| Experiments were performed using eight grape cultivars to study SO2 injury to table gropes in normal and low temperature, and the relationship between SO2 fumigation concentration, exposure time , storage temperature and injury extent of table grapes. The difference of SO2 sensitivity was found in those grapes, and the relationship between the peel structure, physiology and biochemistry and sensitivity to SO2 injury was also searched after. All above may provide some new theoretical basis for applying SO2 in grape preservation more rationally.The result showed that the sensitivity to SO2 was different in the grapes. The sequence of sensitivity at 23℃ or at 0℃ was: "Ribier">"Hongbaoshi" >"Red Globe" >"Niunai" >"kyoho" >"Muscate Hamburg" >"Longyan" >"Black Autumn".The eight grape cultivars can be classified to four types, :the very sensitive to SO2 ("Ribier","Hongbaoshi","Red Globe"), the inferior sensitive to SO2("Niunai"), the inferior tolerant to SO2 ("Kyoho","Muscate Hamburg"), the most tolerant to SO2("Longyan","Black Autumn").The sulfite residues of different parts of grapes were variant greatly after fumigated with SO2, from high to low in pedicel, stem, skin, brush and flesh. Facts showed that stem, pedicel and skin were the two ways main of SO2 entrances into grape fruit. The large ration of the sulfite residues in skin and in pedicel of the sensitive grapes to SO2 indicated that the grapes sensitivity to SO2 had a close relation to their skin absorbing capacity of SO2 The skin bleaching index was strong correlation with the temperature, fumigation concentration and time, To the sensitive grapes to SO2 ("Ribier","Hongbaoshi","Red Globe","Niunai"),the fumigation concentration and time had very significant effect on the bleaching index, but the fumigation time had insignificant effect on the tolerant grapes to SO2 ("Longyan","Black Autumn").The effect of fumigation time on bleaching index had a negative correlation with the grape tolerance to SO2. After fumigated with the same doze of SO2(400μl/L×3h),the bleaching indexes of "Ribier" grape were obviously different at 0℃and 23℃.The SO2 injury of grapes was positive relative to the temperature.With the difference of grape cultivars , the SO2 injury symptom was also different.SO2 bleaching injury resulted in stem wilting and many bleaching spots in the berry. To the sensitive grapes to SO2, the bleaching spots appeared in whole berry. Through the histological anatomy, the results showed that the wax crystal structure was destroyed by SO2,the wax layer became thin, the cells of flesh and sub-epidermis were out of shape and broke into pieces completely at last, but the epidermis cells kept relatively complete.The LM and SEM observations showed that the peel structures of different grapes were obviously different. The peel structure had a direct correlation with the grape tolerance to SO2. As a tolerant grape cultivar ,it has the following characteristics of anatomical structure: thicker wax layer, higher wax density, well-distributed wax, thicker cuticle, thicker epidermis and sub-epidermis, closer and denser epidermis cells and sub-epidermis cells, more lignose.pH values of the grapes injuried by SO2 were decreased and the intracellular acidification of flesh could be found. SO2 injury also inhibited activities of SOD, POD and CAT , and decreased ASA contents . Hence the membrane lipid peroxidation was accelerated with the contents of MDA and relative electrical conductivity were increased.As a tolerant variety,"LongYan"had higher pH values, ASA contents and activities of SOD. After stimulated by SO2 ,the increasing activities of SOD and POD was higher than that of"Hongbaoshi" .When fumigated for a long term,"Longyan"had lower decreasing activity of CAT and contents of ASA than"Hongbaoshi". |
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