Macrocystis pyrifera Alga Extracts Combined with Azospirillum argentinense Improve Growth and Hormonal Responses in Zea mays Plants under Drought Stress

With increasing economic and nutritional demands that far outpace the addition of new agricultural areas around the world, biofertilizers are increasingly used to ensure the productivity of existing areas without sacrificing sustainability. This study evaluated the combination of algal extracts of Macrocystis pyrifera (a natural biofertilizer) with the plant growth-promoting bacteria Azospirillum argentinense in terms of their effectiveness in stimulating germination and growth of maize plants under different irrigation conditions. The performance of maize plants inoculated with the algae-bacteria formulation under water stress conditions was evaluated. The variables studied included different germination and growth parameters, such as dry and fresh weight of aerial and root part, total height and aerial and root part. The hormonal profile in maize seedlings was determined. The results related to growth parameters and phytohormone content demonstrate a synergistic effect between algae and bacteria, which means that a bioinoculant could be formulated based on their combination to promote the growth of maize in different climatic conditions and/or or water regimes. Such a product would fit well into current or future environmentally friendly plans for growing maize, aiming to reduce dependence on chemical fertilizers while preserving yield.