影响菜豆普通花叶病毒种子传毒的因素

研究了影响菜豆普通花叶病毒(BCMV)种子传毒的一些因素,不同品种,不同感染时期种子的传毒率有显著差异,苗期感病的植株,不同荚位的种子传毒率是:下部>中部>上部,花期感病者则是:中部>上部>下部,感病植株的斑驳荚种子传毒率,依品种的不同,比无斑驳荚者高3.2～9.3倍。     

FACTORS AFFECTING THE PRODUCTION OF CHROMOSOME ABERRATIONS BY CHEMICALS

In the present paper, the results of a study on the influence of temperature, hydrogen ion concentration, and oxygen tension on the production of chromosome aberrations in Vicia root tips by maleic hydrazide (MH), di-(2, 3-epoxypropyl)ether (DEPE), and 8-ethoxycaffeine (EOC), are described. Variations in the hydrogen ion concentration of the treatment solutions did not significantly influence the effect of EOC and DEPE. In contrast, the MH effect was considerably diminished by raising the pH from 4.7 to 7.3. A marked increase in the frequencies of aberrations produced by DEPE and MH was obtained by raising the temperature from 3° to 25°C. The effect of EOC increased with rising temperature up to 12°C. With a further rise in temperature the effect of EOC decreased, so that at 25°C. it was of about the same magnitude as at 3°C. The effect of EOC was completely inhibited, and that of MH partly so, when during the treatment (1) oxygen was excluded from the solution, (2) respiration was inhibited by azide or cyanide, or (3) phosphorylation was uncoupled from respiration by 2, 4-dinitrophenol (DNP). Pretreatments with DNP had a similar effect, but posttreatments did not influence the frequencies of aberrations. The effect of DEPE was unchanged by anoxia. Pre- or posttreatments with DNP did not change the total number of aberrations produced by DEPE, but the appearance of the effect was considerably delayed. The results are discussed.     

FACTORS AFFECTING THE PRODUCTION OF LOCAL LESIONS BY PLANT VIRUSES

Beans inoculated with tobacco necrosis virus were kept in the dark at different temperatures for 1 hr. before and 1 hr. after inoculation; in this experiment the number of lesions increased with temperature over the range 55–82° F.
The effect of 30 min. periods of darkness before or after inoculation depended on the time of day, the number of local lesions usually being decreased. Prolonging the night period before inoculation sometimes increased the number of lesions.
Light appeared to be more important than temperature in controlling the daily variation in susceptibility. However, in a test over a 30 hr. period this variation continued even when plants were placed under constant conditions before and after inoculation.
When plants that had been kept in the dark were exposed to light of about 800 f.c. intensity for 1 min. immediately before inoculation the number of local lesions was doubled.     

影响籼稻体细胞胚胎发生几个因素的研究

以 IR36、IR50、IR52及 IR54等品种的幼穗及成熟种子为材料,研究了蔗糖浓度、2,4-D、NAA、激动素及脱落酸对体细胞胚胎发生、结构的保持及植株分化的影响。6%蔗糖有利于胚性愈伤组织的诱导;3%的有利于胚性结构的保持及植株分化。当培养基中不含2,4-D,而含激动素与 NAA 时,幼穗直接出芽;当不含激动素而含2,4-D与 NAA 时,外植体产生非胚性愈伤组织;当不含 NAA 而含2,4-D 与激动素时,外植体产生胚性愈伤组织。认为,2,4-D与激动素是籼稻体细胞胚胎发生的基本因素,而 NAA 的作用是不明显的。不同外植体(幼穗与成熟种子)的体细胞胚胎发生,对2,4-D 与激动素的反应略有不同,幼穗更为敏感。在继代培养基中,加入低浓度的脱落酸有利于胚性结构的保持。随着继代世代的延续,分化培养中愈伤组织所表现出的绿色生长点状物不能发育成完整植株。     

菹草（Potamogeton crispus）对水中氮、磷的吸收及若干影响因素

菹草（Ｐｏｔａｍｏｇｅｔｏｎ ｃｒｉｓｐｕｓ）对水中氮、磷的吸收与ｐＨ、光照、水温、根／茎生物量比及底泥间隙水与上覆水中营养盐浓度比有关。在ｐＨ为８．０－９．５、水温为１９－２８Ｃ的实验条件下,水中ＮＨ＿４－Ｎ浓度低于０．３５ｍｇ·１左右时;菹草茎、叶优先吸收ＮＯ＿３－Ｎ;水中ＮＨ＿４－Ｎ浓度大于０．３５ｍｇ·１￣（－１）左右时,菹草则优先吸收ＮＮ＿４－Ｎ,这一选择吸收与ＮＨ＿４－Ｎ／ＮＯ＿３－Ｎ比值无关。强光照、高温（３０℃）和高ｐＮ的协同作用严重影响菹草硝酸盐还原酶活性。在自然条件下,菹草根部主要从底泥中吸收ＮＨ＿４－Ｎ、ＰＯ＿４－Ｐ,对ＮＯ＿３－Ｎ吸收甚微;茎、叶主要从水层中吸收ＮＯ＿３－Ｎ,对ＰＯ＿４－Ｐ吸收甚少。一般情况下,浮游植物和菹草对水体中的氮、磷吸收无多大矛盾。菹草倒伏后腐败分解释放大量营养盐,为浮游植物的增殖创造了条件。     

THE INFLUENCE OF HEAT ON SOME APHIDS

The thermal death-points of five species of aphids removed from their host plants lay between 38 and 41°C., when tested for 1 hr. at 60% r.h . Many aphids alive after 1 hr. at high temperatures died within the next day; no Myzus persicae recovered and reproduced after 1 hr. above 37.5°C. Third and fourth instars and adult apterae withstood heat better than first and second instars and alatae. More aphids died at 90% r.h . than at 60% r.h , and more at 60% than at 30% r.h . Aphids kept at 15% r.h . for 4 hr. before being heated showed a higher mortality than those kept at 95% r.h . Aphids on plants withstood temperatures higher than their thermal death-point off the plant. Presumably aphids can continue to cool themselves by evaporation while feeding; also lower temperatures on the surface of transpiring plant tissues will aid survival.     

FACTORS AFFECTING TRANSMISSION AND RECOVERY IN THE PASSIVE IRON NERVE MODEL

1. The speed of transmission of the activation wave along passive iron wires enclosed in glass tubes containing dilute (70 per cent) nitric acid increases with the conductivity (sectional area) of the column of electrolyte but at a slower rate. The speed is closely proportional to the square root of the conductivity See PDF for Equation. The reasons for this relationship are discussed and an explanation is proposed. 2. The recovery of transmissivity after the passage of an activation wave is gradual and follows a characteristic course. After an interval of partial or decremental transmission (having a high temperature coefficient and lasting several minutes at 20°), the wire recovers its power of transmitting an activation wave for an indefinite distance. In such a recovered wire the speed of transmission is at first slow and increases by degrees up to a maximum, the increase following a curve apparently of the type v_t = v ₀ (1 – e^_kt). The approximate time required to attain this maximum (corresponding to complete recovery) at the different temperatures is 15 to 20 minutes at 20°, 30 to 45 minutes at 15°, ca. 60 minutes at 10°, and 90 minutes or more at 5°. 3. The character of the curve of recovery (the curve relating speed of transmission to interval since previous activation) agrees with the assumption that the increase in speed depends on a progressive chemical change in the molecules forming the passivating film, this change involving the transformation of (relatively) nonreactive into reactive molecules and following the course of a monomolecular reaction. 4. The temperature coefficient of the speed of transmission (between 5° and 20°) is low, of the order Q ₁₀ = 1.3 to 1.6. That of the rate of recovery, on the contrary, is high (Q ₁₀ = ca. 3). The parallel to the conditions in nerve and other transmitting protoplasmic systems is pointed out and discussed. 5. Passive wires enclosed in acid-containing continuous and interrupted glass tubes immersed in a large volume of acid exhibit characteristic phenomena of distance action; under appropriate conditions the velocity of transmission of the activating influence between different areas may thus be greatly increased. Characteristic instances are cited and some possible physiological parallels are pointed out.     

THE DETECTION OF CUCUMBER MOSAIC VIRUS IN SINGLE APHIDS

Abstract  Cucumber mosaic virus (CMV) was detected in single aphids Myzus persicae and Aphis gossy pii by dot immunobinding assay (DIBA). The DIB A procedure with the lowest detectable concentration endpoint of 0.16ng/ml of purified CMV, or 0. 32pg per sample dot of 2μI antigens, satisfied the sensitivity required for the detection of CMV in single virus-carrying aphids. The aphid extracting method of dipping the stylets dissected from aphid heads in the droplets of small volume (2–5p1) of suitable buffer not only ensured the highly concentrated Firuses fully released from the aphid stylets, but decreased the interference of non-virus materials from aphids to minimum as well, and thus overcame the two major difficulties in the detection of plant viruses in vectors. The virus-carrying rates tested by DIBA had good coincidence with the transmission rates by bioassay. Undoubtedly, such breakthroughs in the technique of detecting nonpersistent viruses in aphid vectors are of great epidemiological importance.     

THE TRANSMISSION BY MITES, HOST-RANGE AND PROPERTIES OF RYEGRASS MOSAIC VIRUS

A virus that causes chlorotic streaks on ryegrass leaves was transmitted by the eriophyid mite Abacarus hystrix (Nalepa). Virus-free mites acquired the virus in 2 hr. feeding on infected ryegrass and the proportion that became infective increased with increased feeding time up to 12 hr.; vectors lost infectivity within 24 hr. of leaving the infected leaves. All instars of A. hystrix transmitted the virus.
The virus was transmitted by manual inoculation of sap to other species of Gramineae, including oats, rice, cocksfoot and meadow fescue, but none of these hosts seemed to contain as much virus as ryegrass; their saps did not precipitate specifically with antiserum prepared against the virus in ryegrass, whereas sap from infected ryegrass precipitated up to a dilution of 1/32. Infective sap of S22 Italian ryegrass contained flexuous rod-shaped particles; the dilution end-point of the virus was about 1 in 1000; the virus was inactivated when held for 10 min. at 60°C. and most of its infectivity was lost after 24 hr. at room temperature.