ROOT EXUDATES AND THEIR ROLE IN ADAPTATION TO Fe DEFICIENCY IN GRAMINACEOUS PLANTS

The role of root exudates in the adaptation to Fe deficiency in graminaceous plants was studied in nutrient solution and model experiments under controlled environmental conditions. The results demostrated that the specific root exudates were most important marks of the genetic control of the mineral nutrition in plants. The enhancement or inhibition of biosynthesis and release of specific root exudate was controlled by specific nutrient stress. The efficiency of this mechanism was dependent on both element and plant specificity.The results indicated that the release of phytosiderphores are not a specific reaction to iron deficiency, but also to zinc deficiency. The phytosiderophores were able to mobilze not only iron, but also zinc, copper and manganese from calcareous soil. The uptake of phytosiderophore chelated Fe (Ⅲ) was specific to iron deficiency in comprison to zinc and manganese deficiency. The higher efficiency of Fe (Ⅲ) uptake by phytosiderophore chelate compared with synthetic and microbial chelates indicated a specific transport mechanism of phytosiderophore chelated Fe(Ⅲ) in graminaceous plants.