Salinity effects on water relations of Sarcocornia perennis in Patagonian sea coast marshes.

FIEDOROWICZ KOWAL RUTH; ARIAS, NADIA; ASKENAZI, JAVIER; IOGNA, PATRICIA; PEREYRA, DANIEL; PESCHIUTTA, MARIA L.; SCHOLZ, FABIAN G.; BUCCI, SANDRA J.

Buzios

Congreso; XIII Congresso Brasileiro de Fisiologia Vegetal, XIV Reuniao Latino-Americana de Fisiologia Vegetal; 2011

Salt marsh ecosystems are characterized by a high primary productivity, despite the constant stress conditions they are subjected to like deficit of water and excess of salinity. Physiological and chemical changes often  occur,  within  the  plants,  to  minimize  damage  from  changing environment  conditions.  Sarcocornia  species  (Chenopodiaceae) are  obligate  halophytes  found  generally  in  sea  coast  marshes.  We evaluated  morfo-physiological  changes  of  Sarcocornia  perennis between seaward (low marsh) and landward (high marsh) portion of Bahia  Bustamante  marsh  (45° 07´ 33´´ S  y  66° 32´ 13´´ W).  Soil  osmotic potential (øs) was determined at 10-30-50 and 70cm. We determined in both sites: midday leaf water potential (øL), xylem osmotic potential øx, osmotic potential at turgor loss point (øTLP), Leaf area index(LAI) and  chlorophyll  content. Soil  osmotic  potential  in  the  0-70cm  soil layer  was  higher  in  low  marsh  than  in  high  marsh  (-1.96MPa  and -2.31MPa respectively). These differences in øs between  sites  were more pronounced at 10cm depth (-2.5MPa and -1.4MPa in high and low marsh respectively). Low marsh site showed higher LAI than high marsh site (1.81±0.66 m2 m-2 and 0.63±0.32m2 m-2 respectively). Plants in  low  marsh  portion  presented  a  higher øL,  (-3.5±1.04MPa)  than plants in high marsh portion (-6.18±0.46MPa). Consistent with this, øTLP was also more negative in this site; however this decrease was not enough to avoid turgor lost at midday. The øx-øs gradient was lower in low marsh (-1.06MPa and 0.6MPa respectively) than in high marsh (0.94MPa and 1.44MPa respectively). Chlorophyll a and b contents were lower in S. perennis in landward site (7.59x10-4 and 2.36x10-4mol L-1 respectively) than in plants inseaward site (3.13x10-3 and 9.89x10-4mol L-1 respectively).  These results suggest that plants from the high marsh have better salt exclusion mechanisms at the roots but they need  to  produce  compatible  solutes  to  decrease  water  potential  to continue up taking water from a more saline soil. The lower LAI in high marsh  could  be  consequence  of  lower  chlorophyll  content  in  addition of higher energetic cost to develop osmotic adjustment in detriment of growth rate.