Changes in growth, biochemical, and chemical characteristics and alteration of the antioxidant defense system in the leaves of tea clones (Camellia sinensis L.) under drought stress

In this study, we measured the morphological, biochemical, and chemical responses to soil drying in nine tea clones [Camellia sinensis (L.) O. Kuntze] grown in a field. Thirteen-year-old tea plants at Shahid Eftekhari Fashalam Experimental Station, Tea Research Center of Iran, were subject to drought stress by withholding water for 40 days. The control group of the clones was regularly watered. The soil moisture content of the non-irrigated and irrigated plants was monitored throughout the experiment. The effects of drought stress were measured by studying physiological (Relative Water Content), biochemical (Proline and Total Sugar Content), and antioxidant activities (Catalase and Peroxidase) after 20 days and 40 days of drought imposition. Green leaf yield and chemical parameters included total polyphenol, caffeine, water extract, and total ash were measured after 40 days of drought stress. Drought stress resulted in a decrease in total polyphenol, water extract, and total ash and an increase in proline, total sugar concentration and, in CAT and POD activities, as a consequence of reduced RWC of the leaves. Thus, drought stress caused a range of biochemical, physiological, and chemical variations, resulting in membrane damage and loss in the functions of the cell and finally a decrease in the tea growth as one of the most important economic crops. The results of grouping the clones under irrigation and drought stress conditions and comparing them with the results of mean comparison of the traits showed that in all cases, clones 276, 100, 285, and 277 were in the group that can be identified as the drought-tolerant group. Also, the results showed that in most cases, clones 278 and 74 were placed in a group that had low values for all the traits and could be considered as a group that is susceptible to drought stress. Overall, these findings provide new insight into the mechanisms of tolerance to drought in tea plants.