14C-Studies on Apple Trees. VIII. The Seasonal Variation and Nature of Reserves

The nature, seasonal variation and mobilization of reserves in Malus × domestica have been studied by means of ¹⁴C, carbohydrate analyses and extractions of xylem sap. Following exposure to ¹⁴CO₂ in the autumn, the majority of the ¹⁴C absorbed is found in the root. During the winter and in particular the spring the amounts of ¹⁴C in the top and root are reduced to approximately 40 per cent of the autumn values; in the root the amount of dry matter was also considerably reduced. In the tops, most of the ¹⁴C absorbed was found as methanol (80 %)-soluble ¹⁴C which also showed the greatest seasonal reduction; sorbitol, sucrose or glucose in particular are responsible for the decrease in concentration within this fraction. Maximum values for methanol-insoluble ¹⁴C were found in March. In the root, the highest values for absolute changes were found for methanolinsoluble ¹⁴C. Hydrolysis of this fraction showed considerable activity in glucose. In the root there was also considerable activity in a precipitated fraction of the methanol extract. Eluates of xylem sap from apple branches contained primarily sorbitol, the highest concentration of which was found at the beginning of March. For a tree with a dry matter weight of about 300 g, the utilization of reserves from the tree in the spring was calculated to be at least 13 g of dry matter. However, only a minor part (less than 25 per cent) of the latter appears to serve as building material for new growth.     

Antibiotic Activity of the Chrysophyte Ochromonas malhamensis

The effects were studied of extracts from the chrysophyte Ochromonas malhamensis on Staphylococcus aureus, Bacillus megaterium, Bacillus subtilis and Escherichia coli. The extracts contained three different antibiotically active substances, one of which was produced during the extraction. The other two had no effect on E. coli, but inhibited the growth of the three other bacteria. The present experiments show that one of the products increases its antibiotic activity when exposed to visible light, and that its activity is enhanced by boiling the extracts for 5 minutes. The other active substance is not affected by light, but shows increased activity after being boilt for 5 minutes.     

Effects of auxin and irradiance on the rooting of cuttings of Pinus sylvestris

Abstract Seedlings of Pinus sylvestris L. were grown under controlled conditions (temperature 20°C, photoperiod 17 h) at two irradiances, 8 or 40 W m^-2. Hypocotyl cuttings were excised and rooted at different irradiances in tap water solutions of indolebutyric acid (IBA). The fastest rooting and highest rooting percentage were obtained with cuttings from stock plants grown at 8 W m^-2 and treated with 10^-5M IBA for 21 days. The concentration of 10^-4M IBA inhibited root formation. In comparable treatments rooting was always better in cuttings from stock plants grown at 8 W m^-2 than in cuttings from stock plants grown at 40 W m^-2. The irradiance during the rooting period had only a minor influence on rooting. When cuttings from plants irradiated with 40 W m^-2 were treated with 10^-5M IBA for 21 days the rooting percentage almost reached the same level as in untreated cuttings from stock plants given 8 W m^-2. In cuttings treated with IBA during the whole rooting period, rooting was depressed in comparison to untreated cuttings. Aeration of the 10^-4M IBA solution increased the rooting percentage, but aeration had no effect on untreated cuttings and on cuttings treated with lower IBA concentrations.     

Two species of Foraminifera of the genus Turrilina with different wall structure

Two species of the foraminiferal genus Turrilina Andreae, 1844, occurring in the Tertiary beds of Denmark and Holland, can be distinguished by their wall structure only. In consequence it is recommended that the wall structure as a systematic character may in this and similar cases be of specific value only.     

The experimental silicification of Aquificales and their role in hot spring sinter formation

Archean microfossils provide some of the earliest physical evidence for life on Earth, yet there remains a great deal of uncertainty regarding which micro‐organisms were actually preserved. Because of the limited cellular detail remaining, interpretation of those microfossils has been based solely on size and morphology. This has led to significant controversy surrounding the presence or absence of cyanobacteria as early as 3.5 billion years. Accordingly, there has been an experimental bias towards studying their silicification. Here we report the very first findings on thermophilic bacteria–silica interactions, and investigate how Sulfurihydrogenibium azorense, a representative of the Aquificales often found as prominent members of modern hot spring vent communities, interacts with highly siliceous hydrothermal fluids. We show that adsorption of silica is limited to silica polymers and colloids, and that the magnitude of silica adsorption is dependent on its chemolithoautotrophic pathway. Intriguingly, when S. azorense is grown as a H₂‐oxidizer, it responds to increasing silica concentrations by producing a protein‐rich biofilm that may afford the cells protection against cell wall silicification. Although the biofilms of Aquificales could potentially contribute to or accelerate siliceous sinter formation under certain growth conditions, the cells themselves show a low preservation potential and are unlikely to have been preserved in the ancient rock record, despite phylogenetic analyses suggesting that they represent one of the most primordial life forms.     

Isolation of Histomonas meleagridis from Embryonated Eggs of Heterakis gallinarum*

SYNOPSIS. Histomonas meleagridis was isolated from eggs of Heterakis gallinarum by culturing artificially hatched eggs in a modified DeVolt's alkaline serum medium. The presence of the protozoon in the cultures was established by microscopic examination and confirmed by producing histomonosis in turkeys by intracecal inoculation with quantities of the cultures.