Some Biofertilizers Relieved the Stressful Drawbacks of Calcareous Soil upon Black Seed (Nigella sativa L.) Through Inhibiting Stress Markers and Antioxidant Enzymes with Enhancing Plant Growth

Calcareous soils have stressful properties to plant growth; they represent about 25-30% of the Egyptian total area. To improve soil characteristics, and hence plant growth, a number of biofertilizers (diatomaceous earth, Nostoc, sewage effluent and yeast) in addition to Hoagland medium were applied at successively increasing concentrations. Growth of Nigella sativa (black seed), a folk medicinal plant famous for its oils, was enhanced by all the applied treatments. Enhancement in plant biomass showed highest levels at a certain concentration of each treatment; sewage (20%) followed by diatomaceous earth (6g/5Kg), Nostoc (1mg/5 Kg), yeast (4*1012 cell/L) and Hoagland (1/4x). The applied treatments variably altered carbohydrates, proteins and amino acid proportions in plant biomass. Stress marker (malondialdehyde and proline) contents and antioxidant enzymes activity (superoxide oxidase, catalase and ascorbate peroxidase) have been all significantly reduced in shoots and roots of the treated plants, compared with those of the control plants grown on calcareous soil alone. Subsequently, it could be inferred that calcareous soil triggered oxidative stress and the applied biofertilizers extinguished it and overcame the stressful drawbacks of calcareous soil in terms of enhanced plant growth. Energy and carbon skeletons that are usually leaked into defense molecules (MDA, proline and antioxidant enzymes), have been saved for growth upon amendment of the stressful calcareous soil.