Agronomic and Metabolic Responses of Citrus clementina to Long-Term Irrigation with Saline Reclaimed Water as Abiotic Factor

Int J Mol Sci. 2025 Apr 7;26(7):3450. doi: 10.3390/ijms26073450.

Abstract

The Panel on Climate Change has predicted an intensification of drought and heat waves. The aim of this study was to determine the physiological response of mandarin trees in a semi-arid area to the effects of a long period of irrigation with saline reclaimed water (RW) and freshwater (FW) in terms of leaf mineral constitution, free amino acids and phytohormone balance, and their influence on yield and fruit quality. Results showed that higher foliar levels of Cl-, B, Li+, and Br- were found in the RW treatment. In addition, fruit quality (juice content, soluble solid content, titratable acid, and maturity index) and yield (fruit weight and diameter) parameters and growth canopy were negatively affected by irrigation with RW. Regardless of the treatments, L-alanine (Ala) and proline were the most abundant amino acids, with Ala being described as a majority for the first time in the literature. Concretely, in FW, the total amino acid content was twice as high as the concentration in RW (51,359.46 and 23,833.31 ng g-1, respectively). The most abundant hormones were 1-Aminocyclopropane-1-carboxylic acid and trans-zeatin in both treatments. The saline stress response would be reflected in the higher concentration of salicylic and abscisic acids in the leaves of RW trees. In view of the high correlations found in a simplified correlation matrix of (i) Ala with the canopy growth and (ii) the salicylic acid (SA) with most of the evaluated agrometabolic parameters, it can be concluded that the exogenous application of the Ala and SA would increase tree size and could mitigate the effects of salt stress, respectively. However, these treatments could be completed with the external application of ACC since this phytohormone presents the lowest parameter during treatment with RW.

Keywords: amino acids; fruit quality; leaf nutrients; mandarin trees; phytohormones; reclaimed water; salt stress.

MeSH terms

  • Agricultural Irrigation* / methods
  • Amino Acids / metabolism
  • Citrus* / growth & development
  • Citrus* / metabolism
  • Fruit / growth & development
  • Fruit / metabolism
  • Plant Growth Regulators / metabolism
  • Plant Leaves / metabolism
  • Saline Waters*
  • Stress, Physiological
  • Water

Substances

  • Plant Growth Regulators
  • Amino Acids
  • Water

Grants and funding

This study formed part of the AGROALNEXT program and was supported by MCIN with funding from the European Union NextGenerationEU (PRTR-C17.I1) and by Fundación Séneca with funding from Comunidad Autónoma de la Región de Murcia (CARM) (22015/PI/22). Also, this research was funded by the CARM through the call for Project Grants for the Generation of New Scientific Leadership “Young Leaders in Research”, included in the Regional Program for the Promotion of Scientific and Technical Research (2022 Action Plan) of the Fundación Séneca-Science and Technology Agency of the Region of Murcia (AGRISEN Project 21962/JLI/22), by MITECO through the call for strategic projects aimed at the ecological and digital transition, of the State Plan for Scientific, Technical and Innovation Research for the period 2021–2023 (TED2021-130501B-I00 Project), by MITECO, through the Fundación Biodiversidad, in the call of grants for environmental restoration and improvement in the agricultural sector, to contribute to the recovery of the ecological functionality of the Mar Menor (FERTECO Project) and by MICIU through the “ThinkInAzul” project: Joint Strategy for Research and Innovation in Marine Sciences to sustainably address new challenges in Marine-Maritime Monitoring and Observation, Climate Change, Aquaculture, and other Sectors of the Blue Economy. The authors also acknowledge the support of the Seneca Foundation (19903/GERM/15). María Pinciroli has enjoyed an AUIP grant during her stay at CEBAS-CSIC in Murcia (Spain) to carry out this work.