精量施氮对烤烟成熟期叶片碳氮代谢的影响

Effects of Precise Nitrogen Application on Carbon and Nitrogen Metabolism of Flue-cured Tobacco Leaves at Maturity Stage

为了揭示基于SPAD仪精量施氮条件下烤烟叶片成熟期的碳氮代谢变化规律,以K326品种为材料,设置了基于SPAD仪精量施氮模式(SPAD阈值为43)和传统农家施氮模式处理。分别在烟叶下部叶成熟采收期和中部叶成熟采收期对烟株上偶数叶位的烟叶碳氮代谢化合物含量及酶活性进行了测定。结果表明:与传统农家施氮模式相比,基于SPAD施氮模式下烟株在下、中部叶成熟采收期所有偶数叶的游离氨基酸、可溶性蛋白质、总氮、谷氨酰胺合成酶、硝酸还原酶及蔗糖转化酶活性均降低,而总糖、还原糖含量及淀粉酶活性均升高。基于SPAD仪的烤烟精量施氮模式能够促进烟株不同部位烟叶碳氮代谢平稳过渡和转化,使烟叶成熟时碳氮代谢适时协调过渡,体现为总氮含量适时适量减少以及糖类物质适时适量的积累,烤烟糖氮比较为协调,烟叶品质提高。

In order to reveal the carbon and nitrogen metabolism in flue-cured tobacco leaves precisely fertilized with nitrogen by SPAD meter at maturity stage, treatments of SPAD-based N-fertilization （SPAD value of 43） and conventional N-fertilization by farmer on cv. K326 were compared. The contents of compounds involved in carbon and nitrogen metabolism and enzyme activities in every other leaf, starting from the second one on tobacco stalk were separately determined at the maturity stages of lower leaves and middle leaves. The results showed that comparing with the leaves fertilized by conventional N-fertilization by farmer, the contents of free amino acid, soluble protein and total nitrogen and the activities of glutamine synthase, nitrate reduetase and invertase decreased in the leaves fertilized by SPAD-based N-application, while the contents of total sugar, reducing sugar and amylase activities increased. It indicated that precise nitrogen application based on SPAD meter promoted smooth transition and transformation of carbon and nitrogen metabolism in all those leaves, thetimely coordinated transition of carbon and nitrogen metabolism at maturity stage was reflected by decreasing total nitrogens and increasing sugars to the right levels at the right time, the ratio of sugar to nitrogen was more harmonious, and the quality of tobacco leaves improved.