Effects of Ruta graveolens leaves on soil characteristics and on seed germination and early seedling growth of four crop species

Effects of rue (Ruta graveolens) leaves on soil characteristics and on germination and seedling growth of four crop species (radish, zucchini, cauliflower and tomato) were investigated. Soil not previously associated with rue was mulched and amended with its fresh leaves. The objectives of the present study were to determine: (i) the changes in soil chemical characteristics after addition of rue leaves, (ii) the growth responses in soils treated with R. graveolens leaves, and (iii) whether the soil chemistry changes affect plant growth. Results indicate that soil incorporated with rue leaves had higher values of water‐soluble phenolics, electrical conductivity and nitrate, and lower pH values compared to untreated soil. Seed germination of radish and tomato was suppressed in covered and amended soils compared to control soil. Seedling development for all the species was suppressed in incorporated and amended soil, compared to the rue‐free soil. Correlations between soil chemical characteristics, germination and seedling growth of plants are also discussed.     

Influence of Temperature on the Autolytic Phase of Growth of Aspergillus niger

The variation in the extent to which autolysis of Aspergillusniger van Tieghem occurs in response to alteration of temperatureand of the length of the period of autolysis has been studied.The degree of autolysis at 10, 15, 20, 25, 30 and 35 °Cwas 15–8, 23–9, 35–2, 40–8, 49–1and 56–2 per cent, respectively. Autolysis increased sharplywith the length of the period of autolysis reaching a plateautowards the second day at the lowest temperatures (0–20°C) and towards the fourth day at the higher temperatures.Theextent of the increase of autolysis plotted against temperatureindicates a linear relationship between these two parameters.The release of protein from autolysing mycelium of A. nigeris greatly affected by temperature, amounting to 1–9 percent at 10 °C, whereas at 30 °C it reached 5–1per cent. On the other hand, gradual increase of temperatureduring autolysis seems not to alter the content of mycelialcarbohydrates of A. niger.     

Effect of temperature and dark pretreatment on the germination of three species of Jamesonia (Pteridaceae,Polypodiopsida)

To study the influence of temperature on the germination ability of three species of Jamesonia (Jamesonia imbricata, Jamesonia scammaniae and Jamesonia rotundifolia), spores were cultured at 10°C, 15°C and 20°C. A temperature of 15°C was selected as representative of the natural annual average temperature of the paramo environment that Jamesonia species inhabit. In addition, a dark pretreatment of 2 days was tested to verify if germination was enhanced. The results indicated that germination of Jamesonia, considering the three species as a whole, is affected by temperature, but is independent of the dark treatment. All species showed higher and faster germination at 20°C, and exhibited a threshold minimum temperature around 10°C, below which germination is avoided or extremely low and delayed. This could suggest that spore germination in Jamesonia is adapted to establish gametophyte populations during frost‐free periods.     

Stability of the Cell Walls of Neurospora crassa during Autolysis

The influence of autolysis upon the cell walls of Neurosporacrassa has been studied. This fungus was grown at 24 °Cin agitated and aerated cultures in a synthetic medium during60 days. At convenient intervals samples of culture were taken,mycelium separated, and dried to constant weight. From aliquotsof these mycelia cell walls were prepared, dried, weighed, andanalysed for total nitrogen, phosphorus, amino acids, lipids,and protein. No changes in the chemical composition of the wallscould be detected. The percentage of walls continuously increasedduring autolysis. These results strongly suggest that cell wallsof N. crassa are unaffected by autolysis. Examination of thefine structure of the whole mycelium at different ages duringautolysis seemed to confirm these findings.     

Biochemical Changes in Cultures of Nectria galligena during the Autolytic Phase of Growth

Some biochemical changes occurring in cultures of Nectria galligenaduring its autolytic phase of growth have been investigated.In nitrate-grown and autolysed cultures of this fungus the degreeof autolysis amounted to 57 per cent. The amount of myceliallipids decreased continuously with the age of the culture. Totalmycelial nitrogen did not substantially change within the first50 days of autolysis. The constancy in the amount of bound aminoacids released from mycelium of Nectria galligena strongly suggeststhat mycelial protein are not affected by autolysis.