Citrus rootstock responses to water stress

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Scientia Horticulturae 126 (2010) 95–102

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Citrus rootstock responses to water stress
Juan Rodríguez-Gamir, Eduardo Primo-Millo, Juan B. Forner, M. Angeles Forner-Giner ∗
Centro de Citricultura y Producción Vegetal, Instituto Valenciano de Investigaciones Agrarias,Apartado Oficial, 46113 Moncada, Valencia, Spain

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Tolerance to drought-stress (DS) of the citrus rootstock Forner–Alcaide no. 5 (FA-5) was tested and compared with that of its parents, Cleopatra mandarin (CM) and Poncirus trifoliata (PT). Nine-monthold seedlings of CM, PT and FA-5 and 15-month-old grafted trees of ‘Valencia’ orange scions on these threerootstocks were cultivated in sand under glasshouse conditions and irrigated with a nutrient solution. Plants were drought-stressed by withholding irrigation until leaves were fully wilted. Survival time of both seedlings and grafted trees under DS was linked to the water extraction rate from the soil, which depended mainly on leaf biomass and on transpiration rate. Seedling responses to DS affectingleaf water relationships and gas exchange parameters varied among genotypes. FA-5 seedlings survived longer than the other seedlings, maintaining the highest levels of water potential, stomatal conductance, transpiration rate and net CO2 assimilation towards the end of the experiment, when water stress was most severe. Thus, FA-5 was more resistant to DS than its parents (CM and PT). Moreover,rootstock affected the performance of grafted trees under water stress conditions. The higher drought tolerance induced by FA-5 rootstock could be related to the greater osmotic adjustment (OA), which was reflected by smaller reductions in leaf relative water content (RWC) and in higher turgor potentials and leaf gas exchange than the other rootstocks. © 2010 Elsevier B.V. All rights reserved.Article history: Received 8 March 2010 Received in revised form 22 June 2010 Accepted 24 June 2010 Keywords: Cleopatra mandarin Poncirus trifoliata Water potential Stomatal conductance Transpiration Forner–Alcaide 5

1. Introduction Water deficit in citrus diminishes vegetative growth and yield, and reduces fruit size, and sometimes quality, causing important economic losses in orchards (Hilgeman andSharp, 1970; Levy et al., 1978, 1979; Castel and Buj, 1990; Ginestar and Castel, 1996; Gonzalez-Altozano and Castel, 1999, 2000; Romero et al., 2006). Additionally, drought-stress reduces CO2 assimilation, stomatal conductance and transpiration (Sinclair and Allen, 1982; Syvertsen et al., 1988; Gomez-Cadenas et al., 1996; Arbona et al., 2005; Perez-Perez et al., 2007; Garcia-Sanchez et al., 2007).Root systems can respond to soil drying by sending signals to the leaves, where stomatal closure is induced to reduce water loss (Davies and Zhang, 1991). A drought-induced signaller can be abscisic acid (ABA), which is synthesized in the roots and transported through the transpiration stream to the leaves (Zeevaart and Boyer, 1984; Zhang et al., 1987; Zhang and Davies, 1989a,b, 1990a,b;Gomez-Cadenas et al., 1996). Moreover, plants have developed other mechanisms to resist drought, such as increased root development or leaf mass reduction (Zhang and Davies, 1989b, 1990b;

∗ Corresponding author at: Departamento de Citricultura y otros frutales, Instituto Valenciano de Investigaciones Agrarias, Apartado Oficial, 46113 Moncada, Valencia, Spain. Tel.: +34 963 424 000; fax: +34 963 424 001.E-mail address: forner (M.A. Forner-Giner). 0304-4238/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2010.06.015

Yin et al., 2005; Lei et al., 2006). Also, osmotic adjustment enables plants to maintain the leaf turgor necessary for stomatal opening, thus sustaining photosynthesis and growth (Syvertsen and Smith, 1983; Morgan, 1984; Delauney...
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