Physiological and biochemical responses of maize plants exposed to seed coating and foliar spray of distinct seaweed nanopowder

Abstract

Seaweeds carry a wide array of metabolites and nutrients that facilitate growth, development, and physiological and biochemical changes in plants, which vary among seaweed species. Among the seaweeds, three distinct seaweed species, viz., brown (Sargassum muticum (SM)) and red (Gracilaria edulis (GE) and Kappaphycus alvarezii (KA)) were collected from the coastal area of Mandapam, Tamil Nadu, and studied. Size reduction using a high-energy ball mill at 500 rpm for 3 h produced seaweed powders with sizes of 30–190 nm (KA), 70–120 nm (GE) and 40–220 nm (SM). Characterization was done using PSA, TEM, SEM, XRD and FTIR. The FTIR profile reveals major functional groups like alkenes, carboxylic acids, alcohols and amines. The seaweeds contained macro- and micronutrients, especially potassium (2.67–13.4%). Biochemical profiling indicated high levels of amino acids, vitamins, fatty acids and growth hormones. Maize seeds were coated with 100 g of seaweed powder per kg of seeds using gum acacia (0.1%) as a sticky agent. Furthermore, the maize seedlings were sprayed three times (20, 30, 40 DAS) with seaweed powder at 0, 25, 50 and 100 mg L⁻¹. The combined application of seed coating and foliar spray of GE significantly increased the growth and physiological and biochemical parameters of the plants. The results demonstrated that seaweeds are rich in metabolites and nutrients that enhance maize growth and physiological parameters. This paper provides foundational information for utilizing seaweed as an organic resource to improve crop growth and productivity.