Recycled Wastewater and Reverse Osmosis Brine Use for Halophytes Irrigation: Differences in Physiological, Nutritional and Hormonal Responses of Crithmum maritimum and Atriplex halimus Plants

María José Gómez-Bellot,Ángel Gil-Izquierdo,María Fernanda Ortuño,Sonia Medina,Beatriz Lorente,Sebastián Bañón,María Jesús Sánchez-Blanco

doi:10.3390/agronomy11040627

Abstract

Halophytes are capable of coping with excessive NaCl in their tissues, although some species may differ in their degree of salt tolerance. In addition, it is not clear whether they can tolerate other confounding factors and impurities associated with non-conventional waters. The experiment was performed in a greenhouse with Crithmum maritimum and Atriplex halimus plants, growing on soil and irrigated with two different water types: reclaimed wastewater (RWW) (EC: 0.8–1.2 dS m−1) and reverse osmosis brine (ROB) (EC: 4.7–7.9 dS m−1). Both species showed different physiological and nutritional responses, when they were irrigated with ROB. Atriplex plants reduced leaf water potential and maintained leaf turgor as consequence of an osmotic adjustment process. Atriplex showed higher intrinsic water use efficiency than Crithmum, regardless of the type of water used. In Crithmum, the water status and photosynthetic efficiency were similar in both treatments. Crithmum presented a higher leaf accumulation of B and Ca ions, while Atriplex a higher amount of K, Mg, Na and Zn. Crithmum plants irrigated with ROB presented higher concentrations of 1-aminocyclopropane-1-carboxylic acid and trans-zeatin-glucoside, whereas abscisic acid concentration was lower. Atriplex showed a lower concentration of trans-zeatin-riboside and scopoletin. The characteristics associated to water irrigation did not influence negatively the development of any of these species, which confirms the use of brine as an alternative to irrigate them with conventional waters.

Highlights

The Mediterranean region is characterized by a climate with prolonged drought periods where isolated and torrential rains are frequent
Based on the above considerations, in this study we evaluate if the irrigation with reclaimed wastewater and brine from a reverse-osmosis water treatment of two halophytes species (Crithmum maritimum and Atriplex halimus) growing on soil, is suitable for revegetation purposes
The lowest values of these parameters were found in Atriplex plants, especially in those irrigated with reverse osmosis brine (ROB) (Figure 1A,B)

Summary

Introduction

The Mediterranean region is characterized by a climate with prolonged drought periods where isolated and torrential rains are frequent. Wastewater reclamation, recycling and reuse has gained attention in many countries, to ensure water security and to develop effective strategies for sustainable utilization of water resources in agricultural and landscape irrigation [5,6,7,8]. This kind of water is recovered from domestic, municipal, and industrial wastewater treatment plants and it may have specific treatments depending of its purpose [9]. In the case of plants with gardening and reforestation purposes, in addition to the problems related to the high salt concentrations and heavy metals which may affect growth, stabilization and quality of plants [16], the presence of persistent organic pollutants such as organochlorine pesticides can pose threats to ecosystems due to their biological accumulation through the trophic chain

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