Tolley-Henry L, Raper C D
Department of Soil Science, North Carolina State University, Raleigh 27695-7619, USA.
Bot Gaz. 1986 Dec;147(4):400-6. doi: 10.1086/337607.
This study reports on the effects of nitrogen stress and restoration of nitrogen availability after a period of stress on expansion and photosynthetic rate of soybean leaves of differing maturity. We hypothesized that nitrogen resupply would lead to additional accumulation of reduced nitrogen in the leaves and, ultimately, resumption of leaf initiation and expansion and photosynthetic activity. In continuously nitrogen-stressed plants, expansion of middle trifoliolates of main-stem trifoliates and leaf area at full expansion were severely restricted. Leaves showing the greatest effects were initiated after removal of nitrogen. When the reduced nitrogen concentration in mature leaves of continuously stressed plants fell below 9 mg dm-2, the photosynthetic rate per unit leaf decreased rapidly, reaching a minimum of ca. 6-8 mg dm-2 h-1. The older mature leaves tended to abscise at this point, while the youngest leaves remained on the plant and continued to photosynthesize slowly. When nitrogen was resupplied, leaf expansion and final leaf area increased. Leaf initiation was also stimulated as reduced nitrogen levels rose in the leaves. Photosynthetic rates of the oldest and youngest pair of mature leaves returned to values comparable to those of similar-aged leaves of nonstressed soybean plants.
本研究报告了氮胁迫以及胁迫一段时间后恢复氮供应对不同成熟度大豆叶片扩展和光合速率的影响。我们假设，重新供应氮会导致叶片中还原态氮的额外积累，并最终使叶片的起始和扩展以及光合活性恢复。在持续氮胁迫的植株中，主茎三出复叶的中间小叶的扩展以及完全展开时的叶面积受到严重限制。受影响最大的叶片是在氮去除后形成的。当持续胁迫植株成熟叶片中的还原态氮浓度降至9毫克/平方分米以下时，单位叶面积的光合速率迅速下降，最低达到约6 - 8毫克/平方分米·小时-1。此时，较老的成熟叶片往往会脱落，而最幼嫩的叶片仍留在植株上并继续缓慢进行光合作用。当重新供应氮时，叶片扩展和最终叶面积增加。随着叶片中还原态氮水平的升高，叶片起始也受到刺激。最老和最幼的一对成熟叶片的光合速率恢复到与未受胁迫大豆植株同龄叶片相当的值。
