Thigmomorphogenesis: The Interaction of Wind and Temperature in the Field on the Growth of Phaseolus vulgaris L.

Field and laboratory experiments were performed to determinethe interaction of wind and temperature on thigmomorphogenesis(defined here as decreased elongation and increased internodalradial enlargement due to mechanical perturbation). Kidney beanplants (Phaseolus vulgaris L. cv. Red Cherokee Wax) were shelteredor exposed to wind for 10 days. Wind velocity, wind gusting,temperature, light and rainfall were measured for the durationof each of ten experiments. Stem elongation and diameter weremeasured and it was found that thigmomorphogenesis due to windoccurs naturally. There was more internodal secondary xylemproduced in the wind-exposed plants than in the sheltered plants.The experimental data were analyzed by multiple linear regressionand the wind was found to be a significant factor in the predictionof bean stem elongation and thickening. Laboratory experimentsshow that as wind velocity increases, thigmomorphogenesis increasesin an approximate linear fashion. Furthermore, it was foundthat low temperatures interact with mechanical perturbationto reduce the amount of thigmomorphogenesis, both in the fielddue to wind and in the laboratory due to rubbing. Other environmentalfactors do not seem to interact with the wind to modulate thigmomorphogenesiseven though these factors affect plant growth. Phaseolus vulgaris L., kidney bean, thigmomorphogenesis, wind, temperature, ethylene, multiple linear regression     

Breeding of waders (Charadrii) and Brent Geese Branta bernicla bernicla at Pronchishcheva Lake, northeastern Taimyr, Russia, in a peak and a decreasing lemming year

During summer 1991, lemmings occurred at high densities in Arctic tundra at Pronchishcheva Lake in the northeastern Taimyr Peninsula, whereas, in 1992, lemming densities were substantially lower and decreased further during the summer. In 1991, avian predators such as Snowy Owls Nyctea scandiaca, gulls and skuas bred well; Arctic foxes Alopex lagopus were rarely observed in the study area but bred in the immediate vicinity. In both years there was a late thaw, but this did not deter breeding by birds. The insect food supply for waders showed similar patterns of abundance in both years. In 1991, 73 nests of nine species of wader were found within a 14-km² study area, and Dark-bellied Brent Geese Branta bernicla bernicla nested in association with Snowy Owls. The overall density of wader nests was estimated to be 7 per km². Clutches disappeared at only two wader nests and no Brent Goose nests, and the Mayfield estimate of the daily probability of predation for waders was 0.0022. In contrast, the daily probability of predation was 0.20 in 1992, when there was a similar breeding density of waders. Arctic foxes were seen searching for food daily within the study area, and fox droppings were found associated with nests taken by predators. The predicted scenarios for peak and decreasing lemming years (the Roselaar-Summers hypothesis), i.e. low predation and high nest success in the peak year and high predation and low nest success in the decreasing year, therefore occurred.     

The Biology of Trypanosoma diemyctyli, Tobey. III. Factors influencing the cycle of Trypanosoma diemyctyli in the vertebrate host Triturus v. viridescens.

SYNOPSIS. The effects of some environmental influences on the cycle of Trypanosoma diemyctyli in Triturus v. viridescens are described. Bleeding of the host produced a reduction in the number of trypanosomes but did not affect their growth rate. The temperature at which the host was maintained affected the cycle of the trypanosomes. The length of the post-inoculation latent stage increased from 24 hours at 25°C. to an indefinitely long time at 5°C. The trypanosomes were found to be dimorphic. Adult parasites of the short form had a range of 45–75 μ and those of the long form of 76–116 μ. Growth rate of the trypanosomes was inhibited or greatly retarded at temperatures of 10°C. or lower and was greatest at 25°C. The size attained by the parasites and the number of parasites were greatest at 15°C. At this temperature the infection was pathogenic and the dimorphic parasites were in their long form. At the higher temperatures (20–25°C.) the infection was non-pathogenic with the trypanosomes in their short form.
The infection is primarily one of adult newts. Experiments indicated that the larvae were resistant to the trypanosomes at all temperatures while the red efts were not. The latter are usually free from the trypanosomes because they are not exposed to them. Attempts to infect other newts and to locate any cryptic stages by the injection of blood and tissues from infected newts gave negative results.
Starvation, sodium salicylate, and treatments used to control fungus infection of the newts had no detectable effects on the trypanosomes.     

The Effect of the Calyptra on the Plane of Guard Cell Mother Cell Division in Funaria and Physcomitrium Capsules

The calyptra influences the plane of division in guard cellmother cells of Funaria and Physcomitrium. Normally, capsulesexpand while sheathed by the calyptra and the axes of the stomataare parallel to the axis of the capsule in both genera. Removalof the calyptra from an elongating sporophyte leads to setathickening prior to capsule expansion and an essentially randomorientation of stomata. If the calyptra is removed from a sporophyteof Funaria at the time the division of the guard cell mothercells is expected, guard cells of abnormal shape and undividedguard cell mother cells are found in unusually high frequency.     

Paramecium Transport by Land Snails

SYNOPSIS. Field observations and experiments in a tropical forest revealed that Paramecium multimicronucleatum and other small aquatic organisms are transported between Heliconia flowers by terrestrial snails of the genus Caracolus . It is probable that dispersal is readily accomplished in tropical forests, and that the presence or absence of Paramecium in a given area therefore is determined by biological interactions.