The supply of high-quality water has become increasingly limited in many areas of the world, especially in arid and semiarid regions such as the Mediterranean area. However, this area has a great potential for growing crops as a result of its high solar radiation, and many ornamental growers try to make the most of these climatic conditions although only low-quality water is available. However, the use of low-quality water for irrigation affects plants in different ways, depending on the degree of salt tolerance of the species (Alarcón et al., 1993), the level of water salinity, and the characteristics of the water itself. Typical plant responses to salinity include reduced shoot and root growth and reduced whole plant size (Munns, 2002). As salinity stress becomes more severe, foliar damage such as leaf burn, scorch, necrosis, and premature defoliation may occur (Niu et al., 2010a), negatively affecting plant quality, which is of serious concern because the visual quality of ornamental plants is more important than maximum growth (Niu et al., 2008). Growth reduction is related with the osmotic effect of salinity, which limits a plant’s ability to extract water from the soil (Rodriguez et al., 1997). Leaf damage is related to the Na+ and Cl− accumulated in leaves which are not compartmentalized in vacuoles, making them metabolically toxic (Shannon and Grieve, 1999).
Plant salt tolerance is the ability to withstand the effects of high salt concentrations in the root zone without a significant adverse effect (Shannon and Grieve, 1999). This tolerance may be determined by: 1) the ability to limit uptake and/or transport of Na+ and Cl− to aerial parts, because these ions are retained in the root (Murillo-Amador et al., 2006); 2) the capacity to maintain nutrient uptake (Chaparzadeh et al., 2003); 3) the capacity of plants to maintain a high K+/Na+ ratio in their tissues (Maathuis and Amtmann, 1999); and 4) the capacity to maintain a positive water balance through osmotic adjustment, which involves an active increase in tissue solute concentration (Torrecillas et al., 2003).
As well as environmental conditions, the management of factors that affect humidity and temperature in the substrate can help produce good-quality plants depending on the level of exposure to salinity and the salt tolerance of the species in question. Niu et al. (2010b) reported that salt accumulation in the root zone is affected by the substrate properties, plant size, and environmental conditions because these factors influence the substrate moisture content and cation exchange capacity in the root zone. The factors that can reduce salt accumulation in the substrate may reduce the negative effect of salinity. In this respect, the PIP system compared with AGP reduces root zone temperature stress (Young and Bachman, 1996), which improves roots development (Mathers, 2003), and enhances efficient water use by decreasing container evapotranspiration (Martin et al., 1999), which will reduce salt accumulation as a result of lower substrate water evaporation (Miralles et al., 2009).
The PIP crop system was introduced ≈1990 (Parkerson, 1990) in the United States and combines some of the benefits of both field and container production. In a PIP system, a holder or socket pot is permanently placed in the ground with the top rim remaining above. The container-grown plant is then placed within the holder pot for the production cycle (Ruter, 1998b).
The Euonymus japonicus (Japanese Spindle) is a commercial woody perennial shrub with good aesthetic qualities, which is frequently planted in public areas such as streets, recreation areas, and car parks. Previous studies with this species before this experiment with different levels of salinity showed that it was quite tolerant to saline irrigation (≈6 dS·m−1).
The objectives of this study were to evaluate the potential benefits of the PIP system for reducing the salt stress effect on Euonymus japonicus. To this end, plants of this species were grown in PIP and AGP and irrigated with fresh and saline water. The following points were studied: 1) substrate temperature and leachate EC and pH; 2) growth and development of the plant and any salt damage; and 3) pore water EC, leaf potentials, and ion concentrations.
AlarcónJ.J.BolarínM.C.Sánchez-BlancoM.J.TorrecillasA.1993Water relations and osmotic adjustment in Lycopersicon esculentum and L. Pennellii during short-term salt exposure and recoveryPhysiol. Plant.89441447
BañónS.MirallesJ.OchoaJ.FrancoJ.A.Sánchez-BlancoM.J.2011Effects of diluted and undiluted treated wastewater on the growth, physiological aspects and visual quality of potted lantana and polygala plantsSci. Hort.129869876
ChaparzadehN.Khavari-NejadR.A.Navari-IzzoF.IzzoR.2003Water relations and ionic balance in Calendula officinalis L. under saline conditionsAgrochimicaXLVII6979
GucciR.XiloyannisC.FloreJ.A.1991Gas exchange parameters water relations and carbohydrate partitioning in leaves of field-grown Prunus domestica following fruit removalPhysiol. Plant.83497505
KchaouH.LarbiA.GargouriK.ChaiebM.MoralesF.MsallemM.2010Assessment of tolerance to NaCl salinity of five olive cultivars, based on growth characteristics and Na+ and Cl− exclusion mechanismsSci. Hort.124306315
MartinC.A.McDowellL.B.ShielaB.1999Below-ground pot-in-pot effects on growth of two southwest landscape trees was related to root membrane thermostabilityJ. Environ. Hort.176368
Martinez-BarrosoM.C.AlvarezC.E.1997Toxicity symptoms and tolerance of strawberry to salinity in the irrigation waterSci. Hort.71177188
MirallesJ.NortesP.A.Sánchez-BlancoM.J.Martínez-SánchezJ.J.BañónS.2009Above-ground and pot-in-pot production systems for Myrtus communis LTrans. ASABE5293101
Murillo-AmadorB.Troyo-DiéguezE.García-HernándezJ.L.López-AguilarR.Ávila-SerranoN.Y.Zamora-SalgadoS.Rueda-PuenteE.O.KayaC.2006Effect of NaCl salinity in the genotypic variation of cowpea (Vigna unguiculata) during early vegetative growthSci. Hort.108423441
NavarroA.BañonS.OlmosE.Sánchez-BlancoM.J.2007Effects of sodium chloride on water potential components, hydraulic conductivity, gas exchange and leaf ultrastructure of Arbutus unedo plantsPlant Sci.172473480
NemaliK.S.MontesanoF.DoveS.K.van IerselM.W.2007Calibration and performance of moisture sensors in soilless substrates: ECH2O and Theta probesSci. Hort.112227234
NiuG.RodriguezD.S.AguinigaL.2008Effect of saline water irrigation on growth and physiological responses of three rose rootstocksHortScience4314791484
RodriguezP.Dell’AmicoJ.MoralesD.Sánchez-BlancoM.J.AlarcónJ.J.1997Effects of salinity on growth, shoot water relations and root hydraulic conductivity in tomato plantsJ. Agr. Sci.128439444
RuterJ.M.1998bPot-in-Pot production and cyclic irrigation influence growth and irrigation efficiency of ‘Okame’ cherriesJ. Environ. Hort.16159162
TorrecillasA.RodríguezP.Sánchez-BlancoM.J.2003Comparison of growth, leaf water relations and gas exchange of Cistus albidus and C. monspeliensis plants irrigated with water of different NaCl salinity levelsSci. Hort.97353368
WuL.GuoX.HarivandiA.2001Salt tolerance and salt accumulation of landscape plants irrigated by sprinkler and drip irrigation systemsJ. Plant Nutr.2414731490