RESEARCH ARTICLE Calcium amendment improved the performance of fragrant rice and reduced metal uptake under cadmium toxicity Adam Sheka Kanu 1,2 & Umair Ashraf 1,3 & Zhaowen Mo 1 & Sabeeh-ur-Rasool Sabir 4 & Idris Baggie 2 & Christen Shaka Charley 2 & Xiangru Tang 1 Received: 8 February 2019 /Accepted: 17 June 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Cadmium (Cd) toxicity has detrimental effects on plant metabolism and yield formation. This study examined the effects of Cd stress in rice and the possible role of calcium (Ca) in mitigating oxidative damage caused by Cd in two fragrant rice cultivars, i.e., Guixiangzhan and Meixiangzhan 2. The experimental treatments were composed of various Ca and Cd levels as individual, i.e., Ca at 2.5 and 5.0 mg/kg soil (Ca1 and Ca2, respectively), Cd at 50 and 100 mg/kg soil (Cd50 and Cd100, respectively), and combined, i.e., Ca1+Cd50, Ca1+Cd100, Ca2+Cd50, and Ca2+Cd100. Plants without Ca and Cd application were taken as control (CK). Results showed that Cd stress led to a substantial decline in the photosynthetic pigments, i.e., Chl a, Chl b, and carotenoids, while enhanced oxidative damage in terms of increased levels of hydrogen peroxide (H 2 O 2 ) and malondialdehyde (MDA) and electrolyte leakage (EL) in both rice cultivars. Moreover, Cd stress hampered the activities of enzymatic antioxidants, i.e., superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with lowest antioxidant activities were recorded at Cd100. The overall trend (lowest to highest) for antioxidant activities across treatments was recorded as Cd100 < Ca2+Cd100 < Cd50 < Ca1+Cd100 < CK < Ca1 < Ca1+Cd50 < Ca2+Cd50 < Ca2. Similarly, Ca amendment improved the proline, soluble pro- tein, and soluble sugar contents in both rice cultivars under Cd stress condition. Comparing Ca2 with CK, the yield and related components, i.e., number of panicles, spikelets per panicle, seed setting rate, 1000 grain weight, and grain yield, were found to increase by 13.08, 2.39, 4.03, 5.86, and 27.53% for Guixiangzhan and 16.48, 5.19, 6.87, 15.44, and 51.16% for Meixiangzhan, respectively. Furthermore, Cd contents in roots, stems, leaves, and grains increased with increased Cd concentration applied and reduced with Ca amendment. The Cd contents in grains for all Ca+Cd levels are statistically at par with each other and significantly lower (P < 0.05) than those for individual Cd application. Hence, Ca amendment can be an appropriate approach to ameliorate the toxic effects of Cd in crops grown under Cd-contaminated soils. Keywords Antioxidant defense . Cadmium . Photosynthetic pigments . Oxidative stress . Rice yield Introduction Heavy metal contamination in agricultural lands poses severe threats to safe food production (Ashraf et al. 2015; Ashraf and Tang 2017). The application of phosphatic fertilizers, mining activities and discharged waste from industries, waste inciner- ation, coal combustion, and mining and production of non- ferrous metals have been recognized as the major sources of toxic metals that are threatening the agroecosystems (Li et al. 2014; Robson et al. 2014). Among the toxic pollutants, cad- mium (Cd) is regarded as one of the main pollutants in rice fields. The continuous accumulation of Cd in the soil and subsequent translocation from roots to different rice organs, i.e., stems, leaves, and grains, could have severe consequences to rice growth, yield, and quality. For example, Cd stress Responsible editor: Elena Maestri * Umair Ashraf umairashraf2056@gmail.com; umair.ashraf@ue.edu.pk * Xiangru Tang tangxr@scau.edu.cn 1 Department of Crop Science and Technology, College of Agriculture, South China Agricultural University, Guangzhou 510642, China 2 Sierra Leone Agricultural Research Institute (SLARI)-Rokupr Agricultural Research Centre (RARC), PMB 1313, Freetown, Sierra Leone 3 Department of Botany, University of Education (Lahore), Faisalabad-Campus, Faisalabad, Punjab 38000, Pakistan 4 State Key Laboratory of Grassland Agroecosystem, School of Life Sciences, Lanzhou University, Lanzhou, China Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-05779-7