Studies on the morphogenesis of sesbania sesban root nodule

An investigation has been carried out on the nodulation pattern of Sesbania sesban [L.] Merrill using the light microscope, the anatomical events that occur during growth and senescence as the result of nodule ageing are also studied. Nodules of 2, 3-months old and effective nodule of 2-years old are characterized by the presence of two regions, cortex and the active bacteroide containing cells at various developmental stages. In the 2-months old nodules, the first zone includes the nodule meristem. By ageing [3-months and 2-years old], the nodules lacked the meristematic region in their cortex. Senescent nodules were observed on roots of 2-years old, these nodules were not differentiated into distinctive regions. Senescence was observed in the cytoplasm within nodule cortex where the cells contained mainly cell walls and the nodules were surrounded by periphery periderm

Ex-planta nitrogenase activity in Bradyrhizobium japonicum deficient in cytochromes C and AA3

The ex-planta nitrogenase efficiencies of six electron transport mutant strains of B. japonicum 61A76 were studied in defined liquid media under microaerobic conditions. The extent of cytochrome deficiency of the mutants was associated with the loss of the ability of these strains to develop acetylene reduction activities. Mutants which were totally deficient in cytochrome AA3 and C with reduced amount of cytochrome B, developed little or no nitrogenase activity. Other mutants which were deficient in cytochrome AA3 or which had reduced levels of all cytochromes, had a reduced or delayed nitrogenase as compared with the wild type strain. From the spectral characteristics, it seems that under oxygen limitation, terminal cytochrome oxidase almost resembled those of the symbiotic bacteria. Growth efficiencies were correlated with the cytochrome content of the bacteria

Ultrastructure of soybean nodules formed from electron transport mutants of bradyrhizobium japonicum 61A76

The differentiation and developmental changes of cells and organelles of soybean [Glycine max cv. Williams] nodules infected with Bradyrhizobium japonicum 61A76 wild type or electron transport mutant strains were studied by transmission electron microscopy. The three 61A76 mutant strains; namely, Na1, Na2 and Na0, although totally deficient in C-and aa3-type cytochromes were symbiotically infective but formed ineffective nodules. Geedlings were maintained in Leonard jars in sterilized sand on a N-free nutrient solution. Eleven days after inoculation cells in both effective and ineffective nodules had the features of typical meristematic cells. The three mutant strains provoked different and unusual responses in the cytoplasm of plant cells. A feature induced by strain Na1 was electron-dense cytoplasm; cell vacuoles were not common. The most remarkable structural changes occurred in host mitochondria, which appeared elongated, disrupted or dumbbell-shaped, mitochondrion-amyloplast associations were recorded. The cytoplasm in cells of nodules induced by strain Na3 was heterogeneous, variously sized vesicles and vacuoles were scattered throughout the cytoplasm. Fewer abnormalities were observed in nodules induced by strain Na0. 35-45 days after inoculation, major differences between wild type and mutant strains were observed in bacteroid development. In ineffective nodules, bacterial cells were either still enclosed within intercellular spaces, enveloped in masses of polysaccharide-like material or trapped in large infection thread vesicles surrounded by massive cell walls

effect of growth medium on the levels of trehalose and glycogen content of some yeasts

Yeast cells of Saccharomyces cerevisiae as well as the osmotolarant yeasts Saccharomyces rouxii and Debaryomyces hansenii were grown aerobically and anaerobically. The water activity of the growth medium was regulated either by sodium chloride or glycerol. Levels of trehalose of most of the yeasts decreased with the reduction of water activity of the growth media in the presence of glycerol or sodium chloride when the yeast cells were grown under both aerobic and anaerobic conditions. However, the levels of glycogen in mast cases showed a reciprocal relationship when the yeast cells were grown either aerobically or anaerobically in the presence of either glycerol or sodium chloride

effect of the growth medium on the levels of carbohydrated and proteins in some osmotolerant yeasts

Of the osmotolerant yeasts Saccharomyces rouxii and Debaryomyces hansenii together with baker's yeast Saccharomyces cerevisiae were grown aerobically and anaerobically on media, their water activity was regulated either by glycerol or sodium chloride. Levels of the total carbohydrates and proteins for cells grown on these media were determined. It was found that, in most of the cases, when S. cerevisiae was grown either aerobically or anaerobically in the presence of either glycerol or sodium chloride, levels of both total carbohydrates and proteins decreased with the reduction of the water activity of the growth media. However, levels of total carbohydrates and proteins in both S. rouxii and D. hansenii showed a reciprocal relation when they were grown either aerobically or anaerobically and in the presence of either glycerol or sodium chloride