Alleviation of phosphorus deficiency stress by moderate salinity in the halophyte Hordeum maritimum L.

Abstract

Hordeum maritimum (Poacea) is a facultative halophyte potentially useful for forage production in saline zones. Here, we assessed whether moderate NaCl-salinity can modify the plant response to phosphorus (P) shortage. Plants were cultivated for 55 days under low or sufficient P supply (5 or 60 lmol plant -1 week -1 KH 2 PO 4 , respectively), with or without 100 mM NaCl. When individually applied, salinity and P deficiency significantly restricted whole-plant growth, with a more marked effect of the latter stress. Plants subjected to P deficiency showed a significant increase in root growth (as length and dry weight) and root/ shoot DW ratio. Enhanced root growth and elongation presumably correspond to the well-known root adaptive response to mineral deficiency. However, leaf relative water content, leaf P concentration, and leaf gas exchange parameters were significantly restricted. The interactive effects of salinity and P deficiency were not added one to another neither on whole plant biomass nor on plant nutrient uptake. Indeed, 100 mM NaCl-addition to P-deficient plants significantly restored the plant growth and improved CO 2 assimilation rate, root growth, K ? /Na ? ratio and leaf proline and soluble sugar concentrations. It also significantly enhanced leaf total antioxidant capacity and leaf anthocyanin concentration. This was associated with significantly lower leaf osmotic potential, leaf Na ? and malondialdehyde (MDA) concentration. Taken together, these results suggest that mild salinity may mitigate the adverse effects of phosphorus deficiency on H. maritimum by notably improving the plant photosynthetic activity, the osmotic adjustment capacity, the selective absorption of K ? over Na ? and antioxidant defence.

Long-distance ABA transport can mediate distal tissue responses by affecting local ABA concentrations

“…For example, averaged across all graft combinations, shoot biomass was reduced 30% by low P and 56% by salt stress, yet the combination of these stresses only decreased shoot biomass by 79% (Figure ). Similar non‐additive effects on whole plant biomass (Zribi et al ) and the relative growth rate of wild and cultivated barley (Zribi et al ) were found under combined salt (100 mmol/L NaCl) stress and P deprivation (5 μM P). Moreover, since individual low P and salt stresses had opposing effects on foliar ABA concentrations, the [ABA] leaf of the plants grown under control conditions and those under combined stress were similar (except in the flc /WT plants), although the combined stress substantially increased the [ABA] root and [ABA] xylem compared with the control plants (Figure ).…”

Nutrients, microbial community structure and functional gene abundance of rhizosphere and bulk soils of halophytes

“…The underlying mechanism may be the halophytes taken up the P from rhizosphere and being P is immobile so high P concentration was observed in bulk soil. Previously, P depleted zone was also observed in the rhizosphere (Liangpeng et al, 2008) and salinity mitigate the adverse effects of P deficiency on halophyte (Zribi et al, 2012). Exchangeable K and Na level was greater in the rhizosphere than those in bulk soil.…”

Seasonal Patterns of Microbial Community Structure and Enzyme Activities in Coastal Saline Soils of Perennial Halophytes

“…Contrary to observation of Shao et al (), available P concentration was also significantly influenced by the halophyte plant species; however, P availability is regulated by soil adsorption rather than biological processes (Marschner, ). The underlying mechanism of high concentration of P under halophyte‐covered soils compared with that in control soil may be due to the higher alkaline phosphatase activity under halophyte‐covered soils, which mineralize the P adsorption, and salinity mitigates the adverse effects of P deficiency on halophyte (Chaudhary et al , ; Zribi et al , ). The Na concentration was low under halophyte‐covered soils than in control soil (Table ) because these halophytes can absorb Na and reduce the concentration in soil (Cao et al , ).…”