Studer Christoph, Hu Yuncai, Schmidhalter Urs
Technical University of Munich, D-85350 Freising, Germany.
Funct Plant Biol. 2007 Apr;34(3):228-236. doi: 10.1071/FP06294.
Many physiological mechanisms associated with nutrient supply have been implicated as improving plant growth under drought conditions. However, benefits to plant growth under drought might derive from an increased recovery of soil water through osmotic adjustment in the shoots and especially in the roots. Thus, experiments were carried out to investigate the effects of the nutrients N, P and K applied singly or in combination, on the osmotic adjustment and turgor maintenance in the roots and leaves of maize seedlings. The seedlings were harvested between 18 and 37 days after sowing according to the soil matric threshold potentials. Soil matric potentials and shoot and root biomass were determined at harvest. Turgor pressure and osmotic adjustment of the leaves and roots were estimated by measurements of their water and osmotic potentials. Results showed that plants with either of the combined fertilisation treatments NPK or NP grew faster at a given level of drought stress than those with no fertilisation, N, P or K applied individually or the combined nutrient treatments PK and NK. Among the fertiliser applications with either a single or two combined nutrients, plants treated with any of N, P or NP grew faster than those with either K or NK. The association between the interactive effects of nutrients and drought stress on the osmotic adjustment and turgor maintenance in roots may partially explain the role of nutrients in drought tolerance of maize seedlings. In particular, the roots exhibited a higher osmotic adjustment than the leaves for all nutrient treatments, suggesting that shoot growth shows a higher sensitivity to water deficit compared to root growth. We conclude that the maintained turgor of roots under drought stress obtained with an optimal nutrient supply results in better root growth and apparently promotes overall plant growth, suggesting that osmotic adjustment is an adaptation not only for surviving stress, but also for growth under such conditions.
许多与养分供应相关的生理机制都被认为有助于改善干旱条件下的植物生长。然而，干旱条件下植物生长的益处可能源于通过地上部分尤其是根系的渗透调节作用，使土壤水分的回收率提高。因此，开展了实验来研究单独施用或组合施用氮、磷、钾养分对玉米幼苗根系和叶片渗透调节及膨压维持的影响。根据土壤基质阈值电位，在播种后18至37天收获幼苗。收获时测定土壤基质电位以及地上部分和根系生物量。通过测量叶片和根系的水势和渗透势来估算其膨压和渗透调节能力。结果表明，在给定的干旱胁迫水平下，施用NPK或NP组合肥料处理的植株比未施肥、单独施用氮、磷或钾以及施用PK和NK组合养分处理的植株生长更快。在单一养分或两种养分组合的施肥处理中，施用氮、磷或NP的植株比施用钾或NK的植株生长更快。养分与干旱胁迫对根系渗透调节和膨压维持的交互作用之间的关联，可能部分解释了养分在玉米幼苗耐旱性中的作用。特别是，在所有养分处理中，根系的渗透调节能力均高于叶片，这表明地上部分生长对水分亏缺的敏感性高于根系生长。我们得出结论，在干旱胁迫下，通过优化养分供应维持根系膨压可促进根系更好地生长，并明显促进植株整体生长，这表明渗透调节不仅是一种应对胁迫的适应机制，也是在这种条件下实现生长的适应机制。
