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Yoshiko Yambe and Kiyotoshi Takeno

The germination percentage of Rosa multiflora Thunb. achenes was greatly increased when they were treated with 1% Driselase, a macerating enzyme, for 36 hours. The seeds germinated more rapidly when the achenes were treated with the enzyme for a longer period. Treatment with Cellulase Onozuka improved seed germination at a lower concentration than did Driselase. Pure preparations of pectinase and cellulase had effects similar to treatment with the enzymes noted. Treatment with pectinase was more efficient than treatment with cellulase. These enzymes likely loosened the bond between cells along the suture of the pericarp and forced the pericarp to split.

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Yoshiko Yambe, Kiyotoshi Takeno, and Takashi Saito

Seed germination percentage of multiflora rose (Rosa multiflora Thunh.) was much higher under continuous white light than in complete darkness. Red light was the most effective in inducing germination, and far-red light was ineffective. Exposure to red light for 1 min increased germination; this effect was saturated at an exposure of2 min. The red-light effect was reversed by subsequent exposure to far-red light. The results indicate that rose seeds are positively photoblastic, and that the photoreceptor involved is most likely phytochrome.

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M.V. Bhaskara Reddy, Alain Asselin, and Joseph Arul

We have investigated the relationship between chitosan treatments and maceration of potato tissue by macerating enzymes secreted by Erwinia carotovora causal agent of soft rot of potato. Erwinia isolated from potato showing soft rot symptoms was used for inoculation. The bacteria secreted a wide spectrum of enzymes that degraded potato cell walls. Polygalacturonase (PG), pectate lyase (PL), pectinmethylesterase (PME), cellulase, xylanase, and protease showed the highest activity in potato tissue inoculated with the pathogen. Accordingly increased maceration and cell death were observed. On the other hand, in chitosan-treated tissue and challenged with the pathogen, significant decrease in enzymatic activity and tissue maceration were observed, more so with increasing chitosan concentration. This observation confirmed that chitosan interfered with multiplication and pathogenic powers of the bacteria, thereby improving cell texture and viability. Crude extracts obtained from treatments were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to assess pectinase activity. The electophoretic profiles showed significant lytic zone of pectin degradation in the control, which decreased with increase in chitosan concentrations. No lytic zone was observed at 8 mg·ml–1 chitosan concentration and was comparable to intact activity in untreated potato tissue. Pectic enzyme reaction products were analyzed to see the action pattern of pectinases in the crude extracts. Cellulose choromatographic profiles revealed monomers and dimers of polygalacturonic acid up to 6 mg·ml–1 chitosan concentrations. The results suggest that chitosan significantly inhibits bacterial growth and the production of macerating enzymes by the pathogen and thus chitosan can be a potential anti-bacterial agent.

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M.V. Bhaskara Reddy, Paul Angers, Francois Castaigne, and Joseph Arul

Stem scar application of chitosan inhibited growth and production of pathogenic factors by blackmold rot [Alternaria alternata (Fr.:Fr.) Keissl.] in challenged tomato (Lycopersicon esculentum Mill.) fruit stored at 20 °C for 28 days. Blackmold lesions were visible within 4 days of inoculation in control fruit, compared with >7 days in chitosantreated fruit. Macerating enzyme activity (polygalacturonase, pectate lyase, and cellulase) in the tissue in the vicinity of the lesions was <50% in chitosan-treated fruit compared with control fruit. Chitosan also inhibited production of oxalic and fumaric acids (chelating agents) and host-specific toxins such as alternariol and alternariol monomethylether by the fungus. The pH of the infected tissue decreased from 4.7 to 4.0 in the control fruit, the optimum for polygalacturonase activity, while the pH of chitosan-treated fruit remained at 4.6. In addition, chitosan also induced production of rishitin (a phytoalexin) in tomato tissue. Such chitosan-pathogen-host interactions may be exploited in the control of postharvest pathogens of fresh fruit and vegetables.

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Renee T. Threlfall, Olivia S. Hines, John R. Clark, Luke R. Howard, Cindi R. Brownmiller, Daniela M. Segantini, and Lydia J.R. Lawless

. Agr. Food Chem. 53 3563 3571 Wang, W.D. Xu, S.Y. Jin, M.K. 2009 Effects of different maceration enzymes on yield, clarity and anthocyanin and other polyphenol contents in blackberry juice Int. J. Food Sci. Technol. 44 2342 2349