Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10142983 | Plant Physiology and Biochemistry | 2018 | 39 Pages |
Abstract
In plants, different forms of nitrogen (NO3â or NH4+) affect nutrient uptake and environmental stress responses. In the present study, we tested whether NO3â and NH4+ affect the ability of rice (Oryza sativa) to tolerate the toxic heavy metal cadmium (Cd). Compared with NO3â, NH4+ treatment significantly increased chlorophyll contents and reduced Cd2+ levels in rice cultivars Nipponbare (japonica) and Kasalath (indica) grown in 0.2â¯mM Cd2+. NH4+ significantly reduced the pectin and hemicellulose contents and inhibited the pectin methylesterase (PME) activity in rice roots, thereby reducing the negative charges in the cell wall and decreasing the accumulation of Cd2+ in roots. In addition, NH4+ reduced the absorption and root-to-shoot translocation of Cd2+ by decreasing the expression of OsHMA2 and OsNramp5 in the root. Levels of the signaling molecule putrescine were significantly higher in the roots of both rice cultivars provided with NH4+ compared with NO3â. The addition of putrescine reduced Cd2+ contents in both rice cultivars and increased the chlorophyll content in shoots by reducing root cell wall pectin and hemicellulose contents, inhibiting PME activity and suppressing the expression of OsHMA2 and OsNramp5 in the root. Taken together, these results indicate that NH4+ treatment alleviated Cd toxicity, enabling rice to withstand the noxious effects of Cd by modifying the cell wall Cd-binding capacity due to alterations of pectin and hemicellulose contents and Cd transport, processes induced by increasing putrescine levels. Our findings suggest methods to decrease Cd accumulation in rice by applying NH4+ fertilizers.
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Authors
Chun Quan Zhu, Xiao Chuang Cao, Lian Feng Zhu, Wen Jun Hu, An Yong Hu, Zhi Gang Bai, Chu Zhong, Li Ming Sun, Qing Duo Liang, Jie Huang, Shun Xi Yang, Jun Hua Zhang, Qian Yu Jin,