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Boscaiu M.,Instituto Agroforestal Mediterraneo UPV | Ballesteros G.,Instituto Agroforestal Mediterraneo UPV | Naranjo M.A.,Polytechnic University of Valencia | Vicente O.,Polytechnic University of Valencia | Boira H.,Instituto Agroforestal Mediterraneo UPV
Plant Biosystems | Year: 2011

Responses to increasing salinity, during seed germination and vegetative plant growth, were studied in two related species of Juncus, J. maritimus and J. acutus. In both species, germination was optimal in the absence of salt, reduced by about 50% in the presence of 200 mM NaCl, and completely inhibited by NaCl concentrations above 300 mM. Previous exposure of the seeds to salt, up to 500 mM NaCl, did not affect the germination capacity in J. acutus, and clearly enhanced it in J. maritimus. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl for both species, together with the parallel accumulation of sodium ions in the leaves, as determined by cation exchange HPLC. Regarding the levels of divalent cations, in J. acutus Ca 2+ and Mg 2+ increased up to about two-fold in plants treated with 500 mM NaCl, as compared to control plants, whereas in J. maritimus they were three- to four-fold higher than in J. acutus in the absence of salt, and did not change significantly with increasing NaCl concentrations. These results suggest that Ca 2+ and Mg 2+ participate in defence mechanisms against salt stress, which would be constitutive in J. maritimus and salt-inducible in J. acutus. © 2011 Società Botanica Italiana.

Grigore M.N.,Polytechnic University of Valencia | Grigore M.N.,Al. I. Cuza University | Boscaiu M.,Instituto Agroforestal Mediterraneo UPV | Llinares J.,Polytechnic University of Valencia | Vicente O.,Polytechnic University of Valencia
Notulae Botanicae Horti Agrobotanici Cluj-Napoca | Year: 2012

In Plantago crassifolia, a moderate halophyte characteristic of borders of salt marshes in the Mediterranean region, reproductive development is more sensitive to high soil salinity than vegetative growth. To investigate the possible role of calcium and magnesium salts in the responses of this species to salt stress, adult plants were submitted over a 2-month period to treatments with 300 mM NaCl-a concentration which affects, but does not completely inhibit seed formation in P. crassifolia-either alone or combined with low concentrations of CaCl2 (10 mM) or MgCl2 (20 mM). The NaCl treatment did not affect plant vegetative growth and had a stimulating effect on flowering. Yet almost half the spikes produced had aborted seeds, and the effect on seed number and quality-estimated by their mean weight and germination capacity-was obviously deleterious. Addition of calcium or magnesium chloride during the salt-stress treatment completely counteracted the negative effect of NaCl on the 'reproductive success' of the plants: the number, weight and germination frequency of the seeds were similar to that in the control, non-stressed plants. These results indicate that both divalent cations can suppress or mitigate the deleterious effects of salt stress. While this protective role is well established in the case of calcium, we provide here the first experimental evidence of a similar function for magnesium.

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