Journal of Agricultural Science and Technology A 6 (2016) 324-334 doi: 10.17265/2161-6256/2016.05.004 Ion Accumulation, Water Relations and Osmotic Adjustment in Atriplex argentina, A. crenatifolia, A. lampa and A. nummularia under Saline Conditions Nadia Bárcena, Mónica Ruiz and Carlos Parera Agricultural Experimental Station-San Juan, National Institute of Agricultural Technology (INTA), Integrated Unit INTA-National University of San Juan, San Juan 5400, Argentina Abstract: Salinity is a major stress that adversely affects growth and productivity in plants. There are species that tolerate this stress within the genus Atriplex. Four species, A. lampa, A. crenatifolia, A. nummularia and A. argentina were compared for their ion accumulation and water relations under saline conditions. A greenhouse study was conducted by irrigating the four species with NaCl solutions at concentrations 0%, 1%, 2% and 4% starting when plants were six months old. Plants were harvested 45 d after starting the salinity treatments and analyzed for their ion contents. In the four Atriplex species, Na + and Cl – contents in plants increased, while Ca 2+ and Mg 2+ decreased with the increase of salinity in the irrigation solution. The results suggested that A. argentina and A. nummularia were able to maintain a higher leaf relative water content (RWC) at low leaf water potential, which was associated with a greater capacity of osmotic adjustment. A. lampa showed lower ion accumulation and minor osmotic adjustment than the other species. It can be concluded that the accumulation of ions favors the lower osmotic potential and contributes to osmotic adjustment in these halophytes. Key words: Atriplex sp., salinity stress, osmotic adjustment, ion accumulation, water relations. 1. Introduction Plants growing in arid and saline soils are exposed to wide ranges of water stress and osmotic stress [1-3]. Soil water content and salinity are both factors affecting the soil water potential which modify plant water potential [4-6]. Saline soil environments not only reduce water potential in the plants, but also cause ion imbalance and toxicity, thus decrease plant growth and productivity [7, 8]. Halophytes plants are well adapted to extreme environmental conditions. These plants are able to avoid toxicity caused by specific ions and have the ability to adjust water potential in their tissues to levels more negative than the soil water potential [9-11]. Halophytes in the Atriplex genus are capable to absorb ions in excess of their nutritional needs, Corresponding author: Carlos Parera, Ph.D., research fields: plant physiology, plant stress and seed physiology. particularly Na + and Cl – [12, 13], in order to make osmotic adjustments in their vacuoles, absorb water, and keep cells turgid [14]. The osmotic adjustment is a mechanism where the plants synthesize and accumulate inorganic ions and organic metabolites of low molecular weight to make plants more tolerant to saline environments [15]. The decrease of osmotic potential in leaves is generally regarded as an indicator of osmotic adjustment. However, this decrease in osmotic potential may also be caused by dehydration of tissues and reduction of osmotic volume [16]. In A. triangularis, as more salts are absorbed, the osmotic potential becomes more negative [17]. An osmotic adjustment in A. halimus seems to allow plants to develop normally [13, 16]. In A. lampa, the water potential decreased progressively when salinity in the root media increased [18]. This decline in water potential could be controlled by an osmotic D DAVID PUBLISHING