Nwugo, Chika , Huerta, Alfredo J. .
Interactions between Si and synthetic chelators (EGTA and EDTA) on Cd uptake, photosynthesis and morphology of hydroponically-grown rice seedlings (Oryza ativa L.) under Cd stress.
Silicon is the second most abundant element in the soil but its usefulness in plant biological systems is significantly undermined. Recent studies have shown that silicon (Si) plays a chelator-like role in inducing tolerance to heavy metals such as cadmium (Cd) in plants. However, the mechanisms involved are not well understood. Furthermore, contrary to popular knowledge, studies have shown heavy metal-induced tolerance in plants due to the treatment of soil with synthetic chelators such as EDTA. Additionally, EGTA (a synthetic chelator) has been successfully used in hydroponic studies to buffer the effects of excess metal activity in growth solutions. Rice is the staple food for more than two-thirds of the world’s population and like many members of the poaceae family, is a major silicon-accumulator. Thus, to improve our understanding on the chelator-like role of Si in heavy metal tolerance in plants, we investigated possible effects from interactions between Si and EGTA or EDTA on the physiology and morphology of hydroponically-grown rice (Oryza sativa L.) seedlings under Cd stress. Plants were grown in the presence or absence of Si and/or Cd with or without EGTA or EDTA in a factorial design. Treatments were 0 or 5Î¼M Cd (as CdSO4), 0 or 0.6 mM Si (as NaSi3O7), 0 or 50 Î¼M EGTA, and 0 or 50 Î¼M EDTA. Our results showed a synergistic/complementary relationship between Si and EGTA (more than EDTA) in ameliorating Cd stress effects on net photosynthetic rate, stomatal conductance, rubisco efficiency, chlorophyll fluorescence, plant morphology, and Cd uptake and transport. Interestingly, we also observed that in the absence of Si, EGTA-treated plants showed a highly significant translocation of Cd from roots to shoots. This is the first time that chelator-induced heavy metal hyperaccumulation has been shown in rice. Rice is a natural Si accumulator, thus, the ability of Si deficient rice plants to hyperaccumulate chelated Cd gives further insight into the mechanisms involved in Si-induced heavy metal tolerance in rice.
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1 - MIami University, Botany, East High Street, Oxford, Ohio, 45056, USA
2 - Miami University, Botany
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM