Institute of Biological and Health Sciences, Federal University of Viçosa (UFV), Campus Florestal, Florestal, Minas Gerais, Brazil; Federal University of Western Pará (UFOPA), University Campus of Juruti, Juruti, Pará, Brazil.
Postgradute Program in Management and Conservation of Natural and Agrarian Ecosystems, UFV Campus Florestal, Florestal, Minas Gerais, Brazil.
J Environ Sci (China). 2019 Apr;78:257-266. doi: 10.1016/j.jes.2018.10.005. Epub 2018 Oct 26.
The revegetation of mined areas poses a great challenge to the iron ore mining industry. The initial recovery process in degraded areas might rely on the use of Fe-resistant grasses. Tropical grasses, such as Paspalum densum and Echinochloa crus-galli, show different resistance strategies to iron toxicity; however, these mechanisms are poorly understood. The Fe-resistance mechanisms and direct iron toxicity as a function of root apex removal were investigated. To achieve this purpose, both grass species were grown for up to 480 hr in a nutrient solution containing 0.019 or 7 mmol/L Fe-EDTA after the root apices had been removed or maintained. Cultivation in the presence of excess iron-induced leaf bronzing and the formation of iron plaque on the root surfaces of both grass species, but was more significant on those plants whose root apex had been removed. Iron accumulation was higher in the roots, but reached phytotoxic levels in the aerial parts as well. It did not hinder the biosynthesis of chloroplastidic pigments. No significant changes in gas exchange and chlorophyll a fluorescence occurred in either grass when their roots were kept intact; the contrary was true for plants with excised root apices. In both studied grasses, the root apoplastic barriers had an important function in the restriction of iron translocation from the root to the aerial plant parts, especially in E. crus-galli. Root apex removal negatively influenced the iron toxicity resistance mechanisms (tolerance in P. densum and avoidance in E. crus-galli).
矿区植被恢复对铁矿石开采行业构成巨大挑战。在退化地区，初始恢复过程可能依赖于耐铁草的使用。热带草如 Paspalum densum 和 Echinochloa crus-galli 对铁毒性表现出不同的抵抗策略；然而，这些机制尚不清楚。本研究旨在探究铁抗性机制以及根尖端去除对直接铁毒性的影响。为此，将两种草在含有 0.019 或 7mmol/L Fe-EDTA 的营养液中培养长达 480 小时，在此期间，去除或保留根尖端。过量铁诱导叶片青铜色和根表面形成铁斑，但去除根尖端的植物更明显。铁积累在根部更高，但在地上部分也达到了植物毒性水平。这并不妨碍叶绿体质子色素的生物合成。当根系完整时，两种草的气体交换和叶绿素 a 荧光均未发生显著变化；而去除根尖端的植物则相反。在两种研究草中，根质外体屏障在限制铁从根部向地上植物部分的转运方面具有重要作用，尤其是在 E. crus-galli 中。根尖端去除会对铁毒性抗性机制产生负面影响（在 P. densum 中为耐性，在 E. crus-galli 中为避免）。
