Proline accumulation in salt‐treated tomato: Different proline precursors in lycopersicon esculentum and lycopersicon pennellii

Abstract

Proline levels were measured in leaf discs of the salt sensitive Lycopersicon esculentum (Mill) cv P‐73 and the salt tolerant L. pennellii (Correll), D'Arcy, accession PE 47. Proline accumulation constitutes an index of NaCl sensitivity: when submitted for 8 h to 100 mM NaCl, the excised leaves of the salt‐sensitive tomato accumulated the highest proline content, through a light‐dependent process. Arginine, asparagine, ornithine (in the light) and glutamate (under darkness) were proline precursors in L. esculentum leaf discs; arginine (under darkness), asparagine, glutamine and glutamate (both in the dark or in the light) were proline precursors in L. pennellii. In L. pennellii, the addition of NaCl to the incubation media did not modify the proline accumulation occurring in control leaves; conversely, in L. esculentum, NaCl induced or activated light and dark reactions involving the overall nitrogen (N)‐sources.