中文摘要：

当前玉米产量的提高部分归因于种植密度的增加,但过高的种植密度使冠层中下部叶片光照条件变差,致使单株生长速率降低。因此,如何缓解该条件下群体光合与单株光合性能的矛盾成为当前玉米高产栽培中急需解决的问题。为此,在种植密度为105 000株hm–2的大田试验条件下,研究了紧凑型玉米品种郑单958及半紧凑型玉米品种金海5号的群体光合速率（CAP）、叶面积指数（LAI）、穗位叶净光合速率（Pn）及抗氧化酶活性等对不同程度去叶的响应,以期为高密度栽培条件下稳定或提高单株生产力探讨新的技术途径,同时也为耐密高产品种选育提供借鉴。开花后3 d分别2个品种做不同程度去叶处理,包括去除植株顶部2片叶（S1）、4片叶（S2）、6片叶（S3）,以不去叶植株为对照（S0）。结果表明,去叶可显著改善玉米生育后期群体透光率（LT）,然而S2和S3处理显著降低了LAI,增加了生育后期的漏光损失,不利于光能利用率的提高,致使其实际光化学效率（ΦPSII）和最大光化学效率（Fv/Fm）较低;去除植株顶部两片叶（S1）可显著提高籽粒灌浆期间CAP并延长LAI高值持续期,形成较高的籽粒产量,而过度去叶（S2和S3）则显著降低产量;花后52 d,郑单958 S1处理CAP较对照升高12.49%,而金海5号则升高23.08%;随去叶程度的增强,花后0-26 d内各去叶处理穗位叶Pn、气孔导度（gs）和叶绿素含量明显升高,均显著高于S0,但之后S1处理表现出较优的单叶光合特性。S1处理穗位叶自花后13 d起保持较高的超氧化物歧化酶（SOD）、过氧化物酶（POD）活性及较低的丙二醛（MDA）含量。可见,高密度种植条件下,去除植株顶部2片叶可有效调控两株型玉米生育后期群体光合速率、穗位叶光合特性及活性氧清除能力,能较好地协调高密度群体与个体的关系,获得较高的籽粒产量,且对半紧凑型品种金海5号调

英文摘要：

The improved grain yield of modern maize hybrids is mainly due to the increased plant density.However,the solar radiation intercepted by ear leaves was reduced,and the growth rate of individual plant was suppressed under high plant density.Consequently,how to coordinate the relationship between canopy apparent photosynthesis（CAP） and individual leaf photosynthesis capacity under high plant density is a vital question we are facing.A field experiment was conducted using summer maize（Zea mays L.） Zhengdan 958（a compact cultivar） and Jinhai 5（a semi-compact cultivar） grown at a plant density of 105 000 plants ha–1,to research the impact of leaf removal on CAP,individual leaf photosynthetic characteristics and anti-oxidative metabolism,which will provide theoretical basis and technical supports for super-high-yield cultivation and breeding.The defoliation treatments consisted of no leaf removal（S0）,two（S1）,four（S2） and six leaves（S3） removal from the top of a plant were imposed at three days after anthesis（DAA）.The results indicated that leaf removal could significantly improve light transmission ratio（LT） after anthesis,but decrease leaf area index（LAI） of S2 and S3,resulting in the decrease of effective quantum yield of PSII（ΦPSII） and maximal efficiency of photosystem II photochemistry（Fv/Fm） sharply because of light leakage losses.CAP was significantly affected by defoliation treatments：for S1,CAP increased and longer durations of CAP and LAI were maintained during grain filling,resulting in a higher grain yield,whereas CAP in S2 and S3 treatments was inhibited and drastically declined,indicating that CAP is closely related to the changes in available leaf area.Compared with S0,the CAP in S1 treatment increased by 12.49% for Zhengdan 958,and by 23.08% for Jinhai 5,indicating that the effect of excising two leaves on CAP was more apparent for Jinhai 5 than for Zhengdan 958.Moreover,an increase in net photosynthetic rate（Pn）,stomatal conductance（gs） a