Abstracts Biological Sciences

Magnesium deficiency in maize and effectiveness of nutrient supply through MgSO4 leaf-application

by Mareike Jezek

The plant nutrient magnesium (Mg) is of fundamental importance for optimal plant growth and development. However, Mg nutrition of crops is frequently overlooked and Mg deficiency is increasingly becoming an important limiting production factor in both industrialized crop production and rural subsistence agriculture. This work aimed at providing new insight into the metabolic adaptation to Mg undersupply of maize (Zea mays L.). Moreover, the suitability of a chlorophyll fluorescence-based method for Mg deficiency detection was tested and the effectiveness and efficiency of foliar Mg fertilization for ameliorating Mg deficiency in maize were evaluated. It was shown that neither the glutamine synthetase-mediated ammonium assimilation nor the protein biosynthesis in maize leaves are growth limiting steps in response to low Mg supply in this crop. These findings are in contrast to previous reports in other crops and contradict the assumption that disturbed polypeptide synthesis is the primary effect of Mg shortage and the concomitant growth inhibition. Furthermore, Mg deficiency-induced accumulation of foliar flavonols was shown for the first time. This knowledge can contribute to the future development of devices for rapid early-stage diagnosis of nutrient deficiency in agriculture and plant research. The results of the conducted sugar analysis argue against the prevalent hypothesis that anthocyanins synthesized in response to abiotic stress act as carbon storage compounds in maize leaves. Foliar MgSO4 application proved to be effective and efficient in ameliorating physiological constraints caused by severe Mg deficiency such as decreased photosynthesis and transpiration rate, disturbed homeostasis of potassium and manganese, and reduced overall growth. The results can contribute to the development of environmentally and economically beneficial fertilization strategies for instantaneous amelioration of an acute Mg deficiency. Der Pflanzennährstoff Magnesium (Mg) ist von essentieller Bedeutung für optimales Pflanzenwachstum. Dennoch wird die Mg-Versorgung von Nutzpflanzen vielfach unzureichend beachtet und Mg-Mangel wird zunehmend zum Wachstum-limitierenden Faktor sowohl in industrialisierter Landwirtschaft als auch ländlicher Selbstversorgerwirtschaft. Diese Arbeit zielte darauf ab, neue Einblicke in die physiologischen Anpassungen von Mais (Zea mays L.) an Mg-Mangel zu gewähren. Darüber hinaus wurden die Eignung einer Chlorophyll-Fluoreszenz-basierten Messmethode zur Diagnose von Mg-Mangel getestet und die Effektivität und Effizienz von Mg-Blattdüngung zur Abmilderung von starkem Mg-Mangel in Mais bewertet. Es wurde gezeigt, dass weder die Glutaminsynthetase-vermittelte Ammoniumassimilation noch die Proteinsynthese das Maiswachstum bei Mg-Mangel limitieren. Diese Erkenntnisse stehen im Widerspruch zu vorherigen Berichten in anderen Nutzpflanzen und widerlegen die Annahme, dass eine gestörte Polypeptidsynthese der primäre Effekt von Mg-Mangel und der damit einhergehenden Wachstumsdepression ist. Des Weiteren wurde in…