Hermans Christian, Johnson Giles N, Strasser Reto J, Verbruggen Nathalie
Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050 Brussels, Belgium
Planta. 2004 Dec;220(2):344-55. doi: 10.1007/s00425-004-1340-4. Epub 2004 Sep 17.
Magnesium deficiency in plants is a widespread problem, affecting productivity and quality in agriculture, yet at a physiological level it has been poorly studied in crop plants. Here, a physiological characterization of Mg deficiency in Beta vulgaris L., an important crop model, is presented. The impact of Mg deficiency on plant growth, mineral profile and photosynthetic activity was studied. The aerial biomass of plants decreased after 24 days of hydroponic culture in Mg-free nutrient solution, whereas the root biomass was unaffected. Analysis of mineral profiles revealed that Mg decreased more rapidly in roots than in shoots and that shoot Mg content could fall to 3 mg g(-1) DW without chlorosis development and with no effect on photosynthetic parameters. Sucrose accumulated in most recently expanded leaves before any loss in photosynthetic activity. During the development of Mg deficiency, the two photosystems showed sharply contrasting responses. Data were consistent with a down-regulation of PSII through a loss of antenna, and of PSI primarily through a loss of reaction centres. In each case, the net result was a decrease in the overall rate of linear electron transport, preventing an excess of reductant being produced during conditions under which sucrose export away from mature leaf was restricted.
植物缺镁是一个普遍存在的问题，影响着农业生产效率和质量，但在生理层面，对作物的相关研究却很少。本文展示了对重要作物模型——甜菜缺镁的生理特征研究。研究了缺镁对植物生长、矿物质分布和光合活性的影响。在无镁营养液中进行水培培养24天后，地上部生物量下降，而根部生物量未受影响。矿物质分布分析表明，根部镁含量下降速度比地上部更快，地上部镁含量可降至3毫克/克干重而不出现黄化现象，且对光合参数无影响。在光合活性出现任何损失之前，蔗糖就在最新展开的叶片中积累。在缺镁发展过程中，两个光系统表现出截然不同的反应。数据表明，光系统II主要通过天线损失而受到下调，光系统I主要通过反应中心损失而受到下调。在每种情况下，最终结果都是线性电子传递的总体速率下降，从而防止在蔗糖从成熟叶片输出受限的条件下产生过多的还原剂。
