EFFECTS OF LEAF AGE, NITROGEN NUTRITION AND PHOTON FLUX-DENSITY ON THE DISTRIBUTION OF NITROGEN AMONG LEAVES OF A VINE (IPOMOEA-TRICOLOR-CAV) GROWN HORIZONTALLY TO AVOID MUTUAL SHADING OF LEAVES
EFFECTS OF LEAF AGE, NITROGEN NUTRITION AND PHOTON FLUX-DENSITY ON THE DISTRIBUTION OF NITROGEN AMONG LEAVES OF A VINE (IPOMOEA-TRICOLOR-CAV) GROWN HORIZONTALLY TO AVOID MUTUAL SHADING OF LEAVES
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DOI：
10.1007/bf00325881
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发表时间：
1994-05-01
期刊：
影响因子：
2.7
通讯作者：
KATOH, S
中科院分区：
文献类型：
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作者：
HIKOSAKA, K;TERASHIMA, I;KATOH, S
研究了叶龄、氮素营养和光通量密度(PFD)对水平栽培的三色菜叶片中氮素分配的影响。氮素含量以新生幼叶最高，在低硝酸盐浓度和全光照条件下生长的植株中，氮含量随叶龄的增加而降低。因此，叶片含氮量沿叶龄梯度形成了明显的梯度。然而，在高硝酸盐浓度下生长的植株没有形成叶片含氮量的梯度。PFD对氮素分布的影响是通过遮荫叶片的方式来检验的，这种方式模拟了直立草本树冠的光梯度变化(即，随着树冠的生长，旧叶被放置在越来越暗的条件下)。这种冠层遮荫使低氮条件下生长的植物叶片含氮量的梯度变得陡峭，而在高浓度硝酸盐条件下生长的植物则产生了梯度。PFD梯度越陡，形成的叶片氮素梯度越大。当遮荫的梯度倒置时，即年轻的叶片受到越来越重的遮荫，同时保持最老的叶片暴露在充分的阳光下，在较高的硝酸盐浓度下，叶片氮含量的倒置梯度形成。在氮素供应不足的情况下，叶龄提前或冠层遮荫所产生的叶片含氮量梯度与直立草本植物的冠层所产生的梯度相当。因此，叶龄和叶面积累量都有可能导致叶片氮素分布不均匀。叶龄的贡献随着氮素营养水平的降低而增加。
Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were investigated in a vine, Ipomoea tricolor Cav., which had been grown horizontally so as to avoid mutual shading of leaves. The nitrogen content was highest in newly developed young leaves and decreased with age of leaves in plants grown at low nitrate concentrations and with all leaves exposed to full sunlight. Thus, a distinct gradient of leaf nitrogen content was formed along the gradient of leaf age. However, no gradient of leaf nitrogen content was formed in plants grown at a high nitrate concentration. Effects of PFD on the distribution of nitrogen were examined by shading leaves in a manner that simulated changes in the light gradient of an erect herbaceous canopy (i.e., where old leaves were placed under increasingly darker conditions with growth of the canopy). This canopy-type shading steepened the gradient of leaf nitrogen content in plants grown at a low nitrogen supply, and created a gradient in plants grown at high concentrations of nitrate. The steeper the gradient of PFD, the larger the gradient of leaf nitrogen that was formed. When the gradient of shading was inverted, that is, younger leaves were subjected to increasingly heavier shade, while keeping the oldest leaves exposed to full sunlight, an inverted gradient of leaf nitrogen content was formed at high nitrate concentrations. The gradient of leaf nitrogen content generated either by advance of leaf age at low nitrogen availability, or by canopy-type shading, was comparable to those reported for the canopies of erect herbaceous plants. It is concluded that both leaf age and PFD have potential to cause the non-uniform distribution of leaf nitrogen. It is also shown that the contribution of leaf age increases with the decrease in nitrogen nutrition level.