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K+ accumulation in the cytoplasm and nucleus of the salt gland cells of Limonium bicolor accompanies increased rates of salt secretion under NaCl treatment using NanoSIMS

Feng, Zhong-Tao, Deng, Yun-Quan, Zhang, Shi-Chao, Liang, Xue, Yuan, Fang, Hao, Jia-Long, Zhang, Jian-Chao, Sun, Shu-Feng, Wang, Bao-Shan
Plant science 2015 v.238 pp. 286-296
Limonium, apoplast, cytoplasm, freezing, potassium, salinity, salt tolerance, secretion, sodium, sodium chloride
Recretohalophytes with specialized salt-secreting structures (salt glands) can secrete excess salts from plant, while discriminating between Na+ and K+. K+/Na+ ratio plays an important role in plant salt tolerance, but the distribution and role of K+ in the salt gland cells is poorly understood. In this article, the in situ subcellular localization of K and Na in the salt gland of the recretohalophyte Limonium bicolor Kuntze is described. Samples were prepared by high-pressure freezing (HPF), freeze substitution (FS) and analyzed using NanoSIMS. The salt gland of L. bicolor consists of sixteen cells. Higher signal strength of Na+ was located in the apoplast of salt gland cells. Compared with control, 200mM NaCl treatment led to higher signal strength of K+ and Na+ in both cytoplasm and nucleus of salt gland cells although K+/Na+ ratio in both cytoplasm and nucleus were slightly reduced by NaCl. Moreover, the rate of Na+ secretion per salt gland of L. bicolor treated with 200mM NaCl was five times that of controls. These results suggest that K+ accumulation both in the cytoplasm and nucleus of salt gland cells under salinity may play an important role in salt secretion, although the exact mechanism is unknown.