Morphoanatomical responses induced by excess iron in roots of two tolerant grass species

Abstract

We aimed to verify whether morphoanatomic alterations occur in response to excess iron, in roots of Setaria parviflora and Paspallum urvillei (Poaceae), and to localize the presence of the sites of iron accumulation. Plants were subjected to 0.009, 1, 2, 4, and 7 mM Fe-EDTA in nutrient solution. Both species presented iron contents in the roots above the critical toxicity level. The presence of iron plaque on roots of the two species was confirmed, and it may have reduced iron absorption by the plants. Roots from the two species showed typical visual symptoms of stress by excess iron: change in color and mucilaginous and flaccid appearance. Anatomical damage was observed in both species: aerenchyma disruption, alterations in endodermal cells, and irregular shape of both vessel and sieve tube elements. The metal was histolocalized in the cortex and in protoxylem and metaxylem cell walls in both species, which suggests a detoxification strategy for the excess iron. Phenolic compounds were not histolocalized in roots. Microscopic analyses were therefore effective in evaluating the real damage caused by excess iron.

Characterization of ECM fungal community under three different vegetation restorations in iron tailing

“…In previous studies, many herbaceous (Fernandez et al, 2017;Heckenroth et al, 2016;Mahdavian et al, 2017) and woody plants (Siebielec et al, 2018;Luo et al, 2019), such as Paspalum densum, Setaria parvi ora (Rios et al 2017;Araújo et al, 2015), and Robinia Pseudoacacia (Deng et al, 2020a;Deng et al, 2020b), have proven to be potential candidates for revegetating iron-ore mined areas. In addition, the integration of soil biological indicators with chemical and physical indicators is an important factor in the evaluation of soil quality and the recovery process (Silva et al, 2018).…”

Assessment of Iron Toxicity in Tropical Grasses with Potential for Revegetating Mined Areas

“…Some species are able to accumulate and tolerate high concentrations of iron in their tissues, with only mild visual symptoms. Other species are highly sensitive and exhibit severe effects, even when iron accumulates at only moderate levels [13][14][15][16].…”

Metallic elements in plants: bioaccumulation, phytoremediation potential and physiological responses

“…The main structural alterations, such as the protoplast retraction and collapse of epidermal and mesophilic leaf cells are likely to be related to the ROS-induced plasma membrane damage, especially in plants subject to Fe treatments (Figure 2), as observed by Araújo et al (2015) in two Fe-tolerant grass species. Interestingly, even in combination of the metallic elements, the structural damage was not observed throughout the leaf tissue (Figure 2), remaining restricted to peripheral regions, which may have contributed in part to the maintenance of metabolic processes and mineral transport (Table 2).…”

“…The hydroxyl radical is extremely unstable and harmful to cell membranes, indicating that its production is likely responsible for an increased level of lipid peroxidation, measured by TBARS content (Table 1; El-Beltagi et al, 2020). Plasma membrane deterioration, in turn, was probably the main cause of the anatomical changes observed in the leaves and roots of P. stratiotes, such as protoplast retraction and cell collapse (Araújo et al, 2015;Santana et al, 2014). Similarly, ROS generation may have affected cell wall components, as hydroxyl radicals are capable of non-specifically cleaving cell wall polysaccharides in a site-specific reaction, which would explain the changes in the shape of root cells (Schopfer, 2002).…”

“…Similarly, ROS generation may have affected cell wall components, as hydroxyl radicals are capable of non-specifically cleaving cell wall polysaccharides in a site-specific reaction, which would explain the changes in the shape of root cells (Schopfer, 2002). Araújo et al (2015), studying grass species exposed to excess Fe, argued that nutritional disorders triggered by this metal are also capable of influencing the structure of cell walls. Therefore, the changes observed in P. stratiotes exposed to Fe excess, including necrosis in the margins of the leaves, changes in plant anatomy, and changes in the concentration of biochemical markers (e.g., TBARS and chlorophyll content), have the potential to be used as general bioindicators of contaminated aquatic environments with Fe.…”