Aluminum relieves fluoride stress through stimulation of organic acid production in Camellia sinensis

Abstract

Tea plants (Camellia sinensis O. Kuntze) can hyperaccumulate fluoride (F) in leaves. Although, aluminum (Al) can alleviate F toxicity in C. sinensis, the mechanisms driving this process remain unclear. Here, we measured root length, root activity, soluble proteins content, and levels of peroxidase, superoxide dismutase, catalase, malondialdehyde (MDA), and chlorophyll in tea leaves after treatment with different F concentrations. In addition, we focused on the content of organic acids, the gene transcription of malate dehydrogenase (MDH), glycolate oxidase (GO) and citrate synthase (CS) and the relative enzyme activity involved in the tolerance to F in C. sinensis. We also examined the role of Al in this process by analyzing the content of these physiological indicators in tea leaves treated with F and Al. Our results demonstrate that increased MDA content, together with decreased chlorophyll content and soluble proteins are responsible for oxidative damage and metabolism inhibition at high F concentration. Moreover, increased antioxidant enzymes activity regulates ROS damage to protect tea leaves during F stress. Furthermore, exogenous Al alleviated F stress in tea leaves through the regulation of MDA content and antioxidant enzymes activity. In addition, organic acids in Junting Pan and Dongqin Li contributed equally.

Non-Essential Elements and Their Role in Sustainable Agriculture

“…Moreover, Al fluorides, sulphates, or phosphates have also been proven to be less toxic or even non-toxic to plants, when applied in adequate concentrations adapted to each type of crop [27]. Stimulatory effects have been reported in several plant species supplemented with Al, ranging from increased mineral uptake, including calcium (Ca), potassium (K), boron (B), and phosphorous (P), mitigation of pests and pathogens, and alleviation of unfavourable environmental conditions, such as high H + concentration in acid mineral soils, drought, high and low temperatures, soil salinity, and manganese (Mn) and copper (Cu) toxicity [28][29][30][31].…”

“…In coffee plants, a supply of 100 µM of Al increased K and Ca concentrations in roots [31]. In maize, ammonium enables Al-induced stimulation of N assimilation, leading to increased nitrate accumulation in roots [55].…”

“…In peanut (Arachis hypogaea), shoot and root growth was promoted by adding Al to the nutrient solution (up to 20.4 µM), which was attributed to reduced zinc (Zn) uptake and concentration in shoots, found to be toxic in plants without Al supply [64]. Aluminium can also help to detoxify fluoride (F) through the formation of Al-F complexes, thus alleviating F stress [31,65]. This possibly occurs through the regulation of lipid peroxidation and antioxidant enzymes activity in leaves, or through the exudation of organic acids, which allow the regulation of root pH through the interaction of Al with F [31].…”

“…Aluminium can also help to detoxify fluoride (F) through the formation of Al-F complexes, thus alleviating F stress [31,65]. This possibly occurs through the regulation of lipid peroxidation and antioxidant enzymes activity in leaves, or through the exudation of organic acids, which allow the regulation of root pH through the interaction of Al with F [31]. Recent works also highlight the possibility to exploit Al-rich corn stalk biochar to remove F and cadmium (Cd) from contaminated water bodies [66].…”

SWEET Transporters and the Potential Functions of These Sequences in Tea (Camellia sinensis)

“…Camellia sinensis , which originated from the tropical area of Southwest China, is an important economic beverage crop in China ( Wei et al, 2018 ; Zhang et al, 2020b ). Sugar transport and homeostasis contribute to plant growth and development ( May et al, 1998 ; Lastdrager et al, 2014 ; Rahimi et al, 2019 ; Pan et al, 2020 ; Saddhe et al, 2020 ). Some published papers focused on the genes that participated in sugar metabolism, such as hexose kinase, invertase, and galactinol synthase, in C. sinensis ( Yue et al, 2015 ; Zhou et al, 2017 ; Samarina et al, 2020 ).…”