Methyl jasmonate is a more effective senescence-promoting factor in Cucurbita pepo (zucchini) cotyledons when compared with darkness at the early stage of senescence

• Published in: Journal of plant physiology 2007-09, Vol.164 (9), p.1179-1187
• Main Authors: Ananieva, Kalina, Ananiev, Evgueni D., Mishev, Kiril, Georgieva, Katya, Malbeck, Jiri, Kamínek, Miroslav, Van Staden, Johannes
• Format: Article
• Language: English
• Subjects: Acetates - metabolism; Acetates - pharmacology; Biological and medical sciences; chlorophyll; Chlorophyll - metabolism; chloroplasts; Chloroplasts - metabolism; Cotyledon - drug effects; Cotyledon - growth & development; Cotyledons; Cucurbita - drug effects; Cucurbita - growth & development; Cucurbita pepo; Cyclopentanes - metabolism; Cyclopentanes - pharmacology; Cytokinins; Cytokinins - metabolism; Dark treatment; Darkness; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; lighting; Methyl jasmonate; Oxylipins; photochemical quantum efficiency; photosynthesis; Photosynthesis - physiology; photosystem II; Photosystem II Protein Complex - metabolism; plant ecology; plant physiology; Plant physiology and development; seedling growth; Senescence; Senescence and abscission; senescence-promoting factor; Time Factors; transcription (genetics); Transcription, Genetic; Vegetative apparatus, growth and morphogenesis. Senescence; zucchini
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1016/j.jplph.2006.07.008

The effects of short-term darkening and methyl jasmonate (MeJA) on cotyledon senescence were studied 24 h after transfer of intact 7-day-old Cucurbita pepo (zucchini) seedlings to darkness or spraying with 100 μM MeJA. The jasmonate inhibitory effect on chlorophyll content and chloroplast transcriptional activity was stronger compared with darkness. Further, MeJA reduced the photosynthetic rate whereas darkness did not affect photosynthesis. Neither stress factor affected the photochemical quantum efficiency of photosystem II (PSII) estimated by the variable fluorescence ( F v)/maximal fluorescence ( F m) ratio, suggesting the existence of mechanisms protecting the functional activity of PSII at earlier stages of senescence, thus making this parameter more stable compared to others used to quantify senescence. Both stress factors caused a decrease in the content of physiologically active cytokinins, especially trans-zeatin (Z), with the jasmonate effect being much more pronounced when compared to darkness. Our results indicate that MeJA is a more potent inducer of senescence in zucchini cotyledons, at least within the relatively short period of the 24 h treatment. This is likely due to its stronger down-regulatory effect on the levels of physiologically active cytokinins.