Study on the free-radical production and stress signal transduction of jasmonates and abscissic acid

对“Shiranui”树施加干旱胁迫[Citrus unshiu Marc.?]柑橘（奥斯贝克）？测定了黄皮素、脱落酸（ABA）、相酸（PA）、二氢相酸（DPA）、外延二氢相酸（epi-DPA）和茉莉酸盐在柑橘果实和叶片中的含量。它们分别用氘标记的内标进行定量。在整个发育过程中，干旱胁迫树木的果肉中叶黄素、ABA和DPA的浓度高于水分充足的树木。黄腐素的浓度低于ABA的浓度。这些结果可能意味着叶黄素快速转化为ABA。此外，干旱胁迫的树木叶片中ABA浓度高于水分充足的树木，尽管干旱胁迫和水分充足的树木之间的PA和DPA水平不清楚。DPA是果肉、果皮和叶片中的主要代谢物。在干旱胁迫下，果肉、果皮和叶片中的茉莉酸（JA）和ABA浓度均较高。然而，随着收获的临近，果肉中的JA水平下降。干旱胁迫树的果肉蔗糖浓度高于水分充足的树。施用ABA和茉莉酸诱导叶片气孔关闭。ABA对气孔关闭的影响强于茉莉酸。对几种热带水果的抗氧化活性和抗氧化剂进行了研究。总酚类和抗坏血酸作为抗氧化剂进行了分析。水果中超氧化物和DPPH自由基清除活性的ic50值通常与总酚类物质有关。n-丙基二氢茉莉酸酯（PDJ）处理降低了冻害。总的来说，超氧化物ic50值和DPPH自由基清除活性也与冷伤程度有关。这些结果表明茉莉酸、抗坏血酸和多酚之间存在联系。

Drought stress was applied to ‘Shiranui' trees [(Citrus unshiu Marc.? Citrus unshiu Osbeck)? Citrus reticulata Blanco], and xanthoxin, abscisic acid (ABA), phaseic acid (PA), dihydrophaseic acid (DPA), epi-dihydrophaseic acid (epi-DPA), and jasmonates were monitored in fruit and leaf. They were quantified using the respective deuterium-labeled internal standards. Xanthoxin, ABA, and DPA concentrations in the pulp of the drought-stressed trees were found to be higher than those of the well-watered trees throughout development. Xanthoxin concentrations, however, were lower than those of ABA. These results may imply a rapid turnover from xanthoxin to ABA. In addition, ABA concentrations in the leaf were higher in drought-stressed trees than the well-watered trees, although PA and DPA levels between the drought-stressed and well-watered trees were not clear. DPA was found to be the primary metabolite in the pulp, skin, and leaf. Both jasmonic acid (JA) and ABA concentrations in the pulp, skin, and leaf showed high values in the drought-stressed trees. However, JA levels in the pulp decreased as the harvest approached. Sucrose concentrations in the pulp of the drought-stressed trees were higher than those of the well-watered trees. ABA and jasmonate applications induced stomatal closure in leaf. The effect of ABA on stomatal closure was stronger than that of jasmonate.Antioxidant activities and antioxidants of some tropical fruits were investigated. Total phenolics and ascorbic acid were analyzed as antioxidants. IC 50 values of superoxide and 1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity in fruit are generally linked with total phenolics. n-Propyl dihydrojasmonate (PDJ) treatment decreased chilling injury. In general, IC 50 values of superoxide and DPPH radical scavenging activity were also associated with the degree of chilling injury. These results suggest the connections among jasmonates, ascorbic acid, and polyphenolics.