Wheat and maize are staple cereals that are each cultivated on about 200 million hectares globally. Microalgae and cyanobacteria have potential to be developed as biostimulants for wheat and maize production. This review focuses on biostimulating effects of various microalgae and cyanobacteria on seed priming, soil and foliar treatments applied in pot experiments and field trials. Two case studies on wheat and maize field trials are included. Seed priming with selected microalgal extracts is a promising method to promote plant growth but still needs validation in field trials. Soil biofertilizers based on living N2-fixing cyanobacteria (algalization) applied alone or in combination with plant growth promoting rhizobacteria modulate soil microbial composition and enhance nutrient uptake. However, this requires application of tens or hundreds kg/ha biomass to substitute for N-fertilizers so is not yet an economically viable option. The case studies indicated that a single foliar treatment of wheat at tillering and maize at the V6 growth stage with Chlorella vulgaris or Tetracystis sp. suspensions (0.1–1g DW/L applied at 400L/ha) increased grain yield, grain protein content and improve stress tolerance. These results indicated that certain microalgae could be effective biostimulants. However, producing sufficient microalgae biomass on a commercial scale is still a challenge. Monoalgal mass production in closed photobioreactors is expensive. A promising approach is the cultivation of mixed algal cultures in nutrient rich wastewater using open raceway reactors.

Introduction: Drought stress remains a critical challenge to sustainable agriculture worldwide, threatening crop productivity and food security. Understanding the physiological processes and defense mechanisms that crops employ under water-limited conditions is essential for developing strategies to enhance drought resilience. Plant responses to drought vary widely depending on species, genotype, developmental stage, and the severity and duration of stress. Beyond annual rainfall totals, yield is also shaped by seasonal precipitation patterns and related environmental factors, which influence the choice of cultivars and crop performance. Finding: This review examines the drought responses of maize and wheat, two globally important cereals, across morphological, physiological, biochemical, and molecular dimensions. Key responses include enhanced root development, reduced leaf area, stomatal regulation, decreased photosynthetic activity and water potential, and elevated proline and abscisic acid levels. Although varietal differences are noted, they are discussed only briefly. Water stress is commonly quantified via water potential and measured using tools such as the Scholander pressure chamber or the increasingly adopted ZIM probe, which allows non-destructive, continuous monitoring. While conventional breeding efforts have targeted drought tolerance, progress is constrained by these traits' polygenic and environmentally sensitive nature. Recently, biostimulants such as seaweed extracts and microalgae-based products have emerged as promising tools for enhancing stress tolerance. Conclusion: To meet the demands of a changing climate, future research should prioritize the integration of genetic, physiological, and biochemical strategies to develop crops with robust and durable drought resistance.

Due to global warming, a permanent rainfall deficit and higher temperatures reduce the available water in the soil, which severely influences plant water status. Current research needs to address ways to overcome these problems in order to maintain crop yields. The beneficial effects of seaweed extracts against abiotic and biotic stress factors of plant growth is well known but the use of microalgae for the same purpose is not well described. The aim of the present work was to investigate the plant biostimulating effects of the cyanobacterium Nostoc piscinale on the winter wheat variety “Bőség.” Experiments were carried out over three years in Hungary at the Mosonmagyaróvár Faculty Farm. Freeze-dried cyanobacterium was re-suspended in water (0.3 or 1.0 g/L) and sprayed at 400 L/ha on wheat leaves at tillering or tillering and ear emergence. Root weight, relative water content (RWC), chlorophyll and proline content of leaves were measured during the vegetation period. Ear number, ear length, grain numbers in ear, thousand grain weight and yield were measured at harvest. The most economic and highest yield increase was obtained by 0.3 g/L treatment with N. piscinale at tillering and ear emergence. Beneficial effects included a stronger root system, elevated leaf RWC, higher proline content and increased leaf chlorophyll content, which remained high in plant leaves treated with N. piscinale for one or two weeks longer than in the control leaves. The high chlorophyll content extended the productive vegetation period of the treated plants. Cyanobacterium treatment increased the ear number, ear length, grain number per ear, thousand grain weight and yield of the wheat crop.