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

干旱胁迫处理对‘Shiranui’树[(Citrus unshiu Marc.)柑橘温泉奥斯贝克)？果实和叶片中含有花黄素、脱落酸(ABA)、花黄酸(PA)、二氢菲酸(DPA)、表二氢菲酸(epi-DPA)和茉莉酸。使用各自的氚标记内标对它们进行了定量。在整个生长发育过程中，干旱胁迫树果肉中的花椒毒素、ABA和DPA浓度均高于水分充足的树。然而，花椒毒素浓度低于ABA。这些结果可能意味着花椒毒素迅速转化为ABA。此外，干旱胁迫树叶片中的ABA浓度高于水分充足的树木，但干旱胁迫和水分充足的树木之间的PA和DPA水平尚不清楚。DPA被发现是果肉、皮肤和叶子中的主要代谢物。果肉、果皮和叶片中的茉莉酸(JA)和脱落酸(ABA)含量在干旱胁迫下都表现出较高的值。然而，果肉中的茉莉酸水平随着收获的临近而下降。干旱胁迫下果肉中的蔗糖浓度高于水分充足的植株。ABA和茉莉酸处理诱导叶片气孔关闭。ABA对气孔关闭的作用强于茉莉酸。研究了几种热带水果的抗氧化活性。分析了总酚和抗坏血酸作为抗氧化剂。果实中超氧阴离子自由基和1-二苯基-2-苦基肼(DPPH)清除活性的IC50值一般与总酚有关。二氢茉莉酸丙酯(PDJ)处理可减轻冷害。总体而言，超氧化物歧化产物的IC50值和DPPH清除自由基活性也与冷害程度有关。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.