Krystyna M. Janas

Antioxidant enzymes activity and phenolic compounds content in red cabbage seedlings exposed to copper stress.

The phenolics: anthocyanin (ATH), sinapoyl esters and activity of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POX), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione reductase (GR), in red cabbage seedlings subjected to Cu2+ stress were investigated. Cu2+ at low doses (0.5 mM), increased the levels of ATH and sinapoyl derivatives in red cabbage. High Cu2+ concentration (2.5 mM) provoked oxidative stress and enhanced thiobarbituric acid reactive substances (TBARS) content in tissues. A lower level of TBARS was correlated with high ATH content. It seems that synthesis of these isoflavonoids is an effective strategy against reactive oxygen species (ROS). The analysis of the antioxidant enzymes activity suggested that peroxidases were the most active enzymes in red cabbage seedlings exposed to Cu2+ stress. It could results from the fact that phenolic compounds (PhC), which could be also substrates for different peroxidases, were the first line of defence against metal stress.

Melatonin applied to cucumber (Cucumis sativus L.) seeds improves germination during chilling stress

Abstract:  The relationship between germination and melatonin applied during osmo‐ and hydropriming was studied in cucumber seeds. The proportion of nuclei with different DNA contents, the mean ploidy and the (2C + 4C = 8C)/2C ratio in unprimed and primed, dry and imbibed at 10°C seeds were established by flow cytometry. Thiobarbituric acid reactive substances and protein oxidation were also estimated. Melatonin and indole‐3‐acetic acid (IAA) concentrations in the seeds were determined using high‐performance liquid chromatography with electrochemical detection. Being sensitive to chilling stress, seeds that germinated well (99%) at 25°C showed only 30% germination at 15°C, and almost no germination (4%) at 10°C. Hydropriming in water improved seed germination to 50–60% at 15°C and the addition of melatonin (25–100 m) also increased the rate of germination. Osmopriming in polyethylene glycol increased germination at 15°C to 78%, and 98% when combined with 50 m melatonin. Osmoprimed seeds germinated even at 10°C and reached 43%, and 83% when 50 m melatonin was applied. None of the treatments induced DNA synthesis, although during the first 24 hr of imbibition at 10°C the mean ploidy and the (2C + 4C = 8C)/2C ratio increased, which is indicative of the advanced Phase II of germination. Hydro‐ and osmopriming slightly decreased IAA content in the seeds in most of the cases; only hydropriming with 100 and 500 m melatonin increased it. Melatonin protected membrane structure against peroxidation during chilling, but excessive melatonin levels in cucumber seeds (∼4 μg/g fresh weight) provoked oxidative changes in proteins. There is still lack of information explained clearly the role of melatonin in plant physiology. This molecule acts multidirectionally and usually is alliged to other compounds.

Presowing seed treatment with melatonin protects red cabbage seedlings against toxic copper ion concentrations

Abstract:  One of the targets of modern plant physiology is to identify tools for improving seed germination and plant growth under unfavorable environmental conditions. Seeds of Brassica oleracea rubrum were pretreated with melatonin at concentrations: 1, 10, and 100 μm using a hydropriming method. Air‐dried seeds of each experimental variants that were nonpretreated (control), hydroprimed (H) or hydroprimed with melatonin (HM1, HM10, and HM100) were germinated in darkness for 3 days at 25°C. Young seedlings were then transferred to the light and grown for an additional 5 days. Both germination and growth tests were performed in water and in CuSO4 water solutions in concentrations of 0.5 and 1 mm. H, HM1 and HM10 improved seed germination both in water and in the presence of Cu2+. One or 10 μm melatonin eliminated the inhibitory effect of the 0.5 mm metal concentration on the fresh weight of seedlings. HM100 had a negative effect; thus seed germination was lower and seedlings had poor establishment. The toxic effect of Cu2+ manifested by membrane peroxidation and DNA endoreplication blocking in the seedlings grown from nontreated (control) and H seeds was not observed in the seedlings grown from HM1 and HM10 seeds; in contrast, HM100 enhanced the toxic effect of Cu2+.

Melatonin in plants

A widespread occurrence of melatonin (MEL) in plant kingdom has been reported. MEL is a highly conserved molecule occurring in evolutionary distant organisms. Its role in plants seems to be similar to that in animals. Although MEL function in plants is not well known, yet a hypothesis can be put forward that it probably functions as a night signal, coordinating responses to diurnal and photoperiodic environmental cues. It has also been suggested that MEL is an independent plant growth regulator, probably its action is analogous to IAA and it may mediate the actions of other plant growth regulators. Due to its antioxidant properties MEL may also stabilize cell red-ox status and protect them against reactive oxygen species (ROS) and other harmful environmental influence.

Constitutive elevated accumulation of phenylpropanoids in soybean roots at low temperature

Abstract Changes in phenolic acid and isoflavonoid contents in soybean (Glycine max. (L.) Merr) roots after 24-h of low temperature cultivation were investigated. The level of total phenolic acids (represented by the sum of derivatives of benzoic and cinnamic acids) and genistein, daidzein and genistin (glucosyl conjugate of genistein) increased after 24 h of exposure to low temperature. In chill-treated roots the highest increase in genistin was observed. Application of 2-aminoindan-2-phenylphoshonic acid (AIP), a competitive inhibitor of l -phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) resulted in an increased level of endogenous free phenylalanine. An increase in the content of free phenylalanine is regarded as an indication for the inhibition of PAL in vivo. Chilling with AIP decreased valine level. AIP applied in combination with chilling decreased phenolic acids but did not effect the isoflavonoids content. These findings may indicate that the increase in the phenolics level comes from the pre-formed conjugates of phenylpropanoids.

Melatonin, an underestimated natural substance with great potential for agricultural application

Abstract Melatonin (MEL) was thought to be only a neurotransmitter found in vertebrates until its detection in other organisms including plants. Although the number of publications on MEL function in plants is expanding, the knowledge of this subject is still insufficient. Among many functions which MEL performs in plants, its role as an antioxidant and a growth promoter is most supported by experimental evidence. This compound is an independent plant growth regulator and it may mediate the activities of other plant growth regulators. Due to its antioxidant properties MEL may also stabilize cell redox status and protect tissues against reactive oxygen and nitrogen species which accumulated under stressful environment. Some researchers propose that MEL could be used to improve the phytoremediation efficiency of plants against different pollutants. In this paper we show that exogenous MEL applied into the seeds could be a good biostimulator improving not only seed germination, seedling/plant growth but also crop production especially under stress conditions. We also believe that this compound can increase food quality (the aspect of functional food) and may improve human health. Since MEL is inexpensive and safe for animals and humans its application as a biostimulator could be a good, feasible and cost-effective method useful in agriculture.

The impact of copper ions on growth, lipid peroxidation, and phenolic compound accumulation and localization in lentil (Lens culinaris Medic.) seedlings

Changes in phenolics (PhC) measured as UV-absorbing compounds (UVAC) and their localization as well as growth, lipid peroxidation (TBARS level), H(2)O(2) and Cu accumulation and other ions content in roots of two lentil cultivars (cv. Krak and cv. Tina) contrasting in Cu sensitivity were examined. The aim of this study was to reveal the importance of PhC in Cu tolerance. During Cu treatment, inhibition of growth and increases in lipid peroxidation in roots of both cultivars were observed, but the effects were more pronounced in cv. Tina (more sensitive) than in cv. Krak (less sensitive). Cu at 0.5 mM caused higher Cu and H(2)O(2) accumulation, but lower K(+) content and UVAC levels in the root tips of cv. Tina. Opposite changes were recorded in cv. Krak. Fluorescence microscopic analyses confirmed greater PhC accumulation in cv. Krak (less sensitive) than in cv. Tina (more sensitive) after Cu treatment and showed that these compounds accumulated particularly in vacuoles and the cell wall. Taken together, these results show that, in spite of the high concentration of Cu-stimulated PhC accumulation in cv. Krak, it was not sufficient to counteract the amount of ROS generated by the metal. The role of PhC in different reactions to Cu stress in lentil roots is discussed.

Changes in the nature of phenolic deposits after re-warming as a result of melatonin pre-sowing treatment of Vigna radiata seeds

Changes in phenolics (PhC - phenolic compounds) measured as UV-absorbing compounds (UVAC) and their localization as well as growth, lipid peroxidation (TBARS level) and proline (Pro) level in three-day-old roots of seedlings (T(o) stage) obtained from hydroprimed (H) and hydroprimed with melatonin (H-MEL) seeds after 2 days of chilling (5°C) and 2 days of re-warming were examined. H and H-MEL resulted in inhibition of root growth under optimal conditions, but after re-warming, a positive effect of MEL was noted. The results also showed a positive MEL impact on TBARS level already after chilling and especially after re-warming. Exposure of Vigna radiata seedlings to chilling caused a significant increase in Pro level, especially in H-MEL roots, but after re-warming it drastically decreased. Under chilling stress, accumulation of UVAC also decreased. However, after re-warming it returned to the level observed in the roots grown constantly at 25°C. Even if after re-warming of V. radiata seedlings only slight accumulation of total PhC was observed, phenolic deposits accumulating in the vacuoles of H-MEL roots were completely different from those in the vacuoles of the control and H roots. H-MEL application to the seeds resulted in a significant increase in small granular composite materials, while in the control and H roots, large oval deposits prevailed. Taken together, it is probable that all of these differences were connected with positive effects of MEL on chilled V. radiata seedlings after re-warming.

Ameliorative effect of melatonin on meristematic cells of chilled and re-warmed Vigna radiata roots

Changes in ultrastructure of meristematic cells as well as growth and lipid peroxidation in roots of 3-d-old seedlings obtained from control (C), hydroprimed (H) and hydroprimed with melatonin (H-MEL) seeds after 2 d of incubation at 25 or 5 °C and 2 d of re-warming after chilling were investigated. Under 25 °C hydropriming (H and H-MEL) inhibited root growth, but after chilling and re-warming a positive MEL effect on root elongation was observed. The results show decreased lipid peroxidation in H-MEL roots already after chilling, but the significant extent of MEL impact was seen after re-warming. Similarly at the ultrastructural level, the protective effect of MEL at chilling was also visible, especially in plastids, and this effect maintained also after re-warming.

Red cabbage anthocyanin extract alleviates copper-induced cytological disturbances in plant meristematic tissue and human lymphocytes

Red cabbage is a source of health beneficial substances with antioxidant and antigenotoxic properties. HPLC analysis specifying the content of the investigated extract indicated that mainly anthocyanins (ATH) were responsible for its abilities. Cytological research was conducted with two experimental models: plant tissues—meristematic cells of Vicia faba, and animal tissue elements—human lymphocytes. Positive influence of ATH extract on mitotic activity of Vicia cells exposed to Cu2+ stress, and inhibitory effect of ATH on cytotoxic actions of Cu2+ on lymphocytes were demonstrated. In all experimental series with ATH application in combinations with Cu2+, mitotic index (MI) were higher than those obtained for only Cu2+ stressed tissues. Preincubation in ATH before Cu2+ stress had the best effect. Similarly, after ATH applications in all tested series decrease in frequency of micronuclei (MN) appearance was noticed in comparison with only Cu2+ stressed material. In the case of Vicia cells ATH acted effectively even applied after Cu2+ stress. It suggests that this ATH mixture not only prevents and limits but also heals the cytological injury caused by Cu2+ stress.