Effect of alternative anions (Cl^–vs. SO$ _4^{2-} $) on concentrations of free amino acids in young tea plants

Abstract

The quality of green tea is highly dependent on the concentration of free amino acids, whose profile is dominated by the unique amino acid theanine (N 5 -ethyl-glutamine). A high quality is associated with a high amino acid-to-catechin ratio, but previous results indicated that excessive chloride (Cl -) supply is detrimental for amino acid accumulation. Several experiments were conducted to investigate the effect of chloride on growth and concentrations of free amino acids in young tea plants. Soil-grown tea plants supplied with different levels of potassium (K) as K 2 SO 4 or KCl exhibited increased concentrations of free amino acid in young shoots only when supplied with K 2 SO 4 , and the negative effect of KCl supply was mainly due to a reduced concentration of theanine. Concentrations of other nutrients in plant tissues were not influenced. The uptake of Cland its interaction with nitrogen (N) uptake were further investigated in a second experiment, in which soil-cultivated tea plants were supplied with varying amounts of Cl -. Chloride application reduced yield of young shoots, and severity of leaf damage was related to the con-centration of Clin leaves. Nitrogen uptake was reduced by Claddition. To verify whether the decrease of free amino acids was simply a result of inhibited NO À 3 assimilation, a third experiment was conducted, in which tea plants were NH 4 -fed in the absence or presence (equivalent to the NH 4 concentration) of Cl -. Again, concentrations of theanine and total free amino acids in young shoots were reduced by Clsupply, but changes of the free-amino acid pool did not contribute to the maintenance of charge balance. However, concentration of theanine in roots, where it is synthesized, was not influenced by Cl -. Total N concentrations of roots and mature leaves, uptake rate of NH 4 , and activity of glutamine synthetase in fibrous roots and young leaves were all unaffected by Clas well. It is suggested that translocation of theanine from root to shoot and its catabolism in young shoots might be influenced by Cl -.

Potassium management in tea plantations: Its uptake by field plants, status in soils, and efficacy on yields and quality of teas in China

“…Analysis of chemical components indicates that the quality of young shoots was improved by K fertilization. These findings are in line with previous studies showing positive effects of K application on tea quality in pot and field experiments (Ruan et al, 1999;Ruan et al, 2007;Venkatesan and Ganapathy, 2004;Venkatesan et al, 2005). However, we observed similar effects of K as K 2 SO 4 or KCl on total free amino acid under field conditions.…”

Environmental Factors Variably Impact Tea Secondary Metabolites in the Context of Climate Change

“…Several of the reviewed soil studies assessed the impacts of both deficiency and sufficiency on quality parameters. These studies highlight how soil and nutrient factors notably impact catechin and other phenolic compounds (Hu et al, 2003; Ruan et al, 2007a; 2010, 2013; Chen et al, 2011; Jayaganesh et al, 2011; Duan et al, 2012; Lin et al, 2012; Sae-Lee et al, 2012; Yang et al, 2014), antioxidant defense enzymes (Hajiboland et al, 2013), caffeine (Yang et al, 2014; Sedaghathoor et al, 2019), amino acids (Hu et al, 2003; Venkatesan et al, 2004, 2005; Ruan et al, 2007a; 2010, 2013; Jayaganesh and Venkatesan, 2010; Jayaganesh et al, 2011; Lin et al, 2012; Yang et al, 2014), vitamins (Hu et al, 2003), and flavor (Venkatesan et al, 2006). Each of these is summarized below (Supplementary Table 9).…”

Seasonal Theanine Accumulation and Related Gene Expression in the Roots and Leaf Buds of Tea Plants (Camellia Sinensis L.)

“…As one of the most important components of quality in green tea, theanine and its biosynthesis has been studied intently in tea plants since it was discovered by Yajiro Sakato in 1949 (Ashihara, 2015; Mu et al, 2015). These studies indicated that theanine accumulation was dynamically regulated by seasons (Konishi and Takahashi, 1969; Takeo, 1981; Janet et al, 2015), light (Yang et al, 2012; Deng et al, 2013; Chen et al, 2017; Ji et al, 2018; Sano et al, 2018), nutrient levels (Takeo, 1981; Ruan et al, 2007; Ruan et al, 2010; Ruan et al, 2012; Huang et al, 2018; Kc et al, 2018; Zhu et al, 2019), hormones (Li et al, 2016a), developmental stages (Feldheim et al, 1986; Li et al, 2016b; Liu et al, 2017), and stress (Deng et al, 2012; Wang et al, 2016). Theanine accumulation is also highly tissue-and cultivar-dependent (Fang et al, 2017; Liu et al, 2017; Chen et al, 2018a; Chen et al, 2018b).…”