Differential responses of silver birch (Betula pendula) ecotypes to short-day photoperiod and low temperature.

We investigated interrelations of dormancy and freezing tolerance and the role of endogenous abscisic acid (ABA) in the development of silver birch (Betula pendula Roth) ecotypes in controlled environments. Short-day treatment induced growth cessation, bud set and dormancy development, as well as initiation of cold acclimation and an increase in freezing tolerance. Subsequent low temperature and short days (12-h photoperiod) resulted in a significant increase in freezing tolerance, whereas bud dormancy was gradually released. The concentration of ABA increased in response to short days and then remained high, but ABA concentrations fluctuated irregularly when the dormant plants were subsequently exposed to low temperature during short days. Although there was a parallel development of freezing tolerance and bud dormancy in response to short days, subsequent exposure to low temperature had opposite effects on these processes, enhancing freezing tolerance and releasing dormancy. Compared with the southern ecotype, the northern ecotype was more responsive to short days and low temperature, exhibiting earlier initiation of cold acclimation, growth cessation and an increase in ABA concentrations in short days, and higher freezing tolerance, faster dormancy release and greater alteration in ABA concentrations when subsequently exposed to low temperature during short days. The rates and extent of the increases in ABA concentration may be related to increases in freezing tolerance and dormancy development during short days, whereas the extent of the fluctuations in ABA concentration may play an important role in enhancing freezing tolerance and releasing dormancy during a subsequent exposure to low temperature during short days.

Compounds of parasitic roundworm absorbing in the visible region: target molecules for detection of roundworm in Atlantic cod.

The objective of this study was to contribute to the development of technology that will be able to replace manual operations in processing of fish fillets. Removal of parasites, black lining, remnants of skin, and bloodstains are costly and time-consuming operations to the fish processing industry. The presence of parasites in fish products tends to spoil consumers' appetites. Recent reports questioning the safety of eating cod infected with parasites might lower consumer acceptance of seafood. Presently, parasites are detected and removed manually. An average efficiency of about 75% under commercial conditions has been reported. In this study, we focused on biochemical differences between cod muscle and the prevalent anisakine nematode species (Anisakis simplex and Pseudoterranova decipiens) infecting Atlantic cod (Gadus morhua). Using reversed phase high-performance liquid chromatography equipped with a photodiode array detector, substances absorbing in the range 300 to 600 nm were identified in extracts from parasite material. These substances were not detected in extracts from cod tissue. Significant biochemical differences between cod muscle and parasite material have thus been demonstrated.

Isolation and characterisation of a cytotoxic polyunsaturated aldehyde from the marine phytoplankter Phaeocystis pouchetii (Hariot) Lagerheim.

Several investigators have documented that the marine phytoplankter Phaeocystis pouchetii produce and excrete some compound that has adverse effects on its surroundings, but the chemical composition and structure of the active agent has so far been unknown. In the present study we used mass spectrometry to investigate the structural properties of the putative toxin. Colonial cells of P. pouchetii were collected along the coast of northern Norway and cultivated in the lab for a limited period of time prior to harvesting by filtration. Harvested cells and culture filtrate were extracted separately with organic solvents, and a yeast cell bioassay was used to track the toxic fractions during extraction and purification with HPLC. We found the organic extract from the culture filtrate to be toxic, and after purification with RP-HPLC the cytotoxic activity was recovered as one fraction. When the toxic fractions were pooled and analysed by GC-MS we were able to identify 2-trans-4-trans-decadienal by comparing retention time and fragmentation pattern to a commercial standard. This is the first report of a polyunsaturated aldehyde produced by a marine alga belonging to the class Haptophyceae, and this implies that production and release of these reactive compounds are not limited to diatoms.

Day and night temperature responses in Arabidopsis: effects on gibberellin and auxin content, cell size, morphology and flowering time.

The effect of 16 different day (DT) and night (NT) temperature combinations (DT and NT 12, 17, 22 and 27 degrees C) on rosette leaf growth, flower stem elongation and flowering time in Arabidopsis thaliana Ler was investigated. Final leaf length decreased with increasing NT due to a combination of reduced elongation period and reduced elongation rate. Final stem length increased with increasing DT due to increased elongation rate, and decreased with increasing NT due to a decrease in elongation period. Under NT 27 degrees C, however, stem elongation rate increased greatly, resulting in the same final stem length as under NT 12 degrees C. The transition to flowering was accelerated by increasing NT. A linear regression analysis was performed to clarify the relationship between final leaf length, final stem length and flowering time with DIF (DT minus NT) and/or ADT (average daily temperature). For all three variables, the effect of DIF depended on ADT and vice versa. The relationship of final stem length with DIF also depended on the temperature range. Increased cell volume in flower stems developing at DT/NT 22/12 degrees C gave rise to longer and thicker stems compared with stems developing at DT/NT 12/22 degrees C. GC-MS analysis (gas chromatography-mass spectrometry) showed that the endogenous level of IAA was 56 % higher in stems grown under DT/NT 22/12 degrees C compared with DT/NT 12/22 degrees C. Of the 12 gibberellins analysed, however, only the level of non-bioactive GA29 was affected by the temperature treatment.

Anti-mitotic activity towards sea urchin embryos in extracts from the marine haptophycean Phaeocystis pouchetii (Hariot) Lagerheim collected along the coast of northern Norway.

The marine bloom-forming alga Phaeocystis pouchetii is suspected to produce some toxic compound responsible for reduced growth, fecundity and survival of other marine organisms. Sea urchin early development was used as a model to investigate the degree and nature of toxicity. Colonial cells of P. pouchetii were collected during its spring-bloom along the coast of northern Norway and maintained in culture for a short period of time in order to evaluate the concentration of toxic compounds present inside the cells or excreted to the surrounding seawater medium. Cells were harvested by filtration and toxins were extracted separately from the collected cells and the filtrate using organic solvents. We found that extracts from the filtered seawater at a concentration corresponding to 9.0 x 10(5) cells ml(-1) completely blocked cell divisions in embryos of the sea urchin Sphaerechinus granularis, whereas extracts from intact algal cells were only mildly cytotoxic. When the extracts from seawater culture medium were purified by RP-HPLC, cytotoxic activity towards S. granularis embryos was recovered in three consecutive fractions. Moreover, unfertilised eggs incubated in the active HPLC fractions became unproductive, whereas incubation of sperm gave a reduced fertilisation rate. This anti-proliferative effect was further characterized by immunofluorescence staining of sea urchin embryos. DNA labelling revealed that incubating sea urchin embryos in the purified algal extracts inhibited both pronuclei migration and fusion. Incorporation and detection of the DNA-base analogue 5-bromo-2-deoxyuridine showed that DNA-replication was blocked. Furthermore, staining of alpha-tubulin subunits demonstrated that embryonic tubulin organisation was altered. We conclude that P. pouchetii produce some anti-mitotic compound, and that senescent colonial cells to a great extent excrete this compound to their surroundings.