The effects of salt stress on ornamental plants and integrative cultivation practices

Ornamental horticultural production is closely associated with a high water consumption and yet the availability of freshwater is reducing. The irrigation of ornamental plants with saline water may be an alternative, but an improvement in knowledge of the effects on salinity on species used as ornamentals is essential. In this review, considering the references from the last decade, we summarized the main effects of salt stress on growth, nutrient, photosynthetic and physiological parameters in ornamental plants. At high salinities, plants exhibit a reduction of growth parameters such as biomass or leaf area related to osmotic and ionic effects of salinity. Growth under saline conditions leads to uptake of Na+ and Cl− by plants, which can result in a nutritional imbalance due to the antagonism between nutrients and saline ions with possible effects on the foliage. Salinity can affect water relations in plants and photosynthetic capacity by stomatal limitations. These negative effects can be counteracted by the plants through the accumulation of compatible solutes or osmolytes and the activation of antioxidant machinery. Nevertheless, the performance of these mechanisms is sometimes not enough to avoid damage to the appearance of the plant and in consequence the saleability of an ornamental species. In this review recommendations for the establishment of integrative cultivation practices for nursery growers are made; these include exogenous application of nutrients and osmolytes and enrichment with CO2, in order to mitigate the damage caused by salt stress to ornamental plants.