55 Indian Journal of Agricultural Sciences 90 (3): 507–12, March 2020/Article https://doi.org/10.56093/ijas.v90i3.101458 Soil moisture defcit induced changes in antioxidative defense mechanism of sugarcane (Saccharum offcinarum) varieties differing in maturity POOJA*, A S NANDWAL, MEHAR CHAND, AJAY PAL, ANITA KUMARI, BABITA RANI, VISHAL GOEL and NEERAJ KULSHRESHTHA CCS Haryana Agricultural University, Hisar, Haryana 125 004, India Received: 25 June 2018; Accepted: 15 July 2019 ABSTRACT A split plot experiment was conducted at Regional Research Station, CCS HAU, Uchani, Karnal during 2014–15 and 2015–16 to investigate the effect of different soil moisture regimes on antioxidative defense mechanism of sugarcane (Saccharum offcinarum L.) varieties. The experiment consisted of three moisture regimes based on available soil moisture i.e. irrigation at 50% ASM, 40% ASM and 30% ASM in main plot and four commercial sugarcane varieties, i.e. CoS 767, CoH 128, CoJ 64 and Co 0238 in sub plot with three replications. The observations recorded on antioxidative defense system have suggested possible key characteristics of drought tolerance. Low ASM levels induced the antioxidative defense system by increasing ROS and the specifc activities of antioxidative enzymes, viz. peroxidase, catalase and ascorbate peroxidase. Specifc activity of these enzymes increased in varieties Co 0238 and CoS 767 at 60 and 90 DAP. Severe stress of 30% ASM levels also resulted in a sharp rise in total ascorbic acid content (9.36 to 13.14 mg/g), total soluble proteins (from 9.6 to 13.77 mg/g), and the increase was more in varieties Co 0238 and CoS 767. A gradual decrease was observed in all the parameters after stress revival (120 DAP). ASM levels 30% and 40% signifcantly reduced K + content in leaves (2.93 to 1.83%) as compared to 50% ASM level. So, it might be concluded from this study that biochemical traits had a signifcant varietal variation, indicating that these parameters could be used as screening criteria for selecting the tolerant and sensitive cultivars exposed to water limiting stress. Key words: Antioxidants, Antioxidative enzymes, Available soil moisture, ROS, Sugarcane *Corresponding author e-mail: poojadhansu@gmail.com Sugarcane ( Saccharum officinarum L.), a crop of worldwide economic importance, accounts for approximately 75% of the global sugar production. Being a high water demanding crop, sugarcane has necessitated the need to evolve drought tolerant varieties to sustain sugarcane production (Pooja et al. 2019a, b). Water is the major constituent of cane and approximately 2.97 lakh ha of cane area is prone to drought, affecting the crop at one or other stage of growth in every state of India (Vision SBI 2030). Water stress like other abiotic stresses elicits a complex of responses, which is associated with increased oxidative stress due to the enhanced production of ROS, particularly O 2 •− and H 2 O 2 (Rani et al. 2018). Increased ROS cause damage to various cellular mechanisms, such as enzyme inhibition, protein degradation, DNA/RNA damage, and membrane lipid peroxidation, thus, inhibiting growth and yield which ultimately culminate in cell death (Ishikawa et al. 2010). The equilibrium between the production and scavenging of ROS is commonly known as redox homeostasis. However, when ROS production overwhelms the cellular scavenging capacity, plants initiated their antioxidant mechanisms for scavenging the excess ROS and prevent damages to cells (Mann et al. 2015, 2019). Plants have developed ROS scavenging mechanism, which is categorized as enzymatic and non-enzymatic defense system. Enzymatic system includes superoxide dismutase (SOD), a metalloenzyme catalyzes the dismutation of O 2 - radical to molecular O 2 and H 2 O 2 . The H 2 O 2 is then detoxifed either by catalase (CAT)/peroxidase (POX) or in ascorbate glutathione cycle which involves oxidation and reduction of ascorbate and glutathione through ascorbate peroxidase (APX) and glutathione reductase (GR) action (Noctor and Foyer 1998), and correlate with enhanced cellular protection (Asada 2006, Duan et al. 2012). Keeping in view the burning problem of global warming which may result into yield loss, the present investigation was proposed to understand how plants tolerate water defcit and identifying mechanisms of tolerance in terms of antioxidant potential (Nepomuceno et al. 2001). It is therefore important to understand the response of sugarcane varieties differing in their maturity to water stress and its revival with main emphasis on the role of antioxidants and antioxidative enzymes in imparting tolerance to sugarcane crop. MATERIALS AND METHODS Present study was carried out on four commercial