Studies on Changes of Phenolics in the Apple Fruit Peel in Response to Light Intensity

Fruits from 9-year-old apple trees (Malus domestic Borkh. cv. Fuji) were wrapped by two-layerbag in middle of June, and bags were removed in middle of September. The bag-removed treatmentwas performed in following three ways: once-removing all inner and outer bags; twice-removingbag (removing inner bag 3 d after removing outer bag); dipping 5 s in 1 mM salicylic acid (SA)after once-removing all bags. Changes of phenolic compounds in fruit peel in response to lightenvironment were studied before or after removing bag. The results showed that the baggedtreatment could significantly decrease the contents of UV (ultraviolet)absorbing compounds,rutin and anthocyanins of the fruit peel, but increased chlorogenic acid level. After removalof bag, the level of SA and quercetin in the fruit peel appeared peak 1 d after bag-removed,except that quercetin was decreased in SA-treated fruits. UV absorbing compounds, anthocyaninsand rutin were kept increasing all along after the removal of bag, except that chlorogenic acidwas decreased during being retained inner bag in the treatment of twice removing bag. Thepositive correlations existed between changes of UV absorbing compounds and changes ofanthocyanins or rutin. It was suggested that light played an important role in phenolicsmetabolism.

Response of 14C-Salicylic Acid to Heat Stress After Being Fed to Leaves of Grape Plants

An experiment was conducted to investigate the response of salicylic acid as a second messenger to the heat stress in grape plants. For this purpose, all leaves of grape (Vitis vinifera×V. labrussa L. cv. Jingxiu) plants were removed except the 3rd, 4th, 5th, 6th, and 7th ones. The 5th leaf was fed with C-SA, and the 4th and 6th leaves were exposed to high 14 temperature at 40±0.5°C. It was observed that more C-SA transported out from the 5th leaf and the distribution of C-SA 14 14 in each organ of plant altered in response to heat stress. The accumulation of C-SA in both the 4th and 6th leaves being 14 exposed to high temperature was at least three times higher than that in control. The distribution of C-SA in other distal 14 leaves (the 3rd and 7th leaf) decreased, but more C-SA accumulated in stems adjacent to the 4th or 6th leaf exposed to 14 high temperature. In addition, there was more C-SA being transported upwards or downwards while the 4th and 6th 14 leaves were exposed to high temperature respectively. Therefore, our results suggested that SA was closely involved in signal transduction of heat stress in grape plants. However, the ratio of C radioactivity assayed after SA being extracted 14 to that of direct assay with apparatus was more than 70%, which indicated about 30% C was lost or catabolized during 14 transportation.