Ellis C J, Crittenden P D, Scrimgeour C M, Ashcroft C J
School of Biology, University of Nottingham, University Park, UK.
New Phytol. 2005 Nov;168(2):423-34. doi: 10.1111/j.1469-8137.2005.01524.x.
Nitrogen translocation was measured in Cladonia portentosa during 2 yr growth in Scottish heathland. Translocation was predicted to occur if N is resorbed from senescent basal tissue and recycled within the thallus. (15)N was introduced into either the lower (TU thalli) or upper (TD thalli) 25 mm of 50-mm-long thalli as (15)N-NH(4) (+), (15)N-NO(3) (-) or (15)N-glycine. Labelled thalli were placed within intact lichen cushions, either upright (TU) or inverted (TD). Vertical distribution of label was quantified immediately following labelling and after 1 and 2 yr. Independently of the form of introduced label, (15)N migrated upwards in TU thalli, with new growth being a strong sink. Sink regions for (15)N during year 1 (including new growth) became sources of (15)N translocated to new growth in year 2. Upward migration into inverted bases was minimal in TD thalli, but was again marked in new growth that developed from inverted apices. Relocation of N to regions of growth could facilitate internal N recycling, a process postulated to explain the ecological success of mat-forming lichens.
在苏格兰石南荒原上，对多枝石蕊两年生长期间的氮转运进行了测定。如果氮从衰老的基部组织中再吸收并在叶状体中循环利用，那么就可以预测氮的转运情况。将（15）N以（15）N-NH₄⁺、（15）N-NO₃⁻或（15）N-甘氨酸的形式引入50毫米长叶状体的下部25毫米（TU叶状体）或上部25毫米（TD叶状体）。将标记的叶状体直立（TU）或倒置（TD）放置在完整的地衣垫层中。在标记后以及1年和2年后，立即对标记的垂直分布进行定量。与引入标记的形式无关，（15）N在TU叶状体中向上迁移，新生长部分是强烈的吸收库。第1年（包括新生长部分）中（15）N的吸收区域在第2年成为转运到新生长部分的（15）N的来源。在TD叶状体中，向上迁移到倒置基部的情况很少，但从倒置顶端发育而来的新生长部分中再次明显。氮重新分配到生长区域可以促进内部氮的循环利用，这一过程被认为可以解释形成垫状地衣的生态成功。
