Trehalose-induced metabolic responses in basil (Ocimum basilicum) seedlings under salt treatment

Trehalose (Tre) is an osmoprotectant known to be an important player in regulating response to salinity. In this research, the effect of Tre foliar application on the growth rate, the content of photosynthetic pigments, accumulation of metabolites, and activity of antioxidant enzymes of basil seedlings under salt stress has been investigated. Basil seedlings were factorially treated twice a week with levels of 0, 25, 50, 100, and 150 mM NaCl and weekly with concentrations of 0 and 5 mM Tre for 4 weeks. Growth characteristics, the content of photosynthetic pigments including chlorophyll and carotenoid, and starch content decreased in response to salt stress, while the activity of antioxidant enzymes and the accumulation of metabolites including soluble sugars, proteins, amino acids, and proline increased. Tre treatment caused severe inhibition of plant growth, further reduction of photosynthetic pigments, and amount of soluble proteins during salinity stress. Also, starch, total protein, amino acids, and proline were hyperaccumulated in response to Tre. These results indicate that Tre not only does not reduce the detrimental effects of salinity in basil seedlings but also inhibits plant growth possibly by diverting carbon to other metabolic pathways.