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The effects of NaCl and mannitol iso-osmotic stresses on calli issued from sugarcane cultivars (cvs.) R570, CP59-73 and NCo310 were investigated in relation to callus growth, water content, ion and proline concentrations. Callus growth and water content decreased under both stresses with the highest reduction under mannitol-induced osmotic stress. The ion concentration was drastically affected after exposure to NaCl and mannitol. Salt stress induced an increase in Na + and Cl -accumulation and a decrease in K + and Ca 2+ concentrations. Under mannitol-induced osmotic stress, K + and Ca 2+ concentrations decreased significantly while Na + and Cl -concentrations remained unchanged. Free proline accumulation occurred under both stresses and was more marked in stress-sensitive cv. than in stress-resistant one. Our results indicated that the physiological mechanisms operating at the plant cell level in response to salt-and osmotic-induced stress in sugarcane cvs. are different. Among the cvs., we concluded that the stress resistance is closely related to the maintain of an adequate water status and a high level of K + and Ca 2+ under both stresses and a low level of Na + concentration in the presence of NaCl. Thus, sugarcane (Saccharum sp.) can be regarded as a Na + excluder. We also provided evidence that proline accumulation is a stress-sensitive trait rather than a stress resistance marker.

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Stable callus cultures tolerant to NaCl (68 mM) were developed from salt-sensitive sugarcane cultivar CP65-357 by in vitro selection process. The accumulation of both inorganic (Na + , Cl -and K + ) and organic (proline and soluble sugars) solutes was determined in selected and non-selected calli after a NaCl shock in order to evaluate their implication in in vitro salt tolerance of the selected lines. Both salt-tolerant and non-selected calli showed similar relative fresh weight growth in the absence of NaCl. No growth reduction was observed in salt-tolerant calli while a significant reduction about 32% was observed in nonselected ones when both were cultivated on 68 mM NaCl. Accumulation of Na + was similar in both salt-tolerant and non-selected calli in the presence of NaCl. Accumulation of Cl -was lower in NaCl-tolerant than in non-selected calli while proline and soluble sugars were more accumulated in salt-tolerant than in non-selected calli when both were exposed to salt. K + level decreased more severely in non-selected calli than in NaCl-tolerant ones after NaCl shock. The results indicated that K + and Cl -may play a key role in in vitro salt-tolerance in sugarcance cell lines obtained by in vitro selection and that organic solutes could contribute mainly to counteract the negative water potential of the outside medium.

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The following study was conducted to investigate the efficacy of several leaf and berry extracts against a range of food-borne pathogens and food spoilage bacteria. The methanol, ethanol, and ethyl acetate extracts of Myrtus communis leaves and berries were examined for in vitro antibacterial activity. The methanolic leaf extract of M. communis, which was seen to have antibacterial activity against Listeria monocytogenes CECT 4032 and Pseudomonas aeruginosa IH, was further investigated to determine the effect of the extract on viable counts of bacteria using the bacterial cell-death time. Most of the extracts showed relatively high antibacterial activity against most of the tested microorganisms. None of the extracts was active against Escherichia coli K12. The results obtained confirm the antibacterial potential of the extracts of M. communis.

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