Yousfi Sabah, Wissal M'sehli, Mahmoudi Henda, Abdelly Chedly, Gharsalli Mohamed
Laboratoire d'Adaptation des Plantes aux Stress Abiotiques, Centre de Biotechnologie, Technopole de Borj-Cedria, BP 901, 2050 Hammam-Lif, Tunis, Tunisia.
Plant Physiol Biochem. 2007 May;45(5):309-14. doi: 10.1016/j.plaphy.2007.03.013. Epub 2007 Mar 14.
Iron chlorosis is very common on alkaline soils such as calcareous ones, since iron availability is limited by high pH. Under these conditions of iron deficiency, graminaceous plant species induce special mechanisms for iron acquisition, involving enhanced release of iron chelators called phytosiderophores. On the other hand, it is known that most of salt soils have alkaline pH. So, plants growing on this kind of soils are often subjected simultaneously to salinity and iron deficiency. This work aimed at (i) studying the physiological responses of barley (Hordeum vulgare L.) to iron deficiency, and (ii) evaluating the effect of salt on the iron nutrition and the phytosiderophore release. For this purpose, seedlings of Hordeum vulgare L. were cultivated under controlled conditions, either in a complete nutrient solution with or without NaCl, or in an iron free nutrient solution containing or not NaCl. The plant morphological aspect, chlorophyll content of young leaves, iron status, biomass production, and phytosiderophore release by roots were assessed. Plants subjected to Fe deficiency exhibited a severe chlorosis, accompanied by a significant biomass reduction. These plants developed more lateral roots than the control with a highly stimulated phytosiderophore release. However, the latter was greatly diminished when iron deficiency was associated to salinity. A depressive effect of salt on iron acquisition in plants subjected only to salt stress which was also observed and further confirmed by the important decrease of efficiency in iron acquisition. These results suggest that salinity may reduce capacity of plants to acquire iron from alkaline soils by inhibiting phytosiderophore release.
缺铁黄化病在石灰性等碱性土壤中非常常见，因为高pH值会限制铁的有效性。在缺铁的这些条件下，禾本科植物物种会诱导特殊的铁获取机制，包括增强称为植物铁载体的铁螯合剂的释放。另一方面，已知大多数盐土的pH值呈碱性。因此，生长在这类土壤上的植物常常同时遭受盐胁迫和缺铁胁迫。这项工作旨在：（i）研究大麦（Hordeum vulgare L.）对缺铁的生理反应，以及（ii）评估盐分对铁营养和植物铁载体释放的影响。为此，将大麦（Hordeum vulgare L.）幼苗在可控条件下培养，分别置于添加或不添加NaCl的完全营养液中，或添加或不添加NaCl的缺铁营养液中。评估了植物的形态特征、幼叶的叶绿素含量、铁状况、生物量生产以及根系植物铁载体的释放情况。缺铁处理的植物表现出严重的黄化病，同时生物量显著减少。与对照相比，这些植物长出了更多的侧根，植物铁载体的释放受到高度刺激。然而，当缺铁与盐胁迫同时存在时，植物铁载体的释放量大大减少。仅受盐胁迫的植物中，盐分对铁获取也有抑制作用，铁获取效率的显著降低进一步证实了这一点。这些结果表明，盐分可能通过抑制植物铁载体的释放来降低植物从碱性土壤中获取铁的能力。
