Gregor Osterc

Juvenile stockplant material enhances root development through higher endogenous auxin level

Stockplants with various physiological characteristics were compared in a propagation experiment with leafy cuttings of ornamental cherry Prunus subhirtella ‘Autumnalis’. At the time of severance, cuttings harvested from juvenile 3-year-old in vitro-derived plants contained in their bases nearly twice as much IAA (indole-3-acetic acid) as cuttings derived from mature 40-year-old trees. Juvenile cuttings showed better rooting success in the propagation season. They developed a significantly higher number of primary roots and grew better than physiologically older cuttings. IAA time-course levels in cutting bases in the days after severance were similar in both cuttings types. They decreased over the first day (rooting late initiation phase) after severance until the third day after severance when the levels increased again (rooting induction phase and beginning of the root developing phase). At the time of severance, juvenile cuttings also contained higher concentrations of IAAasp (indole-3-acetyl aspartic acid) in their bases than mature cuttings. IAAasp time-course levels were similar to those measured for IAA.

Phase change modifies anthocyanin synthesis in Acer palmatum Thunb. (Japanese maple) cultivars.

The potential markers of juvenility (cyanidin 3-glucoside and cyanidin 3-rutinoside) in autumn leaves of seven Acer palmatum Thunb. cultivars were investigated. Three shoot positions were marked on each cultivar—crown shoot, middle shoot, and basal shoot—and the anthocyanins were analyzed using HPLC-MS. The results showed great differences in cyanidin 3-glucoside and cyanidin 3-rutinoside concentrations among seven cultivars; moreover, significant differences in cyanidin 3-glucoside content levels were also observed among three shoot positions regardless of the cultivar analyzed. The concentration decreased basipetally and reached levels up to 52 times higher in leaves obtained from crown shoots in comparison to basal shoot leaves. Therefore, the content level of cyanidin 3-glucoside can be defined as a quantitative marker of positional effect in all the Acer palmatum Thunb. cultivars analyzed. The content level of cyanidin 3-rutinoside did not express the same positional dependence.

Potential involvement of flavonoids in the rooting response of chestnut hybrid (Castanea crenata × Castanea sativa) clones

The involvement of different quercetins [quercetin-3-O-rhamnoside (quercitrin), quercetin-3-D-galactoside (hyperoside) and rutin] and catechins (catechin, catechol) in the rooting process of leafy cuttings was studied in two hybrid chestnut (Castanea crenata × Castanea sativa) clones, Maraval and Marsol. Both clones differed strongly in rooting results. The Maraval clone cuttings, which had a high rooting rate, contained, on average, higher amounts of all quercetins in different plant parts (leaves and basal cuttings) than the Marsol clone, which had a low rooting rate. There was a highly significant correlation between the quercetin contents of the cutting leaves and the rooting process (number of main roots). The catecechin contents of the cutting leaves did not show any correlation with the rooting process.

Branching of annual shoots in common walnut (Juglans regia L.) as affected by bud production and indol-3-acetic acid (IAA) content

Relationship of bud production (axillary and terminally) of annual shoot (1Y) and/or the content of bud-derived indol-3-acetic acid (IAA) to branching of the 1Y was studied in common walnut (Juglans regia L.), cvs. Franquette and Lara. Cultivar-related branch architecture was determined. Lara tended to branch more densely than Franquette (53 vs. 42%). Significantly more fruiting off-spring shoots (FO) than vegetative ones (VO) grew-out per 1Y in both cultivars, whereas the ratio FO/VO of Lara exceeded that of Franquette by four times. An acrotonic branching pattern was more strongly expressed in Lara compared to Franquette. Bud-derived IAA was influenced by the cultivar (Franquette had 3.6 times more cumulative IAA along the 1Y than Lara), and by the relative position (terminal, subterminal, medial and basal) of the buds along 1Y. An opposite relationship between branching density and cumulative IAA content was established in both cultivars. At the 1Y relative position level, the opposite ratio between branching density and IAA content was clearly shown only on the basal position of the bud along 1Y in the Lara cultivar. Such an inconsistent linkage between bud production and the IAA spatial distribution along the 1Y illustrated that hormonal factors probably weakly affect the branching of Franquette and Lara. The length of the parent 1Y, the position of the buds along the 1Y-length, and the fate of the buds seemed to have a stronger influence on the bud out-growth and further development of the off-springs. In further analyses, seasonal fluctuations of the IAA, and the following activity of the buds should be investigated in order to improve the understanding of a complex branching phenomenon in walnut.