Metabolite-Targeted Analysis and Physiological Traits of Zea mays L. in Response to Application of a Leonardite-Humate and Lignosulfonate-Based Products for Their Evaluation as Potential Biostimulants

Abstract

The main aim of this study is to identify and investigate specific humates (Hs) as potential biostimulants. Five specialty lignosulfonates (LS1-5), one commercial leonardite-humate (PH), and one commercial lignosulfonate (LH), were analyzed for their carbon, nitrogen, and sulfur contents, and the distribution of functional groups using Fourier transform infrared (FTIR) and Raman spectroscopies. Hs were further supplied for two days to Zea mays L. in hydroponics to test their capacity to trigger changes in physiological target-responses. LS1, LS2, LS3, and LS5 determined the most pronounced effects on plant growth and accumulation of proteins and phenolics, perhaps because of their chemical and spectroscopic features. Root growth was more increased (+51–140%) than leaf growth (+5–35%). This effect was ascribed to higher stimulation of N metabolism in roots according to the increased activity of N-assimilation enzymes (GS and GOGAT) and high consumption of sugars for energy-dependent processes. Increased values of RuBisCO, SPAD (Soil Plant Analysis Development values), and leaf sugar accumulation refer to enhanced photosynthesis attributed to Hs. We conclude that Hs tested in this study functioned as biostimulants, but the specialty lignosulfonates were more efficient in this role, possibly because of the type of starting material and process used for their production, which may have influenced their chemical properties.

Manure Fertilization Gives High-Quality Earthworm Coprolites with Positive Effects on Plant Growth and N Metabolism

“…Elevated contents of photosynthetic pigments are known to positively correlate with the photosynthetic process in plants, which is responsible for the production of photosynthates contributing to plant growth. Consistently with our findings, higher SPAD (Soil Plant Analysis Development) values, which are indicative of higher chlorophyll content in plants, and enhanced Rubisco activity and sugar production were previously observed in maize plants treated with lignohumates [53]. The same HS from earthworm coprolites of FM and FMM soils also improved plant nutrition.…”

“…HS have been additionally reported to stimulate plant growth by targeting pivotal pathways of plant metabolism, primarily nitrogen assimilation [52][53][54]. The activity of the nitrogen assimilation enzyme GS, was more increased by HS extracted from earthworm coprolites collected in FM, likely because of higher N uptake and accumulation by plants.…”

Arbuscular Mycorrhizal Fungi and K-Humate Combined as Biostimulants: Changes in Antioxidant Defense System and Radical Scavenging Capacity in Elaeagnus angustifolia

“…This field includes increasing plant growth and development efficiency, e.g., increasing yield, enhancing crop quality, increasing plant tolerance to and recovery from abiotic stresses, facilitating nutrient assimilation, translocation and use, enhancing the quality of produce, enabling more efficient water utilization, and enhancing certain physicochemical properties of the soil (Calvo et al 2014). However, the mechanisms activated by biostimulants are often difficult to identify and are still under investigation (Rouphael et al 2015;Nardi et al 2016;Ertani et al 2019;Paul et al 2019).…”

Toward a Sustainable Agriculture Through Plant Biostimulants: From Experimental Data to Practical Applications

“…Ertani et al [27] carried out a short-term trial on hydroponically grown maize to assess the physiological responses to leonardite-humate-and lignosulfonate-based biostimulants. The biostimulants application in particular lignosulfonates boosted root and leaf growth by 51-140% and 5-35%, respectively.…”

“…The biostimulants application in particular lignosulfonates boosted root and leaf growth by 51-140% and 5-35%, respectively. The authors concluded that a putative mechanism involved in the biostimulant action of these products might be the stimulation of N metabolism in the belowground organs (i.e., roots) according to the increased activity of key enzymes such as glutamine synthetase and glutamate synthase [27]. Moreover, Kim et al [28], elucidated the hormonal effects of a commercial vegetal-based biostimulants containing amino acids, lateral root promoting peptide, lignosulfonates and micronutrients on cuttings of basil, tomato and chrysanthemum, characterized by different relative root ability: easy, moderate and difficult, respectively.…”