Abstract

Cd is partly absorbed through OsIRT1 transporter in rice.1) Here, we show in a paddy field experiment that frequently sprayed Fe(II)-compound (Tetsuriki-aqua) to the top of rice during the time between panicle formation and late maturing stage increased Fe and reduced Cd contents in brown rice.  On the other hand, in the pot experiment of Cd-contaminated soil, the foliar-sprayed Fe(II)-component to young rice seedlings did not suppressed the Cd transport from the roots to the shoots.  These results suggest that the foliar-sprayed Fe(II) after panicle formation suppressed the re-translocation of Cd from the leaves to the seeds, or enhance the transport of Fe into the seeds by competitively inhibiting Cd transport into the seeds.

Exp.1  Fe(II)-spray test in rice of reproductive stages in the paddy field

Fig. 1. Foliar Fe(II) spray in the paddy field Click image below to enlarge. Table 1. Effect of Fe(II) spray on grain yield No defect was observed in Fe spray treatment	Click image below to enlarge. Fig. 2. The process of Fe foliar application in paddy field Click image below to enlarge. Fig. 3. Metal concentration in brown rice  Cd in brown rice was significantly reduced by the  foliar Fe(II)-spray.  Fe and Zn in brown rice was significantly reduced by the foliar Fe(II)-spray.

Exp.2  Fe(II) spray test in rice of young seedling stage


Conclusion

1.	Foliar-sprayed organic-Fe(II) (Tetsuriki-aqua) during reproductive stages increased Fe and reduced Cd contents in brown rice.
2.	This technology would be applicable not only for rice but also other crops like wheat, maize, barely, etc. cultivated under upland condition.

Reference: 1) Nakanishi H, Ogawa I, Ishimaru Y, Mori S, Nishizawa NK. Iron deficiency enhances cadmium uptake and translocation mediated by Fe²⁺ transports OsIRT1 and OsIRT2 in rice. Soil Sci Plant Nutr 52, 464-469 (2006)