NaCl Responses in Tomato Calli and Whole Plants

Abstract

Summary The comparative salt responses between calli and whole plants were studied in the cultivated tomato species ( L. esculentum Mill.) and its wild salt-tolerant relative L. pennellii (Correll) DArcy. Based on the reduction in both the callus relative growth rate and plant growth, L. pennellii was more salt-tolerant than L. esculentum , which indicates a positive correlation between the salt responses at both organizational levels. The changes induced by salinity in water contents and osmotic potential (ψ s ) were different in calli (initiated from leaves) and in leaves of whole plants. In calli, both the water contents and ψ s decreased with salinity in the two tomato species, with the reductions being higher in the salt-treated calli of L. esculentum than in those of L. pennellii . In contrast to the callus response, the leaf water contents increased with salinity in both species, especially in the wild species. Moreover, a higher ψ s reduction as well as a higher solute contribution to the osmotic adjustment were observed in NaCl-treated leaves of L. pennellii than in those of L. esculentum . In both species, the accumulation patterns of Na + were quite similar in calli and leaves when the contents were calculated on a dry weight basis, with the Na + accumulation being greater in the wild species. However, the Na + accumulation was even slightly higher in salt-treated calli of L. esculentum when the contents were calculated on a tissue water basis. The different physiological responses found at both organizational levels were due to the different water uptake capacities of calli and leaves in saline medium; thus, the higher ψ s reduction and the higher Na + accumulation found in the L. esculentum calli were related to the higher callus dehydration by salinity, which did not occur in leaves of whole plants. Notwithstanding, the higher K + levels as well as the higher K + /Na + selectivity were shown at both organizational levels, although the greatest differences were found at the whole plant level.