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T HIS STUDY evaluated the impact of cobalt (Co) nutrition at the optimum concentration on growth and oxidative stress in two Egyptian rice varieties (Sakha 104 and Giza 178) under drought stress. The stress was applied at different irrigation intervals (six and eight days), and irrigation after four days was set as control through the reproductive stage. The roots and shoots parameters (lengths, and fresh and dry weights), oxidative stress biomarkers; membrane injury, lipid peroxidation, proline accumulation, protein content, total phenols, and flavonoids contents, along with the activities of catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO) enzymes, were used to evaluate the strength of reactive oxygen species (ROS) detoxification in both rice varieties. Water deficit and oxidative stress affected Giza 178 less than Sakha 104. Stressed rice plants of both varieties treated with Co at the optimum concentration reduced the hurtful impact of drought, particularly in Giza 178, by enhancing root and shoot growth and biomass and the efficiency of the oxidative defense system. This was obvious in a substantial decrease in membrane injury and lipid peroxidation, while a significant increase was apparent in proline and protein content, total phenols, and total flavonoids. Additionally, the dynamic activities of antioxidant enzymes were substantially higher in Giza 178 than Sakha 104, when compared to untreated plants. The findings could be helpful in research projects aimed at developing anti-drought stress techniques for rice plants.

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Addition of a recommended dose of phosphorein biofertilizer into salinized soil, induced significant increases in all growth and reproductive parameters determined in growing lettuce plants throughout the entire period of the experiment. On the other hand, fertigation of such sodic salty soil with a recommended dose of nitrobein biofertilizer, induced slight, if any decreases, in growth and reproductive parameters at vegetative, flowering and fruiting growth stages. The contents of carbohydrates fractions as well as the pigment contents and the activity of PS II, of salinized lettuce plants fertigated with phosphorein biofertilizer, were increased throughout the three successive growth stages, above the control levels. On the other hand, with nitrobein biofertilizer slight, if any changes, in all metabolites determined, throughout the entire period of the experiment were obtained. Strong positive and negative correlations were observed between the changes in all growth and reproductive parameters and the changes in all metabolites determined in salinized lettuce plants fertigated with phosphorein and nitrobein, respectively.