Growth responses and ion accumulation in the halophytic legume Prosopis strombulifera are determined by Na₂SO₄ and NaCl

Abstract

Halophytes are potential gene sources for genetic manipulation of economically important crop species. This study addresses the physiological responses of a widespread halophyte, Prosopis strombulifera (Lam.) Benth to salinity. We hypothesised that increasing concentrations of the two major salts present in soils of central Argentina (Na2SO4, NaCl, or their iso-osmotic mixture) would produce distinct physiological responses. We used hydroponically grown P. strombulifera to test this hypothesis, analysing growth parameters, water relations, photosynthetic pigments, cations and anions. These plants showed a halophytic response to NaCl, but strong general inhibition of growth in response to iso-osmotic solutions containing Na2SO4. The explanation for the adaptive success of P. strombulifera in high NaCl conditions seems to be related to a delicate balance between Na(+) accumulation (and its use for osmotic adjustment) and efficient compartmentalisation in vacuoles, the ability of the whole plant to ensure sufficient K(+) supply by maintaining high K(+)/Na(+) discrimination, and maintenance of normal Ca(2+) levels in leaves. The three salt treatments had different effects on the accumulation of ions. Findings in bi-saline-treated plants were of particular interest, where most of the physiological parameters studied showed partial alleviation of SO4(2-)-induced toxicity by Cl(-). Thus, discussions on physiological responses to salinity could be further expanded in a way that more closely mimics natural salt environments.

Growth responses to sulfate and chloride are related to different phytohormone profiles in the halophyte Prosopis strombulifera

“…Plants grown in the presence of Na2SO4 showed immediate and sustained reduction of growth parameters, accompanied by senescence symptoms such as chlorosis, necrosis, and leaf abscission Reginato et al 2014). In this study, root length, shoot height and number of leaves of Na 2 SO 4 -treated plants were also more affected than those in NaCl-treated plants, confirming previous observations on the inhibition and toxicity induced when sulfate anion is present in the medium.…”

“…Atriplex leucoclada had maximum ABA/IAA ratio as well as higher K + /Na + ratio and higher proline and protein contents, while Haloxylon salicornicum and Salicornica verginica had lower K + /Na + ratio, lower ABA/IAA ratio as well as lower proline and protein content (Samiullah and Bano, 2011). In P. strombulifera higher ABA/IAA ratio was observed only in Na 2 SO 4 treated plants, however, no increased K + /Na + ratio or proline and protein content was observed (Reginato et al, 2014;Llanes et al, 2012).…”

“…In the absence of secretory glands, anatomical adaptations of this halophytic plant are related to metabolic changes that result from a complex and accurately tuned physiological regulation involving an improved water uptake, ion compartmentalization and compatible solute synthesis to protect the cytoplasm in high NaCl salinity Reginato et al, 2014), all of which allowed optimum growth at -1.9MPa (500 mM NaCl). These plants showed anatomical and histological differences between control, tolerant, and non-tolerant-treated seedlings, mainly in the speed of tissue differentiation, tissue organization and tannin accumulation (Reinoso et al, 2004).…”

“…ABA levels were much higher in leaves than in roots, probably because of rapid biosynthesis in leaves and transport from roots. Leaves of Na 2 SO 4 -treated plants had the highest ABA levels, associated with sulfate toxicity symptoms (Reginato et al, 2014). In this species, ABA metabolism occurred mainly through conjugation; high levels of ABA-glucose ester (ABA-GE) were accumulated in both roots and leaves in all treatments, whereas levels of hydroxylated metabolites (PA and DPA) were low.…”

Response of two halophyte plants (Nitraria schoberi and Halocnemum strobilaceum) to potassium sulfate under saline condition

“…Previously many studies has been well reported close and positive correlation between antioxidant capacity and crops salinity tolerance (Hernandez et al, 2010, Rezazadeh et al, 2012Reginato et al, 2014b;Hand et al, 2017). Also application of potassium enhances plant vitality under stressful condition by increasing antioxidant levels and reducing ROS production (Cakmak 2005;Devi et al, 2012).…”