A System for Continuous Measurement of Photosynthetic Rate and Dark Respiration at Constant CO2-Level

A system for maintaining a constant CO₂-level during photosynthesis and dark respiration in an assimilation chamber is described. The assimilation chamber has two loops for control of the CO₂-level. If the CO₂-concentration is increased over a preset value, CO₂ is removed by passing the gas flow over a lime filter. If CO₂ is consumed, concentrated CO₂ is added to the system. The system is operated through the computer in the Phytotron and has been constructed mainly for studies of dusk and dawn effects on photosynthesis where a high degree of control of the CO₂-level in the system is of the utmost importance.     

Multivariate analysis of morphometric differentiation within the Laonice cirrata-group (Polychaeta, Spionidae)

Principal component, and canonical variate analysis based on six characters show that there are morphological differences between three Laonice forms (L. bahusiensis, L. sarsi, and Laonice sp.). This supports Söderström's division of L. cirrata into four species; a decision often questioned by other taxonomists. We cannot exclude the possibility that the morphological differences are caused by polymorphism or seasonal variation within a single species. There is, however, no information to vindicate this and we conclude that the three forms should be regarded as separate species until this hypothesis can be rejected.