The effects of mannitol and salinity stresses on growth and biochemical accumulations in lemon balm

The effects of saline irrigation water and mannitol on the growth and content of essential oil, photosynthetic pigments, soluble sugars, proline, Na, macroelements (N–P–K) and microelements (Mg–Zn–Fe–Mn) of lemon balm (Melissa officinalis L.) plants were investigated. Saline irrigation water decreased certain growth characters (total leaf area, leaf number, and total fresh and dry mass). The photosynthetic pigments (chlorophylls a and b, total carotenoids) and mineral content (N–P–K–Mg–Zn–Fe–Mn) also decreased as saline irrigation water level increased. Saline irrigation water promoted the accumulation of essential oil content and its main components (citronellal, citronellol and geranyl acetate) as well as total soluble sugars, proline and Na+ contents. The plants treated with saline irrigation water × mannitol resulted in higher plant growth, essential oil, total soluble sugars, proline, macro and micronutrient values than those treated with saline irrigation water alone, photosynthetic pigments and Na demonstrated an opposite trend.