title: Foliar potassium nitrate application improves the tolerance of Citrus macrophylla L. seedlings to drought conditions.
abstract: Scarcity of water is a severe limitation in citrus tree productivity. There are few studies that consider how to manage nitrogen (N) nutrition in crops suffering water deficit. A pot experiment under controlled-environment chambers was conducted to explore if additional N supply via foliar application could improve the drought tolerance of Citrus macrophylla L. seedlings under dry conditions. Two-month-old seedlings were subjected to a completely random design with two water treatments (drought stress and 100% water/field capacity). Plants under drought stress (DS) received three different N supplies via foliar application (DS: 0, DS + NH4NO3: 2% NH4NO3, DS + KNO3: 2% KNO3). KNO3-spraying increased leaf and stem DW as compared with DS + NH4NO3 and DS treatments. Leaf water potential (Ψw) was decreased by drought stress in all the treatments. However, in plants from DS + NH4NO and DS + KNO3, this was due to a decrease in the leaf osmotic potential, whereas the decrease in those from the DS treatment was due to a decrease in the leaf turgor potential. These responses were correlated with the leaf proline and K concentrations. DS + KNO3-treated plants had a higher leaf proline and K concentration than DS-treated plants. In terms of leaf gas exchange parameters, it was observed that net assimilation of CO2 [Formula: see text] was decreased by drought stress, but this reduction was much lower in DS + KNO3-treated plants. Thus, when all results are taken into account, it can be concluded that a 2% foliar-KNO3 application can enhance the tolerance of citrus plants to water stress by increasing the osmotic adjustment process.
authors.affiliation: Department of Agronomy, ISA University, Av. Antonio Guzmán Fdez. Km 5½, PO Box 166 La Herradura, Santiago, Dominican Republic. Electronic address: tenoves@gmail.com.
authors.forename: V
authors.initials: V
authors.lastname: Gimeno
authors.affiliation: Centro de Bioplantas, Universidad de Ciego de Ávila, Ctra a Morón, Km 9½, Ciego De Ávila, Cuba.
authors.forename: L
authors.initials: L
authors.lastname: Díaz-López
authors.affiliation: Centro de Edafología y Biología Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Espinardo, 30100 Murcia, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Simón-Grao
authors.affiliation: Centro de Edafología y Biología Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Espinardo, 30100 Murcia, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Martínez
authors.affiliation: EPSO, Univ. Miguel Hernández, Ctra. Beniel Km 3.2, 03312 Orihuela, Alicante, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: Martínez-Nicolás
authors.affiliation: Centro de Edafología y Biología Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Espinardo, 30100 Murcia, Spain.
authors.forename: F
authors.initials: F
authors.lastname: García-Sánchez
mesh_terms: D002957:Citrus / Q000378:metabolism*; D055864:Droughts; D053834:Explosive Agents / Q000494:pharmacology*; D009566:Nitrates / Q000494:pharmacology*; D018515:Plant Leaves / Q000378:metabolism*; D017680:Potassium Compounds / Q000494:pharmacology*; D036226:Seedlings / Q000235:genetics*; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D053834:Explosive Agents; D009566:Nitrates; D017680:Potassium Compounds; C023844:potassium nitrate
keywords: Drought stress; Fertilisation; Growth; Leaf gas exchange; Mineral nutrition; Rootstock