Differences in photosynthetic performance and its correlation with growth among tomato cultivars in response to different salts

Previous works into photosynthesis regulation under salt stress have focused on the effect of NaCl, although other salts may significantly contribute to the toxicity of saline soils. In this paper, the effects of different salt sources (NaCl, Na2SO4, MgCl2 and MgSO4) on photosynthesis and vegetative growth in three tomato (Solanum lycopersicum L.) cultivars (Marmande RAF, Leader and Daniela) are presented. Differences were found in the net photosynthetic rate and vegetative growth among the studied cultivars and salinity treatments. Cultivar photosynthetic performance related not only to capability for toxic ion exclusion, but also to the maintenance of appropriate essential macronutrient concentrations in leaves. In addition, the role of metabolic and diffusion limitations in regulating photosynthesis varied depending on the studied genotypes. These data, along with variation in biomass and ion distribution in leaves and roots, show that distinct tomato cultivars can address salt tolerance differently, which should be considered when designing strategies to overcome plant sensitivity to salt stress.

► Photosynthesis and growth were more affected by Na2SO4, MgCl2 and MgSO4 than by NaCl.
► Photosynthetic limitations under salt stress were cultivar-dependent.
► Salinity differentially affected photo-assimilate utilisation among tomato cultivars.
► Salt tolerance has been related to toxic ion exclusion and macroelement homeostasis.