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

FIEDOROWICZ KOWAL R.; ARIAS NS; ASKENAZI J; IOGNA PA; PEREYRA D; SCHOLZ FG; BUCCI SJ.

Congreso; Brazilian Congress of Plant Physiology; 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Œ33S y 66‹32Œ13W). Soil osmotic potential (pS) was determined at 10-30-50 and 70cm. We determined in both sites: midday leaf water potential (YL), xylem osmotic potential pX, osmotic potential at turgor loss point (ptlp), 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 pS 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 YL, (-3.5}1.04MPa) than plants in high marsh portion (-6.18}0.46MPa). Consistent with this, ptlp was also more negative in this site; however this decrease was not enough to avoid turgor lost at midday. The pX-pS 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 in seaward site (3.13x10-3 and 9.89x10-4 mol 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.