《植物生理学报》 2017, 53(12): 2167-2180
通信作者：沈宏；E-mail: hshen@scau.edu.cn
摘 要：
干湿交替(AWD)是水稻(Oryza sativa)种植过程中常用的水分管理措施, 该措施有利于提高根系氧化力, 并促进大量根表红棕色铁膜的形成。然而, AWD诱导根表红棕色铁膜形成的根层机制并不清楚。本文利用简易AWD装置, 采用砂-液联合培养, 研究了AWD诱导水稻根表红棕色铁膜形成的机制。AWD强度试验表明, 落干和淹水均为12 h时, 水稻根系活力和根表铁膜形成量最高。在此基础上, 随着AWD次数的增加, 根表铁膜含量逐渐增加。根系灭活试验表明, 水稻活根的根系活力为805.0~958.5 μg·g-1 (DW)·h-1, 根表铁膜含量为15.1~18.0 g·kg-1 (DW), 而灭活根系没有根系活力, 也无根表红棕色铁膜形成。H2O2促进剂氨基三唑(AT)和清除剂二甲基硫脲(DMTU)试验表明, 与对照相比, AT处理的水稻根系H2O2含量、根系活力和根表铁膜含量分别增加了31.8%、20.1%和26.7%, 而DMTU处理的水稻根系H2O2含量、根系活力和根表铁膜含量分别降低了27.2%、19.8%和18.4%。AWD 3次和5次处理与AWD 0次相比, 水稻根系H2O2含量分别增加了29.1%和35.6%, 根系活力分别增加了11.8%和16.8%。根层试验表明, 在0~48 h的根表铁膜诱导过程中, AWD 5次处理与AWD 0次相比, 水稻根际氧化还原电位(Eh)最大增加了9.3%, 根际溶液中Fe2+浓度最大降低了49.6%; 相应地, 以Fe3+形态在根表沉积的铁膜最大增加了110.1%。上述结果表明, AWD通过诱导根系H2O2的累积, 提高根系活力和根际Eh, 促进根际Fe2+氧化成Fe3+, 从而在水稻根表形成红棕色铁膜。关键词：干湿交替; 根层; 过氧化氢; 红棕色铁膜; 水稻
收稿：2017-06-13 修定：2017-10-16
资助：国家自然科学基金(31372125)和广东省科技计划项目(2014J4100240)。
Corresponding author: SHEN Hong; E-mail: hshen@scau.edu.cn
Abstract:
Alternate wetting and drying (AWD) is a common water management in rice (Oryza sativa) plantation, which contributes the elevation of root oxidation capacity, and induces the formation of reddish-brown iron plaque on root surface. However, the mechanism remains unclear in root layers. In this study, we investigated how AWD induced the formation of reddish-brown iron plaque by using quartz-sand combining nutrient solution culture and a simplified AWD device. Results from different AWD intensities indicate the most iron plaque and highest root activity were occurred when cycles of 12-h alternate wetting and 12-h drying were performed. On this basis, iron plaque on root surface was increased gradually with the increase of AWD times. The root inactivation experiment showed that normal roots had the activity of 805–958.5 μg·g-1 (DW)·h-1 and iron plaque of 15.1–18.0 g·kg-1 (DW) on root surface, while dead roots had no activity and reddish-brown iron plaque. 3-amino-1,2,4-triazole (AT), a H2O2 promoter, increased H2O2 content, root activity, and iron plaque by 31.8%, 20.1% and 26.7%, while H2O2 content, root activity, and iron plaque were reduced by 27.2%, 19.8% and 18.4% in response to dimethylthiourea (DMTU, a H2O2 scavenger) treatment. The contents of endogenous H2O2 in roots with 3 and 5 times AWD were 29.1% and 35.6% higher, respectively, than that with 0 time AWD. The corresponding values were 11.8% and 16.8%, respectively, for root activity. During the induction of iron plaque for 0–48 h in the rhizosphere of rice seedlings, oxidation reduction potential (Eh) was increased maximally by 9.3% with 5 times AWD in comparison to 0 time AWD treatment, the concentration of Fe2+ was decreased maximally by 49.6%, and iron plaque on root surface was increased maximally by 110.1%. Based on the above, our results suggest that AWD treatment induces the formation of reddish-brown iron plaque on root surface by enhancing accumulation of endogenous H2O2 and root activity, as well as elevating rhizosphere Eh value and oxidation of Fe2+ into Fe3+.Key words: alternate wetting and drying; root layer; hydrogen peroxide; reddish-brown iron plaque; rice
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