物量明显高于无林地。本研究指出,应适当缩短主林带间距,并可在林带附近种植浅根、矮秆和耐荫性作物,以提高整个林网的生产力和经济效益。     

The mycobiota from seeds of Shrunken-2 (sh2) Sweet Corn

Sixteen species of fungi were isolated from the pericarp, endosperm, scutellum, and embryo of low (<75% germination), moderate (75–89%), and high vigor (>89%) seedlots of supersweet sweet corn (sh2) hybrids over two years. Most frequently isolated species werePenicillium oxalicum, Rhizopus arrhizus (14.5%), andRhizopus spp (17.4%).Fusarium moniliforme, a common inhabitant in field or dent corn, was isolated from only 2.4% of the samples. The low mean isolation values may be the result of poor conditions for infection or the data may reflect the methods used including sterilization techniques or random tissue selection.Aspergillus niger, F. moniliforme, andP. oxalicum, were isolated at a significantly greater level than other fungi from the high vigor hybrids at 0.89, 0.46 m and 4.46 respectively compared to 0.04, 0, and 1.82 for the low vigor hybrids. When Total Fungi were compared mean isolations were significantly greater from the high vigor hybrids at 11.96, the moderate 8.79, or low 4.86 vigor groups. When data from seed sources for all vigor groups were compared, significantly greater mean isolations were obtained from Illinois Foundation Seed hybrids forCladosporium sp,R. arrhizus, andRhizopus spp., but greater rates were obtained forFusarium oxysporum from the Asgrow hybrids. Isolation frequencies for the 16 species were not significantly different between the seed tissue types from any of the hybrids evaluated during this investigation. Results from this study showed that there is a diverse group of fungi present within thesh2 seed and seed treatments must be developed which will minimize seed rot and seedling blight from both internal seedborne and external pathogens.     

利用玉米种子白蛋白和球蛋白乳酸聚丙烯酰胺电泳鉴定品种( 英文)

采用改进的乳酸 - PAGE技术对不同玉米 (Zea mays)自交系和杂交种种子的白蛋白和球蛋白进行了系统电泳分析 ,发现此方法具有高度的分辨力和稳定性。把电泳图依其迁移率分为 α、β、γ和 ω4个带区。各自交系和杂交种的电泳图均有其鲜明特征 ,彼此可以区别 ,视作它们各自的“指纹”。全籽粒电泳谱带与胚的电泳谱带基本相同。胚乳产生谱带少而弱 ,且大都和胚的谱带发生重叠。亲本自交系的不同谱带在杂种 F1 发生互补。杂种谱带等于两亲本共同谱带与各自独有谱带之和。而且正、反交 F1 谱带以及它们两亲本种子提取液机械混合产生的谱带完全相同 ,表明谱带的差异是一种由核基因控制的遗传性状。F1 的谱带类型可由两亲本谱带类型预测 ,也可由两亲本种子提取液混合而产生的电泳图所演示     

Influence of Unrefined Corn Oil and Surface-active Agents on the Germination and Infectivity of Alternaria helianthi

A dew immediately after inoculation is normally required for the mycoherbicidal activity of Alternaria helianthi on common cocklebur. The formulation of A. helianthi conidia in an emulsion of unrefined corn oil enabled the pathogen to infect the weed, regardless of whether dew was immediate or delayed for 24 h. Corn oil emulsion and the surface-active agents Tween 20, 40, 60 and 80 maintained the germination ability of 14-day-old conidia to some degree for up to 4 days in suspension. Both the corn oil emulsion and Silwet stimulated the germination of A. helianthi on common cocklebur leaves, but Silwet did not enhance infectivity when dew was delayed. Unrefined corn oil enhanced mycoherbicide efficacy by protecting the conidia during a dew-free period and by stimulating germination when a dew occurred. Corn oil emulsion, Silwet and Tween 20, 40, 60 and 80 reduced the dew period required for disease activity. Unrefined corn oil emulsion has potential as a formulation for the application of this mycoherbicide in the field because it maintained the germination ability and virulence of conidia on the weed during a dew-free period.     

Efficiency of nitrogen,phosphorus, and potassium use by corn,sunflower, and sugarbeet for the synthesis of organic matter

Summary A three-year experiment was conducted in natural conditions on chernozem soil to examine the efficiency of nitrogen, phosphorus, and potassium use by corn (C₄ type), sunflower and sugarbeet (C₃ type) grown in optimum conditions of mineral nutrition (N₁₀₀P₁₀₀K₁₀₀ kg/ha). Plant materials were analysed for the concentration of nitrogen, phosphorus, and potassium and dry matter mass per individual plant parts and the whole plant.Leaves of different age, of all three plant species, were analysed to find eventual differences in the efficiency of use of nitrogen, phosphorus, and potassium in the synthesis of organic matter depending on leaf age.It was found that corn had the lowest concentration of the elements studied but the highest dry matter mass. In other words, corn was more efficient than sunflower or sugarbeet in the use of these elements for the synthesis of an organic matter unit. Such results were arrived at in both sets of analyses, i.e., the analyses of leaves performed in the course of ontogenetic plant development as well as the analyses of leaves of different age.     

Photosynthate partitioning into leaf starch as affected by daily photosynthetic period duration in six species

Starch accumulation rates increased up to five-fold in the leaves of five out of six species examined when plants were shifted from a long (12 or 14-h) to a short (7-h) photosynthetic period. The five species that responded were corn (Zea mays L.), pangola (Digitaria decumbens Stent.), soybean (Glycine max L.) Merr.), spinach (Spinacia oleracea L.), and sugarbeet (Beet vulgaris L.) However, the rate of starch accumulation in alfalfa (Medicago sativa L.) was unaltered following a shift from a long to a short photosynthetic period. We conclude that photosynthate partitioning into chloroplast starch, at least in a wide variety of species, is a programmable process that can be manipulated by altering the length of the daily photosynthetic period.     

Aflatoxin contamination caused by natural fungal infection of preharvest corn

Summary Aflatoxin contamination of developing corn (Zea mays L.) kernels caused by natural infection byAspergillus flavus Link ex Fries was studied in hybrids developed for the U.S. corn belt and for the southern U.S. and grown at diverse locations in 1977. Planting dates were staggered to examine the effect of crop maturity on infection by the toxin-producing fungus. A broad range of toxin values was observed at harvest; some levels exceeded the highest that had been previously recorded in corn. The highest concentration of aflatoxin B₁ detected was 8030 ppb. Levels of toxin differed significantly among planting dates in Florida and Georgia; the second planting date at these locations contained the highest toxin levels. Elevated concentrations of toxin were characteristic of kernel samples from southern locations and southeast Missouri; at these locations samples from hybrids developed for the south had significantly lower levels of toxin than hybrids developed for the corn belt. Ears with heavy insect damage had higher toxin levels than ears with less evidence of insect attack.Mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Zinc-phosphorus relationship in the nutrition of corn plants (Zea mays L.) grown on some calcareous soils

Summary Positive relationships were observed between Zn and P in the studied calcareous soils and in the corn plants grown thereon. The high content of carbonates in these soils affected greatly the levels of extractable Zn and the Zn–P relationships. In the pot experiment, application of P increased the Zn content of the corn plants and application of Zn increased that of P.     

A study of natural populations of the celery leaf-minerPhilophylla heraclei L. (Diptera,Tephritidae)

The study of the population dynamics of the celery leaf-miner, Philophylla heraclei, must take into account the fact that the host-plant is not present permanently and that it develops between the two annual generations of the insect. This development affects in particular the quality and quantity of the leaves fed upon by the mining larvae. It is possible to know the numerical change of the populations from one annual generation to the next (bivoltine insect) and from one year to the next by counting the populations in the various larval instars, responsible for the injury caused to celery. An accurate method of counting of larval numbers, taking into account their change parallel with that of the host-plant, is described in this text. It makes it possible to know with accuracy the duration and importance of the infestations in relation to external factors and to factors inherent to the host-plant itself. Certain traits of larval behaviour, particularly the transfer of a larva from its original mine to a secondary mine as a result of food shortage can thus be established and estimated quantitatively.