Article

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

Academy of Sciences of the Czech Republic, Praha, Praha, Czech Republic
Journal of Plant Physiology (Impact Factor: 2.77). 10/2007; 164(9):1179-87. DOI: 10.1016/j.jplph.2006.07.008
Source: PubMed

ABSTRACT The effects of short-term darkening and methyl jasmonate (MeJA) on cotyledon senescence were studied 24h after transfer of intact 7-day-old Cucurbita pepo (zucchini) seedlings to darkness or spraying with 100 microM 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 24h treatment. This is likely due to its stronger down-regulatory effect on the levels of physiologically active cytokinins.

1 Follower
 · 
152 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Effect of methyl jasmonate (MeJA) in the concentrations of 10 or 100 μM on selected physiological parameters in Scenedesmus quadricauda (Turp.) Bréb. after 24 h of exposure was studied. Results were compared with the application of general toxic metal (cadmium, Cd) to identify MeJA-specific responses. Accumulation of reactive oxygen species (ROS; hydrogen peroxide and superoxide) was the most elevated by 10 μM MeJA and 100 μM Cd, while total chls showed decrease (Cd) and increase (MeJA) in these variants. The amount of carotenoids and cell viability were affected neither by MeJA nor by Cd application. The sum of free amino acids was considerably elevated by 10 μM Cd (increase in histidine, threonine, arginine, leucine, and lysine mainly) but depleted by 100 μM MeJA (14 from 17 compounds decreased), while accumulation of soluble proteins was unaffected by Cd and enhanced by MeJA. Cadmium application reduced the amount of Ca and also Mg in the case of 100 μM Cd, while MeJA had no effect on the content of mineral nutrients. Total Cd content reached 557 and 1,334 μg · g−1 dry weight (dwt) in 10 and 100 μM Cd variant, respectively. Intracellular Cd uptake was ca. 55% from total Cd content in both Cd variants. The present findings are discussed in the context of the available literature, and possible explanations are suggested.
    Journal of Phycology 10/2011; 47(5). DOI:10.1111/j.1529-8817.2011.01027.x · 2.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Local darkening of zucchini cotyledons or the primary leaf affected in an organ-specific manner the adjacent ones which remained under the initial light regime. Individual darkening of either the pair of cotyledons or the primary leaf led to acceleration of senescence expressed by lowering of chlorophyll content and net photosynthetic rate. Darkening of the pair of cotyledons induced a reduction in total cytokinin (CK) levels and increased CK oxidase/dehydrogenase (CKX) activity in the adjacent illuminated primary leaf. In addition, abscisic acid (ABA) content was increased which correlated with reduced stomatal aperture leading to decreased stomatal conductance and transpiration rate. In contrast, darkening of the adjacent primary leaf led to increased metabolic activity in the illuminated cotyledons including increased total CK levels in parallel with decreased CKX activity, decreased ABA content in correlation with increased stomatal aperture, stomatal conductance and transpiration rate. On the other hand, the functional activity of the photosynthetic apparatus as well as the transcript levels of the three photosynthesis-related genes psbA, psaB and rbcL remained almost unaffected in both illuminated organs. Thus, compared with the primary leaves, cotyledons appeared to be much more resistant to the dark stress applied either directly or to the adjacent primary leaf. Our results indicated the involvement of CKs and ABA signalling in the control of the communication mechanisms between cotyledons and the primary leaf that could operate in response to changing environmental factors like shading during earlier stages of plant development.
    Plant Growth Regulation 12/2011; 65(3). DOI:10.1007/s10725-011-9616-8 · 1.63 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Changes in cell wall polysaccharides in oat (Avena sativa L.) leaf segments during senescence promoted by methyl jasmonate (JA-Me) were studied. During the incubation with water at 25 °C in the dark, the loss of chlorophyll of the segments excised from the primary leaves of 8-day-old green seedlings was found dramatically just after leaf excision, and leaf color completely turned to yellow after the 3- to 4-day incubation in the dark. Application of 10 µM JA-Me substantially promoted the loss of chlorophyll corresponding with the chloroplast degradation. Cell wall polysaccharides in oat leaf segments mainly consisted of hemicellulosic and cellulosic ones. During the process of leaf senescence, the amount of hemicellulosic I and II, and cellulosic polysaccharides decreased, but little in pectic polysaccharides. JA-Me significantly enhanced the decrease in cellulosic polysaccharides, but little in hemicellulosic ones. Arabinose, xylose and glucose were identified as main constituents of neutral sugars of hemicellulosic polysaccharides. The neutral sugar compositions of hemicellulosic polysaccharides changed little during leaf senescence both in the presence or absence of JA-Me. These facts suggest that JA-Me affects sugar metabolism relating to cellulosic polysaccharides during leaf senescence.
    Acta Physiologiae Plantarum 09/2013; 35(9). DOI:10.1007/s11738-013-1299-5 · 1.52 Impact Factor

Full-text (2 Sources)

Download
186 Downloads
Available from
May 17, 2014