Response of potato species to salt and osmotic stress in vitro and the role of acetylsalicylic acid: non-enzymatic antioxidants

In a series of experiment, the response of two contrasting potato species, namely, Solanum acaule (tolerant) and Solanum tuberosum cv. Agria (intolerant) to salt (80 mM NaCl) and drought stress (15% polyethylene glycol; PEG) was studied in vitro. Furthermore, the role of acetyl salicylic acid (ASA) (1 and 10 µM) in alleviating oxidative stress was investigated. In Agria cultivar, NaCl and PEG reduced shoot dry weight, carotenoids, phenolics, anthocyanins, flavonoids, ascorbate and glutathione pool, proline dehydrogenase (ProDH) and phenylalanine ammonia-lyase (PAL) activity. NaCl and PEG also increased proline content, malondialdehyde (MDA) level and the activity of ?1-pyrroline-5-carboxylate synthetase (P5CS) and the effect of PEG was more severe. In S. acaule, on the contrary, NaCl had no effect on shoot dry weight and MDA, but increased the contents of carotenoids, phenolics, anthocyanins, flavonoids, ascorbate and glutathione pool as well as the activity of P5CS and PAL and proline content. However, the response of this species to PEG was different from that of NaCl and reductions in shoot dry weight and in most antioxidants and an increase in MDA were observed. ASA, especially 1 µM, profoundly improved plant performance in both species and under both types of stress via increasing the PAL and P5CS activity and most non-enzymatic antioxidants contents and decreasing ProDH activity.