Pea seedlings (Pisum sativum L.) were used as materials to test the timings and compartments of hydrogen peroxide (H2O2) triggered by wounding and exogenous jasmonic acid (JA). The results showed that H2O2 could be systemically induced by wounding and exogenous JA. H2O2 increased within 1 h and reached the peak 3―5 h after wounding in either the wounded leaves or the unwounded leaves adjacent to the wounded ones and the inferior leaves far from the wounded ones. After this, H2O2 decreased and recovered to the control level 12 h after wounding. The activities of antioxidant enzymes, however, were rapidly increased by wounding. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, could significantly inhibit H2O2 burst that was mediated by wounding and exogenous JA. Assay of H2O2 subcellular location showed that H2O2 in response to wounding and exogenous JA was predominantly accumulated in plasma membrane, cell wall and apoplasmic space. Numerous JA (gold particles) was found via immu- nogold electron microscopy to be located in cell wall and phloem zones of mesophyll cell after wounding.
LIU Yan 1,2 , HUANG Weidong 1 , ZHAN Jicheng 1 & PAN Qiuhong 1 1. College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
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.
