水稻根系生长对不同氮形态响应的动态变化

土壤养分供应变异很大,植物根系生长对这种养分变异的响应非常敏感.为了探索水稻根系生长对N素供应响应的动态变化规律以及这种适应性变化与水稻N效率之间的关系,采用水培方法,以两个苗期不同N效率水稻品种桂单4号和南光为研究材料,比较了不同铵硝比、不同浓度NH4、不同浓度NO3-和不同浓度NH4NO3对水稻根系构型参数的影响.结果表明:NH4 和NH4NO3供应显著降低了总根长、总根表面积和总根体积,且有增加平均根直径的趋势;而NO3-供应在0～1 mmol/L浓度范围内,增加了总根长、总根表面积和总根体积,降低了平均根直径,但当NO3-供应超过1 mmo1/L后,NO3-却有降低总根长、总根表面积和总根体积的趋势,对平均根直径没有明显影响.苗期N高效基因型桂单4号总根长和总根表面积在各种N素营养条件下均显著高于N低效基因型南光.上述结果表明,NH4 和NH4NO3都抑制了水稻根系生长,而NO3-为低浓度诱导、高浓度抑制根系生长,根长和根表面积,对提高水稻N效率贡献较大.

Dynamic Responses of Rice in Root Growth to Different NH4+ and NO3- Supply

Plant root systems are extremely sensitive to availability and distribution of nutrients within soil. In order to explore how rice roots respond to NH4 and NO3- supply and whether the responsibility is related to rice N efficiency, effects of NH4 :NO3- ratio in N supply on parameters of root architecture through solution culture experiment using rice plants of two different genotypes, GD4 and NG, was tested. The results showed that both NH4 and NH4NO3 significantly decreased total root length, total root surfarea, and total root volume but slightly increased average root diameter. NO3- less than 1 mmol/L increased total root length, total root surfarea, and total root volume but decreased average root diameter, whereas when rice roots were exposed to NO3- concentration more than 1 mmol/L, the situation was contrary to that of NO3- concentration less than 1 mmol/L. Total root length and total root surfarea of N-efficient rice genotype GD4 were higher than that of N-inefficient rice genotype NG. In conclusion, NH4 and NO3- had different effects on rice root growth, inhibitory effects for NH4 , stimulative effect for low NO3- concentrations whereas inhibitory effects for high NO3- concentrations, and root length and root surfarea may contribute to the improvement of rice N efficiency.