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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.
The effects of potassium fertilization on the nitrogen transport and distribution, photosynthetic characteristics and nitrogen metabolism enzyme activities in aerial and understory of sweet potato rooting stage, tuberous tuberosity stage were studied using ~ (15) N tracing technique. The results showed that: During the root tuberization stage, the potassium application significantly increased the translocation and distribution of ~ (15) N to shoots, and K_3 (300 mg · kg -1) Increased by 76.2%, and the accumulation of ~ (15) N increased by 92.1% .In the tuber expansion stage, the total distribution of ~ (15) N in upper leaves decreased from 33.7% to 24.4% 15), the N partitioning rate increased from 5.8% to 17%, and the accumulated amount of ~ (15) N in the root of K_3 treatment was 3 times of that of the control.The nitrate reductase, glutamate dehydrogenase, glutamine The synthase, glutamate synthase and net photosynthetic rate (P_n) increased with the increase of potassium application. The stepwise regression analysis showed that the activities of nitrogen metabolism enzymes and P_n were the main factors affecting the transfer and distribution of ~ (15) N in sweet potato (R = 0.965 and 0.942, respectively). Path analysis showed that nitrogen was mainly distributed to aerial parts of potato by promoting nitric acid reductase and glutamate dehydrogenase-mediated nitrogen catalysis. Block swelling Nitrogen mainly promote the distribution of the ground portion by increasing nitrogen assimilation capacity of glutamine synthase / glutamate synthase cycle mediated.