Laboratory experiments on prey selection by perch fry (Perca fluviatilis)

SUMMARY. In laboratory experiments, prey selection of zooplankters by starved perch fry ( Perca fluviatilis ) from Windermere, English Lake District, is temporally variable and there is usually, in the short-term, a persistent succession from one actively selected prey species to another. Provided that the prey is visible, the patterns of prey selection are maintained irrespective of the accessibility of the prey. The fish do not optimize their energy intake per effort. The method of observing predation activity by fish shows qualitative and quantitative prey selection as time progresses in great detail.     

Root Initiation in Cuttings of Pinus radiata Seedlings: I. DEVELOPMENTAL SEQUENCE

Adventitious root initiation in hypocotyls of Pinus radiataD. Don consists of three distinct phases. In the pre-initiativephase, following selection of the cuttings, no histologicalchanges are observed. The initiative phase begins with swellingof a single parenchymatous cell, the meristematic locus. Distinctcytoplasmic changes within the meristematic locus are followedby cytoplasmic migration and asymmetric division in the surroundingcortical or peripheral cells. The third, or post-initiative,phase includes continued division of derivatives of the peripheralcells to form meristemoids which subsequently differentiateinto root primordia.     

Glucose Oxidation during Shoot Initiation in Tobacco Callus Cultures

Involvement of the Embden-Meyerhof Parnas and the pentose phosphatepathways in glucose oxidation in glucose oxidation in tobaccocallus was examined. Marked changes in the activities of glucokinase,aldolase, glucose-6-phosphate dehydrogenase, and phosphogluconatedehydrogenase were observed during culture of tobacco callusunder shoot-forming and non-shoot-forming conditions. Activitiesof these enzymes were higher in shoot-forming tissue than innon-shoot-forming tissue. Furthermore, the activities of thepentose phosphate pathway enzymes showed greater differencesthan those of the Embden-Meyerhof-Parnas pathway. Confirmationof these findings was obtained by investigating the contributionsof ¹⁴C from [14C-1]- and [¹⁴C–6]-glucose to CO2 released.The significance of these findings on glucose oxidation in relationto the shoot-initiation process are discussed.