汞胁迫下氮磷减施及铁膜形成对水稻幼苗根系生长的影响

Effects of reduced nitrogen and phosphorus applications and iron plaque formation on root growth of rice seedlings under mercury stress

以水稻(绿旱1号)为供试材料,通过对根系形态及生物量分配的测定,探索了汞胁迫下水稻根系生长对缺氮、缺磷和铁膜诱导的响应。结果发现:减少氮、磷供应和铁膜诱导均可促进水稻根系的生长,其中根长分别提高了35.8%、75.3%、102.2%,根表面积分别提高了46.6%、47.8%、60.8%,根冠比分别从对照组的22.1%提高到29.9%、27.3%、28.23%。与此同时,在汞胁迫条件下(0.5 mg Hg(II)·L-1),减少氮、磷供应及铁膜诱导的处理对水稻根系生长的影响没有达到显著水平。单独的汞胁迫处理对水稻根系的生长有抑制作用,但效果并不显著。另一方面,在汞胁迫且减少氮磷施用的条件下,进行铁膜诱导能够促进根系的生长,表现为:铁膜诱导处理提高了汞胁迫下缺氮水稻的根长,增幅为64.6%;对于汞胁迫下的缺磷水稻,铁膜的形成对根长、根表面积、根尖数均有提高作用,增幅分别为74.9%、56.5%和94.7%。研究表明:汞胁迫对水稻根系的生长有抑制作用,减弱了水稻根系对养分缺乏的响应,而铁膜的生成可以在一定程度上减弱汞离子对根系的危害。

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.