Iron toxicity in field-cultivated rice: contrasting tolerance mechanisms in distinct cultivars

Oxidative damage and photosynthetic impairment in tropical rice cultivars upon exposure to excess iron

“…For the most sensitive cultivar, BR IRGA 409, the oxidative damage might have been inflicted earlier since important changes in the chlorophyll a fluorescence were detected after only one day of excess Fe exposure (see below). This finding is consistent with the high shoot iron concentration observed in this cultivar (BR IRGA 409), and the most tolerant cultivar (EPAGRI 107) maintaining its shoot iron concentration below the critical toxicity level (500 mg Fe kg −1 DM ) (Stein et al, 2014). In fact, the iron uptake rate of the BR IRGA 409 cultivar continued to increase throughout the experimental period, reaching values of 143 mg Fe kg…”

“…In fact, the oxidation of Fe 2+ to Fe 3+ at the root surface, resulting in a typical orange precipitate known as iron plaque, was reported previously for the EPAGRI 107 cultivar (Pereira et al, 2014). However, even resistant cultivars, closely related to the EPAGRI 107 cultivar, may present different tolerance strategies to cope with iron overload (Stein et al, 2014). As recently reported, while the EPAGRI 108 cultivar accumulates higher levels of iron in its roots thus lowering translocation to shoots, its counterpart, EPAGRI 109 showed higher iron concentration in leaf tissues coupled with an effective antioxidant response (Stein et al, 2014).…”

“…After five days of exposure to excess Fe, the differences between cultivars became visible. The BR IRGA 409 cultivar showed subsequent increases in iron uptake, reaching values above 600 mg kg ) (Stein et al, 2014). At the end of the experiment, the differences in shoot Fe concentration among the most sensitive (BR IRGA 409) and the other cultivars became greater leading to an interaction between Fe treatments and cultivars (p < 0.001).…”

“…The BR IRGA 409 cultivar is widely cultivated in the state of Rio Grande do Sul since its release to farmers in 1979, being previously characterized as susceptible to Fe toxicity (Stein et al, 2014). The EPAGRI 107 cultivar was released in 1994 in the state of Santa Catarina.…”

“…In addition to its abundance in the earth's crust, iron in aerobic soils is found mostly in the form of insoluble Fe 3+ oxides or hydroxides, which decrease Fe bioavailability to plants (Stein et al, 2014). However, iron toxicity may occur in waterlogged soils as a consequence of the high amounts of reducible Fe, low pH, and low cation-exchange capacity (Becker and Asch, 2005).…”