Plant- and Seaweed-Based Extracts Increase Yield but Differentially Modulate Nutritional Quality of Greenhouse Spinach through Biostimulant Action

Youssef Rouphael,Marios Kyriacou,Giuseppe Colla,Mariateresa Cardarelli,Maria Giordano,Eugenio Cozzolino,Mauro Mori,Paolo Bonini

doi:10.3390/agronomy8070126

Abstract

Plant biostimulants (PBs) such as protein hydrolysates and seaweed extracts are attracting the increasing interest of scientists and vegetable growers for their potential toenhance yield and nutritional quality. The current study assessed crop productivity, leaf colorimetry, mineral profile and bioactive compounds of greenhouse spinach in response to the foliar application of three PBs: legume-derived protein hydrolysate [PH], extract of seaweed Ecklonia maxima or mixture of vegetal oils, herbal and seaweed Ascophyllum nodosum extracts. Plants were PB-treated at a rate of 3 mL L−1 four times during their growth cycle at weekly intervals. Foliar PB applications enhanced fresh yield, dry biomass and leaf area of spinach in comparison with untreated plants. Improved yield performance with PB applications was associated with improved chlorophyll biosynthesis (higher SPAD index). The three PB treatments elicited an increase in bioactive compounds (total phenols and ascorbic acid), thus raised the functional quality of spinach. The application of PH enhanced K and Mg concentrations and did not result in increased nitrate accumulation as observed with the other two PB treatments. Our findings can assist vegetable farmers and the agro-food industry in adopting innovative and sustainable tools such as PB for complementing a high yield with premium quality.

Highlights

The pressing issue of global food security coupled with the projections for global population increase and climate change pose major challenges for the horticultural industry and researchers with respect to sustainability, dictating maximization of the production per unit area while minimizing the environmental impact of vegetable cropping systems [1]
The main components of commercial protein hydrolysates (PHs) are a mixture of free amino acids, oligo- and polypeptides sourced from animal or plant origins [11]; whereas commercial seaweed extracts (SWE), in particular the brown macro-algae (Ascophyllum nodosum and Ecklonia maxima), are important sources of polysaccharides, phenolic compounds as well as phytohormones [10,12,13]
The increase in crop productivity induced by PHs, SWEs and plant extracts (PEs) application under both optimal and sub-optimal conditions could be associated with several direct and indirect interactive mechanisms, including: (i) stimulation of enzymatic activities involved in C

Summary

Introduction

The pressing issue of global food security coupled with the projections for global population increase and climate change pose major challenges for the horticultural industry and researchers with respect to sustainability, dictating maximization of the production per unit area while minimizing the environmental impact of vegetable cropping systems [1]. The increase in crop productivity induced by PHs, SWEs and PEs application under both optimal and sub-optimal conditions could be associated with several direct and indirect interactive mechanisms, including: (i) stimulation of enzymatic activities involved in C and N metabolism, the Krebs cycle and glycolysis; (ii) elicitation of hormone-like activity, that attributed to auxin and gibberellins; and (iii) enhancement of the nutritional status of treated plants through the modulation of root system architecture (length, density and number of lateral roots) [2,8,9,10]

Methods

Results

Conclusion