Long-term survival of sclerotia of Sclerotium cepivorum and Stromatinia gladioli

In an experiment with pure-culture sclerotia of Sclerotium cepivorum and Stromatinia gladioli a large proportion of the sclerotia survived burial for 20 years in the field in the absence of host plants. Some evidence for metabolic activity or leakage leading to the gradual erosion of the sclerotial contents was obtained with S. cepivorum . The results of other experiments suggested that, for unknown reasons, a variable proportion of sclerotia formed naturally on infected plants may decay shortly after their formation, but those which survive beyond this limited period are likely to remain viable for many years. The viability of sclerotia was also reduced by prolonged flooding, but the period for which land would have to be under water excludes this as a method of eliminating sclerotia from infested land in the UK. Treatment with the mycoparasite Teratosperma oligocladum did not affect the survival or infectivity of sclerotia of S. cepivorum or S. gladioli .     

Computer simulations of homeward-migrating Fraser River sockeye salmon: is compass orientation a sufficient direction-finding mechanism in the north-east Pacific Ocean?

Computer simulations were used to investigate whether compass orientation is a sufficient guidance mechanism for sockeye salmon migrating to the Fraser River from their ocean foraging grounds in the north-east Pacific Ocean. Daily surface ocean currents, simulated by the ocean surface current simulations (OSCURS) model, were used to test the influence of currents on the return oceanic migration of Fraser River sockeye salmon. High seas tagging and coastal recover data of Fraser River sockeye salmon were used for the migration simulations. Surface currents were shown to increase the speed of the homeward-migrating sockeye salmon, as well as to deflect the fish in a north-eastward direction. In spite of ocean currents, all Fraser River sockeye salmon were able to reach their destination with a fixed direction and bioenergetically efficient swimming speed when migration was delayed until the last month at sea. Compass orientation alone was shown to be a sufficient direction-finding mechanism for Fraser River sockeye salmon.     

Effect of some substituted benzonitriles on photosynthetic activity of spinach and wheat in vivo and in vitro

The inhibitory effects of nine nitro and/or bromo-substituted benzonitrile compounds on the photosynthetic electron flow in isolated chloroplasts and on the in vivo CO₂ fixation of spinach (Spinacia oteracea L.) and wheat (Triticum aesticum L. cv. Bezoslaya) were investigated. Bromoxynil and 3-nitro-5-hromo-4-hydroxy-bcnzonitrile were the strongest and equally effective inhibitors of Ihe in vivo CO₂ fixation of spinach, hut in wheat the nitro-bromo-compound is ineffective and 3-nitro-benzonitrile is even more inhibitory than bromoxynil. None of the substances affected DCPIPH → methylviologen reduction. In the inhibition of the DCPIP reduction only the 3,5-disuhstituted 4-hydroxy-derivatives were effective. The fact that these compounds affect only the PS II reaction with both H₂O and DPC as electron donors suggests a site of inhibition on the reducing side of PS II, between Ihe PS II reaction centre and ihe DCPIP Site. It is suggested that in the inhibition of the DCPIP reduction only steric factors are important and the different electron configuration of the sterieally similar molecules may be involved only in the absorption and translocation processes of the compounds.