Potential benefit of microalgae and their interaction with bacteria to sustainable crop production

Abstract

Agriculture is undergoing a paradigm shift as it moves away from relying only on agrochemicals toward natural-based product to enhance plant growth and productivity while sustainably maintaining soil quality and productivity. In this sense, microalgae and bacteria offer a unique potential due to the growing use of novel and eco-friendly products such as biofertilizers, biostimulants, and biopesticides. Microalgae improve crop growth and health by fixing nitrogen, releasing soil trace elements, solubilizing potassium, and phosphorus, producing exopolysaccharides, and converting organic matter into utilizable nutrients. They also release bioactive substances including, carbohydrates, proteins, enzymes, vitamins, and hormones, to promote plant growth, control pests, and mitigate plant stress responses. Even though it has long been known that microalgae produce various bioactive and signaling molecules (like phytohormones, polysaccharides, lipids, carotenoids, phycobilins, and amino acids) which are effective in crop production, the targeted applications of these molecules in plant science are still in the very early stages of development. Microalgae are beneficial to bacteria because they produce oxygen and extracellular chemicals, and bacteria, in turn, provide microalgae with carbon dioxide, vitamins, and other nutrients in exchange. This review discusses the possible role of microalgae in increasing crop yield, protecting crops, and maintaining soil fertility and stability, and it points out that interactions of microalgae and bacteria may have a better enhancement of crop production in a sustainable way than using either of them alone.

A critical review of soil algae as a crucial soil biological component of high ecological and economic significance

“…Microalgae and cyanobacteria can potentially improve soil health and agricultural productivity (Ramakrishnan et al., 2023; Solomon et al., 2023), where soil carbon content and algal activities can favor the soil flora and fauna. Conventionally, algae in soils have been considered primary producers, contributing to soil biomass (Alvarez et al., 2021; Hoffmann, 1989; Isichei, 1990; Jassey et al., 2022).…”

“…However, apart from cyanobacterial applications in paddy fields (Chatterjee et al., 2017), specific field studies and experimental investigations on the interrelationships of algae with particular plants or crops and their influence on nutrient availability is a gap in terrestrial algal studies. Furthermore, research on soil algae and their beneficial roles in soils (Solomon et al., 2023), mainly algal release of plant growth‐stimulating compounds, algal involvement in mineral solubilization, and soil aggregation, could contribute tremendously to integrating algae into sustainable agriculture and improving soil health.…”

“…Microalgae have been shown to secrete mucilage and many other compounds into the growing environment (Kumar et al., 2018; Pichler et al., 2020; Shoarnaghavi et al., 2022). Soil algae may influence plant growth directly by secreting growth‐stimulating compounds (Solomon et al., 2023) and indirectly through mineral solubilization (Devi et al., 2022; Mustoe, 2018). Additionally, the details of wet adhesive biomolecules secreted by epilithic microalgae on soil particles and their economic possibilities, like those identified from some macro algae (Bitton & Bianco‐Peled, 2008) or epiphytic roots of orchids (Tay et al., 2021), remain unexplored.…”

Harnessing the Synergy of the Cyanobacteria-Plant Growth Promoting Bacteria for Improved Maize (Zea mays) Growth and Soil Health

“…Primarily, bacteria utilize organic carbon released during algal photosynthesis. In return, they facilitate their growth by consuming oxygen, producing carbon dioxide, providing essential nutrients, vitamins, and trace elements to support microalgal growth, and generating growth-promoting substances, chelators, and phytohormones [29,30]. Numerous research investigations indicate that heterotrophic bacteria play a widespread and crucial role in the growth and survival of algae through the provision of hormones and nitrogen sources [31][32][33][34].…”

“…Maize (Zea mays) exhibits promising responses when the soil was treated with cyanobacteria as a biofertilizer, demonstrating enhanced growth, nutrient use efficiency, and increased tolerance to abiotic stress [10,14,30,35,36]. Similarly, positive results were obtained by applying cyanobacterial extracts as foliar biostimulants and seed priming, which further contributed to the overall development and well-being of the plants [37][38][39].…”