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The current study presents a method for the plant regeneration from stem segments of Cordyline australis (G. Forst.) Endl. ‘Red Star’ through somatic embryogenesis. We tested the effect of 3 kinds of auxin 4-amino-3,5,6-trichloropicolinic acid (picloram), 2,4-dichlorophenoxyacetic acid (2,4-D), and 2-methoxy-3,6-dichlorobenzoic acid (dicamba), with a combination of 2 kinds of cytokinin, 6-benzyladenine (BA) and thidiazuron (TDZ), on the induction of embryogenic callus and its capacity to induce somatic embryogenesis under dark culture condition. The highest percentage of explants forming callus (nodular and friable) was observed on medium containing 25 μM picloram and 0.5 μM BA. The embryogenic callus, with white-yellowish nodular structures, was proliferated in the initial media and finally produced somatic embryos on all media with picloram and 2,4-D. Somatic globular embryos were obtained with a higher frequency from explants cultured on MS medium supplemented with 25 μM picloram and 0.5 μM BA. On this medium, a mean number of 23.0 embryos developed per gram of callus. Globular embryos developed most efficiently into cotyledonary stage on MS medium supplemented with 5 μM picloram and 1 μM BA. The addition of zeatin (5 and 2.5 μM) and NAA (0.5 and 0.25 μM) to the medium was found to be essential for the highest conversion of somatic embryos into plants. Plantlets were successfully acclimatized in the greenhouse with 90% survival rate. Callus was tested for phenolic compounds, sugars, peroxidase activity and protein contents in order to find if these compounds might be the indicators of further embryos development. The embryogenic callus of C. australis with various stages of embryo development had higher level of protein than the non-regenerable one, whereas level of sugars increased only in callus with embryos in cotyledonary stage. Callus with globular embryos contained high concentration of phenolics and low activity of peroxidase, comparing to other types of callus. [ABSTRACT FROM AUTHOR]

Summary: The purpose of this study was to know the mechanism of jasmonates to induce gummosis in tulip (Tulipa gesneriana L. cv. Apeldoorn) shoots, especially on the focus of sugar metabolism. Gummosis in the first internode of tulip plants was induced by the application of methyl jasmonate (JA-Me, 1% w/w in lanolin) and jasmonic acid (JA, 1% w/w in lanolin) 5 days after application and strongly stimulated by the simultaneous application of ethylene-releasing compound, ethephon (2-chloroethylphosphonic acid, 1% w/w in lanolin), although ethephon alone had little effect. JA-Me stimulated ethylene production of the first internodes of tulips, ethylene production increasing up to more than 5 times at day 1 and day 3 after the application. On the other hand, application of ethephon did not increase endogenous levels of jasmonates in tulip stems. Analysis of composition of tulip gums revealed that they were consisted of glucuronoarabinoxylan with an average molecular weight of ca. 700kDa. JA-Me strongly decreased the total amount of soluble sugars in tulip stems even in 1 day after application, being ca. 50% of initial values 5 days after application, but ethephon did not. However, both JA-Me and ethephon had almost no effect on the neutral sugar compositions of soluble sugars mainly consisting of glucose, mannose and xylose in ratio of 20:2:1 and traces of arabinose. Both JA-Me and ethephon applied exogenously stimulated senescence of tulip shoots shown by the loss of chlorophyll. These results strongly suggest that the essential factor of gummosis in tulips is jasmonates affecting the sugar metabolism in tulip shoots. The mode of action of jasmonates to induce gummosis of tulip shoots is discussed in relation to ethylene production, sugar metabolism and senescence. [Copyright &y& Elsevier]

• Seed germination of Stevia rebaudiana could be improved by adding a specific dose of phytohormones to the germination substrate. • GA 3 at the concentration of 1 μM was the most favorable for seed germination. • Kinetin at the concentration of 10 μM shows the best effect on seedling development (fresh weight, stem, and root length, leaf number). • Effects of phytohormones on biochemical parameters (chlorophylls and antioxidants) of stevia plantlets can be various and dose-dependent. Poor germination and the long period required for the development of seedlings suitable for planting in the field are among the major problems that affect the cultivation of Stevia rebaudiana. We investigated the abilities of different phytohormone concentrations to improve stevia seed germination and seedling growth. Seeds were germinated on agar gel (AG), supplemented with various concentrations (0, 1, 10 and 100 μM) of gibberellic acid (GA 3), thidiazuron (TDZ), kinetin (KN) and N6-benzyladenine (BA) under in vitro conditions. The resultant seedlings were transferred onto Murashige and Skoog (MS) medium for further growth. In most cases, a phytohormone concentration of 1 μM was most favorable for germination. The highest germination was achieved in cases of AG enrichment at a concentration of 1 μM GA 3. Regarding the seedlings, the optimal effect on fresh weight, stem, and root length, as well as leaf number was observed when KN was added at a concentration of 10 μM during the germination stage. Generally, a high negative correlation was observed between the phytohormone concentration and the plantlets' appearance. Conversely, higher chlorophyll and carotenoid contents were observed when 100 μM of GA 3 , KN and BA was applied at the germination stage. In most cases, antioxidant enzyme activity was also higher under phytohormone treatments. We concluded that the addition of a certain phytohormone concentration at the germination stage enhanced stevia germination and improved seedling development. [ABSTRACT FROM AUTHOR]

Highlights • Intensity of DNA synthesis in rape seeds could be an indicator of their vigour. • Naturally aged Brassica napus seeds contain low levels of abscisic acid. • Expression of BnRSH1 and BnRSH3 is low in aged seeds. • BnRSH1 and BnRSH3 levels could be used as markers of rape seed quality. • Proline content and antioxidative enzymes activity – markers of rape seed quality. Abstract Seed aging occurs relatively fast in crops and it is a process that delays germination as well as reducing its rate and even causing total loss of seed viability. Hence, it is a problem for seed banks, farmers and seed companies that deal with seed storage. The purpose of the research was to unravel genetic, biochemical and molecular events accompanying natural oilseed rape (Brassica napus L.) seed aging and thus to find potential markers of seed deterioration advancement, in order to facilitate the checking of seed quality and the ability to quickly take measures to protect them from dying. In this study, it is shown that low seed vigour is characterised by low intensity of DNA synthesis, which can quickly be measured by means of flow cytometry, changes in RNA quality, low sugar levels, increased proline content and superoxide dismutase activity, decreased ascorbate peroxidase activity, as well as abscisic acid content. Furthermore, it is demonstrated that the expression of BnRSH1 and BnRSH3 , encoding for enzymes responsible for metabolism of the effectors of the stringent response (guanosine tetra- and pentaphosphate) that function in chloroplasts to regulate transcription, translation and metabolites levels, is downregulated in seeds of low vigour. Besides indicating potential markers of oilseed rape seed quality, we also propose a mechanism of seed dormancy regulation via the abscisic acid-stringent response module. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alarmone ppGpp was detected in the seed of B. napus L., non-leaf organs. • ppGpp accumulation peaked at the last stage of seed development. • Alarmone accumulation did not prevent build-up of storage compounds. • ppGpp concentration negatively correlates with chlorophyll content in seeds. Rapeseed oil, constituting 12% of global vegetable oil production, is susceptible to quality degradation due to stress-induced incomplete seed degreening, fatty acid oxidation, or poor nutrient accumulation. We hypothesise that the hyperphosphorylated nucleotide alarmone ppGpp (guanosine tetraphosphate), acts as a pivotal regulator of these processes, given its established roles in nutrient management, degreening, and ROS regulation in leaves. Using qPCR, UHPLC-MS/MS, and biochemical methods, our study delves into the impact of ppGpp on seed nutritional value. We observed a positive correlation between ppGpp levels and desiccation, and a negative correlation with photosynthetic pigment levels. Trends in antioxidant activity suggest that ppGpp may negatively influence peroxidases, which are safeguarding against chlorophyll decomposition. Notably, despite increasing ppGpp levels, sugars, proteins and oils appear unaffected. This newfound role of ppGpp in seed development suggests it regulates the endogenous antioxidant system during degreening and desiccation, preserving nutritional quality. Further validation through mutant-based research is needed. [ABSTRACT FROM AUTHOR]

Poor germination of Stevia rebaudiana Bertoni seeds is a phenomenon with unknown reason and the research concerning the improving of germination are still in progress. We investigated the influence of light-emitting diodes (LEDs) spectra on Stevia seed germination as well as seedling growth and selected morphological and biochemical parameters. Blue LED light increased seed germination and affected the development of the largest number of leaves and roots in 4-week-old Stevia plantlets. It has also the most favourable effect on the number and opening of stomata. Red LED light however, significantly increased the length of stems and roots, although there was not correlation with the fresh weight (FW). The highest FW of Stevia plantlets achieves under combined red and white LED light at temperature of 20 °C as well as under white fluorescent light at temperature of 25 °C. Blue LED light also positively affected the carotenoids concentration, whilst the highest concentration of chlorophyll a and b was found, in plantlets grown under white fluorescent light. The less favourable effect on the synthesis of all the examined pigments was exerted by red LED light. The largest amounts of phenolics and soluble sugars accumulated plantlets growing in the darkness and irradiated blue LED light. In addition, all LEDs affected the activity of antioxidant enzymes. The blue LED light increased the activity of catalase (CAT) and peroxidase (POD), especially at 25 °C. Red LED light significantly increased activity of superoxide dismutase (SOD) whilst for the activity of CAT and POD opposite effect was observed. The combined red with white LED light was the most favourable for the activity of CAT at 25 °C. We conclude that the seed germination and the quality of Stevia plantlets could be improved by controlling light quality. [ABSTRACT FROM AUTHOR]

• Amaryllidaceae alkaloid biosynthesis in Leucojum aestivum plants was investigated. • Melatonin and NaCl were added to the culture medium. • The melatonin (10 μM) added to the culture medium led to maximum plant biomass. • Melatonin enhanced the galanthamine and lycorine accumulation in plants. • The highest distribution of alkaloids was observed with melatonin. Leucojum aestivum L. is a highly demanding pharmaceutical plant which is a natural source of pharmacologically active Amaryllidaceae alkaloids, especially galanthamine and lycorine. To establish an efficient method for the production of these alkaloids Leucojum aestivum plants derived from somatic embryos were subjected to various concentrations of melatonin (N -acetyl-5-methoxy tryptamine), NaCl and melatonin combined with NaCl. The maximum L. aestivum plant biomass was obtained when 10 μM of melatonin was applied to the medium. These plants were characterised by normal growth and did not reveal signs of browning. Enrichment of the medium with NaCl caused a reduction in plant biomass, plant pigment contents (chlorophyll a , chlorophyll b and carotenoids) and an increase in the activities of antioxidant enzymes catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD). The addition of melatonin to the medium containing NaCl neutralised the negative effect of salt stress. Moreover, the stimulating effect of melatonin on Amaryllidaceae alkaloids biosynthesis was observed. In plants grown in the medium enriched with melatonin the galanthamine content was, on average, 58.6 times higher, and the lycorine content was 1.5 times higher as compared with the control. In vitro plants obtained from the medium supplemented with melatonin also showed the highest distribution of alkaloids. It is noteworthy that only the plants grown in the medium with melatonin showed the presence of tazettine and chlidanthine, 1,2-dihydro-. This study presents a promising biotechnological approach for the commercial production of alkaloids, including galanthamine and lycorine. [ABSTRACT FROM AUTHOR]