Understanding salinity tolerance of three high plains bedding plant species in a hydroponics setting

Increased salinity levels in irrigation water are often attributed to natural weathering, as well as runoff from industrial and agricultural production. As fresh water sources rapidly deplete on a global scale, availability of quality irrigation water has become an issue in many regions of the United States. Salinity tolerance mechanisms in plants are generally sorted into one or more of three established salt responses (exclusion, excretion, and accumulation). Although poorly understood, tolerance mechanisms may be enhanced through any number of environmental variables including presence of soluble calcium in soil or water. Three species of bedding plants, Artemisia schmidtiana ‘Silver Mound’ (Silver Mound Artemisia), Eustoma exaltatum ssp. russellianum (Texas Bluebells) and Anisacanthus quadrifidus (Hummingbird Bush) were evaluated for their respective salinity tolerance to increased levels of sodium (Na) and calcium (Ca). Species were suspended in a hydroponic system using a randomized complete block design with a control (~1.5 dS/m) and three salinity treatments (3 mS/cm, 6 mS/cm and 12 mS/cm) mixed using a 2:1 ratio of Na to Ca. Nutrients were provided via a half-strength Hoagland’s solution. After 90 days, dry weight and length measurements were taken on root and shoot tissue. Tissue was then dried and ground for tissue analysis to determine % Na, % Ca and Cl ppm and identify salt mobility into the leaves. Tissue analysis could only be performed on A. schmidtiana ‘Silver Mound’ and A. quadrifidus, as E. exaltatum ssp. russellianum had insufficient tissue. Generally, no differences were found between treatments with either A. schmidtiana ‘Silver Mound’ or E. exaltatum Texas Tech University, Rebecca Grubbs, June 2013 iv ssp. russellianum. Linear regression analyses indicate there was a decrease in root and shoot lengths in A. quadrifidus with increasing salinity levels. Additional regression analysis also indicates shoot dry weights decreased with increasing salinity. However, there was no relationship between root dry weight and salinity level. As expected, an increase in salinity yielded a positive slope with % Na and Cl ppm. There was no relationship determined between higher salinity and % Ca suggesting the possibility that limited calcium mobility may have been overwhelmed by sodium influx resulting in the overall decline in plant health.