Application of chlorophyll fluorescence for the diagnosis of salt stress in tomato "Solanum lycopersicum (variety Rio Grande)"

To study the response of tomato (Solanum lycopersicum cv. Rio Grande) to salinity, the effect on plant growth, water relations, stomatal conductance and Chlorophyll fluorescence was investigated. Tomato plants were grown in peat Culture under controlled conditions and submitted during 28 days to saline stress ranging from 0 to 25, 50, 100, 150 and 200 mM of NaCl. At the end of the experiment period, plant growth was significantly decreased with increasing salinity. During the three weeks following the application or NaCl, stomatal conductance (g,) and water potential (psi(w)) decreased gradually with the increase of salinity. Indeed, salinity treatment showed no changes in all chlorophyll fluorescence parameters. In the fourth week, the water potential and stomatal conductance decreased significantly. PSII photochemistry in light-adapted leaves was modified in salinity-stressed plants: while in dark-adapted leaves, there were no changes in the maximum quantum efficiency of the PSII photochemistry. The strong correlations between the foliar content of Na(+) and Chl a fluorescence characteristics (the actual PSII efficiency (Phi(PSII)), the photochemical quenching (q(p)), the non photochemical quenching (NPQ), and the linear electron transport rate (ETR)) suggest that these parameters can be used to screen genotypes for salt tolerance. (C) 2008 Elsevier B.V. All rights reserved.