In higher plants, the supply of metals such as Zn and Fe via phloem is important for the growth and physiology of young organs. However, little information is available on the speciation (chemical forms) of these metals in the phloem fluids. Because the pH of phloem fluids is slightly alkaline and the concentration of phosphate, which may bind to metals, is high, Zn and Fe in phloem fluids could be precipitated if these metals do not form complexes with some ligand compounds. In the present experiment, we examined the chemical forms of Zn and Fe in phloem sap collected from rice (Oryza sativa L.) by separating the phloem sap using size-exclusion and anion-exchange chromatography, and identifying the contents using electrospray ionization time-of-flight mass spectrometry. The low molecular weight chemical forms of Zn and Fe were identified as Zn-nicotianamine and Fe(III)-2'-deoxymugineic acid complexes, respectively. This report is the first to identify metal-chelate complexes in rice phloem sap.

In rice (Oryza sativa L.), cadmium (Cd), a toxic heavy metal, is found in phloem sap and eventually accumulates in the grains. To further characterize phloem-transported Cd, the chemical forms of Cd and other metals and varietal differences in phloem sap Cd concentrations were investigated in young rice plants. The size-exclusion chromatography elution times for Cd-bound compounds indicated that phloem Cd in cv. Nipponbare exists mainly as an approximately 13 kDa complex. Protease digestion of rice phloem sap reduced the bound Cd content from 92 to 19%. The remaining Cd may bind to low-molecule SH compounds. An experiment examining in vitro addition of Cd 2+ to phloem sap from non-Cd-treated plants revealed that rice phloem sap constitutively contains Cd chelators. The major Cd peak is distinguishable from those of Fe, Zn, Cu, Mn, Ni and Co, which probably bind to nicotianamine, 2¢-deoxymugineic acid, citrate and histidine. The Cd concentrations of the phloem saps in three varieties (Milyang 23, LAC 23 and Koshihikari) grown under the same soil conditions were correlated with their grain Cd concentrations, which had been reported previously, whereas the concentrations of the xylem saps were not. In conclusion, rice phloem sap Cd differs from other metals as it may bind to a novel approximately 13 kDa protein and SH compounds, and the concentration of Cd in rice phloem sap may be a key determinant of its grain content.

Xylem and phloem transport of cadmium (Cd), a toxic element, into rice grains was compared with transport of the nutritional elements zinc (Zn) and iron (Fe) in rice plants (Oryza sativa L.) grown under continuously flooded soil conditions. To explore their transport, the concentrations of Cd, Zn and Fe in xylem and phloem saps and in different tissues were determined at four (10th-leaf, 14th-leaf, early grain-filling, mature) stages using semi-dwarf rice plants (cv. Kantou) grown on soil contaminated with Cd fourfold higher than average Cd contamination in Japan. Phloem saps were collected from mature leaf sheathes at the first two stages and from the uppermost internodes at early grain filling. Xylem saps were collected from cut stems. The Cd concentrations in the xylem and phloem saps collected at the 14th-leaf and early grain-filling stages were lower than those at the 10th-leaf stage, and the Cd concentration in dehusked grain was low (0.05 mg kg )1 dry weight [DW]). In contrast, Zn and Fe concentrations in the xylem and phloem saps were maintained throughout the growing season, and their grain concentrations were high (57 mg Zn and 29 mg Fe kg )1 DW). Schemes of metal transport to the grains during early grain-filling to mature stages for different metals are proposed. Cadmium may be transported from the flag leaf blade to the grains via the phloem and additionally after xylem-to-phloem transfer at the stem and spikelet nodes if supplied from the roots. Zinc in the grains and partly in the husks may be actively supplied via the phloem after mobilization from the blades of the flag and upper leaves and also by xylem-tophloem transfer in the nodes. Iron stored in the leaves may be transported to the grains via the phloem.

Medication errors, including overdose and underdose, have a significant impact on patients and the medical economy. We need to prevent or avoid recurring medication errors. Therefore, we conducted a survey to identify medication and prescription background risk factors contributing to the administration of medication by nurses. This study surveyed cases of medication administration errors. This study was conducted at Higashinagoya National Hospital from April 1, 2018, to October 31, 2019. Patients’ backgrounds and medication and prescription background risk factors were investigated. Three control cases were randomly selected for each medication error case. We defined the group of medication error cases as the medication error group and the group of control cases as the no-medication-error group. A logistic regression analysis was performed for factors related to medication errors. A total of 202 patients were included in the medication error group. The median age and number of medications were 78 years and 7, respectively. A total of 606 cases were included in the no-medication-error group. The median age and number of medications were 77 years and 6, respectively. The factors that exhibited a relationship with the medication error group were the number of administrations per day, dosing frequency on indicated days, prescription and start dates were the same, medications from multiple prescriptions, and continuous use of a medication received prior to admission. This study identified existing medication and prescription background risk factors. Overlapping risk factors from these groups might contribute to medication administration errors. Therefore, reviewing these factors is necessary to avoid recurring medication administration errors.