Garden tea waste-derived carbon dots nanoformulation: A sustainable approach to alleviate cold stress in tea cultivation

Tea plantations under cold stress face severe disruption of their physiological processes, leading to reduced photosynthesis and yield. Cold resistant tea plants and efficient exogenous substances to mitigate cold stress are still lacking. Carbon Dots (CDs) are potential carbon nanomaterials that can modulate several physiological and biochemical processes to enhance plant cold tolerance. CDs with the characteristics of small size (<10 nm), excellent water solubility, biocompatibility and tunable photoluminescence properties make them a suitable candidate for a wide range of applications, including agriculture. In this investigation, carbon dots nanoformulation (CDs NF) derived from garden tea waste was foliar-sprayed on tea plants to assess their potential for enhancing cold stress tolerance. Tea plants treated with CDs NF @ 250 ppm exhibited increased photosynthetic rate (56 %), stomatal conductance (78 %) and transpiration rate (123 %), total chlorophyll content (51 %), reduced electrolyte leakage (78 %) and ultimate increase in yield (16 %) when compared to the control. Our findings demonstrated that CDs NF increases cold stress tolerance in tea plants by modulating photosynthetic processes, maintaining membrane integrity and improving plant water status, besides promoting the circular economy by effectively utilizing garden tea waste.