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

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.

Detection of physiological and genotoxic damages reflecting toxicity in Kalanchoe clones

“…Also, it was revealed that Cd was progressively accumulated in all parts of Kalanchoe plants when increasing amount of exogenous Cd was applied. Similar results from previous studies were also reported (Salt et al, 1995;Hart et al, 1998;Uraguchi et al, 2009;Prasad et al, 2001). The reductions in photosynthetic pigment contents in Kalanchoe plants exhibited an inverse relationship with the level of Cd applied (except the level of 100 µM) and our findings were in agreement with previous the studies (Hou et al, 2007;Maurya et al, 2008;Mishra et al, 2008).…”

Reduced translocation of cadmium from roots is associated with increased production of phytochelatins and their precursors

“…The mechanisms that control Cd translocation have not yet been determined. In lettuce and barley (Akhter and Macfie, 2012), rice (Oryza sativa, Uraguchi et al, 2009) and maize (Florijn and Beusichem, 1993) increased translocation of Cd to the shoots in some plants could not be explained by greater volumes of water transpired. Uraguchi et al (Cys, Glu, and γ-Glu-Cys) in roots could contribute to reduced xylem loading and reduced translocation.…”

Phosphate deficiency signaling pathway is a target of arsenate and phosphate transporterOsPT1is involved in As accumulation in shoots of rice

“…The seeds were surface-sterilized with bleach and sown onto 0.8% agar (Wako, Osaka, Japan) medium supplemented with 0.5 mM calcium chloride [CaCl 2 , containing 2mM 2-morpholinoethanesulfonic acid (MES) (pH 5.7)]. After 5 d of germination, the seedlings with proper growth were transferred to a half-strength Kimura B solution (Uraguchi et al 2009) and grown hydroponically for 10 d. The solution was renewed every 5 d. This growth condition was used in the experiments for Fig. 1 to Fig.…”

“…After transplanting, plants were treated with 5 μM As(V) with Pi or without Pi for 24 h. For the -Pi nutrient solution, potassium chloride (KCl) was added to supplement potassium. Xylem sap was collected following the method described by Uraguchi et al (2009).…”