Co-Authors:
Vassil, A.D., AgBiotech Center, Rutgers University, Cook College, New Brunswick, NJ 08903, United States
Kapulnik, Y., Agronomy and Nat. Rsrc. Department, Volcani Center, Bet Dagan 50250, Israel
Raskin, I., AgBiotech Center, Rutgers University, Cook College, New Brunswick, NJ 08903, United States
Sait, D.E., Chemistry Department, Northern Arizona University, Flagstaff, AZ 86011, United States
Abstract:
Indian mustard (Brassica juncea) plants exposed to Pb and EDTA in hydroponic solution were able to accumulate up to 55 mmol kg-1 Pb in dry shoot tissue (1.1% [w/w]). This represents a 75-fold concentration of Pb in shoot tissue over that in solution. A threshold concentration of EDTA (0.25 mM) was found to be required to stimulate this dramatic accumulation of both Pb and EDTA in shoots. Below this threshold concentration, EDTA also accumulated in shoots but at a reduced rate. Direct measurement of a complex of Pb and EDTA (Pb-EDTA) in xylem exudate of Indian mustard confirmed that the majority of Pb in these plants is transported in coordination with EDTA. The accumulation of EDTA in shoot tissue was also observed to be directly correlated with the accumulation of Pb. Exposure of Indian mustard to high concentrations of Pb and EDTA caused reductions in both the transpiration rate and the shoot water content. The onset of these symptoms was correlated with the presence of free protonated EDTA (H-EDTA) in the hydroponic solution, suggesting that free H-EDTA is more phytofoxic than Pb-EDTA. These studies clearly demonstrate that coordination of Pb transport by EDTA enhances the mobility within the plants of this otherwise insoluble metal ion, allowing plants to accumulate high concentrations of Pb in shoots. The finding that both H-EDTA and Pb-EDTA are mobile within plants also has important implications for the use of metal chelates in plant nutritional research.
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ניגודיות עדינה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
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