ORIGINAL ARTICLE Role of foliar application of sulfur-containing compounds on maize (Zea mays L. var. Malka and hybrid DTC) under salt stress Shagufta Perveen 1 • Naeem Iqbal 1 • Muhammad Saeed 1 • Sara Zafar 1 • Zunaira Arshad 1 Received: 27 February 2018 / Accepted: 17 October 2018 Ó Botanical Society of Sao Paulo 2018 Abstract Soil salinity is one of the major abiotic stresses that drastically reduce crop yield worldwide. The problem of soil salinity is further aggravated when soil is depleted of essential major nutrients such as sulfur. Exogenous application of sulfur can ameliorate negative effects of salt stress on plants. Keeping this in view, a pot experiment was conducted to assess the effect of different sulfur-containing (SC) compounds on maize (Zea mays L. var. Malka and hybrid DTC) under salt stress. Two-week-old maize plants were subjected to two levels of salt (i.e., 0 and 90 mM NaCl) stress. After 2 weeks of salt stress application, plants were foliarly sprayed with different levels of SC compounds, i.e., control (non-spray), FeSO 4 (10 mM), LiSO 4 (10 mM), cysteine (20 mM) and mixture (in 1:1:2 ratio). Foliar application of SC compounds was performed twice (30 ml per pot each time) at 1-week-interval after salt stress application. Data of 7-week-old maize plants were collected for the determination of various growth and physicochemical parameters. Salt stress significantly decreased the growth of both maize genotypes. However, foliar application of different SC compounds significantly increased root and shoot biomass, length of root and shoot, relative water content (RWC% sprayed with mixture), total soluble proteins, total soluble sugars, ascorbic acid contents and total phenolics, while it (cysteine) decreased RWC (%) (in var. Malka), free proline, glycinebetaine (GB) and flavonoid contents. A differential response among the used SC compounds was observed in increasing the growth parameters of both maize genotypes. Overall, FeSO 4 (10 mM), LiSO 4 (10 mM) and mixture (in 1:1:2 ratio) were better than cysteine (20 mM) alone. Keywords Cysteine Á Flavonoids Á Glycinebetaine Á Metabolites Á Phenolics Á Proline 1 Introduction Maize (Zea mays L.) is a member of the grass family Poaceae. It is extensively cultivated as fodder as well as cereal food crop. It is ranked third in the world and occupies the fourth position in Pakistan on cultivation basis. In Pakistan, it is grown on an area of 1144 thousand hectares with total annual production of 4.920 million tons and national average yield of 4301 kg ha -1 (Anonymous 2016). Maize is considered as a moderately salt-sensitive crop (Zhang et al. 2016). Soil salinity exerts adverse effects on plant growth and reduces crop yield globally (Munns and Gilliham 2015). FAO (2017) estimated that of the total irrigated land (230 million ha), 19.5% (45 million ha) is salt-affected; and of the dryland agriculture (1500 million ha), 2.1% (32 million ha) is salt-affected (Aflaki et al. 2017). It has been reported that by the year 2050, the process of salinization will decrease the land for crops cultivation by up to 50% in the agriculture system (Bahmani et al. 2015). Sulfur (S) is an essential macronutrient for the growth and development of plants. It is involved in the synthesis of chlorophyll, proteins, oil and amino acids—cysteine (27%) and methionine (21%) (Aulakh et al. 1980). After its uptake in the form of sulfate, sulfur is stored in the vac- uoles of leaf cells (Bell et al. 1994). It is reduced to sulfide (S 2- ) and incorporated into organic molecules such as proteins with thiol (–SH), i.e., cysteine residue, and non- protein thiols, such as reduced glutathione (GSH), in the cytoplasm (Tausz et al. 2003; Droux 2004; Anjum et al. 2008; Koprivova and Kopriva 2016). However, sulfate & Shagufta Perveen perveens1@yahoo.com 1 Department of Botany, Government College University, Faisalabad 38000, Pakistan 123 Brazilian Journal of Botany https://doi.org/10.1007/s40415-018-0506-4