Inoculation of different plant wastes with microorganisms resulted in a release of maximum reducing sugars (33%) from sugar-cane leaves when subjected toPenicillium oxalicum. Maximum protein was formed from sugar-cane bagasse inoculated withAspergillus fumigatus. Association of sugar-cane leaves withP. oxalicum showed the highest digestibility. The use of such microorganisms may help to provide additional and valuable proteins ultimately for human use.

Survival and nitrogenase efficiency ofNostoc commune andN. austinii were evaluated monthly in four carrier materials (sugarcane bagasse, wheat straw, wheat bran and peat) at 10, 30 and 40 °C. Survival, as well as nitrogenase activity, of both species was much better in peat, followed by wheat bran, sugarcane bagasse than in wheat straw at 10 and 30 °C up to three months, the activity ofN. commune being better thanN. austinii. None of the materials tested was found to be superior to peat as carrier ofNostoc species but the results indicated that wheat bran and sugarcane bagasse can be used as inoculant carriers with relative success. Storage of inoculants in these carriers is feasible at 30 °C up to three months.

The ability of different microorganisms to alleviate the noxious effect of salinity was tested. Barley grains were planted under salt stress and were inoculated with cyanobacteria, Pseudomonas fluorescens and Dunaliella tertiolecta. All tested microorganisms improved growth of barley plants as indicated by dry weight, photosynthetic pigments and vitality of the plants. Cyanobacterial inoculant was the most effective and significantly diminished the adverse effect of salinity. Results of the present study hold promise for use of such microorganisms to cultivate plants in saline soils.

Faba bean cv. Giza 3 was grown in hydroponic cultures and inoculated with Rhizobium leguminosarum bv. viceae TAL 1402. Salinity levels at 40, 80 and 120 mM NaCl were applied at transplanting and inoculation. The highest level of salinity level (120 mM) significantly suppressed nodulation, nitrogenase activity and plant growth. This salinity level also significantly decreased the concentrations of macro and micro nutrients in faba bean leaves. X-ray microanalyses of nodules under high levels of NaCl indicate that Ca, K, Mg and S were lower in the infected and uninfected cells of faba bean nodules than control ones, whereas, Na and Cl were higher. Nitrogen content of nodules was significantly higher in plants treated with high salinity levels than nonsalinized ones. However, the N content of shoots was lower than the controls. The inhibition of nitrogenase activity at high levels of salt stress could be explained in terms of product inhibition of the enzyme as an efficient feedback regulation mechanism. The X-ray microanalysis results revealed that the N export from nitrogen-fixing cells is sensitive to salinity and is controlled by element distribution in nodules.

The effects of nitrogen applied at increasing levels of 0, 4, 8, 16 and 32 mM N (KNO 3 or NHaCI ) were studied in faba bean (Vicia faba) nodulated by Rhizobium leguminosarum bv. viceae RCR 1ool. Nitrogenase activity was higher at 4 and 8 mM N than the zero N treatment (control), but 16 and 32 mM N significantly reduced the efficiency of nodule functions. Nitrate reductase activities (NRA) of leaves, stems, roots, nodules and nodule fractions (bacteroid and cytosol) were increased with rising the NO 3" or NH4 + levels. NRA decreased in the order of nodules > leaves > stems > roots. Cytosolic NR was markedly higher than that recorded in the bacteroid fractions. Nitrate levels were linearly correlated to NRA of nodules. Accumulation of NO 2" within nodules suggests that NO 2 inhibits nodule's activity after feeding plants with NO 3" or NH4 §

Two strains (RCR 1001 and 1044) and a commercial inoculant (Okadin) ofRhizobium leguminosarum biovarviceae were tested for their ability to survive in autoclaved clay soil for up to four months under heat, salinity and drought stress. Resistance to heat was tested by incubating rhizobia in soil at 27, 37 and 42 °C. Tolerance of rhizobia to salinity was investigated by growing rhizobia in soil salinized with 1 and 2 % NaCl (m/m). Drought resistance was tested by subjecting bacteria to soil moisture contents of 20, 10 and 5%. Strain RCR 1001 was more resistant to heat and nodulated faba bean better than other tested strains. A commercial inoculant Okadin survived more (plate count method) and nodulated faba bean (plant infectivity, most probable number, MPN) at moisture content of 5% and 2% NaCl. Although, strains RCR 1001 and 1044 resisted these stress conditions (plate count) they lost their abilities to nodulate faba bean (MPN-test). There is a possibility for selection of effective rhizobia which are more tolerant to harsh conditions.

Six Bradyrhizobium (lupin) strains were evaluated for their ability to produce in vitro siderophores using four chemical assays. Bradyrhizobium strains WPBS 3201 D and 3211 D gave positive reactions with the chrome azurol S assay (CAS) and produced hydroxamate-type siderophores. The other four strains (USDA 3040, 3041, 3042 and CB 2272) gave negative results for siderophore production with the four assays. The generation time, growth yield and hydroxamate production of strain WPBS 3201 D were affected by the iron concentration of the culture medium and the previous culture history of the cells. Resuspension of washed cells grown previously in media supplemented with 0 and 20 μmol·L−1 Fe into differing iron regimes (0 and 20 μmol·L−1 Fe) suggest that the extent of hydroxamate production was dependent on the growth history of the cells. Cells pre-grown in 20 μmol·L Fe produced a high amount of hydroxamates compared with cells pre-grown in iron-free medium when resuspended in medium containing up 4 μmol·L−1 Fe. Cells pre-grown in 20 μmol·L−1 Fe were also more sensitive to iron repression than those pre-grown in 0.5 μmol·L Fe. Mannitol was the best carbon source for siderophore production. Siderophore synthesis was inhibited by 4-chloromercuribenzenesulfonic acid, 2,4-dinitrophenol, sodium azide and MgCl2 suggesting that an energized membrane and a mercapto group are essential and required for hydroxamate synthesis in Bradyrhizobium (lupin) strain WPBS 3201 D.