Comparison of the response of ion distribution in the tissues and cells of the succulent plants Aloe vera and Salicornia europaea to saline stress

Abstract

There exists a great variability among plant species regarding their sensitivity and resistance to high salinity in soil, and most often this variability is related with the ability of a particular plant species to regulate ion homeostasis and transport. In this study, we have investigated the effects of NaCl on growth rate, water status, and ion distribution in different cells and tissues of two succulent plants, Aloe vera and Salicornia europaea. Our results showed that the growth of A. vera seedlings was significantly decreased in response to salinity. However, the growth of S. europaea seedlings was greatly stimulated by high concentrations of NaCl. Under saline conditions, S. europaea seedlings maintained K + and Ca 2+ uptake in roots and showed a higher root-toshoot flux of Na + and Cl -as compared to A. vera. Despite great accumulation of Na + and Cl -in photosynthetically active shoot cells in S. europaea, its growth was enhanced, indicating S. europaea is capable of compartmentalizing salt ions in the vacuoles of shoot cells. Aloe vera seedlings, however, showed a low transport rate of Na + and Cl -to leaves and suppressed uptake of K + and Ca 2+ in roots during NaCl treatment. Our results also implicate that A. vera may be able to accumulate Na + and Cl -in the metabolically inactive aqueous cells in leaves and, as a result, the plant can survive and can maintain growth under saline conditions.

Overexpression of Arabidopsis thaliana Na+/H+ antiporter gene enhanced salt resistance in transgenic poplar (Populus × euramericana ‘Neva’)

“…might be sequestrated into vacuoles by overexpression of AtNHX1. Growth inhibition by salinity is widely reported in most species, and can be attributed to the consequence of specific ion toxicity, ion imbalance or ion homeostasis disturbance (Sultana et al 1999;Zhao et al 2007;Zheng et al 2009). External high salinity induced accumulation of Na ?…”

“…Salinity interferes with growth almost in all plants, but their resistant levels and growth rate decrease at high salt concentration vary widely among different plants. Generally, salt stress reduces water potential, impairs cell metabolism and photosynthesis, causes ion imbalance or disturbances in ion homeostasis, and also leads to ion toxicity, which inhibits enzymatic functions of key biological processes (Kramer 1983;Zheng et al 2009). …”

“…Among different mechanisms of salt resistance, intracellular compartmentalization, intended for keeping toxic ions away from cytoplasm, involves an energy-dependent transport of ions into the vacuole (Glenn and Brown 1999;Zheng et al 2009). The ability to compartmentalize Na ?…”

Seawater‐irrigation effects on growth, ion concentration, and photosynthesis of transgenic poplar overexpressing the Na+/H+ antiporter AtNHX1

“…6A-6C) was higher in the roots, stems, and leaves of TR than WT. Superior K + retention would be beneficial under salt stress, since it would permit the maintenance of osmotic balance without the need for uptake and vacuolar accumulation of Na + and its concomitant cytoplasmic intoxication (Bayuelo-Jiménez et al, 2003;Rodríguez-Rosales et al, 2008;Zheng et al, 2009). High K + concentration in leaves maintains steady-state leaf photosynthetic rates and stomatal conductance (Bayuelo-Jiménez et al, 2003).…”

“…Moreover, the saline soil area is being accompanied increasingly by environmental pollution, unreasonable irrigation, and excessive application of chemical fertilizers (Lu et al, 2008). Thus, salinity, which is one of the major factors that limit plant growth and yield, is becoming an increasingly serious problem around the world (Munns, 2002;Zheng et al, 2009). The selection of salt-resistant crops for seawater irrigation and comprehension of plant adaptation mechanisms to saline stress has become imperative (Netondo et al, 2004).…”