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Root-to-shoot Cd translocation via the xylem is the major process determining shoot and grain cadmium accumulation in rice.

Uraguchi S, Mori S, Kuramata M, Kawasaki A, Arao T, Ishikawa S - J. Exp. Bot. (2009)

Bottom Line: Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar 'Habataki' compared with 'Sasanishiki'.The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions.Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants.

View Article: PubMed Central - PubMed

Affiliation: Soil Environment Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan.

ABSTRACT
Physiological properties involved in divergent cadmium (Cd) accumulation among rice genotypes were characterized using the indica cultivar 'Habataki' (high Cd in grains) and the japonica cultivar 'Sasanishiki' (low Cd in grains). Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar 'Habataki' compared with 'Sasanishiki'. On the other hand, rapid and greater root-to-shoot Cd translocation was observed in 'Habataki', which could be mediated by higher abilities in xylem loading of Cd and transpiration rate as a driving force. To verify whether different abilities in xylem-mediated shoot-to-root translocation generally account for the genotypic variation in shoot Cd accumulation in rice, the world rice core collection, consisting of 69 accessions which covers the genetic diversity of almost 32,000 accessions of cultivated rice, was used. The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions. Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants.

Show MeSH
Time-dependent analysis of root-to-shoot Cd translocation in a low-Cd-accumulating japonica cultivar ‘Sasanishiki’ and a high-Cd-accumulating indica cultivar ‘Habataki’. 14-d-old seedlings were exposed to a nutrient solution containing 0.18 μM CdSO4 for 14 d. (A) Cd concentration in xylem sap. (B) Cd amount in the xylem sap collected for 2 h. Data are presented as means with SD (n=3). Error bars do not extend outside some data points.
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fig3: Time-dependent analysis of root-to-shoot Cd translocation in a low-Cd-accumulating japonica cultivar ‘Sasanishiki’ and a high-Cd-accumulating indica cultivar ‘Habataki’. 14-d-old seedlings were exposed to a nutrient solution containing 0.18 μM CdSO4 for 14 d. (A) Cd concentration in xylem sap. (B) Cd amount in the xylem sap collected for 2 h. Data are presented as means with SD (n=3). Error bars do not extend outside some data points.

Mentions: The Cd concentration in the xylem sap was determined to examine the translocation dynamics of Cd into the shoots. In both cultivars, the Cd concentration in the xylem sap always exceeded the concentration in the solution (20 μg l−1) and was maintained at certain levels 6 h from the start of the treatment (Fig. 3A). The Cd concentration in the xylem sap was 1.3–3.5 times higher in ‘Habataki’ than in ‘Sasanishiki’ throughout the treatment period (Fig. 3A). The concentration of Cd in the xylem sap was calculated and the amount of Cd transported for 2 h in the xylem sap was estimated (Fig. 3B). In ‘Habataki’, a greater amount of Cd was translocated through the xylem sap, which was 1.6–8.9 times higher than that of ‘Sasanishiki’ (Fig. 3B). The remarkable increase of Cd translocation via the xylem sap was observed in ‘Habataki’ after 14 d of the treatment, although ‘Sasanishiki’ exhibited a slight increase according to the duration of Cd exposure (Fig. 3B).


Root-to-shoot Cd translocation via the xylem is the major process determining shoot and grain cadmium accumulation in rice.

Uraguchi S, Mori S, Kuramata M, Kawasaki A, Arao T, Ishikawa S - J. Exp. Bot. (2009)

Time-dependent analysis of root-to-shoot Cd translocation in a low-Cd-accumulating japonica cultivar ‘Sasanishiki’ and a high-Cd-accumulating indica cultivar ‘Habataki’. 14-d-old seedlings were exposed to a nutrient solution containing 0.18 μM CdSO4 for 14 d. (A) Cd concentration in xylem sap. (B) Cd amount in the xylem sap collected for 2 h. Data are presented as means with SD (n=3). Error bars do not extend outside some data points.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2692013&req=5

fig3: Time-dependent analysis of root-to-shoot Cd translocation in a low-Cd-accumulating japonica cultivar ‘Sasanishiki’ and a high-Cd-accumulating indica cultivar ‘Habataki’. 14-d-old seedlings were exposed to a nutrient solution containing 0.18 μM CdSO4 for 14 d. (A) Cd concentration in xylem sap. (B) Cd amount in the xylem sap collected for 2 h. Data are presented as means with SD (n=3). Error bars do not extend outside some data points.
Mentions: The Cd concentration in the xylem sap was determined to examine the translocation dynamics of Cd into the shoots. In both cultivars, the Cd concentration in the xylem sap always exceeded the concentration in the solution (20 μg l−1) and was maintained at certain levels 6 h from the start of the treatment (Fig. 3A). The Cd concentration in the xylem sap was 1.3–3.5 times higher in ‘Habataki’ than in ‘Sasanishiki’ throughout the treatment period (Fig. 3A). The concentration of Cd in the xylem sap was calculated and the amount of Cd transported for 2 h in the xylem sap was estimated (Fig. 3B). In ‘Habataki’, a greater amount of Cd was translocated through the xylem sap, which was 1.6–8.9 times higher than that of ‘Sasanishiki’ (Fig. 3B). The remarkable increase of Cd translocation via the xylem sap was observed in ‘Habataki’ after 14 d of the treatment, although ‘Sasanishiki’ exhibited a slight increase according to the duration of Cd exposure (Fig. 3B).

Bottom Line: Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar 'Habataki' compared with 'Sasanishiki'.The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions.Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants.

View Article: PubMed Central - PubMed

Affiliation: Soil Environment Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan.

ABSTRACT
Physiological properties involved in divergent cadmium (Cd) accumulation among rice genotypes were characterized using the indica cultivar 'Habataki' (high Cd in grains) and the japonica cultivar 'Sasanishiki' (low Cd in grains). Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar 'Habataki' compared with 'Sasanishiki'. On the other hand, rapid and greater root-to-shoot Cd translocation was observed in 'Habataki', which could be mediated by higher abilities in xylem loading of Cd and transpiration rate as a driving force. To verify whether different abilities in xylem-mediated shoot-to-root translocation generally account for the genotypic variation in shoot Cd accumulation in rice, the world rice core collection, consisting of 69 accessions which covers the genetic diversity of almost 32,000 accessions of cultivated rice, was used. The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions. Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants.

Show MeSH