【作者】 魏亚萍；

【导师】 王璞；

【作者基本信息】 中国农业大学 ， 作物栽培与耕作， 2004， 博士

【摘要】 通过不同氮肥运筹在夏玉米生长前、中、后期形成不同的植株碳氮代谢水平，系统研究不同碳氮代谢水平下植株物质生产与运转、粒数形成、不同粒位籽粒库容建成和充实特点，并采用籽粒离体培养技术，研究离体条件下不同氮素供应时期对籽粒发育的影响及生理原因。从整株水平上对氮肥影响籽粒库容建成和充实的机理进行了探讨。主要研究结果如下： 1 夏玉米果穗强、弱势粒发育差异较大。弱势粒占单穗重的比例很小，但对穗粒重提高的贡献较大。适当增加生育前期和中期供氮水平明显提高了粒数，促进强、弱势粒(尤其是弱势粒)发育，显著增加产量。前期氮素供应不足使弱势粒发育明显受影响，粒数和粒重下降，产量降低。前期供氮过多及生育后期增加供氮对粒数、粒重和产量效果不明显。 2 雌穗小花分化数受氮肥影响不大，氮肥主要通过影响籽粒结实来影响粒数。生育前期和中期适量施氮可以提高粒数决定期植株生长速率，为粒数形成提供充足的碳氮供应，同时在灌浆期提高植株碳氮代谢水平和物质生产力，为籽粒发育提供更多的同化物。生育后期增加供氮对提高植株物质生产力作用不大，反而由于碳氮代谢竞争影响同化物向籽粒的供应。 3 氮肥通过影响籽粒碳氮代谢水平和库活性来影响籽粒库容建成和充实。前期和中期适量施氮增加了同化物向籽粒的供应，提高了籽粒(尤其是弱势粒)碳氮代谢水平，胚乳细胞分裂受促进，单粒和单穗库容量都增加，与糖代谢相关的酶活性(蔗糖转化酶、蔗糖合成酶、ADPG焦磷酸化酶和淀粉合成酶等)增强，籽粒库活性提高，淀粉积累受促进，粒重增加，其中氮肥对弱势粒发育的作用大于强势粒，增施氮肥使强、弱势粒发育差距明显缩小，穗粒重提高。生育前期或中期氮供应不足使籽粒库容量减少，库活性下降，粒重降低。生育后期增加供氮对强、弱势粒库容建成和充实的作用不大。 4 离体培养条件下，强、弱势粒发育存在差异，弱势粒对氮素缺乏更敏感。整个灌浆期氮素供应充足提高了籽粒库活性和碳氮代谢水平，促进了籽粒库容建成和库充实；整个滞浆期缺氮显著降低籽粒库活性和碳氮代谢水平，蔗糖分解和淀粉合成受阻；库容建成期缺氮影响了籽粒库容建成，但库充实期恢复供氮后，籽粒库活性和碳氮代谢水平有所提高；库充实期缺氮对籽粒库容大小没有影响，但对库充实影响明显。不同缺氮时期对粒重的影响程度与缺氮时间长短有关，表现为：整个灌浆期缺氮＞库充实期缺氮＞库容建成期缺氮。 5 氮肥一方面通过影响植株物质生产力来改变同化物向籽粒的供应，间接作用于粒重形成；另一方面也通过调节与粒重形成相关酶的活性直接作用于籽粒发育。在90～180kgN／hm~2施氮范围内，基肥：雌穗小花肥=1：3的氮肥运筹方式可以显著促进弱势粒发育，增加粒重，获得高产。更多还原

【Abstract】 Nitrogen supply affects the carbon-nitrogen metabolism during plant growth in summer maize (Zea mays L.). Dry matter production, kernel number determination and kernel development were investigated under different rates and times of nitrogen application. The influence of nitrogen availability on kernel growth in vitro was also studied. The mechanism of nitrogen affecting kernel development was discussed by comparing the results of in vitro culture and field trials.The growth of upper and middle kernels was quite different in summer maize. The upper kernels were very important to increase ear weight although they were only a small part of the ear. Increasing the nitrogen supply appropriately during early and middle growth stage of summer maize promoted kernels growth (especially for upper kernels), which led to high kernel number (KN), kernel weight (KW) and grain yield significantly. Nitrogen deficiency during early growth stage resulted in reduction of KN, KW and grain yield. Excess nitrogen supply.in early growth or silking stage had no obvious effects on KN, KW and grain yield.The increased KN by nitrogen was mainly due to the reduced kernel abortion while spikelet number was not influenced. Increasing the nitrogen supply during early and middle growth stage improved the assimilate and nitrogen level of plant, so as to enhance dry matter production and plant growth rate, which was helpful to kernel growth. Increasing the nitrogen supply in the silking stage had no effect on the dry matter production, but the assimilate supply for kernel growth was reduced due to the competition between carbon and nitrogen metabolism.Increasing the nitrogen supply during early and middle growth stage enhanced carbon-nitrogen metabolism and the assimilate supply for kernel, so as to promote the endosperm cell division and to enlarge the sink capacity of kernel and ear. Meanwhile, the activity of enzymes related sucrose metabolism (sucrose invertase, sucrose synthase, ADPG-ppase and starch synthase) and starch deposition were also increased, which led to high KW. Nitrogen had more obvious effect on the growth of upper kernels than that of middle kernels. Increasing nitrogen supply reduced the difference between upper and middle kernels growth, and improved the ear weight. Nitrogen deficiency in the early and middle growth stage reduced the sink capacity and activity, which resulted in lower KW. Increasing nitrogen supply in silking stage had little effect on the kernel development.The growth difference of upper and middle kernels was still obvious in vitro culture, and upper kernels were more sensitive to nitrogen stress. Sufficient nitrogen supply during grain filling period promoted kernel growth by improving carbon-nitrogen metabolism and sink activity of kernels. Nitrogen shortage during grain filling period decreased the sink metabolism and activity, which hindered the sucrose decomposition and starch synthesis, and finally resulted in small KW. Nitrogen stress during endosperm cell division or linear filling stage reduced the kernel sink capacity and influenced grain filling rate separately, and all of them was unfavorable to kernel weight increase. The impact of nitrogen stress at different stage on kernel growth was: stress during grain filling period > during linear filling period > during endosperm cell division.Nitrogen supply had both indirect and direct effects on the kernel development. On the one hand,nitrogen influenced the plant dry matter production so as to change the assimilate supply for kernel growth. On the other hand, nitrogen affected the activity of enzymes related to kernel growth. Within the range of 90~180kg N/hm2, kernel weight and grain yield could be improved significantly by the fertilizer application with the ratio of 1:3 for sowing stage and spikelet differentiation stage.更多还原