Growth and physiological responses of landscape plants and nursery crops to elevated salinity levels in alternative water sources

Water shortages and poor water quality are critical issues in southwestern and southern states. With rapid increases in population and diminishing water supplies in urban areas, use of alternative water sources, such as municipal reclaimed water and other poor-quality, non-potable and saline waters, for irrigating landscapes and horticultural crops is inevitable. The major concern of using these alternative waters for irrigating ornamental plants is their high salinity, which often causes damage and reduces growth on salt sensitive species. Our multi-year research results indicate that salt tolerance in a number of bedding plants, herbaceous perennials, groundcovers and woody ornamental plants is highly species dependent and a wide range of tolerance to salinity has been found. Salinity tolerance is often evaluated according to the time it takes a plant/crop to exhibit foliar salt damage (visual quality) and growth reduction, or in other words, the duration of salt stress tolerance without significant reduction in quality and growth.  A number of mechanisms of salinity tolerance have been observed among the tested ornamental species: restriction of ion uptake, selective ion uptake, tolerating high concentrations of sodium and/or chloride, and osmotic adjustment.  In addition to plant species and salinity level, dominant salt type, substrate/soil type, and irrigation practices also impact plant responses to salinity stress.