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`Seascape' strawberries were harvested and treated with various concentrations of riboflavin and placed on a lab bench for 0, 1, 2, 3, or 4 days, respectively, in a cold room at 4 °C. After each day, samples were taken and stored in a freezer at -20 °C until they were evaluated for anthocyanins content. Both exogenously applied riboflavin and storage time increased cyaniding 3-glucoside and pelargonidin 3-glucoside in the strawberry fruits. This result indicates that riboflavin could be used to increase red color in strawberries destined for processing as well as be included as a vitamin supplement in the processed products.

Foliar application of a mixture of methionine and riboflavin was effective in reducing the severity of powdery mildew [Sphaerotheca macularia (Wallr. ex Fr.) Jacz. F. sp. Fragariae] infection in 72 strawberry progenies and over 110 clonal genotypes. This biocidal activity was enhanced by supplement of copper, iron, and surfactants [such as sodium dodecyl sulfate (SDS), Triton X-100, or Tween-20]. Compounds free radical scavengers (n-propyl gallate, thiourea), or antioxidants (α-tocopherol, -carotene) reduced its biocidal activity. Plants treated with the MR formulation (26.6 μM riboflavin, 1 mM D,L-methionine, 1 mM copper sulfate pentahydrate and 1 mg·ml–1 SDS) or 29% SP formulation of MR (Technical Division of the American Cyanamid Corporation, Taiwan Subsidiary at Taipei) not only showed decreased powdery mildew infection but also showed increased chlorophyll content and leaf area and improved fruit quality. Results in this study suggest that treatment with mixture of methionine and riboflavin is beneficial to strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.

Foliar application of a mixture of methionine (1 mm) and riboflavin (26.6 μm) reduced the severity of powdery mildew [Sphaerotheca macularia (Wallr. ex Fr.) Jacz. f. sp. fragariae] infection in `Earliglow' strawberry (Fragaria × ananassa Duch.) plants. Efficacy of this mixture on controlling powdery mildew infection was enhanced by supplements of copper, iron, and surfactants [sodium dodecyl sulfate (SDS), Triton X-100, Tween-20, or oxyalkylenemethylsiloxane (Silwet L-77)]. Free-radical scavengers (n-propyl gallate, thiourea) and antioxidants (α-tocopherol, β-carotene) reduced the efficacy of this mixture. Plants treated with a mixture of riboflavin (26.6 μm), d,l-methionine (1 mm), copper sulfate pentahydrate (1 mm), and surfactants (SDS or Silwet L-77 at concentrations of 0.05% to 0.1%) showed a decrease in powdery mildew infection. Results of this study suggest that treatment with a mixture of methionine and riboflavin is beneficial to strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.

3-Methyleneoxindole (MO), a metabolite of the plant auxin 1- H-indole-3-acetic acid (IAA), is a potent sulfhydryl reagent that can profoundly affect bacterial growth and metabolism. For investigative purposes, MO is obtained from the degradation of 3-bromooxindole-3-acetic acid (3-Br-lAA) in aqueous media. Alternatively, it can be prepared from the riboflavin-catalyzed photooxidation of IAA. My earlier claims that MO possesses auxin activity were refuted by independent investigators either because the results could not be reproduced when 3-Br-IAA was used, or the results were ascribed to contamination with residual IAA if MO obtained from photooxidation was used. Recent investigations indicate that, contrary to previous assumptions, the quantitative degradation of 3-Br-lAA resulting in the formation of MO is not instantaneous; depending on the purity of 3-Br-lAA, it may take several hours to several days to reach completion. Furthermore, aqueous solutions of MO ≥0.1 mm are rapidly polymerized, thus causing a loss of biological activity. These findings may explain why MO that is derived from 3-Br-lAA often fails to produce auxin action. Ultrapure MO, obtained from either 3-Br-IAA or photooxidation, is 50- to 1000-fold as effective as IAA in the straight growth assay, induction of xylogenesis in parenchymatous tissue, and rooting of explants in tissue culture.

Photorespiration provides a protection mechanism in plants by diverting excessive energy accumulated from photochemical reaction, metabolizing toxic products and producing some protective molecules. The authors report cloning and characterization of a glycolate oxidase gene (GOX; NCBI accession DQ442286) and a NADH-dependent hydroxypyruvate reductase gene (HPR; NCBI DQ442287) from Pachysandra terminallis. The DQ442286 had the predicted GOX-like–Riboflavin-5′-phosphate (FMN) conserved domain and the DQ442287 had the predicted adenosine 5′-(alpha-thio)diphospho-5′-ribofuranosylnicotinamide nicotinamide adenine dinucleotide (NAD) binding domain (2-Hacid_DH_C). C-terminal peroxisome targeting signal was predicted to be -ARL for DQ442286 and –SKL for DQ442287. Both genes encoded enzyme proteins that are located in peroxisome and are involved in the photorespiration process. Real-time quantitative reverse-transcriptase polymerase chain reaction was performed to compare transcript level of the cloned genes after cold treatment. The 18s Ribosomal RNA (rRNA) was included to calibrate the data. The relative cycle threshold values (gene/18s rRNA) were 1.4, 1.5, and 1.5 for GOX and 1.2, 1.3, and 1.3 for HPR in the treatments of 4 °C 4 h, 4 °C 12 h, and control. The data revealed that gene expression was enhanced by only short-term (4-h) cold treatment. A ribulose-1, 5-biphosphate carboxylase/oxygenase (Rubisco) activase gene (DQ 486905) was also cloned and analyzed following the same procedure.

The enzyme superoxide dismutase (SOD; EC 1.15.1.1) catalyzes the conversion of the superoxide radical (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}_{2}^{-}\) \end{document}) to O₂ and H₂O₂. SOD is thought to be critical in delaying aging and senescence in plant tissues such as apple fruit and potato tubers. A variety of assays have been reported for the quantitation of SOD based on the inhibition of O₂-driven reactions. Four assays were examined, including 1) the reduction of nitro blue tetrazolium (NBT) by \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}_{2}^{-}\) \end{document}generated by the reaction of cysteine and FeCl₃; 2) the reduction of NBT by \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}_{2}^{-}\) \end{document}generated by photochemical activation of riboflavin; 3) the inhibition of nitrite formation from hydroxylammonium chloride (nitrite subsequently converts sulfanilic acid to a diazonium compound, which reacts with α-naphthylamine to form a red azo compound); and 4) the autoxidation of hematoxylin to hematein by \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}_{2}^{-}\) \end{document}. In all cases, the production of colored compounds was inversely proportional to SOD activity. Although all of the assays were successful in quantitating SOD activity, assays 1 and 4 appeared simplest to use and had the fewest drawbacks.