Combined deficiency of nitrogen and iron increases senescence induced remobilization of plant immobile iron in wheat

摘要

Iron (Fe), an important micronutrient and a critical determinant of plant growth and human nutrition, is deficient in cultivable soils and limits crop productivity and nutritional quality of food grains. Plants tolerant to Fe deficiency reveal either or all of these i.e., a higher uptake of Fe, better root to shoot partitioning of Fe or a higher remobilization of relatively immobile Fe. The physiological and biochemical regulators of in-plant Fe-remobilization are not clearly understood. The present study was conducted to elucidate the effect of Fe and nitrogen (N) deficiency, either alone or in combination, on plant growth attributes, shoot, root Fe and N uptake and Fe remobilization from a fully developed 2nd older leaf (OL) to a younger developing 3rd leaf (YL) in bread and durum wheat. Dual nutrient deficiency of N and Fe induced senescence, measured in terms of reduced chlorophyll and higher expression of NAM-B1activity. High nitrogen availability reduced Fe translocation as evident from a higher Fe retention in OL under N sufficient treatments (N+Fe+ and N+Fe-) than the N deficient treatments (N-Fe+ and N-Fe-) and could be correlated with transcript level expression of the DMAS gene. The present study provides evidence for the N and Fe deficiency induced senescence as the key determinant of Fe-remobilization in wheat, facilitated by a hyped biosynthesis of phytosiderophore. The results indicate that any favourable manipulation or selection for higher Fe remobilization process could improve nutrient deficiency tolerance of wheat and aid in grain biofortification.