不同小麦品种(系)吸收利用氮素效率的差异及有关机理研究　Ⅲ.影响利用效率的因素分析

Genotype variations for nitrogen use efficiency in winter wheat (Triticum aestivum L.)Ⅲ. Factors affecting utilization efficiency of nitrogen

用盆栽试验研究了12个冬小麦品种（系）在成熟期以生物学产量为基础的利用效率（UtEB=生物学产量／吸氮量）、收获系数、氮素收获系数和籽粒氮浓度对以籽粒产量为基础的利用效率（UtEG=籽粒产量／吸氮量）的影响。相关分析证明，这4个因子对UtEG的影响各不相同。无论是低氮还是高氮处理，UtEG与UtEB和收获指数呈正相关，而与籽粒氮浓度呈负相关，与氮素收获指数的相关性较差。从相关系数的高低判断，在这名个因子中，籽粒氮浓度对UtEG的影响最大，其次是UtEB和收获指数。虽然氮素收获指数与UtEG的相关性较差，但它在高氮处理的水平较低，致使利用效率（UtEG）降低。此外还分析了开花期单株顶3叶叶绿素含量与利用效率（UtEG和UtEB）的关系。开花期单株顶3叶叶绿素含量与吸氮量的比值（UtEC）因品种（系）而异，且大多数品种（系）的UtEC受供氮水平的影响小，推测该性状可能受遗传控制。相关分析表明，在低氮处理中，UtEC分别与UtEG和UtEB呈显著或极显著正相关，说明UtEC可能是导致品种间利用效率差异的内在因素之一。在高氮处理中，由于叶绿素含量不是光合作用的限制因素，UtEC与UtEG、UtEB相关性较差，对其原因的深入研究，可为采取措施提高高肥条件下的利用效率提供理论依据。

A pot experiment with 12 wheat genotypes (Triticum aestivum L.) were grown in green house with three replications at low N and high N treatment in 1997 to l998.The factors affecting utilization efficiency of nitrogen were analyzed. Utilization efficiency of nitrogen (UtEG) here is defined as the ratio of grain yield over N accumulated at maturity. The results indicated that UtEG positively related with N utilization efficiency based on biomass (UtEB =biomass/N uptake at maturity) and harvest index,negatively related with grain N concentration,and poorly related with N harvest index.Of the four factors,grain N concentration had the strongest influence on genotypic variations for UtEG. Although N harvest index had the weakest influence on genotypic variations for UtEG,the low levels of N harvest index resulted in the low levels of UtEG at the high N treatment.The ratio of the chlorophyll content of top three leaves over N accumulated in above ground part at anthesis (UtEC) related well with UtEG,and UtEB at the low N treatment,indicating that genotypic variations for UtEC maybe one of the intrinsic reasons for genotypic variations for UtEG and UtEB. But UtEC did not relate with UtEG,and UtEB at the high N treatment,for the chlorophyll content of top three leaves was not the limiting factor for photosynthesis. We observed great differences for UtEC among wheat genotyps at both N levels,but UtEC of most genotypes did not vary with N supply levels,suggesting that UtEC is possibly under genetic control.