Uptake, Translocation, and Remobilization of Zinc Absorbed at Different Growth Stages by Rice Genotypes of Different Zn Densities

Abstract

Zinc (Zn) is an essential micronutrient for humans, and increasing Zn density in rice ( Oryza sativa L.) grains is important for improving human nutrition. The characteristics of Zn translocation and remobilization were investigated in high Zn density genotype IR68144, in comparison with the low Zn density genotype IR64. Stable isotope tracer (68)Zn was supplied at various growth stages, either to the roots in nutrient solution or to the flag leaves to investigate the contribution of (68)Zn absorbed at different growth stages to grain accumulation and the remobilization ability of (68)Zn within plants. Significant differences in (68)Zn allocation were observed between the two rice genotypes. Much higher (68)Zn concentrations were found in grains, stems, and leaves of IR68144 than in IR64, but higher (68)Zn was found in roots of IR64. More than half of the Zn accumulated in the grains was remobilized before anthesis, accounting for 63 and 52% of the total Zn uptake for IR68144 and IR64, respectively. Without supply of external Zn, at vegetative or reproductive stages, more (68)Zn was retranslocated from "old tissues" to "new tissues" in IR68144 than in IR64. Retranslocation of (68)Zn from flag leaves to grains was twice as high in the former when (68)Zn was applied to the flag leaves during booting or anthesis. These results indicate that Zn density in rice grains is closely associated with the ability to translocate Zn from old tissues to new tissues at both early and late growth stages and with phloem remobilization of Zn from leaves and stems to grains.

Moving micronutrients from the soil to the seeds: Genes and physiological processes from a biofortification perspective

“…Remobilization of Fe and Zn increased when these micronutrients were withheld from the hydroponic solution post-anthesis, indicating that remobilization mechanisms might be upregulated under nutrient limitation [24]. In this wheat study, flag leaf and lower leaves were the major sources of remobilized micronutrients, in contrast to results from rice, where stems accounted for the major source of Zn remobilized to grain [13]. In another rice study, the authors concluded that remobilization accounted for very little grain Zn, and that uptake after anthesis supplied the majority of Zn to grain, with most Zn passing through stems, and only a small amount passing through leaves [25].…”

“…In pea (Pisum sativum), 59 Fe applied to leaflets, stipules, and pod walls was translocated into seeds [11]. In wheat and rice, 65 Zn applied to leaf tips was translocated to grain [12,13]. Foliar Zn fertilization was highly effective at increasing Zn concentration in wheat grain, especially when applied at various times during the grain filling period [1,14].…”

Nutritionally Enhanced Staple Food Crops

“…For example, Wu et al (2010) studied the uptake, translocation, and remobilization of Zn absorbed at different growth stages by rice genotypes of different Zn densities using Zn 68 stable isotope tracer. They found that significant differences in Zn allocation existed between two rice genotypes.…”

Contribution of mineral nutrients from source to sink organs in rice under different nitrogen fertilization

“…In soybean and wheat, seed/grain Mg appears to be mobilized from leaves, partially because of its high phloem mobility (Maillard et al 2015). Zinc is also essential for rice plants, and more than half of grain Zn is remobilized from that accumulated and stored in leaf, sheath, and stem before anthesis (Wu et al 2010;Yilmaz et al 2016). In this study, a considerable contribution rate of Mg and Zn nutrients of the bracts was detected, with values as high as 12.56 and 12.34%, respectively, in comparison with that of the leaf (16.58 and 9.79%), and sheath (18.27 and 26.67%).…”