灭幼脲Ⅲ号在好气水环境中的降解代谢的初步研究

本文研究了新农药灭幼脲Ⅲ号在好气水环境中的降解与代谢。在避光条件下,观察了灭菌组与实验组中灭幼脲Ⅲ号及其主要代谢产物的消长过程,比较了它的化学水解与微生物降解的差异。在室内模拟好气系统中,研究了母体化合物在水体中的残留动态和生物降解半衰期,及其初期主要代谢途径的转化产物,同时分别用高效液相色谱法,紫外吸收光谱扫描,以及特征有机质谱图,对灭幼脲Ⅲ号的两种主要代谢产物进行了定性定量测定。结果表明:灭幼脲Ⅲ号在室内好气环境中较易水解,而且水中微生物的存在能加速它的降解,母体化合物在水体中初期代谢主要途径为分子中的苯甲酰碳与脲氮键首先开裂,生成邻氯苯甲酸(CBA)和对氯苯基脲素(CPU)。     

THE ROLE OF ROOTS IN THE NUTRITION OF AQUATIC VASCULAR PLANTS

Rooted stems of three aquatic species were cultured in a two-compartment apparatus which allowed the upper and lower portions of the stem to be kept in different nutrient solutions. P³² was supplied to either the upper or lower compartment. At the end of a 10-day growth period, the specific activity of phosphate was determined in axillary shoots which developed during the course of the experiment from buds in the upper compartment. The results indicated that most of the phosphate in these shoots was not absorbed from the ambient medium but was derived from the rooted stem base in the lower compartment (over 90 % in Myriophyllum brasiliense, 59 % in M. spicatum, and 74 % in Elodea densa). These results give a very different but probably more accurate picture of phosphate absorption in rooted aquatic vascular plants than short-term experiments, in which phosphate is readily taken up from the ambient medium by leaves of M. spicatum and E. densa. In M. brasiliense the amount of phosphate translocated is related to the mass of roots present. Evidence is presented that normal growth of axillary shoots occurs even when all mineral ions have to be obtained by translocation from the lower compartment.     

STUDIES ON THE GENETIC CONTROL OF RESISTANT SPORANGIUM FORMATION IN ALLOMYCES

The diploid sporophyte of the phycomycetous fungus Allomyces arbuscula bears two types of sporangia: thin-walled, colorless, ephemeral zoosporangia (ZS) and thick-walled, dark-brown, resistant sporangia (RS). Normal wild-type cultures (strain Portugal IE) under standard conditions produce approximately 90% of their total sporangia as RS. These RS give the cultures a dark-brown color. A mutant was induced with UV irradiation in which the ratio of ZS to RS was shifted so that only 20% of the total sporangia are RS. These cultures are a pale, tan color. Hybrids between the mutants and wild-types produce ca. 65% RS and are also intermediate in the color of the culture. Meiotic segregation in the RS of the hybrid sporophytes gives gametophytes half of which when selfed produce mutant sporophytes and half of which produce wild-type sporophytes. The shift from RS to ZS formation is thus considered to be the result of a one-gene mutation at a locus ‘R.’ The haploid gametophytes of wild-type strains have in addition to male and female gametangia a small number (2-4%) of RS. In mutant gametophytes the percent RS has dropped to 0.1-0.2%. The proposed genotypes at the ‘R’ locus in Allomyces arbuscula are: wild-type sporophytes (RR), hybrid sporophytes (Rr), mutant sporophytes (rr), wild-type gametophytes (R) and mutant gametophytes (r).     

THE NUTRITION AND SOME BIOCHEMICAL STUDIES OF VIBRIO CYCLOSITES AND VIBRIO NEOCISTES

SUMMARY: Vibrio cyclosites and V. neocistes grew in a defined medium consisting of a mineral basis, nicotinamide or nicotinic acid and the amino acids methionine, histidine, aspartic acid, phenylalanine and iso leucine. Washed suspensions failed to oxidize any of these substances in the Warburg apparatus. It was not possible with these organisms to demonstrate transamination between the five essential amino acids and α-ketoglutaric acid or pyruvic acid.     

THE DEVELOPMENT OF BASAL BODIES AND FLAGELLA IN ALLOMYCES ARBUSCULUS

The development of basal bodies and flagella in the water mold Allomyces arbusculus has been studied with the electron microscope. A small pre-existing centriole, about 160 mµ in length, was found in an inpocketing of the nuclear membrane in the vegetative hypha. Thus, formation of a basal body does not occur de novo. When the hyphal tip started to differentiate into gametangia, the centrioles were found to exist in pairs. One of the members of the pair then grew distally to more than three times its original length, whereas the other remained the same size. The larger centriole would correspond to the basal body of a future gamete. Gametogenesis was usually induced by transferring a "ripe" culture to distilled water. Shortly after this was done, a few vesicles were pinched off from the cell membrane of the gametangium and came in contact with the basal body. Apparently, they fused and formed a large primary vesicle. The flagellum then started to grow by invaginating into it. Flagellar fibers were evident from the very beginning. As the flagellum grew so did the vesicle by fusion with secondary vesicles, thus coming to form the flagellar sheath. The different stages of flagellar morphogenesis are described and the possible interrelationships with other processes are discussed.     

NITROGEN METABOLISM OF AQUATIC ORGANISMS. II. THE ASSIMILATION OF NITRATE,NITRITE, AND AMMONIA BY BIDDULPHIA AURITA1

Biddulphia aurita, a centric diatom, can grow on either nitrate, nitrite, or ammonia as its sole nitrogen, source. Cells remove ammonium nitrogen from the medium 2.3–2.4 times faster than either nitrate or nitrite nitrogen and, when grown for 24 hr in the ammonium medium, contain higher levels of non-protein nitrogen than cells grown in the nitrate or nitrite medium for the same period of time. The nitrogenous compounds in the nonprotein nitrogen fraction from cells grown in the nitrate, nitrite, or ammonium medium contain the same level of soluble-free amino nitrogen, combined amino nitrogen, and ammonium nitrogen. The high level of soluble nonprotein nitrogen in the medium of the cells grown in the ammonium medium is due to soluble amide nitrogen which represents 18% of the total soluble nitrogen present in these cells, whereas it represents only 2% in cells from the nitrite medium, and its level is negligible in cells from the nitrate medium. Cells grown in the nitrate medium have both nitrate- and nitrite-reductase activity. Cells grown in the nitrite medium have only nitrite-reductase activity in significant levels, while cells grown in the ammonium medium lack both enzymes.     

植物的硅素营养研究综述

本文阐述了硅在植物中的形态、分布、吸收、积累、生理作用及其与其它元素的关系。研究表明：１硅主要以二氧化硅胶（ＳｉＯ２．ｎＨ２Ｏ）的无机物形态存在于植物表皮细胞和细胞壁。植物体内硅的含量在不同物种间差异很大。根据硅的含量,可将一般栽培植物分为三种类群;同时根据植物硅钙摩尔比值可将植物分为喜硅植物和非喜硅植物。硅在植物各部分分布不均匀,并且随着植株的生长发育,植株中的硅含量不断变化。植物中硅的积累受环境中多种因素的影响。２植物主要以单硅酸形态吸收硅,不同植物吸收硅的能力不同。水稻具有主动吸硅能力,其吸收过程受体内代谢活动影响＜请合法使用软件＞其它大多数植物主要以被动方式吸收硅,但不排除具有选择性吸收硅的可能性。３硅对植物的生长发育产生影响。硅是一些植物（如禾本科植物、甜菜、木贼属植物及某些硅藻）的必需元素。硅对其它很多植物具有有益作用。硅对植物的作用主要表现在对形态结构、生理过程和抗逆能力三方面的影响上。在去硅条件下,多种植物表现出缺硅症状。４硅对植物吸收利用对其它营养元素产生影响。硅对不同元素的影响方式和程度不同,同时随着植物的生长发育,对某种元素的作用常发生变化。