Comparison of salinity and drought stress effects on abscisic acid metabolites activity of cytokinin oxidase/dehydrogenase and chlorophyll levels in radish audtabacco

Stronger negative impact of salinity (100 mM NaCl for 4 days) on radish plants in comparison with tobacco ones, correlated with more profound decrease of bioactive cytokinins and higher elevation of activity of the main cytokinin degrading enzyme cytokinin oxidase/dehydrogenase and abscisic acid in the former species

Efekti salicilne kiseline na morfološke osobine i formiranje krtola kod netransformisanog i AtCKX2-transformisanog krompira (Solanum tuberosum L. cv Désirée) gajenog in vitro

Salicilna kiselina (SA) je biljni regulator rastenja čije su glavne fiziološke funkcije odbrana od biotičkog stresa i termogeneza tokom cvetanja kod određenih biljnih vrsta. U novije vreme sve je više podataka o ulozi SA u odbrani biljaka od abiotičkog stresa. SA se često označava kao biljni hormon, mada su podaci o njenim specifičnim efektima na rastenje i razviće kod biljaka sporadični i ograničeni na mali broj vrsta. U literaturi nema podataka o efektima SA na rastenje i razviće krompira, kao ni o interakciji SA sa biljnim hormonima koji regulišu ekonomski značajan proces tuberizacije kod ove vrste. Cilj sprovedenog istraživanja je bio da se utvrdi da li egzogeno primenjena SA ima efekte na morfološke osobine i tuberizaciju kod krompira gajenog in vitro. Ispitivan je efekat SA kod netransformisanog krompira (K) i jedne linije AtCKX2-transformisanog krompira (AtCKX2-51), koju karakteriše veoma nizak sadržaj bioaktivnih citokinina (CK).1 SA je primenjivana u niskim koncentracijama (0,01–10 μM), dodavanjem u podloge za gajenje izdanaka krompira in vitro, a morfološki parametri, uključujući i parametre tuberizacije, određivani su u kulturama starim 30 dana. Rezultati su pokazali da SA (u najvećoj primenjenoj koncentraciji) ima efekat samo na pojedine procese rastenja i razvića, a da ne remeti tuberizaciju. Uočeni efekti se razlikuju kod K i AtCKX2-51 krompira. Prikazani rezultati sprovedenog istraživanja ukazuju na moguću interakciju između SA i CK u regulaciji rastenja i razvića krompira in vitro

Heat Stress Targeting Individual Organs Reveals the Central Role of Roots and Crowns in Rice Stress Responses

Inter-organ communication and the heat stress (HS; 45°C, 6 h) responses of organs exposed and not directly exposed to HS were evaluated in rice (Oryza sativa) by comparing the impact of HS applied either to whole plants, or only to shoots or roots. Whole-plant HS reduced photosynthetic activity (Fv/Fm and QY_Lss), but this effect was alleviated by prior acclimation (37°C, 2 h). Dynamics of HSFA2d, HSP90.2, HSP90.3, and SIG5 expression revealed high protection of crowns and roots. Additionally, HSP26.2 was strongly expressed in leaves. Whole-plant HS increased levels of jasmonic acid (JA) and cytokinin cis-zeatin in leaves, while up-regulating auxin indole-3-acetic acid and down-regulating trans-zeatin in leaves and crowns. Ascorbate peroxidase activity and expression of alternative oxidases (AOX) increased in leaves and crowns. HS targeted to leaves elevated levels of JA in roots, cis-zeatin in crowns, and ascorbate peroxidase activity in crowns and roots. HS targeted to roots increased levels of abscisic acid and auxin in leaves and crowns, cis-zeatin in leaves, and JA in crowns, while reducing trans-zeatin levels. The weaker protection of leaves reflects the growth strategy of rice. HS treatment of individual organs induced changes in phytohormone levels and antioxidant enzyme activity in non-exposed organs, in order to enhance plant stress tolerance

Hormonal regulation of flower development in the tomato (Solanum lycopersicum L.) mutant stamenless

Extensive genetic and molecular studies have led to the broadly accepted ABCE model of flower development. Floral homeotic genes encoding transcription factors combinatorially specify organ identity in each floral whorl. However, less is known regarding how these genes control changes at the cellular level during floral organ formation. Recently, an important role for phytohormones as transducers of genetic information during floral development has been suggested in model species. We investigated the hormonal regulation of floral organ development in a strong stamenless (sl-Pr) mutant - in the tomato Primabel cultivar - that exhibits homeotic conversion of petals into sepals and stamens into carpels. This phenotype results from mutations in the coding sequence of the class B Tomato APETALA3 (TAP3) gene. Treatments with phytohormones revealed that gibberellins could partly revert the sl-Pr phenotype but affected neither the SL (TAP3) nor the other ABCE gene expression. Quantification of endogenous polyamines and phytohormones content in the sl flowers along their development showed that the sl-Pr mutation reduced gibberellins, auxins, cytokinins, salicylic acid, spermine and tyramine concentrations and increased jasmonic acid and abscissic acid in tomato flowers. Together, our results revealed a role of phytohormones in flower development downstream of the SL (TAP3) gene in tomato

Positive impact of vermicompost leachate on salt stress resistance in tomato (Solanum lycopersicum L.) at the seedling stage: a phytohormonal approach

Background and aim Vermicompost leachate (VCL) produced by earthworms is a valuable biostimulant but its hormonal impact on salt-treated plants remains elusive. Methods Plants of Solanum lycopersicum L. were cultivated in nutrient solution and exposed during 7 days to 125 mM NaCl in the presence or absence of VCL (18 mL.L−1). Mineral nutrition, water and hormonal status were quantified in roots, young and old leaves and analyzed in relation to phytohormone content of VCL. Results VCL improved plant growth and reduced Na+ accumulation in salt-stressed plants. It delayed senescence in young leaves through a decrease in ethylene synthesis and an increase in proline and anthocyanin contents. VCL contains high amounts of salicylic acid, benzoic acid and aminocyclopropane carboxylic acid (ACC) but low concentrations of jasmonates, cytokinins and proline. VCL did not increase abscisic acid content in salt-stressed plants and did not lead to ACC accumulation while it increased jasmonate accumulation and modified the pattern of cytokinin profile with an increase in dihydrozeatin-types in old leaves and N6-(Δ2- isopentenyl)adenine-types in young ones. Conclusion VCL reduces the impact of salinity on leaf senescence, which is related to its impact on endogenous phytohormones rather than to a passive absorption of exogenous hormonal compounds

Evolutionary Aspects of Hypericin Productivity and Endogenous Phytohormone Pools Evidenced in Hypericum Species In Vitro Culture Model

Shoot cultures of hypericin non-producing H. calycinum L. (primitive Ascyreia section), hypericin-producing H. perforatum L., H. tetrapterum Fries (section Hypericum) and H. richeri Vill. (the evolutionarily most advanced section Drosocarpium in our study) were developed and investigated for their growth, development, hypericin content and endogenous phytohormone levels. Hypericins in wild-growing H. richeri significantly exceeded those in H. perforatum and H. tetrapterum. H. richeri also had the highest hypericin productivity in vitro in medium supplemented with 0.2 mg/L N6-benzyladenine and 0.1 mg/L indole-3-butyric acid and H. tetrapterum—the lowest one in all media modifications. In shoot culture conditions, the evolutionarily oldest H. calycinum had the highest content of salicylic acid and total jasmonates in some of its treatments, as well as dominance of the storage form of abscisic acid (ABA-glucose ester) and lowest cytokinin ribosides and cytokinin O-glucosides as compared with the other three species. In addition, the evolutionarily youngest H. richeri was characterized by the highest total amount of cytokinin ribosides. Thus, both evolutionary development and the hypericin production capacity seemed to interact closely with the physiological parameters of the plant organism, such as endogenous phytohormones, leading to the possible hypothesis that hypericin productivity may have arisen in the evolution of Hypericum as a means to adapt to environmental changes

Auxins and Cytokinins in Plant Development 2018

The international symposium “Auxins and Cytokinins in Plant Development„ (ACPD), which is held every 4⁻5 years in Prague, Czech Republic, is a meeting of scientists interested in the elucidation of the action of two important plant hormones—auxins and cytokinins. It is organized by a group of researchers from the Laboratory of Hormonal Regulations in Plants at the Institute of Experimental Botany, the Czech Academy of Sciences. The symposia already have a long tradition, having started in 1972. Thanks to the central role of auxins and cytokinins in plant development, the ACPD 2018 symposium was again attended by numerous experts who presented their results in the opening, two plenary lectures, and six regular sessions, including two poster sessions. Due to the open character of the research community, which is traditionally very well displayed during the meeting, a lot of unpublished data were presented and discussed. In this report, we summarize the contributions in individual sessions that attracted our attention

Effects of Explant Types and Different Cytokinins on Kohlrabi Regeneration

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