Effects of Exogenous Gibberellic Acid3 on Iron and Manganese Plaque Amounts and Iron and Manganese Uptake in Rice.

Gibberellins (GA) regulate various components of plant development. Iron and Mn plaque result from oxiding and hydroxiding Fe and Mn, respectively, on the roots of aquatic plant species such as rice (Oryza sativa L.). In this study, we found that exogenous gibberellic acid₃ (GA₃) spray decreased Fe plaque, but increased Mn plaque, with applications of Kimura B nutrient solution. Similar effects from GA₃, leading to reduced Fe plaque and increased Mn plaque, were also found by scanning electron microscopy and energy dispersive X-ray spectrometric microanalysis. Reduced Fe plaque was observed after applying GA₃ to the groups containing added Fe²⁺ (17 and 42 mg•L^-1) and an increasing trend was detected in Mn plaques of the Mn²⁺ (34 and 84 mg•L^-1) added treatments. In contrast, an inhibitor of GA₃, uniconazole, reversed the effects of GA₃. The uptake of Fe or Mn in rice plants was enhanced after GA₃ application and Fe or Mn plaque production. Strong synergetic effects of GA₃ application on Fe plaque production were detected. However, no synergetic effects on Mn plaque production were detected. [ABSTRACT FROM AUTHOR]