Abstract: Through the measurement of root morphology and biomass distribution, this paper studied the response of rice (Oryza sativa L. cv. Lvhan No. 1) root growth to nitrogen deficiency, phosphorus deficiency and iron plaque formation under mercury stress. The results showed that nitrogen deficiency, phosphorus deficiency and iron plaque formation all promoted the growth of root. The three treatments (nitrogen deficiency, phosphorus deficiency and iron plaque formation) lengthened the root by 35.8%, 75.3% and 102.2%, respectively. In addition, the root surface area promoted by 46.6%, 47.8% and 60.8%, respectively, and the rootshoot ratio raised to 29.9%, 27.3% and 28.23%, respectively, compared to 22.1% in the control group. When mercury was added into the culture solution (0.5 mg Hg(II)·L^-1), however, the growth promoting effect faded away. Mercury stress alone could inhibit the root growth, but the effect was not statistically significant. However, induced iron plaque could promote the root growth with nutrition deficiency under mercury stress, showing that the root length increased by 64.6% under nitrogen deficiency and the length, surface area and tips improved by 74.9%, 56.5% and 94.7% under phosphorus deficiency, respectively. Overall, mercury has negative effects on root system establishment of rice seedlings, weakening rice root’s response to nutrition deficiency. On the other hand, iron plaque formation can improve the growth of root system, and protect the roots from mercury stress to a certain extent.

Key words: non-photochemical quenching, light intensity, photosynthesis, photosyntheticinduction, Panax notoginseng.