施钾时期对甘薯济徐23块根淀粉积累 与品质的影响及酶学生理机制

【目的】阐明施钾时期对甘薯“济徐23”块根淀粉积累和粒度分布特征的影响及其酶学生理机制。【方法】在大田栽培条件下，以淀粉型品种“济徐23”为材料，设置不施钾肥（T1）、基施钾肥（T2）、封垄期追施钾肥（T3）和茎叶生长高峰期追施钾肥（T4）4个处理，于2008-2009年2个生长季在山东农业大学农学试验站进行试验。采用甘薯块根膨大过程中定期取样的方法留样，测定块根中淀粉、直链和支链淀粉含量，同时测定块根淀粉粒体积分布的中位粒径和大（>19.76 μm）、中（3.359-19.76 μm）、小（<3.359 μm）型淀粉粒所占的体积百分比以及淀粉合成相关酶（SS、ADPGPPase、UDPGPPase、GBSS和SSS）活性，分析不同时期施用钾肥对甘薯各生育时期块根内淀粉及组分含量、淀粉粒度分布特征及淀粉合成相关酶活性的影响。【结果】与对照（T1）相比，施用钾肥提高了块根干物质积累量和淀粉产量，3个施钾处理淀粉产量的增幅分别为24.90%、16.57%和9.24%，随施用时间的推迟淀粉产量增幅降低。封垄期和茎叶生长高峰期追施钾肥显著降低直链淀粉含量而提高支链淀粉含量。基施钾肥提高了大型淀粉粒的体积百分比，茎叶生长高峰期追施则提高中、小型淀粉粒的体积百分比，增幅均达到显著水平。不同时期施钾均可提高块根中SS、ADPGPPase和UDPGPPase的活性，提高淀粉合成前体物质的供应能力，施用钾肥对SS和ADPGPPase活性的作用时间最长为130 d，基施钾肥主要作用时期为块根膨大的前、中期，追施钾肥的主要作用时期为块根膨大的中、后期，施钾越早对UDPGPPase活性的作用时间越长；追施钾肥提高了块根膨大后期SSS活性、而降低了块根膨大后期GBSS活性。总淀粉含量与SS和ADPGPPase活性呈极显著正相关，直链淀粉含量与GBSS和SS活性呈极显著正相关，支链淀粉含量与ADPGPPase和SSS活性呈显著正相关关系。【结论】基施或封垄期追施钾肥显著提高块根干物质积累量和淀粉产量，追施钾肥显著提高支链淀粉含量、降低直链淀粉含量，基施钾肥处理的大型淀粉粒体积百分数高，高峰期施用钾肥处理的中、小型淀粉粒体积百分数高。施钾时期显著影响直链淀粉含量、支链淀粉含量和淀粉产量，这与块根中SS、ADPGPPase、UDPGPPase、GBSS和SSS活性的变化密切相关。

Effect of Potassium Application Time on Starch Accumulation and Related Enzyme Activities of Sweet Potato Variety Jixu 23

【Objective】A field experiment was conducted to clarify the regulatory effects of potassium application time on starch accumulation and its physiological mechanism, starch granule distribution of storage roots of sweetpotato variety Jixu 23. 【Method】Jixu 23 (cultivar for starch use) was planted at Tai’an experimental site in Shandong Province, with randomized block design in 2008-2009 growing season. There were four treatments in all, including the control (non-potassium fertilizer, T1), potassium applied as basal fertilizer (T2), as top cover fertilizer (T3) and as top-growth peak fertilizer (T4). Samples were obtained by using periodic sampling during storage roots development. The content of starch, amylose and amylopectin of storage root were determined at different growth stages. Meanwhile the medium diameter of starch grain was determined and the volume fraction of different diameters starch granules (＞19.76 μm, 3.359-19.76 μm and ＜3.359 μm) was calculated. The activities of enzymes (SS, ADPGPPase, UDPGPPase, GBSS and SSS) related to starch synthesis were also studied. The effects of potassium application time on starch and its components, starch granule distribution and activities of enzymes related to starch synthesis in storage roots at different growth stages were analyzed.【Result】Compared with the control (T1), dry matter accumulation and starch yield of storage roots in treatments with potassium applied increased, and the increase of starch yield of T2, T3 and T4 treatments was 24.90%, 16.57%, and 9.24%, respectively. And the increase decreased when the application time delayed. The amylose content of storage root in treatments of topdressing (T3, T4) increased while amylopectin content was decreased significantly. The volume fraction of large starch granules in treatment with potassium applied as basal fertilizer (T2) was larger, and the volume fraction of medium and small starch granules in treatment with potassium applied as top-growth peak fertilizer (T4) was larger than that in the other treatments. Potassium application increased the activities of SS, ADPGPPase and UDPGPPase, and enhanced the supply capability of precursors for the synthesis of starch. And the longest action time of potassium on SS and ADPGPPase activities was 130 days, and potassium applied as basal fertilizer (T2) worked effectively mainly at early and middle stages of storage roots development, while treatments of topdressing (T3, T4) worked effectively mainly at middle and late stages of storage roots development. For UDPGPPase activity, the earlier the potassium applied, the longer action time was got. Potassium applied as topdressing (T3, T4) increased SSS activity but reduced GBSS activity of storage roots during the later expanding period. There was a significant positive correlation between total starch content and SS and ADPGPPase activities, and the significant positive correlation was also found between amylose content and GBSS and SS activities. And amylopectin content had a significant positive correlation with ADPGPPase and SSS activities.【Conclusion】Potassium applied as basal fertilizer (T2) and top cover fertilizer (T3) increased dry matter accumulation and starch yield of storage root significantly. Potassium applied as topdressing increased amylopectin content but decreased amylase content significantly. Treatments with potassium applied as basal fertilizer got a higher volume fraction of large starch granules, while treatments with potassium applied as top-growth peak fertilizer got a higher volume fraction of medium and small starch granules. The significant effects of potassium application time on amylase content, amylopectin content and starch yield were closely related with the changes of SS, ADPGPPase, UDPGPPase, GBSS and SSS activities.