Microalgae-Derived Biostimulant: A Promising Approach for Improving Beet Seed Germination and Early Development

Abstract

Seed germination is a critical and sensitive phase of plant development that directly impacts seedling establishment and agricultural productivity. The present study evaluated the biostimulant potential of microalgal biomass cultivated in two types of agro-industrial effluents on the germination and early growth of beet seeds (Beta vulgaris L., cv. Maravilha). The experiment was conducted using a randomized block design (RBD), with four treatments and four replicates. Each experimental unit consisted of a Petri dish containing 10 seeds. The treatments were as follows: T1 – deionized water (control); T2 – Chlorella sp. cultivated in synthetic effluent from the soymilk industry; T3 – Chlorella sp. cultivated in effluent from a bioprocessing industry; and T4 – a combination of T2 and T3. After ten days, we evaluated the following variables: first germination count (FGC), germination percentage (G%), mean germination time (MGT), germination speed index (GSI), and the fresh (FW) and dry (DW) weights of the seedlings. Additionally, the quantification of phytohormones in the microalgal extracts was performed using UPLC-MS/MS. The results showed that the seeds treated with T4 had the highest FGC, GSI, and FW values and the lowest MGT compared to the control treatment (T1). Phytohormone analysis revealed the presence of auxin (indole-3-acetic acid, or IAA), gibberellins (GA1, GA20, and GA29), cytokinins (t-zeatin, DHZ, iP, IPA, and iPAMP), and abscisic acid (ABA) in all the microalgal substrates tested. These findings suggest that microalgal biomass has the potential to serve as a biostimulant and could be a promising alternative for enhancing seed germination and initial seedling vigor in beet cultivation.