New Insights Into the Activity of Apple Dihydrochalcone Phloretin: Disturbance of Auxin Homeostasis as Physiological Basis of Phloretin Phytotoxic Action.

Apple species are the unique naturally rich source of dihydrochalcones, phenolic compounds with an elusive role in planta, but suggested auto-allelochemical features related to "apple replant disease" (ARD). Our aim was to elucidate the physiological basis of the phytotoxic action of dihydrochalcone phloretin in the model plant Arabidopsis and to promote phloretin as a new prospective eco-friendly phytotoxic compound. Phloretin treatment induced a significant dose-dependent growth retardation and severe morphological abnormalities and agravitropic behavior in Arabidopsis seedlings. Histological examination revealed a reduced starch content in the columella cells and a serious disturbance in root architecture, which resulted in the reduction in length of meristematic and elongation zones. Significantly disturbed auxin metabolome profile in roots with a particularly increased content of IAA accumulated in the lateral parts of the root apex, accompanied by changes in the expression of auxin biosynthetic and transport genes, especially PIN1, PIN3, PIN7, and ABCB1, indicates the role of auxin in physiological basis of phloretin-induced growth retardation. The results reveal a disturbance of auxin homeostasis as the main mechanism of phytotoxic action of phloretin. This mechanism makes phloretin a prospective candidate for an eco-friendly bioherbicide and paves the way for further research of phloretin role in ARD.

Advancement in protocol for in vitro seed germination, plant regeneration and cryopreservation of Viola cornuta.

The aim of this study was to develop a fast, reliable and true-to-type protocol for in vitro plant regeneration and long-term storage of horned pansy (Viola cornuta L). Seed germination over 60% was recorded after 12 weeks of growth at 10 °C or 4 °C. Calli formation and shoot induction were obtained in petiole and hypocotyl culture on half-strength MS mineral salts with full concentration of Na-FeEDTA and vitamins (½MS medium) with 2,4-dichlorophenoxyacetic acid (2,4-D, 0.1 mg/L) and 6-benzylaminopurine (BAP, 2.0 mg/L) and leaf culture on ½MS medium with thidiazuron (TDZ,1.0 mg/L). The highest frequency of adventitious shoot induction (50%) with six shoots/explant was achieved in hypocotyl culture from top hypocotyl segments, close to epicotyl which was grown 8 weeks at 16 h light/8 h dark photoperiod. Subsequent shoot multiplication was achieved on ½MS medium with α-naphthaleneacetic acid (NAA, 0.1 or 0.5 mg/L) and BAP (1.0 mg/L). Rooting of shoots was obtained on ½MS medium with low concentration (0.1 mg/L) of auxins: indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) or NAA, or without growth regulators. In vitro-derived plantlets were acclimatized under greenhouse conditions. All plants developed normally, bloomed and set seeds. Shoot tips were cryopreserved succssefully using modified plant vitrification 3 (PVS3-based vitrification procedure). Cold acclimation for 2 weeks significantly improved shoot regrowth (64%) after thawing in comparison to non-acclimated shoots (39%). Clonal fidelity of regenerated plantlets at ploidy level was confirmed by chromosome counting. The presented protocol can be useful for mass propagation, genetic transformation studies and long-term storage of valuable Viola spp.

Relationship between the vertical craniofacial disproportions and the cervicovertebral morphology in adult subjects.

INTRODUCTION: Orthodontic diagnosis includes the interpretation of the relations between the craniofacial and cervical system, given the potential impact of the irregularities from one system to another. OBJECTIVE: The aim of this study was to examine morphological characteristics of the cervical spine, depending on the parameters of the vertical craniofacial growth and gender in adult subjects. METHODS: The sample comprised lateral cephalograms of 120 subjects with different vertical facial growth, aged 17.5-35 years. Measured parameters were the following: anterior and posterior vertebral body height (ABHC2-C5, PBHC2-C5), anterior and posterior intervertebral space (AISC2-C5, PISC2-C5), distance between vertebrae and point sella (SC2, SC3, SC4), pterygomaxillare (PmC2), gonion (GoC2) and basion (BaC4); cervical spine angulation (OPT/CVT) and inclination (OPT/HOR, CVT/HOR). RESULTS: Results showed that subjects with anterior facial growth rotation have greater values for BaC4, OPT/HOR, CVT/HOR, OPT/CVT, anterior and posterior vertebral body heights and intervertebral spaces, and lower values for GoC2 and PmC2. Higher values in males were found for anterior and posterior vertebral body heights, distances SC2, SC3, SC4, and BaC4. In females, the greater values were found for GoC2 and OPT/CVT. CONCLUSION: Subjects with anterior facial growth rotation have greater cervical spine inclination and angulation, higher cervical vertebrae and intervertebral spaces, longer upper cervical spines and shorter distances GoC2 and PmC2. Males show smaller cervical column curvature, but higher cervical vertebrae and greater length of the upper cervical spine.