摘要: To explore the mechanistic differences of Cd accumulation pattern by investigating key factors involved in Cd accumulation in Nicotiana rustica and Nicotiana tabacum. Using seedlings of N. rustica(mainly a root accumulator)and N. tabacum(mainly a leaf accumulator)cv. K326, a series of pot culture experiments were undertook to study the ability of root Cd uptake, root-to-shoot Cd translocation and Cd xylem loading. The results showed that the difference of Cd accumulation between N. rustica and K326 was mainly determined by the genetic variations. Similar time-and dose-dependent Cd uptake kinetics were observed between the two genotypes. However, the K_m and V_max of N. rustica root(9.70 μmol·g^-1DW·h^-1 and 6.79 μM respectively)were significantly higher than those of K326(2.34 μmoL·g^-1DW·h^-1and 4.36 μM, respectively), which suggested that N. rustica is more efficient than K326 in root Cd uptake. On the other hand, K326 exhibited more rapid and greater root-to-shoot Cd translocation, which was demonstrated by quicker uptake saturation and higher Cd xylem loading ability(Cd concentration in xylem sap 4.36-14.08 times higher compared to N. rustica). There was a positive relationship between Cd concentration in xylem and tobacco leaf(R²=0.9902 and 0.9919 for N. rustica and K326, respectively). Higher Cd accumulation in the shoots of K326(N. tabacum) and roots of N. rustica were observed. These differences in pattern of Cd accumulation were mainly related to the different capabilities of Cd retention in root and root-to-shoot Cd translocation via xylem loading in N. rustica versus K326.