Thornton B, Millard P, Duff E I, Buckland S T
Plants Division, Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB9 2QJ, Scotland, UK.
Environment Modelling Unit, Scottish Agricultural Statistics Service, Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB9 2QJ, Scotland, UK.
New Phytol. 1993 Aug;124(4):689-694. doi: 10.1111/j.1469-8137.1993.tb03859.x.
Miniswards of Lolium perenne, Festuca rubra, Agrostis casteUana and Poa trivialis were grown in a sand-limestone mixture and fed with a complete nutrient solution containing 3 mol m NH NO . The miniswards were cut weekly to a height of 4 cm until a steady state of growth, based on weight of clippings removed, was achieved. After clipping (day 0) the nutrient solution was replaced by one in which all the nitrogen (N) was enriched with N to 5 atom per cent, but was otherwise identical. This allowed discrimination of remobilization from current root uptake when considering the supply of N for regrowth of laminae. Destructive harvests were made over the following 28-d period, while unharvested plants continued to receive a weekly clip. The proportion of the total uptake of labelled N which appeared in the clipped material was of the order L. perenne > P. trivialis > A. castellana > F. rubra. The change in unlabelled N in the roots plus leaf bases over time was modelled as a proportion of the amount present on day 0. A simple exponential model with a non-zero asymptote was found to model the data; the asymptote was assumed to represent the proportion of unlabelled N not readily available for remobilization. Species differences in the asymptotes were found, with F. rubra having a significantly larger asymptote than A. castellana and P. trivialis, which in turn both had significantly larger asymptotes than L. perenne. All species used both root uptake and remobilization to supply N for post-defoliation regrowth of laminae. However, the relative contribution of each source was species-dependent. The proportion of N in the clipped material derived from remobilization was significantly greater for F. rubra than A. castellana, which in turn had a significantly greater proportion derived from remobilization than P. trivialis and L. perenne.
多年生黑麦草、紫羊茅、匍匐翦股颖和普通早熟禾的微型草皮生长在沙子与石灰石的混合物中，并施以含有3摩尔/立方米硝酸铵的完全营养液。每周将微型草皮修剪至4厘米高度，直至基于去除的修剪物重量达到稳定生长状态。修剪后（第0天），将营养液换成一种所有氮（N）均用¹⁵N富集至5原子百分比但其他方面相同的营养液。这使得在考虑叶片再生长的氮供应时，能够区分再利用氮和当前根系吸收的氮。在接下来的28天内进行破坏性收获，而未收获的植株继续每周修剪。出现在修剪材料中的标记氮总吸收量的比例顺序为：多年生黑麦草＞普通早熟禾＞匍匐翦股颖＞紫羊茅。随着时间推移，根和叶基部中未标记氮的变化被建模为第0天存在量的比例。发现一个具有非零渐近线的简单指数模型可以模拟数据；渐近线被假定代表不易用于再利用的未标记氮的比例。发现渐近线存在物种差异，紫羊茅的渐近线显著大于匍匐翦股颖和普通早熟禾，而匍匐翦股颖和普通早熟禾的渐近线又都显著大于多年生黑麦草。所有物种都利用根系吸收和再利用来为叶片脱叶后再生长提供氮。然而，每个来源的相对贡献因物种而异。紫羊茅从再利用中获得的氮在修剪材料中的比例显著高于匍匐翦股颖，而匍匐翦股颖从再利用中获得的氮比例又显著高于普通早熟禾和多年生黑麦草。
