Table 3.

Chemical forms of Zn, Cd. Fe, and Cu in xylem and phloem saps from rice plants. Metal speciation analyses in xylem and phloem saps were conducted by using SE-HPLC, ICP-MS, CE-MS, and ESI-TOF MS.

Metal	Chemical Forms in Xylem Sap (pH 6)	Chemical Forms in Phloem Sap (pH 8)
Zn	Free ions and partially bound 1	Bound dominantly to NA 2
Cd	Primarily in free ions 3	Bound largely to specific proteins and slightly to thiol-compounds 4
Fe	Bound largely to citrate (around 65%) and slightly to DMA (around 5%)and some in free ions 5	Bound to DMA, citrate, and proteins 2
Cu	Bound dominantly to DMA 6	Bound to NA, histidine and proteins 6

¹ Nishiyama [41]; ² Nishiyama et al. [43]; ³ Mariyo Kato [42]; ⁴ Kato et al. [44]; ⁵ Ariga et al. [36]. ⁶ Ando et al. [45].