Effect of boat noise and angling on lake fish behaviour.

The effects of disturbances from recreational activities on the swimming speed and habitat use of roach Rutilus rutilus, perch Perca fluviatilis and pike Esox lucius were explored. Disturbances were applied for 4 h as (1) boating in short intervals with a small outboard internal combustion engine or (2) boating in short intervals combined with angling with artificial lures between engine runs. The response of the fish species was evaluated by high-resolution tracking using an automatic acoustic telemetry system and transmitters with sub-minute burst rates. Rutilus rutilus swimming speed was significantly higher during disturbances [both (1) and (2)] with an immediate reaction shortly after the engine started. Perca fluviatilis displayed increased swimming activity during the first hour of disturbance but not during the following hours. Swimming activity of E. lucius was not significantly different between disturbance periods and the same periods on days without disturbance (control). Rutilus rutilus increased their use of the central part of the lake during disturbances, whereas no habitat change was observed in P. fluviatilis and E. lucius. No difference in fish response was detected between the two types of disturbances (boating with and without angling), indicating that boating was the primary source of disturbance. This study highlights species-specific responses to recreational boating and may have implications for management of human recreational activities in lakes.

Changes in the Number, Viability, and Amino-acid-incorporating Activity of Rhizobium Bacteroids during Lupin Nodule Development.

Between days 10 and 21 after inoculation of Lupinus angustifolius seedlings with Rhizobium NZP 2257, the average nodule fresh weight increased 3-fold and the number of bacteroids per nodule increased more than 10-fold.The viability of Rhizobium bacteroids, as judged by their ability to form colonies on yeast-extract agar, declined from about 10% on days 10 and 11 after inoculation to about 0.3% on days 14 to 25. Bacteroid viability was highly sensitive to osmolarity.At optimal pH and K and Mg ion concentrations, the incorporation of (14)C-glycine into isolated bacteroids was also very sensitive to osmolarity, and fell in parallel with bacteroid viability during nodule development.WE SUGGEST THAT AT LEAST TWO PROCESSES CONTRIBUTE TO BACTEROID NONVIABILITY: a reversible change in the cell wall structure occurring between days 10 and 14 after inoculation, and a subsequent irreversible change.

Studies with detached lupin root nodules in culture: I. Maintenance and induction of acetylene reduction activity.

A method has been developed for culturing detached nitrogen-fixing root nodules of lupin (Lupinus angustifolius L.) on a simple nutrient medium. Under the best conditions devised, the acetylene reduction activity of mature detached nodules was maintained at 10 to 25 nmoles of ethylene hr(-1) mg(-1) fresh weight for 3 days. Under the same culture conditions, immature nodules increased their acetylene reduction activity from 0.01 nmole or less to about 1 nmole hr(-1) mg(-1) fresh weight.

Plants under Climatic Stress: III. Low Temperature, High Light Effects on Photosynthetic Products.

An investigation has been made of the combined effects of low temperature and high light on the level of several photosynthetic products in the leaves of a group of plants differing widely in their tolerance to this stress. Starch levels in these plants after chilling are dependent on the time of day that temperatures are lowered and seem related to rates of CO(2) assimilation under this stress. Prolonged low-temperature, high-light treatment (10 C at 160 wm(-2)) of Sorghum bicolor induced a rapid starch hydrolysis after a lag of some 24 hours. Differing rates of starch loss at the cellular level and a rapid migration of chloroplasts toward the base of upper mesophyll cells were also seen in leaves of this stress-sensitive species.Chilling increased the level of almost all free amino acids in tolerant and in semi-tolerant species, while amino acids related to intermediates of the C(4)-pathway show a sharp or transitory decrease in Sorghum. These and other changes observed in Sorghum suggest that some time- and temperature-dependent blockages develop in the interconversion of C(4)-pathway intermediates and possibly in the flow of other intermediates to and from the sites of C(4)-photosynthesis.Levels of ATP in the leaves of Sorghum, Paspalum, and Amaranthus increased at night and following chilling and did not fall until pronounced necrosis of the leaves commenced.