不同硝响应型水稻品种苗期根系生长对增硝营养的响应

利用控制条件下的水培试验方法,研究了两种铵硝配比(NH4+/NO3-为100/0和75/25)营养条件对4种不同硝响应型水稻品种苗期根系生长的影响。结果表明,在增硝营养(NH4+/NO3-为75/25)条件下,不同水稻品种NO3-的反应差异明显。与全NH4+营养条件相比,增硝营养条件下对NO3-强响应的水稻品种南光的根系干重和氮积累量显著增加,增幅达50%和79%;同时南光的根系总根长、总不定根长和总侧根长增幅均达到显著水平;不定根数、新根数和侧根数亦显著增加;平均不定根长和平均侧根长差异不显著;对硝弱响应型的水稻品种上海97、辽粳和Elio在增硝营养培养下的根系不定根、新根和侧根的长度和数量差异均不显著。这表明增NO3-营养仅仅促进了对NO3-强响应型水稻南光根系的不定根和侧根的发生,进而促进根系对氮素的吸收,并没有促进不定根和侧根的伸长。从本试验的结果可推论,水稻根系对硝态氮的响应度强弱可能是水稻品种氮素效率差异性的因子之一。

Response of rice plants different in response to nitrate to enhanced nitrate supply in root growth at the seedling stage

Nitrogen is one of the most important nutrients affecting production of cereal crops. Evidence available shows that although nitrate (NO3-) enhances growth of rice, the crop prefers ammonium (NH4+ ) to NO3-. A hydroponic experiment was carried out to study effects of two NH4+/NO3- ratio (100/0 and 75/25) on response of rice different in responsivility to nitrate in root growth at the seedling stage. Four rice genotypes were tested, i.e. Nanguang, Elio (low in NO3- responsivity), Shanghai-97 (low in nitrate responsivity) and Liaojing (low in nitrate responsivity). Compared to supply of sole NH4+, enhanced NO3- supply increased root biomass and nitrogen accumulation of Nanguang (high in NO3- responsivity) by 50% and 79%,respectively, and the total length and number of roots, adventitious roots and lateral roots of the plant increased significantly, however, the mean length of adventitious and lateral roots did not vary much. No such significant effects were observed on other three genotypes of rice. It is clearly indicated that enhanced NO3- nutrient stimulates emergence of adventitious and lateral roots only, but does not promote their elongation. From the findings it is inferred that responsivity of rice to NO3- in root development differs with the genotype and is one of the factors that affect nitrogen use efficiency by rice.