Physiology and modelling of zinc allocation in aerobic rice.

Zinc (Zn) deficiency in humans is widespread in many regions of the world, especially in the developing world. Rice, the staple food of more than half of the world’s population, is potentially an important source of Zn for people whose diet consists mainly of cereal grain. Therefore, this thesis aimed at exploring the allocation of Zn in rice plants, as a basis for establishing the potential for enhancing their grain Zn mass concentration (ZnMC).

Two solution culture experiments, covering wide ranges in Zn supply levels, showed that increased Zn supply resulted in increased plant Zn uptake throughout crop development and in higher ZnMC in all plant organs, but to varying degrees. With higher plant Zn uptake, ZnMC increased most in stems, and least in grains. Two apparent barriers for Zn transport were identified, one between stem and rachis and one between bran and endosperm, since their ZnMCs strongly differed at high plant ZnMC.

Using radioactive 65Zn applied to root or leaf after flowering, we found that when rice plants were grown under sufficient or surplus Zn supply, most of the Zn accumulated in the grains originated from uptake by roots after flowering, rather than from Zn remobilised from leaves...