Yasumura Yuko, Hikosaka Kouki, Hirose Tadaki
Graduate School of Life Sciences, Tohoku University, 6-3 Aoba, Aramaki, Sendai 980-8578, Japan.
Funct Plant Biol. 2007 Jun;34(5):409-417. doi: 10.1071/FP06307.
The extent of nitrogen (N) resorption and the degradability of different protein pools were examined in senescing leaves of an annual herb, Chenopodium album L., grown in two light and N conditions. Both N resorption efficiency (R; the proportion of green-leaf N resorbed) and proficiency (R; the level to which leaf N content is reduced by resorption) varied among different growth conditions. During leaf senescence, the majority of soluble and membrane proteins was degraded in all growth conditions. Structural proteins were also highly degradable, implying that no particular protein pool constitutes a non-retranslocatable N pool in the leaf. Leaf carbon/N ratio affected the timing and duration of senescing processes, but it did not regulate the extent of protein degradation or N resorption. Sink-source relationships for N in the plant exerted a more direct influence, depressing N resorption when N sink strength was weakened in the low-light and high-N condition. N resorption was, however, not enhanced in high-light and low-N plants with the strongest N sinks, possibly because it reached an upper limit at some point. We conclude that a combination of several physiological factors determines the extent of N resorption in different growth conditions.
在两种光照和氮素条件下生长的一年生草本植物藜（Chenopodium album L.）衰老叶片中，研究了氮（N）的再吸收程度和不同蛋白质库的降解能力。不同生长条件下，氮再吸收效率（R；绿叶中再吸收的氮的比例）和熟练程度（R；通过再吸收使叶片氮含量降低的程度）均有所不同。在叶片衰老过程中，所有生长条件下大部分可溶性蛋白和膜蛋白都会降解。结构蛋白也具有高度可降解性，这意味着叶片中没有特定的蛋白质库构成不可再转运的氮库。叶片碳氮比影响衰老过程的时间和持续时间，但它并不调节蛋白质降解或氮再吸收的程度。植物中氮的源库关系发挥了更直接的影响，在低光照和高氮条件下，当氮库强度减弱时会抑制氮再吸收。然而，在氮库最强的高光和低氮植物中，氮再吸收并未增强，这可能是因为它在某个点达到了上限。我们得出结论，多种生理因素共同作用决定了不同生长条件下氮再吸收的程度。
