Changes in radiocaesium uptake and distribution in wheat during plant development: a solution culture study

Spring wheat plants were grown in a ¹³⁷Cs labelled nutrient solution, either in the presence or absence of NH₄ as a secondary N source. Between 11 and 64 days after sowing (DAS), plants were harvested on nine occasions. The plants supplied with NH₄ and NO₃ had lower root ¹³⁷Cs Activity Concentrations (AC) than those supplied with NO₃ only. Shoot AC were equal in both nutrition treatments. Shoot and root ¹³⁷Cs AC (dry weight basis) showed the same trends with plant age in both nutrition treatments. Shoot AC almost doubled between 11 and 28 DAS after which they gradually decreased concomitant with a similar decrease in K concentrations. Root AC were always higher than shoot AC and increased to a maximum at 35 DAS after which they fluctuated. Expressed on a tissue water basis, the ¹³⁷Cs AC varied less during plant age than did dry weight based AC. Furthermore, root and shoot AC expressed on a tissue water basis were almost equal. It is shown that the initial increase in ¹³⁷Cs AC in both root and shoot can largely be explained by the initial dilution of absorbed ¹³⁷Cs in the unlabelled seedling tissues. No correlation was found between K and ¹³⁷Cs distribution among ears, leaves, stems and roots in 64 old wheat plants. NH₄ as a secondary N source in a nitrate nutrient solution marginally affected ¹³⁷Cs distribution.Abbreviations AC activity concentrations - DAS days after sowing FAX no corresponding author: +3216321997     

Isolation,culture and regeneration of protoplasts from birdsfoot trefoil (Lotus corniculatus)

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus L. cv. Leo). Green cotyledons from in vitro grown seedlings were preplasmolyzed in CPW salts containing 13% mannitol (CPW 13 M) for 1 h prior to the enzyme treatment. The enzyme formula consisted of 2% (w/v) Onozuka Cellulase R-10, 1% (w/v) Macerase and 0.1% (w/v) Pectolyase Y-23 in CPW 13 M. This method produced high yields of viable protoplasts after purification. The procedure is reproducible and takes approximately 2.5 months from protoplast isolation to plantlet establishment in a greenhouse. More than 100 plantlets were grown in soil. Two somaclonal variants, a chimeric plant for chlorophyll production and an albino cell line, have been obtained by this procedure.     

赤霉素与脱落酸对番茄种子萌发中细胞周期的调控

利用细胞流检仪检测番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ．） ＧＡ－缺陷型、ＡＢＡ－缺陷型和相应的正常品种（野生型）成熟种子胚根尖细胞倍性水平时发现：ＧＡ－缺陷型和野生型种子绝大多数细胞ＤＮＡ 水平为２Ｃ,而ＡＢＡ－缺陷型种子则含有较多的４Ｃ细胞。在标准发芽条件下,ＡＢＡ－缺陷型和野生型种子浸种１ ｄ 后胚根尖细胞ＤＮＡ 开始复制,随后胚根突破种皮而发芽。然而ＧＡ－缺陷型种子除非加入外源ＧＡ,否则既不发生细胞ＤＮＡ 复制,也不发芽。这说明内源ＧＡ 是启动番茄种子胚根尖细胞ＤＮＡ 复制的关键因素,同时也说明番茄根尖细胞ＤＮＡ 复制是种子发芽的必要条件。实验证明：ＡＢＡ 不抑制细胞ＤＮＡ 合成,但阻止Ｇ２ 细胞进入到Ｍ 期。外源ＡＢＡ处理野生型种子与渗控处理结果相似,可以大幅度提高胚根尖４Ｃ／２Ｃ细胞的比例,但抑制种子的最终发芽     

番茄种子发芽及渗控处理过程中的水分关系

干燥番茄（Ｌｙｃｏｐｅｒｓｉｃｏｎ ｅｓｃｕｌｅｎｔｕｍ Ｍｉｌｌ． ｃｖ． Ｍｏｎｅｙｍ ａｋｅｒ）种子浸种吸水有明显的３ 个阶段,尽管种子不同部分吸水的速度不一样,但整粒种子需１０～１２ ｈ 才能基本完成第一阶段的吸水。胚乳对种胚伸长和生长的机械压力明显阻碍种胚的吸水,即使在第二阶段整个种子水势与浸种溶液基本达到水分平衡时,种胚的水势仍然低于整个种子水势０．６～０．９ ＭＰａ。发芽过程中ＧＡ 和ＡＢＡ不直接影响番茄种子吸水。番茄种胚水势与含水量的关系呈幂指数的正相关。无论在浸种还是渗控处理过程中,番茄种胚压力势的总变化趋势是下降的     

An improved method for the generation and transfection of protoplasts from Cucumis sativus Cotyledons

Summary A protocol was developed for the preparation of Cucumis sativus var Straight 8 protoplasts that incorporates a two-step Ficoll^® gradient and results in a high percentage of viable, debris-free protoplasts suitable for the transient expression of foreign genes. Polyethylene glycol and electroporation were compared for their effect on protoplast transfection with commonly used reporter genes. Using a polyethylene glycol method, cucumber protoplasts transfected with a plasmid containing the -glucuronidase gene showed high expression levels, while protoplasts transfected with a plasmid containing the chloramphenicol acetyl transferase gene showed levels of activity that were barely distinguishable from mock-transfected controls. Tomato ringspot virus genomic RNA was also transfected into the protoplasts, and the assembly of viral particles was confirmed.     

Photodynamic herbicides: 1. Concept and phenomenology

A new approach to the design of conceptually and phenomenologically new herbicides is described. It involves the joint utilization of tetrapyrrole precursors, such as δ-aminolaevulinic acid (a biodegradable amino acid) and activators of the chlorophyll biosynthetic pathway, such as 2,2′-dipyridyl, in order to induce treated plants to biosynthesize and accumulate massive amounts of tetrapyrrole intermediates of the chlorophyll biosynthetic pathway in the dark (i.e. at night). During the subsequent light period (daylight) the accumulated tetrapyrroles act as potent photodynamic sensitiziers, which in turn result in the death of susceptible plants in a matter of hours. We have therefore proposed to name herbicides that act via this mechanism as photodynamic herbicides, or more pictorially as laser herbicides. From a limited survey of agricultural plant and weed species it appears that photodynamic herbicides exhibit a very pronounced organ, age and species-dependent selectivity. For example, dicotyledonous weeds such as mustard, red-root pigweed, common purslane and lambsquarter are very susceptible while monocotyledonous plants such as corn, wheat, barley and oats are not. The biochemical basis of this selectivity seems to lie, among other things, in the rates of tetrapyrrole turnover and in a differential enhancement by the applied chemicals of the monovinyl and divinyl tetrapyrrole biosynthetic pathways in the various species. A survey of various groups of chemicals (herbicides and other selected biochemicals) that are likely to exhibit photodynamic herbicidal properties is currently under investigation.     

The evaluation of pollen quality,and a further appraisal of the fluorochromatic (FCR) test procedure

Summary Methods currently available for evaluating pollen quality in vitro include, (a) tests of germinability; (b) tests of the stainability of the vegetative cell contents; (c) tests for enzyme activity, and (d) the fluorochromatic procedure (FCR), which tests principally the integrity of the plasmalemma of the vegetative cell. Using germinability in vitro as a standard, a comparison has been made between histochemical methods of classes (b), (c) and (d) in application to various pollens, immature, mature, and treated in ways known to affect viability and membrane state. Predictably, the lowest correlation was obtained with tests of stainability. The highest was given by the FCR, which generally provided an excellent guide to potential germinability. The FCR procedure is subject to various limitations, however, (a) A high correlation between FCR and germinability can only be expected when mature, ripe pollen is used; with immature pollen, the FCR will predict excessively high potential germinability. (b) The FCR may also predict a higher potential level of pollen function than in vitro germinability when the germination medium is sub-optimal. In this situation, however, it will generally give a better guide to fertilising capacity, (c) The FCR is not a test of pollen viability. Like germinability in vitro, it can yield a negative score with pollen which is nevertheless capable of functioning. For example, false negatives will be obtained with some species if the pollen is not properly pre-conditioned by rehydration before testing, an important point in monitoring stored pollen. The paper includes a brief discussion of the rationale of pollen testing.     

Multivariate analysis applied to tomato hybrid production

Summary Twenty characters were measured on 60 tomato varieties cultivated in the open-air and in polyethylene plastic-house. Data were analyzed by means of principal components, factorial discriminant methods, Mahalanobis D² distances and principal coordinate techniques. Factorial discriminant and Mahalanobis D² distances methods, both of which require collecting data plant by plant, lead to similar conclusions as the principal components method that only requires taking data by plots. Characters that make up the principal components in both environments studied are the same, although the relative importance of each one of them varies within the principal components. By combining information supplied by multivariate analysis with the inheritance mode of characters, crossings among cultivars can be experimented with that will produce heterotic hybrids showing characters within previously established limits.     

Effects of Cycloate on Development of Heterodera schachtii and Growth of Three Beta Species

Greenhouse tests were set up to evaluate the effects of the herbicide, cycloate (S-ethyl cydohexylethylthiocarbamate), oil development of Heterodera schachtii and growth of three Beta species. Cycloate added to infested soil enhanced cyst development/gm root on B. vulgaris and larvae/gm of root in B. patellaris and B. procumbens at 4, 16, and 16 μg(a.i.)/gm of soil, respectively. Total numbers of nematodes/individual root system decreased because of poor root growth of seedlings in cycloate-amended soil. Penetration and larval development through stage three did occur in the wild Beta species in any treatment. Thus, resistance of B. patellaris and B. pocumbens to development of H. schachtii was not altered by cycloate. Cycloate also retarded growth (P = 0.05) of the sugarbeet cultivars and B. patellaris at 4 μg(a.i.)/gm and B. procumbens at 16 μg(a.i.)/gm of soil. Higher concentrations of nematodes/gm root in plants growing in cycloate-amended soil may be attributed to factors such as fewer roots available for penetration, possible effects of cycloate on egg hatch, greater attraction of nematodes to roots, and increased susceptibility of roots to larval penetration. Suppression of seedling growth in cycloate-amended soil may be attributed in part to higher nematode density and in part to direct root damage from cycloate.     

In vivo measurement of cadmium (115mCd) transport and accumulation in the stems of intact tomato plants (Lycopersicon esculentum,Mill.)

The internal distribution processes of cadmium (^115mCd) in the stems of tomato plants have been investigated using in vivo -spectrometric measurements with semiconductor detectors. The initial penetration into the xylem after root uptake and the subsequent lateral redistribution in the surrounding tissues were monitored continuously in each individual plant. The kinetics of the lateral migration toward the epidermis can be described by a diffusion process, characterized by an apparent diffusion coefficient of about 10^-8 cm² s^-1. After two days of cadmium supply this heavy metal is accumulated in relatively large amounts in the epidermal and cortical layers, from which it can be released only very slowly. On the contrary, the exchange processes with other divalent cations cause in the xylem a quick release, its rate being dependent on the duration of the preceding cadmium treatment.