ORIGINAL ARTICLE Effect of salinity and waterlogging on growth, anatomical and antioxidative responses in Mentha aquatica L. Bahareh Sadat Haddadi 1 • Halimeh Hassanpour 2 • Vahid Niknam 1 Received: 5 August 2015 / Revised: 31 March 2016 / Accepted: 8 April 2016 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2016 Abstract Salinity and waterlogging are two stresses which in nature often occur simultaneously. In this work, effects of combined waterlogging and salinity stresses are studied on the anatomical alteration, changes of enzy- matic antioxidant system and lipid peroxidation in Mentha aquatica L. plants. Seedlings were cultured in half- strength Hoagland medium 50 days after sowing, and were treated under combination of three waterlogging levels (well drained, moderately drained and waterlog- ging) and NaCl (0, 50, 100, 150 mM) for 30 days. Moderately drained and waterlogging conditions induced differently aerenchyma formation in roots of M. aquatica salt-treated and untreated plants. Moreover, stele diameter and endodermis layer were also affected by salt stress and waterlogging. Salt stress significantly decreased growth, relative water content (RWC), protein level, catalase (CAT) and polyphenol oxidase (PPO) activities, and increased proline content, MDA content, H 2 O 2 level and activities of superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX). Waterlogging in salt-untreated plants increased significantly growth parameters, RWC, protein content, antioxidant enzyme activity, and decreased proline content, H 2 O 2 and MDA levels. In salt-treated plant, waterlogging caused strong induction of antioxidant enzymes activities especially at severe stress condition. These results suggest M. aquatica is a waterlogging tolerant plant due to significant increase of antioxidant activity, membrane stability and growth under water stress. High antioxidant capacity under waterlogging can be a protective strategy against oxida- tive damage, and help to salt stress alleviation. Keywords Waterlogging Á Salt stress Á Mentha aquatica Á Antioxidant activity Á Growth Abbreviations ROS Reactive oxygen species TCA Trichloroacetic acid TBA Thiobarbituric acid MTT 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide Introduction Salinity stress limits growth and production of major crops by ionic stress, osmotic imbalance and high production of reactive oxygen species (ROS) such as hydrogen peroxide (H 2 O 2 ), superoxide and hydroxyl radical (Aghaleh et al. 2009; Khedr et al. 2003). The ROS substances are harmful to cellular proteins and lipids (Golldack et al. 2014; Miller et al. 2010). To counteract ROS, plants can up regulate their antioxidative enzymes and non-enzymatic antioxi- dants (Ashraf 2009; Kachout et al. 2013). Communicated by U Feller. & Halimeh Hassanpour hassanpour@ari.ac.ir & Vahid Niknam vniknam@khayam.ut.ac.ir 1 School of Biology, College of Science, Center of Excellence in Phylogeny of Living Organisms in Iran, University of Tehran, Tehran, Iran 2 Aerospace Research Institute, Ministry of Science Research and Technology, Tehran 14665-834, Iran 123 Acta Physiol Plant (2016) 38:119 DOI 10.1007/s11738-016-2137-3