不同耐氮性甘薯光合产物分配与转运效率对氮肥的响应及其化控效应研究

In recent years, with the improvement of production conditions and soil fertility, it is easy to cause overgrowth in sweet potato. The root cause of overgrowth is that the photosynthetic product is hard to translocate to the root tuber. Nitrogen is one of the main factors influencing the source-sink relationship for sweet potato and excessive application of N fertilizer is easy to cause overgrowth. The translocation efficiency of photosynthetic product is closely related with the nitrogen nutrition. The plant growth regulator can effectively coordinate the growth of above-ground part and underground part for sweet potato. And it can promote photosynthesis products transport, which is the main measure for controlling overgrowth of sweet potato. This project with different nitrogen resistant sweet potato cultivar studies the law of photosynthetic product distribution by using the carbon stable isotope tracer technique; the photosynthate supplying ability of leaves, the distance of source-sink, the vigor of phytosynthate transportations, the speed of sap flow and the offloading capacity in root tuber by using enzymatic method and physiological and biochemical method; the ultrastructure of phloem tissue and vascular microstructure by using transmission electron microscope and light microscope. The project studies the responses of photosynthate distribution and transportation efficiency to nitrogen fertilizer and its chemical control effects by using different sweet potato varieties with different nitroegn resistant. It can reveal the physiological mechanism of photosynthate distribution and transportation efficiency and expound the key link of phytosynthate transportations, which can provide theoretical basis for mechanism research of overgrowth and theoretical basis for reasonable control technology in sweet potato.

近年来，随着生产条件的改善及土壤肥力水平的提高，甘薯茎叶容易徒长，造成徒长的根本原因是光合产物向块根运转不畅。氮素是影响甘薯源库关系的主要因素之一，氮肥施用过多容易引起甘薯徒长，叶片的光合产物能否及时向块根中运输和分配与氮素营养密切相关；植物生长调节剂可有效协调甘薯地上部茎叶生长和地下部块根膨大，促进光合产物向块根转运，是当前控制旺长的主要措施。本项目拟采用耐氮性不同的甘薯品种，采用稳定性同位素13C标记法、光学显微镜和透射电镜制样分析、酶学及生理生化等方法，研究光合产物分配规律、叶片光合产物供应能力、源库距离与运输动力、源库端韧皮部组织超微结构、茎维管束显微结构、茎流速率、块根光合产物卸载能力，研究甘薯光合产物分配与转运效率对氮肥的响应及其化控效应，揭示其对光合产物分配与转运效率调控的生理机制，明确其影响光合产物分配转运的关键环节，以期为研究甘薯徒长机理及建立合理的化控技术提供理论依据。

近年来，甘薯生产中茎叶徒长现象时常发生，氮肥施用不当容易引起徒长，造成徒长的根本原因是光合产物向块根运转不畅；植物生长调节剂可有效抑制甘薯地上部茎叶生长，促进块根膨大。然而关于甘薯光合产物分配与转运效率对氮肥的响应及其化控效应的机制研究较少。本项目采用耐氮性不同的甘薯品种，研究了甘薯光合产物分配与转运效率对氮肥的响应及其化控效应，明确了氮素及烯效唑影响甘薯光合产物转运的关键环节。本项目研究表明，施氮过多降低两甘薯品种主要生育时期块根13C分配比例，提高地上部尤其是侧枝茎、测枝叶和侧枝生长点13C分配比例，不利于建立合理的13C分配格局；显著提高生长中后期平均源库距离，增加过长源库距离比例；降低生长中后期功能叶蔗糖含量和蔗糖/淀粉含量比值，降低叶片ATP含量，光合产物供应和输出能力降低；降低主茎基部维管束面积，降低生长前中期主茎顶部-基部蔗糖浓度降幅，增加生长中后期主茎顶部-基部蔗糖浓度升幅，降低主茎顶部-基部钾离子和氨基酸含量降幅，不利于提高源库间膨压差，造成蔗糖在茎基部积聚；同时块根部位蔗糖合酶和不溶性酸性转化酶活性降低，蔗糖在块根部位卸载受阻。与济薯26相比，在较高氮素下，耐氮性较强的徐薯32可保持较高的13C块根分配比例，较高的叶片蔗糖/淀粉比值及合理的茎部蔗糖、钾离子和氨基酸浓度梯度，同时块根蔗糖分解转化能力强，有利于蔗糖在茎部的向下运输及在块根部位的卸载，是其获得较高产量的原因。在高肥力条件下，烯效唑可有效缩短源库距离，提高源库间转运动力，促进地上部光合产物向块根的转运，长蔓不耐氮型品种济薯26烯效唑施用浓度高于短蔓耐氮型品种徐薯32。在实际生产中，在肥力较高条件下，可考虑不施氮肥或少施氮肥，同时选择耐氮性较强的品种，进行合理化控，有利于提高甘薯种植效益。