小麦旗叶衰老过程中Rubisco周转初探

为了探讨叶片衰老过程中Rubisco的合成与降解的机理，在抽穗期对小麦进行了增施¹⁵N同位素标记的(NH₄)₂SO₄处理以延缓旗叶的衰老进程，同时对旗叶中Rubisco及Rubisco的组成成分LSU、SSU的含量及其相应的¹⁵N丰度进行了测定。结果表明，Rubisco及LSU、SSU等的含量均增加；且在小麦旗叶光合功能高值持续期，Rubisco及LSU、SSU等的丰度均处于较高水平，表明Rubisco仍处于动态的降解、合成这一周转过程中，仍有Rubisco的重新合成，但Rubisco同时也被不断地降解；而在光合功能低值期，Rubisco及LSU、SSU等的¹⁵N丰度均处于低水平，且基本无变化，表明此时无Rubisco的重新合成。另外土壤¹⁵N丰度的降低说明植株在生长发育后期仍有较强的从土壤中吸收氮素的能力。因此抽穗期施氮肥对小麦产量的提高有重要意义。

The Study of Rubisco Turnover in Wheat Flag Leaves During Senescence

In order to study the mechanism of synthesis and degradation about Rubisco, (NH4)2SO4 which was marked by 15N was applied during earing period to delay the falg leaf ageing process, meanwhile the content and 15N abundance of Rubisco, LSU, SSU, etc. were determined. The result showed that the content and the 15N abundance of Rubisco, LSU, SSU were at high level during the RAPD (Relative active photosynthetic duration) of wheat flag leaf, which indicated that Rubisco was at a continuous process of turnover about synthesis and degredation. Rubisco was resynthetized still, while Rubisco was hydrolyzed. During the RPD (rapid photosynthetic duration) of wheat flag leaf, 15N abundance of Rubisco, LSU and SSU were at a lower level, and had little changes. All these indicated that there was little Rubisco resynthesized during RPD. The 15N abundance of soil was declined, and this indicated that plant possessed a powerful ability in absorbing nitrogen from soil during the later upgrowth period. So it was very important for a higher wheat yield to apply nitrogen fertilizer in earing period.