Scientia Horticulturae 319 (2023) 112149 Available online 16 May 2023 0304-4238/© 2023 Elsevier B.V. All rights reserved. Metabolic profling, pigment component responses to foliar application of Fe, Zn, Cu, and Mn for tea plants (Camellia sinensis) Fawad Zaman a, 1 , E Zhang a, 1 , Muhammad Ihtisham b , Muhammad Ilyas c , Wajid Ali Khattak d , Fei Guo a , Pu Wang a , Mingle Wang a , Yu Wang a , Dejiang Ni a , Che Tang e, * , Hua Zhao a, * a National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, PR China b School of Agriculture, Forestry and Food Engineering, Yibin University, Yibin, Sichuan 644000, PR China c CAS Key laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan 666303, PR China d School of Enivornmental and Safety Engineering, Jiangsu University, Zhenjiang 212013, PR China e Hubei Inspection Center for Quality and Safety of Agricultural Products, Wuhan 430070, PR China A R T I C L E INFO Keywords: Tea plant Foliar fertilizer POD Theafavins Tea quality ABSTRACT Foliar application of essential nutrients is a rapid and promising strategy to enhance the concentration and bioavailability of essential nutrients in tea plants (Camellia sinensis). A feld experiment was carried out to explore the effects of iron (Fe), zinc (Zn), copper (Cu) and the hyperaccumulator manganese (Mn) foliar application on the biochemical components of free amino acid (FAA), caffeine (CAF), and tea polyphenols (TP) in the black tea made from the tea plant cultivar ‘HuangDan’. The foliar application of Fe, Zn, Cu, and Mn showed signifcant effects on FAA and TP contents of black tea (P < 0.05), but had no signifcant effect on the CAF content. Iron and zinc spraying signifcantly increased thearubigin and theabrownin content, whereas copper spraying signifcantly decreased thearubigin content while increasing theabrownin content. Additionally, the gene expression patterns of the POD family members CsSPX1, CsAPX1, CsGPX1, CsGPX3, CsPOD13, and CsPOD18 were identifed to investigate the roles of these phenolic constituents infuenced by the foliar appli- cation. The expression patterns of CsGPX3 and CsAPX1 were found to be involved in the production of TFs. POD- catalyzed TFs formation might serve as a molecular marker to identify varieties of tea plants suitable for brewing high-quality black tea beverages by regulating catechin oxidation throughout the tea processing process. 1. Introduction Tea plant (Camellia sinensis (L.) O. Kuntze) is the world’s most widely cultivated beverage crop and the consumption of tea was grad- ually growing over the last decade. The different kinds of tea available in China can be categorized into black, green, oolong, yellow, white, and dark tea. Globally, black tea is the most popular tea consumed, making up 75% of total production, with China being both a major producer and consumer (Wang et al., 2014). Nutrients are essential for plant metabolic processes, development, productivity, stress resistance, and disease prevention etc., (Shahzad and Amtmann, 2017). At optimum levels, iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) are important nutri- ents for most plant species. However, at higher-than-optimal levels, they are hazardous (Shingles et al., 2004). Iron is required for numerous key activities, including DNA synthesis, respiration, photosynthesis, and nitrogen degradation (Rout and Sahoo, 2015). Zn is an essential component of plant enzymes, including alcohol dehydrogenase, alkaline phosphatase, carbonic anhydrase, Cu-Zn SOD, RNA polymerase, and phospholipase, and it is also involved in the response of enzymes in which Zn is not the principal component (Hajiboland, 2012). Several enzymes responsible for DNA transcription as well as protein, nucleic acid, carbohydrate, and lipid metabolism require Zn as a cofactor (Ish- imaru et al., 2011). Moreover, Zn is not easily absorbed by tea plants from soil, and its insuffciency is not easily rectifed by applying Zn compound to the ground. Mn is essential for N metabolism because it acts as an activator for the enzymes nitrite reductase and hydroxylamine reductase, and it is also required for the production of aromatic amino acids and secondary metabolites such as lignin and favonoids (Buchanan et al., 2001). Some plant species potentially accumulate large amounts of Mn in tissue * Corresponding authors. E-mail addresses: TangChe2022@163.com (C. Tang), zhaohua@mail.hzau.edu.cn (H. Zhao). 1 These authors have contributed equally to this work. Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti https://doi.org/10.1016/j.scienta.2023.112149 Received 16 October 2022; Received in revised form 3 May 2023; Accepted 11 May 2023