Preferential accumulation of D-pinitol in Acrostichum aureum gametophytes in response to salt stress

Abstract

Growth and metabolic responses to salt stress were studied in gametophytes of Acrostichum aureum L. (a mangrove fern). Gametophytes were cultured in 0-170 mM NaCl solutions. The growth of gametophytes was best in low NaCl concentrations (35 and 85 mM), and was retarded at higher NaCl concentrations. Photosynthetic rate of gametophytes was also significantly reduced when grown in high NaCl concentrations. Severe salt stress (>120 mM NaCl) led to a preferential accumulation of D-pinitol in gametophytes, whereas the sporophyte accumulated D-1-O-methyl-muco-inositol. The content of D-pinitol reached up to 50% of the soluble carbohydrate pool of gametophytes under 155 and 170 mM NaCl. The accumulation of D-pinitol and other cyclitols in gametophytes was correlated with the retention of photochemical efficiency of photosystem II and the survival of gametophytes after transfer to solutions containing 340 and 600 mM NaCl, respectively.