Motohiro Fukami

Genotypic differences in effects of cadmium on growth and nutrient compositions in wheat

Abstract A solution culture study was conducted to determine the genotypic difference in the effects of cadmium (Cd) addition on growth and on the uptake and distribution of Cd and other 11 nutrients in wheat plants. Cadmium addition at a rate of 1 mg L−1 significantly reduced root and shoot dry matter production, shoot height, root length, chlorophyll content, and tillers per plant. On the average of 16 wheat genotypes used in study, Cd concentrations of Cd‐treated plants were 48.1 and 459 μg g−1 dry weight (DW) in shoots and roots, respectively, and retained 77.91% of total Cd taken up in the roots. On the whole, Cd addition reduced the concentration of sulfur (S), phosphorus (P), magnesium (Mg), molybdenum (Mo), manganese (Mn), and boron (B), and increased iron (Fe), irrespective of the plant parts. The effect of Cd on the concentration of potassium (K), calcium (Ca), and copper (Cu) differed in shoots and roots. The significant difference existed among 16 wheat genotypes in their response to Cd in terms of growth and nutrient concentrations. Genotype E81513, which showed relatively less inhibition in growth, had the lowest shoot Cd concentration and more Cd accumulation in roots, while Ailuyuang had the highest Cd concentration and accumulation in shoot with lower Cd concentration in root. The significant interaction was found between Cd treatment and genotype for all nutrient concentrations in both shoot and root, except S and Zn in root.

Cadmium accumulation in the shoots and roots of 93 weed species

Abstract The present study was conducted to find useful weed species for cadmium (Cd) phytoremediation. Ninety-three weed species and eight crop species were grown for 2 months in pots containing sandy loam soil with 3 mg Cd kg−1 dry weight (DW). The Cd concentrations in the shoots and roots of all species were determined by inductively coupled plasma optical emission spectroscopy and atomic absorption spectrometry. Shoot Cd concentrations (mg kg−1 DW) of Cichorium intybus (77.0) and Matricaria chamomilla (64.4) were higher than that of Polygonum thunbergii (56.2), which is a recognized hyperaccumulator. Root Cd concentrations (mg kg−1 DW) were relatively high (≥ 100) in 11 species, for example, Oenothera biennis (171.9), Calystegia sepium var. americana (122.6) and Cassia obtusifolia (122.2). Shoot–root ratios (ratio of shoot and root Cd concentrations) were higher in Compositae species, for example, Cichorium intybus (3.56) and Bidens frondosa (3.30), than in Gramineae species, for example, Oenothera biennis (0.01), Oryza sativa cv. Milyang 42 (0.02) and Coix lacryma-jobi (0.03). Twelve species, for example, Cyperus brevifolius var. leiolepis (50.0), Polygonum thunbergii (49.7) and Bidens frondosa (40.5), had relatively high plant contents of Cd (≥ 20.0 µg plant−1). These results suggest that: (1) Cichorium intybus and Matricaria chamomilla accumulate high shoot Cd concentrations, (2) Oenothera biennis, Calystegia sepium and Cassia obtusifolia accumulate high root Cd concentrations, (3) Compositae species are better able than Gramineae species to translocate Cd from roots to shoots. As both plant biomass and Cd concentration are related to Cd content, it was concluded that Bidens frondosa, Bidens pilosa and Amaranthus viridis, which not only have a high Cd accumulation ability but also a large biomass, are useful species for Cd phytoremediation.

Brassinosteroid Deficiency Due to Truncated Steroid 5α-Reductase Causes Dwarfism in the lk Mutant of Pea

The endogenous brassinosteroids in the dwarf mutant lk of pea (Pisum sativum) were quantified by gas chromatography-selected ion monitoring. The levels of castasterone, 6-deoxocastasterone, and 6-deoxotyphasterol in lk shoots were reduced 4-, 70-, and 6-fold, respectively, compared with those of the wild type. The fact that the application of brassinolide restored the growth of the mutant indicated that the dwarf mutant lk is brassinosteroid deficient. Gas chromatography-selected ion monitoring analysis of the endogenous sterols in lk shoots revealed that the levels of campestanol and sitostanol were reduced 160- and 10-fold, respectively, compared with those of wild-type plants. These data, along with metabolic studies, showed that the lk mutant has a defect in the conversion of campest-4-en-3-one to 5α-campestan-3-one, which is a key hydrogenation step in the synthesis of campestanol from campesterol. This defect is the same as that found in the Arabidopsis det2 mutant and the Ipomoea nil kbt mutant. The pea gene homologous to the DET2 gene, PsDET2, was cloned, and it was found that the lk mutation would result in a putative truncated PsDET2 protein. Thus it was concluded that the short stature of the lk mutant is due to a defect in the steroidal 5α-reductase gene. This defect was also observed in the callus induced from the lk mutant. Biosynthetic pathways involved in the conversion of campesterol to campestanol are discussed in detail.

Effects of ozone on growth, yield and leaf gas exchange rates of four Bangladeshi cultivars of rice (Oryza sativa L.)

To assess the effects of tropospheric O3 on rice cultivated in Bangladesh, four Bangladeshi cultivars (BR11, BR14, BR28 and BR29) of rice (Oryza sativa L.) were exposed daily to charcoal-filtered air or O3 at 60 and 100 nl l(-1) (10:00-17:00) from 1 July to 28 November 2008. The whole-plant dry mass and grain yield per plant of the four cultivars were significantly reduced by the exposure to O3. The exposure to O3 significantly reduced net photosynthetic rate of the 12th and flag leaves of the four cultivars. The sensitivity to O3 of growth, yield and leaf gas exchange rates was not significantly different among the four cultivars. The present study suggests that the sensitivity to O3 of yield of the four Bangladeshi rice cultivars is greater than that of American rice cultivars and is similar to that of Japanese rice cultivars and that O3 may detrimentally affect rice production in Bangladesh.

Effects of Nitrogen Supply on the Sensitivity to O3 of Growth and Photosynthesis of Japanese Beech (Fagus crenata) Seedlings

To obtain basic information for evaluating critical levels of O3 under different nitrogen loads for protecting Japanese beech forests, two-year-old seedlings of Fagus crenata Blume were grown in potted andisol supplied with N as NH4NO3 solution at 0, 20 or 50 kg ha year and exposed to charcoal-filtered air or O3 at 1.0, 1.5 and 2.0 times the ambient concentration from 16 April to 22 September 2004. The O3 induced significant reductions in the wholeplant dry mass, net photosynthetic rate at 380 μmol mol CO2 (A380), carboxylation efficiency (CE) and concentrations of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and total soluble protein (TSP) in the leaves. The concentrations of Rubisco and TSP were negatively correlated with the concentration of leaf acidic amino acid, suggesting that O3 enhanced the degradation of protein such as Rubisco. The N supply to the soil did not significantly change the whole-plant dry mass and A380, whereas it significantly increased the CE and concentrations of Rubisco and total amino acid. No significant interactive effects of O3 and N supply to the soil were detected on the growth, photosynthetic parameters and concentrations of protein and amino acid in the leaves. In conclusion, N supply to the soil at ≤50 kg ha year does not significantly change the sensitivity to O3 of growth and net photosynthesis of Fagus crenata seedlings.

Cadmium and Nutrient Heavy Metals Uptake by Rice, Barley, and Spinach as Affected by Four Ammonium Salts

ABSTRACT This experiment was conducted to investigate the influence of ammonium salts on the uptake of cadmium (Cd) and nutritional heavy metals (copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe)) by rice, barley, and spinach. These plants were grown in Cd, Cu, and Zn contaminated entisol (ES) or andisol (AS). The following ammonium salts were used: ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium chloride (NH4Cl), and ammonium dihydrogen phosphate (NH4H2PO4). In ES, the Cd concentrations in three plant shoots were higher with NH4Cl than with the other salts. The concentrations of Cd in soil solutions collected from ES were higher with NH4Cl. Thus, the increase of Cd uptake by three plants with NH4Cl treatment would be caused by the increased concentration of Cd in the soil solution. In contrast, in AS, the concentrations of the heavy metals in the shoots of all plants were not different among NH4 applications, with one exception, the Mn concentration in rice increased with NH4Cl in both ES and AS.

Effect of Anions in Simulated Precipitation on the Uptake of Heavy Metals and Aluminum by Brassica Rapa L. Grown in Heavy -Metal -Contaminated Sandy Soil

This study investigated the effect of anions on the uptake of heavy metals and aluminum by Brassica rapa L. from non-contaminated, Cd-contaminated, and sewage sludge compost (SSC)-amended sandy soil. Four types of artificial precipitation were applied: deionized water (pH 5.7) as a control, and solutions of HNO3, H2SO4, and HCl prepared to pH 4.5. Precipitation was applied daily during the last 20 d of cultivation. The pH of the Cd-treated soil after harvest was not affected by any precipitation treatment. Shoot concentrations of heavy metals and Al were unaffected by any treatments on non-contaminated soil. In contrast, all acid treatments increased the Cd concentration in shoots grown on Cd-contaminated soil, but only HNO3 precipitation increased it in SSC-amended soil. These results indicate, even without large soil pH change, there is a possibility that the Cd uptake by B. rapa L. depends on anions in precipitation and chemical form of Cd in the soil under conditions of heavy metal enrichment.

Effects of Ozone and/or Soil Water Stress on Growth and Photosynthesis of Fagaus Crenata Seedlings

The effects of ozone (O3) and soil water stress, singly and in combination, on the growth and photosynthesis of Fagus crenata seedlings were investigated. Four-year-old seedlings were exposed to charcoal-filtered air (<5 nmol mol-1 O3) or 60 nmol mor-1 O3, 7 hours per day (11:00)-18:00), for 156 days from 10 May to 11 October 1999 in naturally-lit growth chambers at 20/15C (6:00-18:00/18:00-6:00). During the same period, half of the seedlings in each gas treatment received 250 mL of water at the 3-day intervals (wellwatered treatment), while the rest received 175 mL of water at the 3-day intervals (water-stressed treatment). The exposure of the seedlings to O3 caused reductions in the leaf, stem, root and whole-plant dry weights. The net photosynthetic rate at 350 μmol mol-1 CO2, the maximum net photosynthetic rate at saturated CO2- concentration, carboxylation efficiency of photosynthesis and Rubisco content were significantly reduced by the exposure to O3. The soil water stress induced reductions in the stem, bud and whole-plant dry weights, transpiration rate and leaf water potential during the midday. The additive effects of O3 and soil water stress were observed on the dry matter production, leaf gas exchange rates and leaf water potential. As a result, the whole-plant dry weight of the seedlings exposed to both stresses was markedly reduced compared with that of the seedlings exposed to charcoal-filtered air and grown in the well-watered treatment.