No abstract

The present study compared the effects of natural senescence and methyl jasmonate (JA-Me) treatment on the levels of terpene trilactones (TTLs; ginkgolides and bilobalide), phenolic acids, and flavonoids in the primary organs of Ginkgo biloba leaves, leaf blades, and petioles. Levels of the major TTLs, ginkgolides B and C, were significantly higher in the leaf blades of naturally senesced yellow leaves harvested on 20 October compared with green leaves harvested on 9 September. In petioles, a similar effect was found, although the levels of these compounds were almost half as high. These facts indicate the importance of the senescence process on TTL accumulation. Some flavonoids and phenolic acids also showed changes in content related to maturation or senescence. Generally, the application of JA-Me slightly but substantially increased the levels of TTLs in leaf blades irrespective of the difference in its application side on the leaves. Of the flavonoids analyzed, levels of quercetin, rutin, quercetin-4-glucoside, apigenin, and luteolin were dependent on the JA-Me application site, whereas levels of (+) catechin and (−) epicatechin were not. Application of JA-Me increased ferulic acid and p-coumaric acid esters in the petiole but decreased the levels of these compounds in the leaf blade. The content of p-coumaric acid glycosides and caffeic acid esters was only slightly modified by JA-Me. In general, JA-Me application affected leaf senescence by modifying the accumulation of ginkogolides, flavonoids, and phenolic acids. These effects were also found to be different in leaf blades and petioles. Based on JA-Me- and aging-related metabolic changes in endogenous levels of the secondary metabolites in G. biloba leaves, we discussed the results of study in the context of basic research and possible practical application.

The interaction of methyl jasmonate (JA-Me) and indole-3-acetic acid (IAA) to induce the formation of the secondary abscission zone in the middle of internode segments of Bryophyllum calycinum was investigated in relation to auxin status and histology. When IAA at 0.1% (w/w, in lanolin) was applied to the segments, the formation of the secondary abscission zone at a few mm above the treatment in the apical direction was observed. On the contrary, IAA at 0.5% (w/w, in lanolin) did not induce the formation of the secondary abscission zone. JA-Me at 0.5% (w/w, in lanolin) applied to the middle of internode segments kept in the normal (natural) or inverted positions also induced the formation of the secondary abscission zone below and above parts of the treatment. IAA at 0.5% applied to the cut surface of the upper part of the segments completely prevented the formation of the secondary abscission zone induced by JA-Me. Simultaneous application of IAA 0.5% with JA-Me 0.5% in the middle part of the internode segments induced the formation of the secondary abscission zone at 10 mm to 12 mm above the treatment. Histological analyses indicated that the formation of the secondary abscission zone was characterized by the presence of newly synthesized cell plates that resulted from periclinal cell division within one layer of mother cells in stems. The effects of IAA (0.1%) and JA-Me (0.5%) on the formation of the secondary abscission zone were histologically similar. Comprehensive analyses of plant hormones revealed that the balance of the endogenous levels of IAA in both sides adjacent to the abscission zone was significantly disturbed when the secondary abscission formation was induced by the application of IAA. These results strongly suggest that an auxin gradient is important in the formation of the secondary abscission zone in the internode segments of B. calycinum, and IAA gradient results from polar IAA transport from the application site. IAA is important in the regulation of formation of the secondary abscission zone induced by JA-Me. Further possible mechanisms of the formation of the secondary abscission zone in the internode segments of B. calycinum are also discussed in the interaction of JA-Me and IAA.

We have found that auxin, indole-3-acetic acid (IAA) substantially induces the formation of the secondary abscission zone in stem and petiole explants and in decapitated stem and petiole after excision of blade in intact plants of <em>Bryophyllum calycinum</em> when IAA at a concentration of 0.1% as lanolin paste was applied in the middle of these organs. The secondary abscission zone was formed at a few mm above of the treatment with IAA, and senescence of the part above abscission zone was observed. IAA additionally applied on the top of explants or top of the dacapitated stem or the debladed petiole totally prevented the secondary abscission zone formation and senescence induced by IAA applied in the middle of these organs. Possible mechanisms of the formation of the secondary abscission zone are discussed in terms of the interaction of auxin and ethylene.

The influence of methyl jasmonate on anthocyanin accumulation in roots of Kalanchoe blossfediana plants was studied. Methyl jasmonate (JA-Me), at a concentration of 5.0 to 40.0 mg.l -1 , substantially increased anthocyanin accumulation in roots of intact plants, when it was applied as a solution under natural light conditions. The production of anthocyanin depended on the concentration of methyl jasmonate and the age of the plant. The stimulatory effect was higher in older plants of K. blossfeldiana than in younger ones. When leaves were removed methyl jasmonate slightly stimulated anthocyanin accumulation compared with intact plants. The obtained results indicate that leaves are necessary for the anthocyanin accumulation in the roots. In isolated roots methyl jasmonate did not affect the accumulation of anthocyanins in light conditions. Seven anthocyanins were documented in the roots of control plants and 8 anthocyanins in the roots of JA-Me treated ones. JA-Me increased the level of anthocyanins in roots of old K. blossfeldiana plants 6.8, 6.0 and 3.6-folds, after 4, 8 and 14-days of treatment, respectively.