水稻苗期不同时段NO_3~-吸收特点及其受NH_4~+的影响

 利用水培方法研究了 4种具代表性的水稻基因型 (常规粳稻、常规籼稻、杂交粳稻、杂交籼稻 )在不同苗期根部NO3 -吸收和叶部硝酸还原酶活性 (NRA)受NH4+ 存在的影响的情况。结果表明 ,在根系NO3 -吸收方面 ,籼稻与粳稻相比 ,杂交稻与常规稻相比 ,前者具有较高的NO3 -吸收速率 ,且籼稻和杂交稻在NO3 -吸收速率上的优势在 2 0d苗龄时主要体现为吸收速率较快 ,而在 5 0d苗龄时主要体现为载体与NO3 -之间的亲和力较强。不论2 0d还是 5 0d苗龄 ,NH4+ 的存在对籼稻吸收NO3 -的影响均很小 ,对杂交稻NO3 -吸收甚至有促进作用 ,但对粳稻吸收NO3 -均有较大程度的抑制。NH4+ 还可以抑制所有供试水稻基因型叶片的NRA ,但抑制程度不同 ,按强弱顺序排列为 :杂交粳稻 >杂交籼稻 >常规籼稻 >常规粳稻。

Nitrate Uptake of Rice and the Effect of Ammonium on it at Different Growth Stages

Solution culture experiments were carried out to study the NO 3 - uptake kinetics by rice roots and the nitrate reductase activity (NRA) in leaves of four typical rice genotypes (conventional indica, conventional Japonica, hybrid indica, and hybrid japonica) and the effects of NH 4 + on the kinetics at different growth stages. Results indicated that the four genotypes responded differently to NO 3 - and NH 4 +. Comparing indica with japonica, hybrid rice with conventional rice, the formers absorbed NO 3 - more rapidly than the latters. The superiority of indica and hybid rice for NO 3 - uptake was mainly due to the higher V max at the early growth stage (20 days) and the stronger affinity of nitrate transporters for NO 3 - at the middle growth stage (50 days). At both growth stages NH 4 + inhibited NO 3 - uptake of japonica rice obviously, but had little effect on that of indica, and even stimulated that of hybrid rice. NH 4 + could repress NRA in leaves of all the four genotypes to different extents, by which the four rice genotypes were sorted descendingly as follows: hybrid japonica > hybrid indica > conventional indica > conventional japonica.