The response of cowpea seeds grown under salinity-induced stress conditions to different cyanobacterial extracts of two strains (Aphanizomenon flos-aquae and Phormidium sp.) was studied during seed germination. The results indicated that aqueous extract was more stimulating to germination than organic extract where higher levels of germination percentage, enzymatic activity, nucleic acid, protein and total soluble sugars contents were obtained. In addition, the indicators of stress such as proline content, lipid-peroxidation and relative permeability of the root membranes were lower than the organic extract. Application of aqueous cyanobacterial extracts of Aphanizomenon flos-aquae and Phormidium sp. stimulated seed germination and the metabolic activities of salt-stressed and unstressed seeds, while the lipid-peroxidation and relative permeability of the root membranes were reduced. Therefore, aqueous algal extracts alleviated the harmful effect of salinity stress on seed germination. This can be used on a vast scale as an inexpensive and eco-friendly farming policy to counteract the hazardous effect of salinity on plants especially during the critical period of seed germination where salinity can inhibit it either partially or completely.

Background: The use of algae as biofertilizers is fast-spreading in order to meet the excessive demands for agricultural products. To achieve this, enough algal biomass needs to be supplied year-round. Hence, algal nutritional components must be optimized through mixotrophic conditions. Materials and methods: Two algal isolates, namely, Phormidium sp. and Synechocystis sp. were tested for their ability to produce mixotrophic growth using different supplementations including molasses, aqueous Lepidium sativum, Trigonella foenum graecum seed extract and liquorice root extract, as well as acetate salt solution. The algae that showed highest growth under optimized mixotrophic conditions was further used in cantaloupe seed growth experiments. GC-MS was also carried out on the biomass of Phormidium on one of the fractions of extract using solvent system to reveal some dominant novel bioactive compounds in algal biomass. Results: The sugarcane molasses significantly enhanced the growth of the two algal strains, followed by Lepidium sativum extract only in case of Phormidium sp. Therefore, it was used in subsequent experiments. All growth parameters for that algae were significantly enhanced by the addition of these nutritional sources with molasses being the best supplement. The Phormidium sp. was rich in its content of chlorophyll, proteins, sugars as well as some novel bioactive compounds as revealed by GC–MS. The germination percentage of seeds treated with Phormidium sp. showed a significant increase over that of control. The different growth-related metabolites of total soluble proteins, total soluble sugars and all photosynthetic pigment contents of the seedlings were all significantly increased using this algal treatment. Discussion: The sugarcane molasses was superior in enhancing the algal growth due to its rich content not only of sugars but also of minerals and nitrogenous compounds. The use of aqueous extracts of seeds of Lepidium sativum enhanced growth significantly more than that of the control set as seeds are rich in proteins, omega-3 fatty acids, phytochemicals and other essential nutrients. In growth experiments carried out on cantaloupe seeds, there was a significant increase in germination percentage as well as all growth parameters due to the rich nutritional content of Phormidium sp. Conclusion: Mixotrophic growth achieved better algal biomass production than autotrophy in the case of Phormidium sp. The use of cheap resources such as sugarcane molasses, which is the waste from the sugar industry, as well as the common herb extract of Lepidium sativum, is a cost-effective approach. The use of this mixotrophically grown blue-green alga as a biofertilizer significantly enhanced plant growth and seed germination, indicating the usefulness of this eco-friendly agricultural strategy for achieving both food security and environmental sustainability.

Fenugreek is a globally important legume that is widely cultivated for its therapeutic benefits in most parts of the world. Seeds on the other hand have a poor germination and growth rate when exposed to salinity. The effect of ultrasonic exposure period on germination and early seedling behaviors of fenugreek seeds under salt stress was investigated in a laboratory experiment. During germination and early seedling stages, all tests were conducted at 40 kHz in a water bath ultrasonic device with two durations (10 and 20 min) under salinity stress using different concentrations of NaCl (0, 1000, 3000, and 5000 mg/l). The results revealed a substantial decrease in germination percentage, all growth criteria, with increasing NaCl concentration and a significant increase in biomass produced by the Fenugreek (total soluble protein, total soluble carbohydrate, and proline), all of which are thought to be mechanisms for salinity resistance. Ultrasonication of fenugreek seeds for 10 and 20 min has a significant impact on seed germination, early seedling development and biochemical constituents under normal and stress conditions. The genetic stability of fenugreek DNA content was affected by these different treatments. This variation was estimated by RAPD-PCR molecular marker, and resulted in a total polymorphism percentage of 49.72% from all the primers. All these different treatments caused variation in the physiological responses and DNA content. This variation enhanced with more ultrasonic and salt treatments. Hence, these stresses can be used for enhancing the variable metabolic processes in fenugreek plant and stimulate its medicinal properties.