Outcome of Microalgae Biomass Application on Seed Germination and Hormonal Activity in Winter Wheat Leaves

The present work aimed to test selected microalgae strains from the Mosonmagyaróvár Algae Culture Collection (MACC) on germination ability and certain physiological processes in winter wheat (<i>Triticum aestivum</i> L.) plants. Germination tests showed substantial differences between the strains, meaning that certain strains (such as MACC-430, MACC-612, MACC-922) improved the germination processes while others performed worse (MACC-438, MACC-755) than the control in a concentration-dependent manner. The germination index of seeds treated with MACC-430 @ 1 g L⁻¹ concentrations was 87, while that of the control was 45. The mungbean rooting bioassay proves that microalgae biomass may exhibit auxin-like activity, especially in strain MACC-612 (<i>Nostoc</i> sp.), which was characterized by the highest endogenous level of plant growth regulator indole-3-acetic-acid among the selected strains. Foliar spray on the leaves of developed plants did not significantly alter the photosynthetic processes, but it influenced the secondary metabolite composition. After the application of microalgae biomass, there were also changes in plant hormones, including salicylic acid, abscisic acid, and jasmonic acid-leucine/isoleucine conjugate compositions, which play a role in plant stress signaling in plants. A decrease in indole-3-acetic acid was also observed in the Mv Nádor cultivar. These results suggest that the application of certain microalgae strains can be used effectively to improve the germination of wheat seeds, and as a foliar spray, they may also modify the acclimation processes in a genotype-dependent way.