SALT-RESPONSES IN LYCOPERSICON-ESCULENTUM CALLI AND WHOLE PLANTS

NaCl response to growth, organic and inorganic solute contents, and N-assimilation enzyme activities were compared in Lycopersicon esculentum cv. St. Pierre whole plants (28-day-old vitroplants cultured in vitro) and their corresponding calli (28-day-old calli from leaves, stems and roots). Relative growth rates of calli from roots increased on 25-50 mM NaCl media, while vitroplant root biomass decreased; conversely, plant shoot biomass increased on 25-50 mM NaCl media, while the growth rate of corresponding calli decreased. Taking into account the solute contents of apoplasm, which decreased under saline conditions, the three types of calli accumulated similar quantities of Na, Ca and Mg. Translocations of Na, Ca and P were not altered in vitroplants while Cl, Mg or N translocations, on the one hand, and K translocation, on the other hand, respectively decreased and increased in shoots. Contrary to organic acid levels (whose succinate was the major organic acid in vitroplants and calli), evolution of total soluble sugar, reducing sugar, total amino acids and free proline contents was similar in calli and vitroplants. Changes in enzyme activities of calli were found as a function of the starting material: NRase activity of calli from leaves were 40-fold lower than NRase of calli from roots. Under saline stress, NRase activity did not change irrespective of the type of calli, while GS and NiRase decreased in all tissues, and GOGAT decreased more in sensitive tissues of calli from stems and leaves. Decreasing NRase and NiRase and increasing GS activities were found in vitroplants shoots; conversely, increasing NRase and decreasing GS activities were found in roots. Cellular and whole plant organization bases for salt tolerance were discussed, comparing callus and vitroplant physiologies under saline stress.