小麦旗叶Rubisco周转与籽粒含氮量的关系

Relationship Between Rubisco Turnover of Flag Leaf and Nitrogen Content of Grains in Wheat

随着旗叶的衰老 ,Rubisco含量逐渐减少。延缓小麦旗叶的衰老进程 (抽穗期施氮肥 ) ,可增加旗叶Rubisco的含量 ,提高籽粒的全氮含量。在小麦旗叶全展后 2 8d内 ,Rubisco的15N丰度处于较高水平 ,表明仍有Rubisco的重新合成 ;而在 2 8d以后 ,Rubisco的15N丰度处于低水平 ,表明无Rubisco的重新合成。但这时籽粒的15N丰度却上升。旗叶全展后 14d内Rubis co的15N丰度高于旗叶中全氮的丰度 ,说明此时期Rubisco重新合成的速率高于其它蛋白质 ;旗叶衰老过程中Rubisco的15N丰度的净转移高于全氮 ,Rubisco净N转移也高于全氮 ,表明Rubisco向籽粒中转移的氮素多于其它蛋白质 。

The Rubisco content of wheat flag leaf declined steadily during senescence(Fig.1). When nitrogen fertilizer in the form of 15 N labeled (NH 4) 2SO 4 was applied at the earing , senescence of wheat flag leaf was delayed, Rubisco and total nitrogen content in both flag leaf and grains was increased(Figs.1,3,5), 15 N abundance of Rubisco was kept high untill 28 d after full expansion of the flag leaf(Fig.2). These facts indicated that Rubisco was in a continuous process of turnover,and Rubisco synthesis was actually maintained. From then on, 15 N abundance of Rubisco was reduced to a lower level and then remained practically unchanged up to wheat flag leaf death(Fig.2). All these indicated that new synthesis of Rubisco was trivial. Additionally, 15 N abundance of grains was enhanced. 15 N enrichment of Rubisco was higher than that of total protein(Tables 1,2), which indicated that the rate of Rubisco resynthesis was faster than other proteins. Net nitrogen and 15 N abundance cyclization of Rubisco were higher than that of total nitrogen. This indicated that there more nitrogen from Rubisco than from other proteins was transported to grains, and so that the contribution of Rubisco nitrogen to grain protein was larger than other proteins.