School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou,China.
Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, China.
Ann Bot. 2021 Jul 28;128(1):17-30. doi: 10.1093/aob/mcab026.
The fern Dicranopteris linearis is a hyperaccumulator of rare earth elements (REEs), aluminium (Al) and silicon (Si). However, the physiological mechanisms of tissue-level tolerance of high concentrations of REE and Al, and possible interactions with Si, are currently incompletely known.
A particle-induced X-ray emission (μPIXE) microprobe with the Maia detector, scanning electron microscopy with energy-dispersive spectroscopy and chemical speciation modelling were used to decipher the localization and biochemistry of REEs, Al and Si in D. linearis during uptake, translocation and sequestration processes.
In the roots >80 % of REEs and Al were in apoplastic fractions, among which the REEs were most significantly co-localized with Si and phosphorus (P) in the epidermis. In the xylem sap, REEs were nearly 100 % present as REEH3SiO42+, without significant differences between the REEs, while 24-45 % of Al was present as Al-citrate and only 1.7-16 % Al was present as AlH3SiO42+. In the pinnules, REEs were mainly concentrated in necrotic lesions and in the epidermis, and REEs and Al were possibly co-deposited within phytoliths (SiO2). Different REEs had similar spatial localizations in the epidermis and exodermis of roots, the necrosis, veins and epidermis of pinnae of D. linearis.
We posit that Si plays a critical role in REE and Al tolerance within the root apoplast, transport within the vascular bundle and sequestration within the blade of D. linearis.
凤尾蕨是一种稀土元素（REEs）、铝（Al）和硅（Si）的超积累植物。然而，目前还不完全清楚组织水平耐受高浓度 REE 和 Al 的生理机制，以及与 Si 可能存在的相互作用。
使用带有 Maia 探测器的粒子诱导 X 射线发射（μPIXE）微探针、扫描电子显微镜和化学形态建模，以解析凤尾蕨在吸收、转运和螯合过程中 REE、Al 和 Si 的定位和生物化学特性。
在根部，超过 80%的 REE 和 Al 位于质外体中，其中 REE 与 Si 和磷（P）在表皮中最显著地共定位。在木质部汁液中，REE 几乎全部以 REEH3SiO42+形式存在，REE 之间没有显著差异，而 24-45%的 Al 以 Al-柠檬酸形式存在，只有 1.7-16%的 Al 以 AlH3SiO42+形式存在。在羽片中，REE 主要集中在坏死病变和表皮中，REE 和 Al 可能在植硅体（SiO2）内共沉积。不同的 REE 在根表皮和外表皮、坏死、叶脉和羽片表皮中具有相似的空间定位。
我们假设 Si 在凤尾蕨根质外体、维管束内运输和叶片内螯合 REE 和 Al 耐受中起着关键作用。
