Mesophyll cells' ability to maintain potassium is correlated with drought tolerance in tea (Camellia sinensis)

Tea plant is an important economic crop and is vulnerable to drought. A good understanding of tea drought tolerance mechanisms is required for breeding robust drought tolerant tea varieties. Previous studies showed mesophyll cells' ability to maintain K+ is associated with its stress tolerance. Here, in this study, 12 tea varieties were used to investigate the role of mesophyll K+ retention ability towards tea drought stress tolerance. A strong and negative correlation (R-2 = 0.8239, P < 0.001) was found between PEG (mimic drought stress)-induced K+ efflux from tea mesophyll cells and overall drought tolerance in 12 tea varieties. In agreement with this, a significantly higher retained leaf K+ content was found in drought tolerant than the sensitive tea varieties. Furthermore, exogenous applied K+ (5 mM) significantly alleviated drought-induced symptom in tea plants, further supporting our finding that mesophyll K+ retention is an important component for drought tolerance mechanisms in tea plants. Moreover, pharmacological experiments showed that the contribution of K+ outward rectifying channels and non-selective cation channels in controlling PEG-induced K+ efflux from mesophylls cells are varied between drought tolerant and sensitive tea varieties.