为研究根际溶氧量和氮素形态对水稻根系生长及对氮素利用的影响，设计了两个试验：1)分别以铵硝混合营养（NH4NO3）和全铵营养[(NH4)2SO4]为氮源，在营养液中将杂交籼稻国稻1号和常规粳稻秀水09培养6周，在第4周和第6周时取样测定植株的生物量和氮素含量；2) 将上述铵硝混合营养下培养4周的国稻1号水稻植株，以分根培养的方式进行不同溶氧量处理，测定水稻生物量、根系形态和氮积累量的差异。结果表明: 1）根际溶氧量较低时(溶氧量0~1.0 mg/L)，铵硝混合营养比单一的铵态氮营养显著提高植株的生物量，国稻1号生物量增加69%，秀水09增加41%；铵硝混合营养显著提高了水稻的根系数量、最长根长、根干质量和根系活力以及植株的氮积累量，国稻1号的地下部和地上部氮积累量分别提高60%和52%，秀水09则分别提高了41%和33%。2) 分根实验中，铵硝混合培养的国稻1号，其增氧(溶氧量8.0~9.0 mg/L)处理的根系生物量增加21.6%， 根系数量、最长根长和根体积分别增加27%、14%和10%，而氮积累量提高了11%。增氧和铵硝混合营养均对促进水稻根系生长和氮素积累具有正互作效应。
Dissolved oxygen and N forms have important effects on rice root growth and N availability. Indica hybrid rice Guodao 1 and conventional japonica rice Xiushui 09 were cultured for six weeks in hypoxic nutrient solution with NH4NO3 or (NH4)2SO4 as nitrogen source; Four weeks later, Guodao 1 was transferred to the split-root system at different dissolved oxygen contents (DOTs). The biomass, root morphological traits and nitrogen accumulation were investigated. Under lower rhizosphere oxygen (DOT 0 to 1.0 mg/L), NH4NO3 -N significantly increased the plant biomass in comparison with sole NH4+ -N, about 69% in Guodao 1 and 41% in Xiushui 09. In addition, the root number, the longest root length, the root dry weight and the root activity for Guodao 1 and Xiushui 09 were also increased under NH4NO3-N nutrition. NH4NO3-N enhanced the N accumulation in roots and shoots of Guodao 1 by 60% and 52%, in roots and shoots of Xiushui 09 by 41% and 33%, respectively. In the split-root system, because of increased rhizosphere oxygen (DOT 8.0 to 9.0 mg/L), the root biomass was increased by 21.6%, the root number by 27%, the longest root length by 14% and the root volume by 10%. The N accumulation in roots was enhanced by 11% under higher rhizosphere oxygen. In conclusion, improvement of dissolved oxygen and ammonium-nitrate N source have positive effect on the root growth and N accumulation of rice plants.
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