Growth and Ion Distribution Is Affected by Irrigation with Saline Water in Selected Landscape Species Grown in Two Consecutive Growing Seasons: Spring–summer and Fall–winter

Abstract

<jats:p>Landscape irrigation is the second largest user of reclaimed water in industrialized countries; however, its high concentration of soluble salts, especially Na<jats:sup>+</jats:sup> and Cl<jats:sup>–</jats:sup>, may induce growth reduction and leaf necrosis or bronzing in ornamental species. The present study was conducted to determine the growth and quality responses and nutritional ion imbalances of selected landscape species during the container production phase when subjected to irrigation with water of increasing NaCl + CaCl<jats:sub>2</jats:sub> concentrations. Plants of boxwood [<jats:italic>Buxus microphylla</jats:italic> var. japonica (Mull. Arg. ex Miq) Rehder &amp; E.H. Wilson], escallonia (<jats:italic>Escallonia</jats:italic> ×<jats:italic>exoniensis</jats:italic> hort. Veich ex Bean), hawthorn [<jats:italic>Raphiolepis indica</jats:italic> (L.) Lind. Ex Ker Gawl. × ‘Montic’], hibiscus (<jats:italic>Hibiscus rosa-sinensis</jats:italic> L.), and juniper (<jats:italic>Juniperus chinensis</jats:italic> L.) were grown in a greenhouse in the Spring–Summer and in the Fall–Winter in separate experiments. Saline irrigation consisted of solutions with electrical conductivities (EC<jats:sub>iw</jats:sub>) of 0.6, 2, 4, 6, and 8 dS·m<jats:sup>−1</jats:sup> in the Spring–Summer experiment and 0.6, 4, 6, 8, and 12 dS·m<jats:sup>−1</jats:sup> in the Fall–Winter. Growth of the five species decreased when irrigated with saline waters. Leaf growth was highly sensitive to salinity and the average decrease in leaf dry weight was the criterion used to rank the tolerance of the species. In the Spring–Summer experiment, the ranking was (higher tolerance to lower tolerance): juniper ∼ boxwood &gt; escallonia &gt; hawthorn &gt; hibiscus, whereas in Fall–Winter, the ranking was: juniper ∼ boxwood &gt; hibiscus &gt; escallonia &gt; hawthorn. The species were ranked according to their visual attractiveness in the Spring–Summer experiment. The threshold EC<jats:sub>iw</jats:sub> at which visual attractiveness was affected gave the following ranking (higher to lower tolerance): hibiscus &gt; juniper &gt; escallonia &gt; hawthorn &gt; boxwood. Estimating the EC of drainage water from threshold EC<jats:sub>iw</jats:sub>, boxwood was classified as sensitive, hawthorn as moderately sensitive, escallonia as moderately tolerant, and hibiscus and juniper as highly tolerant. Tolerance of juniper was ascribed to Na<jats:sup>+</jats:sup> and Cl<jats:sup>–</jats:sup> retention in the roots observed in both growing seasons and to the higher root biomass that allowed a higher accumulation of salts in this organ, preventing translocation to the leaves. Although boxwood exhibited acceptable tolerance in terms of growth, visual quality severely decreased; in contrast, growth of hibiscus was the most severely reduced but was rated as the most tolerant species in terms of visual quality. This opposite response may be the result of an excellent capacity to compartmentalize salts in hibiscus, whereas in boxwood, this mechanism may be absent.</jats:p>

Long‐term effect of salinity on plant quality, water relations, photosynthetic parameters and ion distribution in Callistemon citrinus

“…; Valdez‐Aguilar et al . ). Given that NaCl is the most soluble and widespread salt, it is not surprising that all plants have evolved mechanisms to regulate its accumulation and to preferentially select other nutrients commonly present at low concentrations (Munns ).…”

“…Since the growing season also seems to affect the response of shrubs to salt (Valdez‐Aguilar et al . ), the present research was carried out during the entire growing season (whole year) using a salt level (4 dS·m −1 ) similar to the levels in irrigation water commonly applied in the Mediterranean horticultural sector (nurseries, growers, gardeners; Pedrero et al . ).…”

“…As the competition for high-quality water increases, the use of saline water has become an option for irrigating salt-tolerant ornamentals (Cassaniti et al 2009). However, despite the importance of ornamental shrubs in Mediterranean areas, the salt tolerance of such species has received little attention (Bañ on et al 2005;Valdez-Aguilar et al 2011). Given that NaCl is the most soluble and widespread salt, it is not surprising that all plants have evolved mechanisms to regulate its accumulation and to preferentially select other nutrients commonly present at low concentrations (Munns 2002).…”

“…Both factors must be considered when saline water is used for irrigation water, as the interaction of both parameters will determine the physiological and molecular changes that take place. Since the growing season also seems to affect the response of shrubs to salt (Valdez-Aguilar et al 2011), the present research was carried out during the entire growing season (whole year) using a salt level (4 dSÁm À1 ) similar to the levels in irrigation water commonly applied in the Mediterranean horticultural sector (nurseries, growers, gardeners; Pedrero et al 2010).…”

El calcio imparte tolerancia a alta conductividad eléctrica en Lisianthus (Eustoma grandiflorum Raf. Shinn.)

“…The lower rate of transpiration and leaf conductance detected in the present study to raise the EC should have also allowed an improvement in the water status of plants by reducing water loss. -Aguilar et al (2011) mentioned that the salinity stress causes a reduction in the accumulation of K in various ornamentals, which is due to the competition with the Na ion frequently encountered in high salinity water. The Ca concentration in plant tissues under conditions of high salinity in turn is reduced due to the displacement caused by the excess of Na (Cramer et al, 1985).…”