INFLUENCE OF ULTRAVIOLET RADIATION ON AUXIN-CONTROLLED PLANT GROWTH

Ultraviolet irradiation (254 mμ) of plant test systems results in alterations in growth capacity which can be ascribed to UV-induced modifications of the ability of plant cells to respond to auxin. This conclusion was reached following study of auxin-requiring, auxin-sufficient, and auxin-surfeit test systems representing cell division, cell enlargement, and cell differentiation. The UV effect was usually reversible by subsequently presented near-visible or visible radiation.     

UVA的辐射效应及其分子机理

在光量子血疗法治疗肿瘤及其它疾病中,紫外线已被广泛地用作辐照光源,并取得满意效果。本文综述了近几年关于ＵＶＡ的辐射效应和分子机制研究的某些进展。     

ADAPTATION OF A PSYCHROPHILIC FRESHWATER DINOFLAGELLATE TO ULTRAVIOLET RADIATION1

Little is known about the UV photobiology of psychrophilic dinoflagellates, particularly in freshwater systems. We addressed the life strategies of Borghiella dodgei Moestrup, Gert. Hansen et Daugbjerg to cope with ambient levels of ultraviolet radiation (UVR) under cold conditions. Several physiological parameters related to growth, metabolism, and UVR protection were determined for 4 d in UVR‐exposed and control cells by applying stable isotope analysis, spectrophotometry, and liquid chromatography–mass spectrometry (LC/MS). In UVR‐exposed cells, assimilation of ¹⁵N and ¹³C and content of chl a and carotenoids, specifically diatoxanthin with respect to dinoxanthin and diadinoxanthin, were increased; furthermore, catalase activity showed a cyclic pattern with a strong increase after UVR exposure but a rapid return to preexposure levels. Both in UVR‐exposed and control cells, no lipid peroxidation of galactolipids was observed. However, in UVR‐exposed cells, content of galactolipids was higher and linked to an increase in monogalactosyldiacylglycerols (MGDGs). We concluded that Borghiella's adaptation to UVR depended on a general metabolic enhancement and efficient scavenging of oxygen radicals to mitigate and counteract damage. While Borghiella seemed to be well adapted to ambient UVR, the interactive effects of higher temperature and UVR on psychrophilic species in front of climate change merit further investigation.     

EFFECTS OF VISIBLE AND ULTRAVIOLET RADIATION ON THE GERMINATION OF PHACELIA TANACETIFOLIA

Schulz , Sister M. Richardis , O.P., and Richard M. Klein . (N. Y. Bot. Gard., N. Y., N. Y.) Effects of visible and ultraviolet radiation on the germination of Phacelia tanacetifolia. Amer. Jour. Bot. 50(5): 430–434. Illus. 1963.—Germination of Phacelia tanacetifolia was suppressed by exposure to white light increasing with intensity and length of illumination. The light effect decayed during 24 hr of darkness. Seeds were most sensitive to the suppressive effects of light 13–17 hr after the beginning of imbibition. Light suppression was caused by a photocatalytic reaction. Wavelengths causing the suppression lie in the far-red, red, blue, near-ultraviolet and far-ultraviolet regions of the spectrum. At equal energies, blue light was less effective than far-red, red or ultraviolet radiation. There was no evidence for the existence of the phytochrome system. Simultaneous irradiation with red and blue light or simultaneous irradiation with red and far-red induced a synergistic repression of germination. The presentation of different wavelengths in various sequential patterns markedly altered the germination response. An interaction between elevated temperatures and visible radiation affecting germination response was also noted.     

INFLUENCE OF FLORAL OPTICAL PROPERTIES ON THE ULTRAVIOLET RADIATION ENVIRONMENT OF POLLEN

Pollen in unopened flowers of most species is totally screened from solar ultraviolet-B radiation by imbricated petals that are largely opaque to UV-B. Following flower opening but before anther dehiscence, the anther walls of the species investigated filter out over 98% of the UV-B radiation. Reflectance of UV from corollas of open flowers does not generally appear to add significantly to the solar UV-B radiation environment of pollen.     

THE EFFECTS OF ULTRAVIOLET RADIATION ON SPORES OF THE FUNGUS ASPERGILLUS NIGER

The survival ratio of Aspergillus spores exposed to ultraviolet radiation has been measured as a function of total incident energy for wave lengths of 2537 Å, 3022 Å, 3129 Å, and 3650 Å. The effect of humidity on killing of Aspergillus spores by ultraviolet radiation has been found to be negligible. A delay in germination as a result of irradiation has been found. The Bunsen-Roscoe reciprocity law has been found to hold within the limits of the radiation intensities studied. Certain morphological changes have been observed.     

紫外线辐射增加对大豆光合作用和生长的影响

通过模拟南京地区自然光中有效紫外线Ｂ和紫外线Ａ辐射,增大辐射剂量对大豆光合作用,生长及生物量形成的影响迸行了研究。３个加强的ＵＶ辐射（０．１５,０．３５,０．７０Ｗ·ｍ－２）处理均使大豆植株矮化,抑制根、茎、叶的生长及干物质的积累。在３个ＵＶ处理中,生物效应以０．７０Ｗ·ｍ－２处理力最大,０．１５Ｗ·ｍ－２处理影响最小。ＵＶ辐射匀能使大豆叶片光合作用下降。下降幅度随ＵＶ辐射强度的增大而增大,本文还对ＵＶ影响大豆生长的可能机制进行了探讨。     

紫外线辐射对菜豆幼苗某些胁迫响应基因表达的影响

报道了ＵＶ－Ｃ辐射对菜豆（ＰｈａｓｅｏｌｕｓｖｕｌｇａｒｉｓＬ．）ＰＲＰ、ｄｅｈｙｄｒｉｎ、ＰＲ蛋白、ｐｏｌｙｕｂｉｑｕｉｔｉｎ和ＤａｎＪ－ｌｉｋｅ蛋白等胁迫响应基因表达的影响。Ｎｏｒｔｈｅｒｎｂｌｏｔ杂交结果表明：ＵＶ辐射能强烈地诱导ＰＲ蛋白基因的表达,并能促进ＰＲＰ、ｐｏｌｙｕｂｉｑｕｉｔｉｎ和ＤａｎＪ－ｌｉｋｅ蛋白等基因的转录,而对ｄｅｈｙｄｒｉｎ基因的转录有抑制作用,这些防御蛋白共同作用可能对于保护细胞免受ＵＶ伤害和维持细胞的正常代谢有重要作用。     

DIFFERENTIAL SENSITIVITY OF PROPHASE POLLEN TUBE CHROMOSOMES TO X-RAYS AND ULTRAVIOLET RADIATION

1. Through use of the pollen tube technique it has been possible to study the sensitivity of prophase stages to x-rays and ultraviolet, and to correlate the varying sensitivity with changes in the generative nucleus of Tradescantia. 2. Sensitivity to ultraviolet decreases from the 2 hour stage until at 11 hours after germination there is no further production of breaks. The 0 and 1 hour stages show a decreased sensitivity over the 2 hour stage but it has been suggested that this is not due to a decreased sensitivity but to shielding by the pollen wall. 3. Sensitivity to x-rays rises to a peak at the 4 hour stage, but then subsides until no breaks are realized (at a dose of 370.8 r) after the 10 hour stage. In this respect the effects of x-rays and ultraviolet are similar. Each type of x-ray break shows its own individual trend. 4. Correlation of x-ray breaks with changes in the generative nucleus indicates that the important events determining the sensitivity of the chromosomes to breakage are the uptake of water at the time of germination and the movement involved in spiralization. The total absence of breaks after the 11 hour stage is not understood. 5. The changing sensitivity to ultraviolet may depend on any one or all of three factors: (a) the nucleic acid cycle, (b) changes in the matrix, and (c) the number of subdivisions in the chromosome. These are discussed although their relative importance is not known.     

紫外线辐射对柑桔过氧化物酶活性和电频率特性的影响

介绍了紫外线辐照柑桔后,柑桔过氧化物酶活性等生理参量和电学频率特性等物理参量随贮藏时间变化的实验结果,并对结果作了简单分析。结果表明：适当剂量的紫外辐照,可以降低柑桔的过氧化物酶活性,使柑桔电学频率特性等保持贮藏初期的特点,延缓柑桔内部结构和所含成分的变化,具有一定的保鲜效果。     

THE BACTERICIDAL EFFECT OF ULTRAVIOLET RADIATION ON ESCHERICHIA COLI IN LIQUID SUSPENSIONS

1. The irradiation of bacteria in liquid suspension has been made possible through: (a) the use of a specially balanced physiological salt solution which is practically non-absorbing for the wave lengths used, and which is of such composition that subsequent dilution of the bacterial suspension gives the proper number of organisms; (b) special design of the exposure cell and a very thorough method of stirring which subjects each organism equally to the radiation; (c) practically complete absorption of the incident radiation, through the use of very dense suspensions, thus eliminating the necessity for a separate determination of the absorption coefficients of the bacteria for the wave lengths used. 2. The method also provides a means for determining the effects of sub-lethal doses. 3. A formula is given for calculating from observed survival ratios the energy required to inactivate bacteria with ultraviolet radiation. The formula corrects for the protective action of non-viable organisms. 4. Data are given for the inactivation of 15 hour and 240 hour cultures of E. coli, washed and unwashed) and for 6–7 hour cultures, unwashed. These data are compared with those of other investigators. 5. A possible explanation for the differences in energy required to inactivate old, young, and standard cultures of bacteria is suggested. 6. The possible mechanism of the action of ultraviolet radiation on microorganisms is discussed.     

INFLUENCE OF ULTRAVIOLET RADIATION ON GROWTH AND PHOTOSYNTHESIS OF TWO COLD OCEAN DIATOMS1

The influence of chronic exposure to UV-B and UV-A radiation on growth and photosynthesis of two polar marine diatoms (Pseudonitzschia seriata and Nitzschia sp.) was investigated in cultures exposed to moderate photon fluences for 3–7 days. Population growth rates were diminished 50% by UV-B. Fluorescence induction kinetics of photo-system II (PSII) revealed that UV-B caused lower F_v/F_m ratios and half-rise times, indicating damage to the reaction center of PSII and to related elements of the photosynthetic electron transport chain. Carbon assimilation rates per cell and per chlorophyll a were nonetheless highest for UV-B—exposed populations, which also had the highest chlorophyll a content per cell. The UV-B—exposed cells were, however, more vulnerable to visible light-induced photoinhibition. Exposure to UV-A in the absence of UV-B had little effect on growth, fluorescence induction of PSII, or chlorophyll a contents but did have some inhibitory effects on carbon assimilation per chlorophyll a and per cell. The increased photosynthetic capacity of UV-B-exposed cells suggested some ability to compensate for damage to the photosynthetic apparatus.