Effects of oxidative stress caused by NaCl or Na₂SO₄ excess on lipoic acid and tocopherols in Genovese and Fine basil (Ocimum basilicum)

Abstract

With this investigation, we aimed to study more deeply the antioxidative response to moderate doses of NaCl or Na 2 SO 4 in two cultivars of basil differentially sensitive to salinity. Tolerance to salinity was previously evaluated by the extent of growth inhibition whereas the antioxidant response was assessed studying the changes in the activities of superoxide dismutase (SOD) and catalase as well as in the amounts of tocopherols and lipoic acid. To make possible the comparison of the responses of basil cv. Genovese and cv. Fine to different salts, the experiment was carried out with equimolar concentrations of Na + . The results showed that changes caused by salinity were dependent on cultivar and exposure time. In particular, cv. Genovese was more sensitive to Na 2 SO 4 excess than cv. Fine whereas both of them had higher SOD activity under NaCl salinity. Generally, Fine basil withstood salinity better than Genovese, being endowed with higher constitutive levels of reduced lipoic acid [dihydrolipoic acid (DHLA)] as well as of αand γ -tocopherols. Moreover, cv. Fine showed the ability to utilise DHLA and to synthesise tocopherols during stressful conditions. Thus, more than one mechanism was involved in basil in the detoxification of reactive oxygen species during salt stress. In fact, when lipoic acid did not participate in the regeneration of reduced ascorbate and glutathione form, high amounts of tocopherols were present, likely protecting cell membranes from oxidative damage and making basil tolerant to moderate salinity.

Lipoic acid mitigates oxidative stress and recovers metabolic distortions in salt‐stressed wheat seedlings by modulating ion homeostasis, the osmo‐regulator level and antioxidant system

“…Previous studies have provided evidence that, in animals, LA application restored reduced levels of the antioxidant substances such as AsA and GSH . Up to date, only a few studies have been reported exhibiting the relationship between endogenous levels of LA/DHLA and the other antioxidant substances in plants . We found that salt stress had an important effect on the contents of total AsA and GSH, and levels of their reduced (AsA and GSH) and oxidised (DHA and GSSG) forms.…”

Leaf sodium accumulation facilitates salt stress adaptation and preserves photosystem functionality in salt stressed Ocimum basilicum

“…This tolerance has been earlier attributed to a smaller leaf biomass combined with reduced stomatal density , both of which would contribute to reduced transpiration under saline stress (James et al, 2002). Salt stress tolerance of GEN plants was also documented by Tarchoune et al (2013), who reported no change in shoot fresh weight after 15 days of 50 mM NaCl treatment. The reduction of leaf area, along with the decrease of SLA in salt-treated plants was already visible in the first stages of stress at 13 DAST (Table 1), confirming that the reduction of cell expansion and cell division is an early response to salt stress (Munns, 2002;Ruggiero et al, 2004).…”

Salinity effect on nutritional value, chemical composition and bioactive compounds content of Cichorium spinosum L.

“…Similar amounts of a-tocopherol in C. spinosum have been reported by Vardavas et al (2006), although they also detected c-tocopherol which was not the case in our study. Moreover, Tarchoune et al (2013) reported that tocopherol biosynthesis under stressful conditions is involved in mechanisms responsible for the detoxification of ROS in mildly salt tolerant species such as basil.…”