期刊：Environmental and Experimental Botany（EEB）
标题：Increasing ammonium nutrition as a strategy for inhibition of cadmium uptake and xylem transport in rice (Oryza sativa L.) exposed to cadmium stress
Nitrogen (N) speciation could inﬂuence the eﬃciency of Cd accumulation by plants grown in Cd-contaminated areas. However, limited information has been reported on how the application of N speciation to rice aﬀects the Cd accumulation. Here, we investigated the physiological and genetic mechanisms involved in Cd uptake by roots, xylem translocation and subsequent Cd accumulation in rice (Oryza sativa L.) aﬀected by diﬀerent NO3−/ NH4+ ratios under low-and-high Cd stress.
Results showed that both N speciation and Cd stress aﬀected plant growth, with high NH4+-N ratios treatments having higher tissue biomass, and high Cd treatment reducing tissue biomass. The Cd concentrations in shoots and roots were reduced with the increasing NH4+-N ratios (except for the full NO3−-N treatment), but did not aﬀect the Cd translocation factor (TF). The total Cd accumulation of the whole plant were also reduced with the high NH4+-N ratios (NO3−/NH4+, 1:2 and 0:1) on the low Cd treatment due to the decline both in the Cd accumulation of shoots and roots.
A Non-invasive Micro-test Technology (NMT) showed that the net Cd2+ inﬂuxes at the root hair zone were inhibited with the increasing NH4+-N ratios in absence or pretreatment with diﬀerent NO3−/NH4+ ratios. Additionally, the Cd concentrations in xylem sap were also displayed a decline trend with the increasing NH4+-N ratios under two dose Cd treatments.Furthermore, the gene expression related to Cd uptake (OsIRT1 and OsNRAPM5) and transport (OsHMA2) in roots showed the familiar tendencies with those of Cd uptake and transport at the physiological level treated with diﬀerent NO3−/NH4+ ratios under two dose Cd treatments.
It is concluded that increasing ammonium nutrition contributes to the inhibition of Cd uptake, xylem transport and subsequent accumulation in rice.
中文摘要（谷歌机翻）氮（N）物种形成可能影响镉污染地区生长的植物对Cd积累的影响。然而，关于如何将N形态应用于水稻以影响Cd积累的报道有限。在这里，我们研究了在低和高Cd胁迫下由不同NO3-/NH4+比例影响的水稻（Oryza sativa L.）根系吸收Cd，木质部易位和随后Cd积累所涉及的生理和遗传机制。
Fig. 1. Eﬀect of diﬀerent NO3-/NH4+ ratios (A and B) or pretreatment with diﬀerent ratios of NO3-/NH4+ (C and D) on net Cd2+ inﬂux at root hair zone by Non-invasive Micro-test Technology(NMT). Each point represents the mean values of Cd2+ inﬂux of six roots from six individual plants during the time of 6th-10th minutes. Bars with diﬀerent letters mean signiﬁcantly statistical diﬀerences followed by one-way ANOVA analysis (LSD test, P < 0.05, n=6). 'preCK' indicates 'pretreatment of the rice seedlings with NO3-/NH4+ (1:1)'.