www.plantroot.org 71 O Or r i i g g i i n na al l r r e es s e ea ar r c ch h a ar r t t i i c cl l e e Physiological, biochemical and root exudate response of maize seedlings to hydrogen sulfide applications Kabir Ghoto 1,2 , Gui-Feng Gao 1 , Martin Simon 1 , Zhi-Jun Shen 1 , Huan Li 1 , Ming-Yue Wei 1 and Hai-Lei Zheng 1 1 Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361005, P.R. China 2 Department of Environmental Science, Sindh Madressatul Islam University, Karachi, Pakistan Corresponding author: H-L Zheng, E-mail: zhenghl@xmu.edu.cn Received on September 11, 2022; Accepted on July 30, 2023 Abstract: The efects of hydrogen sulfde (H 2 S), re- leased from the donor sodium hydrosulfde (NaHS), on maize seedlings grown hydroponically for 6 days were investigated. Plant biomass, malondialdehyde (MDA), hydrogen peroxide (H 2 O 2 ), superoxide (O 2 •− ) content, and root exudates (organic acids) were measured. Results showed that 100 and 200 µM NaHS is the most appropriate and suitable concen- tration for the growth and development of maize seedlings, without afecting the MDA and H 2 O 2 con- tents but altering the O 2 •− . In addition, high concen- trations of 500 and 1000 µM NaHS adversely af - fected these parameters compared with the control (CK). The pH of the root exudates declined under NaHS treatments. The organic acids in the root ex- udates, including fumaric, acetic, formic, and malic acids exhibited higher contents at 100 µM NaHS treatment, the lactic and citric acids were higher at both 100 and 200 µM NaHS. In contrast, oxalic acid was reduced at all NaHS concentrations compared with the CK. Low contents of all the organic acids analyzed were found under 500 and 1000 µM NaHS treatment. In conclusion, all the above pa- rameters were afected by the application of NaHS, while higher NaHS concentration was toxic for maize seedlings. Keywords: H 2 S, MDA, organic acids, plant bio- mass, ROS, root exudates, Zea mays Introduction Hydrogen sulfide (H 2 S) is a flammable, corrosive, and colourless gas, having a characteristic foul odour like rotten eggs or clogged sewage. For ages, it has been considered a phytotoxin and harmful to the growth and development of plants. However, recent studies consider H 2 S to have a variety of functions during a plant’s life (Wang et al. 2012). Previously H 2 S was traditionally acclaimed as a phytotoxin, but freshly it appeared as an important gasotransmitter in addition to nitric oxide (NO) and carbon monoxide (CO) with several functions in animals and plants (Lisjak et al. 2013). Plant growth and development can be improved with a lower concentration of H 2 S (Dooley et al. 2013). In addition, an exogenous supply of H 2 S improved seed germination (Zhang et al. 2008). Furthermore, Zhang et al. (2010a) revealed that H 2 S promoted seed germination by increasing the activity of endosperm β-amylase and keeping lower levels of malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ). Li et al. (2010) demonstrated that the H 2 S can promote the growth of the embryonic root of Pisum sativum and induce stomatal opening by decreasing NO accretion. Therefore, H 2 S determines plant metabolism during nearly all life stages and, at the appropriate concentration, promotes biomass accumulation and fruit yield (Dooley et al. 2013). At the same time, H 2 S was found to modulate the expressions of genes related to photosynthesis and thiol production (Chen et al. 2011). It has been demonstrated that the reduction in chlorophyll content induced by osmotic stress could be relieved by spraying the NaHS solution (Zhang et al. 2009). H 2 S was also observed to slow the fowering and senescence in cut flowers and twigs (Zhang et al. 2011). H 2 S adversely influences autophagy and Ghoto K, Gao GF, Simon M, Shen ZJ, Li H, Wei MY and Zheng HL 2023 Physiological, biochemical and root exudate response of maize seedlings to hydrogen sulfde applications. Plant Root 17:71-81. doi:10.3117/plantroot.17.71 Copyright 2023 The authors. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC-BY; https://creativecommons.org/licenses/by/4.0/).