BIODIVERSITAS ISSN: 1412-033X Volume 22, Number 6, June 2021 E-ISSN: 2085-4722 Pages: 3083-3091 DOI: 10.13057/biodiv/d220611 The effect of magnetized seawater on physiological and biochemical properties of different rice cultivars EKRIS SUTIYANTI, DIAH RACHMAWATI  Laboratory of Plant Physiology, Department of Tropical Biology, Faculty of Biology, Universitas Gadjah Mada. Jl. Teknika Selatan, Sekip Utara, Sleman 55281, Yogyakarta, Indonesia. Tel. +62-274-580839,  email: drachmawati@ugm.ac.id Manuscript received: 20 March 2021. Revision accepted: 8 May 2021. Abstract. Sutiyanti E, Rachmawati D. 2021. The effect of magnetized seawater on physiological and biochemical properties of different rice cultivars. Biodiversitas 22: 3083-3091. Seawater is an alternative source to overcome the reduced availability of freshwater in agricultural practices. However, seawater cannot be used directly because it has high salinity that causes various disturbances in plant growth and development. Magnetic field treatment can be used for seawater desalination. The objective of this study was to analyze the potential of magnetized seawater for agricultural irrigation by observing the effect of magnetized seawater on physiological and biochemical properties of different rice cultivars. This research was conducted in a Completely Randomized Design (CRD) with 3 research factors, which were 2 rice cultivars (IR 64 and Inpari 35), 2 levels of salinity (0 and 10 dS m -1 ), and 4 types of magnetic treatment (0 untreated with magnetic device, 1, 2 and 3 cycles treated with magnetic device). Variables including plant growth (plant height, fresh weight and dry weight), physiological characters (chlorophyll content, carotenoid content, membrane stability index, relative water content, proline content) and biochemical properties (superoxide dismutase, malondialdehyde, H2O2 and anthocyanin content) were observed. Magnetized seawater 3 cycles enhanced growth, physiology and biochemical parameters of IR 64 and Inpari 35 in 0 and 10 dS m -1 level salinity with decreasing level salinity of water to minimize effect of salinity. The effect of magnetized seawater treatment is more visible to increase the growth of IR 64 rice plants. Keywords: Inpari 35, IR 64, magnetized water, rice, seawater INTRODUCTION Available freshwater on earth is less than 1% which 70% of it is used for agricultural sector (IWCA 2018) and the increasing population causes a decrease in freshwater availability. An alternative that can be used to overcome the lack of freshwater availability in the agricultural sector is by replacing freshwater with another source of water like seawater (Yermiyahu et al. 2007). However, the salinity of seawater in Java generally ranges from 30-35 ‰ (Bahiyah et al. 2019). The range of surface temperature in seawater is between 25°C-31°C with the pH ranges from 7.5 to 8.5 (Hamuna et al. 2018). Seawater is the largest source of water on earth, i.e., 97%. Seawater contains nutrients, trace elements, and microorganisms that are beneficial for plants (Atzori et al. 2019). But, seawater has high salinity levels cause toxicity to plants. High salinity level can affect the absorption and assimilation of minerals, enzyme activity, photosynthesis, protein expression, and hormone metabolism in plants. These result in reduced leaf area, necrosis, abrasion, disruption of the ionic balance which leads to decreased water content and oxidation damage due to the accumulation of reactive oxygen species (ROS) (Ahanger and Agarwal 2017). Salinity stress in plants affects the absorption and metabolism of essential elements such as N, P, K, S, and Ca leading to changes in photosynthetic efficiency and salinity tolerance mechanisms. Plants carry out tolerance mechanisms by regulating the antioxidant system, osmolytes, and accumulation of secondary metabolites. The use of magnetized water can be used to reduce the salinity of water. Based on this, the use of conjugative seawater with fresh water can be used as an alternative for irrigation water in the agricultural sector (Li et al. 2019). Magnetized water is water that is treated with a magnetic field or magnetic water device. Liu et al (2019) reported that giving magnetized water treatment affects soil pH and increases the availability of nutrients (Ca, Mg, P, and Na) in the soil. Irrigation with magnetized water is useful to maintain the homeostasis of various salt ions by lowering the Na + ion content, increasing the Ca 2+ content and the K + / Na + ratio causing increased adaptation of plants to environments with salinity (Dhawi 2013). Therefore, the salinity of seawater can be reduced using magnetized water which can then be used in the agricultural sector. According to Ali et al (2014), magnetized water decreases the hydration of salt ions, increases the mobility of nutrients in the soil, improves the effectiveness of fertilizers, and increases the availability and absorption of N, P, K, Fe, and Zn in plants. Alikamanoglu and Sen (2011) also reported that magnetized water increases soil microbial content and plant resistance to unfavorable environments. Therefore, magnetic treatment for irrigation water could be one of the encouraging ways in the future to enhance agricultural production in response to climate change (Abobatta 2019). Rice is the largest staple food commodity in Indonesia. Rice productivity decreases due to problems in the planting process, such as drought and salinity stress. Symptoms of