Browsing by Subject "SHOOT ELONGATION"

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  • Mencuccini, Maurizio; Salmon, Yann; Mitchell, Patrick; Hölttä, Teemu; Choat, Brendan; Meir, Patrick; O'Grady, Anthony; Tissue, David; Zweifel, Roman; Sevanto, Sanna; Pfautsch, Sebastian (2017)
    Substantial uncertainty surrounds our knowledge of tree stem growth, with some of the most basic questions, such as when stem radial growth occurs through the daily cycle, still unanswered. We employed high-resolution point dendrometers, sap flow sensors, and developed theory and statistical approaches, to devise a novel method separating irreversible radial growth from elastic tension-driven and elastic osmotically driven changes in bark water content. We tested this method using data from five case study species. Experimental manipulations, namely a field irrigation experiment on Scots pine and a stem girdling experiment on red forest gum trees, were used to validate the theory. Time courses of stem radial growth following irrigation and stem girdling were consistent with a-priori predictions. Patterns of stem radial growth varied across case studies, with growth occurring during the day and/or night, consistent with the available literature. Importantly, our approach provides a valuable alternative to existing methods, as it can be approximated by a simple empirical interpolation routine that derives irreversible radial growth using standard regression techniques. Our novel method provides an improved understanding of the relative source-sink carbon dynamics of tree stems at a sub-daily time scale.
  • Cui, Jin; Mackenzie, Kathryn; Eeckhaut, Tom; Müller, Renate; Lütken, Henrik (2019)
    A high yield of isolated protoplasts and efficient regeneration protocols are prerequisites for successful development of somatic hybrids. In the present study, protoplast isolation and regeneration were evaluated in 12 Kalanchoe accessions belonging to nine species. The highest protoplast yield was obtained from K. blossfeldiana Charming Red Meadow' with 10.780.51x10(5) protoplasts per gram fresh weight. We observed significant differences of protoplast yield while there was no distinct difference in viability among the accessions. Seven accessions reached the microcolony stage and four developed microcalli in medium supplemented with 1.0mg/l 1-naphthaleneacetic acid (NAA), 0.5mg/l 6-benzylaminopurine (BAP) and 0.5mg/l 2,4-dichlorophenoxy acetic acid (2,4-D). Using five selected accessions we optimized the PGR (plant growth regulators) concentrations using combinations of NAA, BAP and 2,4-D. K. blossfeldiana cultivars Charming Red Meadow' and Paris' produced significantly different numbers of calli depending on the PGR concentrations. For plant regeneration, the medium was supplemented with 1mg/l NAA and 2mg/l BAP or 2mg/l zeatin. Shoots were regenerated on medium supplemented with NAA and BAP for K. blossfeldiana Charming Red Meadow' and K. blossfeldiana Paris'. The plants successfully developed roots on the medium supplemented with IAA. The medium containing zeatin induced root formation directly from callus in K. blossfeldiana Charming Red Meadow'. Our findings have the potential to facilitate the use of Kalanchoe species in somatic hybridization breeding programs. Key Message The study revealed a strong genotype-dependent efficiency of colony and microcallus formation. Plants were regenerated from two Kalanchoe blossfeldiana cultivars on medium supplemented with NAA and BAP.