中文摘要：

利用^（15）N示踪技术,研究了施钾对甘薯发根结薯期、薯块膨大期地上和地下部氮素转移分配、光合特性及氮代谢酶活性的影响.结果表明：在发根结薯期,施钾显著提高^（15）N向地上部的转移分配,其中K_3（K_2O,300 mg·kg^（-1））处理与对照相比^（15）N向叶片转移速率提高了76.2%,^（15）N积累量提高了92.1%.在薯块膨大期,随施钾量增加地上部叶片^（15）N总分配率由33.7%降低至24.4%,块根^（15）N分配率由5.8%升高至17%,其中K_3处理块根^（15）N积累量是对照的3倍.两个关键生长期硝酸还原酶、谷氨酸脱氢酶、谷氨酰胺合酶、谷氨酸合酶和净光合速率（P_n）均随施钾量的增加而提高.逐步回归分析表明,氮代谢酶活性和P_n是影响甘薯^（15）N转移和分配的主要因素（R分别为0.965和0.942）,通径分析表明,在发根结薯期主要通过促进硝酸还原酶和谷氨酸脱氢酶介导的氮素催化能力促进氮素向地上部分配;在薯块膨大期主要通过提高谷氨酰胺合酶/谷氨酸合酶循环介导的氮素同化能力促进氮素向地下部分配.

英文摘要：

A pot experiment with 15N tracing techniques was designed to study the effect of potassium application on nitrogen transfer, photosynthetic characteristics and nitrogen metabolism enzyme activities in two different growth stages of sweet potato. Results indicated that potassium application significantly increased the shoot 15N distribution rate. Compared with control, the 15N transfer rate of K3 treatment increased by 76.2% and the total accumulation of tSN increased by 92.1% in tuber for- mation period. Different with tuber formation period, shoot 15N distribution rate decreased from 33.7% to 24.4%, but the root 15N distribution rate increased from 5.8% to 17% with the increase of K application in tuber rapid growth stage. Especially, root 15N accumulation of K3 treatment was 3 times of the CK. During the two growth stages, nitrate reductase, glutamate dehydrogenase, gluta- mine synthetase, glutamate synthase and net photosynthetic rate all increased with the increase of K application. Stepwise regression analysis showed that nitrogen metabolism enzyme activities （nitrate reductase, glutamate dehydrogenase, glutamine synthetase, glutamate synthase） and Pn were the main factors to affect the 15N transfer and distribution of sweet potato （ R1 = 0.965, R2 = 0.942）. Path analysis showed that nitrate reductase and glutamate dehydrogenase activities were the key factors to influence 15N distribution to the shoot in tuber formation period, while glutamate dehydrogenase, glutamate synthase activities were the key factors to influence 15N distribution to the tuber in tuber rapid growth stage.