Simultaneous analyses of chromosomes in root meristems and of the biochemical status of needle tissues of three different clones of Norway spruce trees challenged with moderate ozone levels

Biochemical effects of both low and high ozone impact in long-term and short-term experiments are well investigated and documented; however, short-term treatments with moderate ozone levels have revealed divergent information concerning the biochemistry of needle tissues. Damage to the meristems of spruce trees have been found for several ozone treatments, in the form of an enhanced number of chromosomal aberrations, which appeared to be persistent for up to 2 years after the ozone challenge. One of the main aims of the present study was to determine whether a moderate ozone concentration is able to induce damage in needle biochemistry and/or only in the genetic material of root meristems. In the experiment three different clones of Norway spruce trees (Picea abies) were challenged with moderate ozone concentrations (up to 80 nl/l) for 11 weeks in greenhouses. Simultaneous investigations of root tip meristematic cells and the biochemical status of needle tissues regarding antioxidants and pigments were performed at two different sampling times: directly after the ozone treatment and 1 year later. Ozone effects in needles were absent both at the end of the fumigation and also after 1 year, but different clonal behaviour was found. Effect of ozone on chromosomal aberration rates in root tip meristems were observed and also the types of persisting chromosomal aberrations changed within the time course and within the different clones.     

Lunar Gravity over Large Craters from Apollo 12 Tracking Data

The Doppler residuals from the Apollo 12 lunar module radio tracking data indicate large negative accelerations over the craters Ptolemaeus and Albategnius. The mass deficienicies required to produce these accelerations are approximately equivalent to the removal of the surface material to a depth of 1 kilometer over the entire area of these craters. Several other features of the gravity fine structure can also be correlated with topography.     

PALEOCLIMATE: A Causality Problem for Milankovitch

According to the Milankovitch theory, changes in the incident solar radiation, called insolation, in the Northern Hemisphere provide the driving force for global glacial cycles. In their Perspective, Karner and Muller discuss recent studies of corals from around the world that shed doubt on the applicability of the theory to the termination of the penultimate glaciation. The authors argue that a fresh, unbiased look at the data is warranted.     

A weight‐of‐evidence approach to determine estuarine fish health using indicators from multiple levels of biological organization

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Radioisotope dating with an accelerator: a blind measurement

The age of a sample of carbon dioxide has been determined by accelerating the carbon with a cyclotron and detecting the carbon-14 ions in the beam. Nitrogen-14 was eliminated as a background through the use of a range-separation technique. To avoid all possibility of experimenter bias, the measurement was conducted in a blind fashion.     

Contributions of quisqualate and NMDA receptors to the induction and expression of LTP

The contributions of two subclasses of excitatory amino acid transmitter receptors to the induction and expression of long-term potentiation (LTP) were analyzed in hippocampal slices. The quisqualate/kainate receptor antagonist DNQX (6,7-dinitro-quinoxaline-2,3-dione) blocked 85% of the evoked field potential, leaving a small response that was sensitive to D-AP5 (D-2-amino-5-phosphonopentanoate), an N-methyl-D-aspartate (NMDA) receptor blocker. This residual D-AP5-sensitive response was of comparable size in control and previously potentiated inputs. High-frequency stimulation in the presence of DNQX did not result in the development of robust LTP. Washout of the drug, however, revealed the potentiation effect. Thus NMDA-mediated responses can induce, but are not greatly affected by, LTP; non-NMDA receptors, conversely, mediate responses that are not needed to elicit LTP but that are required for its expression.     

不同灌溉技术条件对冬小麦生产的影响

为了研究并得到3种不同灌溉技术（滴灌、喷灌、漫灌）对冬小麦产量及其构成的影响,在中国农业大学吴桥实验站设计了滴灌、喷灌、漫灌的大田试验.3种灌溉技术条件下,其灌溉总量相同,漫灌和喷灌采用浇底墒水加浇两水,滴灌采用浇底墒水加浇四水的方式;从冬小麦整个生长期内的作物高度、叶面积指数、籽粒重等指标,考察不同灌溉技术对冬小麦生产及其构成的影响.结果表明：滴灌条件下,表层含水量下降速度最小,整个生长期,含水量高于喷灌和漫灌;滴灌处理的叶面积指数最高,其次是喷灌;在成熟期,滴灌条件下,作物高度比漫灌高12%,比喷灌高5%;滴灌和喷灌的条件下产量分别比漫灌高8.63%,7.75%;滴灌、喷灌、漫灌的籽粒千粒重分别为43.36,42.17和41.17 g,滴灌和喷灌籽粒重明显高于漫灌,且生物量分别比漫灌提高了6.9%,3%.这说明3种灌溉技术中,滴灌技术最有利于实现节水保墒、小麦增产,其次是喷灌.