Abstracts |
Micronutrient constraints (especially those of Fe, Mn, and Zn) are among the most serious nutritional problems in calcareous and alkaline soils. Other adverse soil conditions limiting their availability are low cation exchange capacity (CEC), high organic matter content, soil humidity shortage, etc. From the non-soil factors restricting Fe, Mn, and Zn availability and uptake are: low root exudation release, low acidification ability of rhizosphere, low root system colonization by mycorrhiza, etc. Under adverse soil conditions described above, Fe, Mn, and Zn availability is limited; however, many plant species adopt various strategies, which enable them to keep sufficient Fe, Mn, and Zn uptake rates, as well as to remobilize and efficiently use these micronutrients. Sufficient uptake rates may be assured via enhanced root exudation and rhizosphere acidification ability, as well as via increased root colonization by arbuscular mycorrhizal fungi (AMF) and root morphology adaptations. Efficient use of Fe, Mn, and Zn include improved internal utilization efficiency mechanisms, like high efficient photosynthetic rates, enhanced transport from root system to shoots, and high translocation–remobilization of micronutrients from tissues containing higher Fe, Mn, and Zn to other ones containing lower micronutrient quantities. Finally, enhanced antioxidant mechanisms of plants under micronutrient stress conditions (as in other kinds of stress) are also included within the most important physiological mechanisms of tolerance developed by plants in order to survive. |