Rice is the most important staple food in Asia, and approximately 90% of world rice is produced and consumed in Asia (IRRI, 2002). In Malaysia, the current self-sufficiency level for rice is 73%. Rice is imported from neighboring countries such as Thailand, Vietnam, and India to fulfill demand (MARDI, 2002). Therefore, there is pressure to increase rice production in Malaysia.Nitrogen is one of the major macronutrients and has a vast effect on rice production (De Datta and Buresh, 1989). Deficiency and toxicity of nitrogen in the soil significantly affected growth and development of rice plants. Nitrogen affects meristematic tissues, metabolically active cells and major constituents of proteins, nucleic acids, vitamins, and hormones (Swain and Jagtap, 2010). On the other hand, N-acetyl-cysteine (NAC) is an acetylated cysteine residue that has an optimal thiol redox state that protects cells from oxidative stress. It maintains the biosynthesis of reduced glutathione in cells (Sen, 2001;Jahan et al., 2014). NAC increases glutathione content and maintains the cellular redox state in cells (Schafer and Buettner, 2001), improves performance suggestive of oxidative stress (Reid et al., 1994), and promotes a positive redox balance within the cell (Medved et al., 2003). Therefore, NAC is an effective scavenger of free radicals as well as a major contributor to the maintainance of cellular glutathione status in cells (Kerksick and Willoughby, 2005).Glutathione functions in sulfur metabolism, regulation of growth and development, cell defense, redox signaling, and regulation of gene expression (May et al., 1998); however, it is not limited to the antioxidant activity of GSH in plants (Jahan et al., 2011(Jahan et al., , 2012bKhokon et al., 2011;Okuma et al., 2011). High doses of nitrogen are toxic to the plant cells (Pilbeam and Kirkby, 1992) and may increase osmotic stress and oxidative damage and induce reactive oxygen species in cells. Glutathione may play a fundamental role in reducing oxidative stress (Foyer and Noctor, 2003;Okuma et al., 2011). Therefore, GSH could have an important role in modifying metabolic functions associated with GSH-regulated genes in plants. The Abstract: N-acetylcysteine (NAC) biosynthesized reduced glutathione (GSH), which maintains redox homeostasis in plants under normal and stressful conditions. To justify the effects of NAC on rice production, we measured yield parameters, chlorophyll (Chl) content, minimum Chl fluorescence (Fo), maximum Chl fluorescence (Fm), quantum yield (Fv/Fm), net photosynthesis rate (Pn), photosynthetically active radiation (PAR), and relative water content (RWC). Four treatments, N1G0 (nitrogen (N) with no NAC), N1G1 (N with NAC), N0G0 (no N and no NAC), and N0G1 (no N but with NAC), were arranged in a completely randomized design with five replications. Nitrogen significantly increased yield and yield parameters of rice plants. Moreover, NAC treatment increased panicle numbers, filled grains per panicle, and yield of rice plants. Nitrogen significantly increased...
