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.

Effects of various jasmonates (methyl jasmonate, jasmonic acid, cis-jasmone) on anthocyanins and procyanidins content of, as well as on growth of common buckwheat (Fagopyrum esculentum Moench) seedlings were studied. The studied jasmonates were applied as solutions or vapors on four days seedlings, and the seedlings were grown during the next four days in day/night conditions (16/8 h). Afterwards anthocyanins and proanthocyanidins content, as well as elongation of primary roots and hypocotyls were measured. When applied as solutions cis-jasmone (JAS) stimulated the anthocyanins accumulation, but when used as vapors had tendency to decrease its accumulation in buckwheat hypocotyls. Jasmonic acid (JA) solutions slightly stimulated or had no effect on biosynthesis of anthocyanins in buckwheat hypocotyls, but used as vapors caused a decline of anthocyanins in buckwheat hypocotyls. Methyl jasmonate (MJ) clearly inhibited biosynthesis of anthocyanins in hypocotyls of buckwheat seedlings. The studied jasmonates had no influence on anthocyanins level in cotyledons of buckwheat seedlings, except cis-jasmone, which at the lowest solution concentration slightly enhanced biosynthesis of the pigments. Treatment of buckwheat seedlings with solutions of all jasmonates (10-8 M, 10-6 M and 10-4 M) had no influence on the growth of buckwheat hypocotyls. Contrary to that observation vapors of the growth regulators in concentrations 10-4 M, had a strong inhibitory effect on the growth of hypocotyls of buckwheat seedlings. Solutions of JA and MJ, as well as vapors of JA, MJ and JAS strongly inhibited the primary root growth of buckwheat seedlings, while JAS applied as solution had no such influence. MJ and JA caused much higher stimulation of proanthocyanidin biosynthesis in buckwheat hypocotyls than JAS.

Plants can react to environmental stresses through the abscission of infected, damaged, or senescent organs. A possible mode of action of methyl jasmonate (JA-Me) to induce the formation of the secondary abscission zone (SAZ) in the stems of Bryophyllum calycinum was investigated concerning plant hormone dynamics. Internode segments were prepared mainly from the second or third internode from the top of plants with active elongation. JA-Me applied to the middle of internode segments induced the SAZ formation above and below the treatment after 5–7 days. At 6 to 7 days after JA-Me treatment, the above and below internode pieces adjacent to the SAZ were excised and subjected to comprehensive analyses of plant hormones. The endogenous levels of auxin-related compounds between both sides adjacent to the SAZ were quite different. No differences were observed in the level of jasmonic acid (JA), but the contents of 12-oxo-phytodienoic acid (OPDA), a precursor of JA, and N-jasmonyl-leucine (JA-Leu) substantially decreased on the JA-Me side. Almost no effects of JA-Me on the dynamics of other plant hormones (cytokinins, abscisic acid, and gibberellins) were observed. Similar JA-Me effects on plant hormones and morphology were observed in the last internode of the decapitated growing plants. These suggest that the application of JA-Me induces the SAZ in the internode of B. calycinum by affecting endogenous levels of auxin- and jasmonate-related compounds.