Drought stress has detrimental effects on growth and yield of plants under arid or semi-arid environment. Because of their potential for modulating the redox status and changing the growth, performance and quality of plants, nano-scale materials are among the research interests of physiologists. This study evaluated the impacts of different concentrations (0, 10, 100, and 500 mg l-1) of nanosized (10–25 nm) titanium dioxide (TiO2) on growth, seed yield, photosynthetic pigment contents, the values of hydrogen peroxide (H2O2) and malondialdehyde (MDA), seed oil, and protein contents in Linum usitatissimum Linea (Linaceae) under sufficient and scarce water conditions. The results showed that application of nanoscale TiO2 at low concentration better improved the morphological and physiological traits of plant compared to other doses particularly under water scare conditions, leading to better plant performance. Enhanced chlorophyll and carotenoids contents were recorded in leaves of nano-anatase TiO2-treated plants under both normal and drought stress conditions, when compared to the control. The levels of H2O2 and MDA in plants exposed to nano TiO2 at 10 mgl-1 were lower than that of other treatments, therefore, lipid peroxidation was less pronounced in such plants. In both well watered and drought stress conditions, the highest values of seed oil and protein contents were obtained in plants treated with nano TiO2 at 100 mg l-1. Therefore, exogenous application of nano TiO2 particles at appropriate concentrations can ameliorate drought stress damage to Flax seed plants as well as increase the drought tolerance with remarkable improvement in physiological process.
