Diurnal variations in absorption and translocation of a ferrated phytosiderophore in barley as affected by iron deficiency

The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe³⁺ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with ⁵⁹Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of ⁵⁹Fe, The absorption of ⁵⁹Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of ⁵⁹Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of ⁵⁹Fe by roots, The formation of root apoplastic ⁵⁹Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe³⁺ complex by roots did not follow the PS release pattern.     

Effectiveness of Phytosiderophore in Absorption and Translocation of 59Iron in Barley in the Presence of Plant-Borne,Synthetic, and Microbial Chelators

The mechanisms of iron (Fe) absorption and translocation in plants have received much study because they are the key processes in the supply of Fe to plants. The objective of this research was to study the effectiveness of phytosiderophore (PS) in the absorption and translocation of ⁵⁹Fe in Fe-deficient barley (Hordeum vulgare L. cv. ‘Minorimugi’) plants in the presence of plant-borne, synthetic, or microbial chelators. Plants grown under Fe-deficient conditions in a phytotron at pH 5.5 for 7–18 d were fed with Fe³⁺ (10 μ M labeled with ⁵⁹Fe) in the presence of 10 μ M of different chelators with or without 10 μ M PS for 4 h starting at 2 p.m. (6 h after the onset of light period). The absorption and translocation of ⁵⁹Fe in plants treated with PS and Fe^{3 +} were increased relative to plants fed solely with Fe^{3 +} (control). There was no effect found on absorption and translocation of ⁵⁹Fe in plants treated with EDTA or p-coumarate relative to the control, but a differential increase was observed in ⁵⁹Fe absorption and translocation in plants treated with EDTA or p-coumarate in the presence of PS. In comparison with the control, a decrease in ⁵⁹Fe absorption and translocation was observed in plants treated with HEDTA or EDDHA or FOB, but this decrease was avoided in plants treated with HEDTA or EDDHA or FOB in the presence of PS. The enhancement of ⁵⁹Fe absorption and translocation in plants treated with citrate, and the highest ⁵⁹Fe absorption and translocation in plants treated with citrate and PS, indicated that citrate had an additive effect on Fe absorption and translocation in plants. Our results showed that PS effectively played a role in Fe absorption and translocation in plants in the presence of other chelators. Plants treated with any chelators had lower extracellular ⁵⁹Fe in the roots compared with the control.     

Physiological and Mineralogical Properties of Arsenic-Induced Chlorosis in Barley Seedlings Grown Hydroponically

The experiment was carried out to investigate the effects of arsenic (As) on the physiological and mineralogical properties of barley (Hordeum vulgare L. cv. ‘Minorimugi’). The plants were grown in nutrient solution treated with 0, 6.7, 33.5, and 67 μ M As (0, 0.5, 2.5, and 5 ppm As, respectively) in the phytotron. Dry matter yield of shoots and roots decreased significantly with the As treatments, indicating that barley plants are As-sensitive and As-toxicity depends on the As concentration in the rooting medium. Necrosis in older leaves and chlorosis symptoms (whitish color) in the fully developed young leaves were observed at the 33.5 and 67 μ M As treatments. Arsenic concentration, accumulation, and translocation increased with the increase of As concentration in the rooting medium. Arsenic was mostly concentrated in roots and a little amount was moved to shoots, indicating that As was not easily translocated to shoots of barley seedlings. Concentrations and accumulations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu) decreased significantly in shoots for 33.5 and 67 μ M As treatments as compared to the 0 μ M As treatment. Concentrations of P, K, Ca, Mg, Mn, and Cu decreased in roots, but Zn concentration increased in roots at 67 μ M As treatment. Accumulations of P, K, Ca, Mg, Mn, Zn, and Cu in roots also decreased significantly at 67 μ M As treatment. Accumulation of P and the cations showed negative relationship with As. Concentration of Fe decreased in shoots at 33.5 and 67 μ M As treatments where chlorosis was induced in the young leaf but increased in roots at 33.5 and 67 μ M As treatments. It was suggested that As might induce iron (Fe)-chlorosis in the plants. Among the micronutrients, Fe translocation was more affected than others by As. Phytosiderophore (PS) accumulation in roots, which is a symptom of Fe-deficiency in grasses, did not change significantly between 0 and 33.5 μ M As treatments; indicating that As-induced chlorosis did not enhance PS accumulation in roots and decreased due to As-toxicity at 67 μ M As treatment.     

Microbial reduction mechanism of ferric iron in paddy soils (Part I)

In the previous paper¹⁾ the authors proved that the ferric iron reduction in submerged paddy soils is entirely or mostly effected by the activities of microorganisms in the soil. Prior to the study on the ferric iron reducing microorganisms isolated from the soil, the present paper reports the research for the microbial mechanism of iron reduction. working with the soil itself.     

Incorporation of 14C into methionine as an intermediate for phytosiderophore biosynthesis in barley

In order to verify the precursory role of methionine (Met) in the biosynthesis of the mugineic acid family of phytosiderophores (MAs), feeding experiments of ¹⁴C-Iabeled compounds to barley (Hordeum vulgare L. cv. Minorimugi) roots grown hydroponically were conducted. When both ^l4C-Glucose (Glc) and unlabeled Met were fed to segmented roots, ¹⁴C was incorporated into Met and MAs in the roots. Molar-radioactivity of Met was higher than that of the amino-butanoic-acid unit in MAs in the roots. When ^l4C-Glc and unlabeled homoserine (Hse) were fed to decapitated roots, l4C was incorporated into Met but not into Hse. Therefore, it was considered that Hse might not be a major precursor of MAs. In addition, ¹⁴C was incorporated into Met and MAs in the roots when both ¹⁴C-glycerol (Gol) and unlabeled Met were fed to segmented roots. It is suggested that MAs may be synthesized from Glc via Met, bypassing Hse, and that the MAs biosynthesis may involve an unknown pathway associated with Gol and leading to Met.     

Occurrence of Fusarium oxysporum f. sp. melonis Race 1 in Japan

In 1994, Fusarium wilt of melon cultivars which are resistant to races 0 and 2 of Fusarium oxysporum f. sp. melonis was observed in southern area of the Lake Biwa region, Shiga prefecture. In commercial fields, mature plants of cv. Amus which were grafted onto cv. Enken Daigi 2, and of cv. FR Amus showed yellowing, wilting and finally death before harvesting of fruits. Diseased plants had vascular and root discolorations, and their stem sections yielded typical colonies of F. oxysporum. When the Shiga strains were tested for their pathogenicity to 12 species of cucurbits, they caused wilts only on melon. Using race differential cultivars of melon, the Shiga strains were classified as race 1 of F. oxysporum f. sp. melonis, which has not been reported in Japan. To further characterize their pathogenicity, the strains were used to inoculate 46 additional cultivars of melon, oriental melon and oriental pickling melon. All the race 1 strains were pathogenic to the cultivars tested, and their host range was apparently different from those of strains belonging to other races (races 0, 2 and 1,2y). DNA fingerprinting with a repetitive DNA sequence, FOLR3, differentiated race 1 strains from strains of races 0 and 2, but not from race 1,2y strains. Received 2 July 1999/ Accepted in revised form 30 September 1999     

Formation of the density profile and its effects on the properties of fiberboard

Two main types of fiberboards were produced using lauan (Shorea spp.) fibers with an isocyanate resin as the binder; fiberboard with a flat, homogeneous (homoprofile), and typical U-shaped (conventional) density profile along the board thickness. The processing parameters included manipulation of mat moisture content distribution, press closing speed, and hot pressing method. The results are summarized as follows: (1) A larger variation was observed in the peak density (PD) and core density (CD) of fiberboards at 0.5g/cm³ mean density (MD) level than in those at 0.7 g/cm³. Generally, PD showed a greater variation than CD, irrespective of MD level. (2) Boards produced using two-step hot pressing recorded substantially higher PD with reduced CD. (3) Multiple regression analysis showed that CD and PD could be calculated based on the other profile defining factors, and a rough estimation for peak distance and gradient factor was possible. (4) Based on static bending, conventional fiberboard had a higher modulus of rupture (MOR) than the homo-profile board but a similar modulus of elasticity (MOE). (5) At 0.5 g/cm³ the MOR and dynamic MOE of fiberboard increased by up to 67% and 62%, respectively, when the PD increased from 0.5 to 1.07 g/cm³. Similarly, an increase of PD from 0.7 to 1.1 g/cm³ resulted in corresponding increases of 55% and 34% in the MOR and dynamic MOE of 0.7 g/cm³ boards. (6) The internal bond strength and screw withdrawal resistance were almost entirely dependent on the CD and MD, respectively. (7) Homo-profile fiberboards registered higher thickness swelling and water absorption than conventional fiberboards throughout the dry/wet conditioning cycle.     

Analysis of factors affecting milking claw vacuum levels using a simulated milking device

Bovine mastitis is typically caused by microbial infection of the udder, but the factors responsible for this condition are varied. One potential cause is the milking system, and although previous studies have investigated various methods for inspecting these devices, most have not assessed methods for evaluating the milking units. With this in mind, we analyzed the factors that affect the vacuum inside the milking claw by using a simulated milking device and by measuring milking claw vacuum when adjusting the flow rate in five stages. The factors analyzed in each milking system were the vacuum pressure settings (high and low line system) , milk tube length (200‐328 cm), aperture diameter (14‐22.2 mm), constricted aperture diameter (12 mm), tubing configurations, lift formation (0‐80 cm), claw type (bottom and top flow) and use or non‐use of a milk sampler. The study findings demonstrated that all of these variables had a significant impact on claw vacuum and suggest that a diagnostic method using a simulated milking device should be considered when inspecting modern milking systems.     

Randomized clinical trial to evaluate the effectiveness of enrofloxacin as a second‐line antibiotic for treatment of acute Escherichia coli mastitis

The objective of the present study was to evaluate the effectiveness of enrofloxacin (ERFX) as a second‐line antibiotic for treatment of acute Escherichia coli (E. coli) mastitis. Forty‐two cows with naturally occurring acute E. coli mastitis were enrolled. On the first day of treatment (day 0), empirically selected antibiotics (oxytetracycline: n = 32, kanamycin: n = 10) were administered. Although systemic signs improved in 10 cows (first‐line group), the signs remained unchanged or worsened in 32 cows on day 1, including two cows that were found dead. The 30 surviving cows were randomly assigned to second‐line groups constituting an ERFX group (n = 19) or a control group (n = 11) that was treated with other antibiotics. Response to each treatment was evaluated by measuring clinical signs from day 0 to day 3, subsequent quarter milk recovery, and the 60‐day survival rate. Appetite on day 3 was significantly better in the ERFX group compared to the control group. No significant differences were observed in the 60‐day survival rate or the subsequent milk recovery between the ERFX group and the control group. Thus, the use of ERFX as a second‐line antibiotic for the treatment of acute E. coli mastitis could induce a rapid appetite recovery.