Tolley-Henry L, Raper C D
Department of Soil Science, North Carolina State University, Raleigh 27695-7619, USA.
Bot Gaz. 1986 Dec;147(4):392-9. doi: 10.1086/337606.
The study tested the hypothesis that resupplying nitrogen after a period of nitrogen stress leads to restoration of the balance between root and shoot growth and normal functional activity. Nonnodulated soybean plants were grown hydroponically for 14 days with 1.0 mM NO3- in a complete nutrient solution. One set of plants was continued on the complete nutrient solution for 25 days; a second set was given 0.0 mM NO3- for 25 days; and the third set was given 0.0 mM NO3- for 10 days followed by transfer to the complete solution with 1.0 mM NO3- for 15 days. In continuously nitrogen-stressed plants, emergence and expansion of main-stem and branch leaves were severely inhibited as low nitrogen content limited further growth. This was followed by a shift in partitioning of dry matter from the leaves to the roots, resulting in an initial stimulation of root growth and a decreased shoot:root ratio. Reduced nitrogen also was redistributed from the leaves into the stem and roots. When nitrogen stress was relieved, leaf initiation and expansion were renewed. With the restoration of the balance between root and shoot function, the shoot:root ratio and distribution of reduced nitrogen within the plant organs returned to levels similar to those of nonstressed plants.
在一段氮胁迫期后重新供应氮会导致根和地上部生长之间的平衡以及正常功能活性得以恢复。未结瘤的大豆植株在含有1.0 mM硝酸根离子的完全营养液中进行水培培养14天。一组植株在完全营养液中继续培养25天；第二组给予0.0 mM硝酸根离子培养25天；第三组给予0.0 mM硝酸根离子培养10天，随后转移至含有1.0 mM硝酸根离子的完全营养液中培养15天。在持续氮胁迫的植株中，主茎和分枝叶片的出现和扩展受到严重抑制，因为低氮含量限制了进一步生长。随后干物质分配从叶片向根部转移，导致根部生长最初受到刺激，茎根比降低。还原态氮也从叶片重新分配到茎和根中。当氮胁迫解除时，叶片的起始和扩展得以恢复。随着根和地上部功能之间平衡的恢复，茎根比以及还原态氮在植物器官内的分布恢复到与未受胁迫植株相似的水平。
