the shoot multiplication, and to evaluate the effects of auxins on ex vitro rooting of microcuttings in Aglaonema . Materials and Methods Plant material and culture conditions. Stock plants of Aglaonema ‘White Tip’ were grown in a 70
up to 18 weeks, five boxes of each cultivar were subcultured to prerooting medium and the remaining boxes were subcultured to shoot multiplication medium. After 2 weeks in prerooting medium, microcuttings were transferred ex vitro for rooting to 1
Effects of a wet tent (cloth continuously wetted), an intermittent mist, and a shade system were examined for establishment, survival, and growth of microcuttings of three cultivars of Euphorbia fulgens Karw. ex Klostch. The wet tent system resulted in high survival rates and rapid plantlet growth. Microcuttings placed in the mist system had survival rates close to that in the wet tent, but had the poorest plantlet growth. Microcuttings placed directly in the shade had a poor survival rate, but plantlets that survived grew as well as those from the wet tent. In all three acclimatization systems, microcuttings of the white cultivar had the highest survival rate; those of the orange and red cultivars were second and third, respectively. No difference was found in plantlet growth among the surviving cultivars after removal from treatment in acclimatization systems. Microcuttings 41 to 50 mm long survived best; survival rate increased with microcutting length. The minimum microcutting length for satisfactory survival rates (79%) was 31 mm. Microcuttings rooted a month earlier than did conventional stem-tip cuttings in the wet-tent system.
We investigated the role of ethylene on adventitious rooting of `Gala' (easy-to-root) and `Triple Red Delicious' (difficult-to-root) apple (Malus domestica Borkh.) microcuttings. Root count increased significantly as IBA level increased, with highest root counts on `Gala'. Ethylene evolution increased significantly with IBA level without significant differences between cultivars. Basal section removal of microcuttings in the area of root origin reduced root count without changing ethylene evolution. Ethylene treatment of proliferated shoots before microcutting excision failed to enhance rooting. IBA-induced ethylene evolution was eliminated nearly by AVG, but root count remained IBA dependent. ACC reversed IBA plus AVG rooting inhibition, but ACC alone failed to influence root count. Polar auxin transport inhibitors NPA and TIBA stimulated ethylene evolution without increasing root count. Adventitious rooting of apple microcuttings was not associated with ethylene. Chemical names used: 1-H-indole-3-butyric acid (IBA); aminoethoxyvinylglycine (AVG); 1-aminocyclopropane-1-carboxylic acid (ACC); 2,3,5-triiodobenzoic acid (TIBA); N-1-naphthylphthalamic acid (NPA).
Three experiments were performed to establish rooting procedure of Amygdalus arabica Oliv. Two-centimeter shoots grown in vitro on MS medium supplemented with IBA at 0.01 mg/L, BA 0.2 mg /L, sucrose 30.0 g/L, and agar 6.0 g/L were used in rooting microcuttings using three experiments: 1) IAA, IBA, and NAA at concentrations of 0.5, 1.0, and 1.5 mg/L during the whole experiment with 4 days of dark period; 2) effect of dark and light conditions and IBA and NAA treatments during root induction period (4 days), then shoots were transferred onto free plant bioregulators (PBR), MS medium until end of the experiment; 3) Rooting microcuttings after quick dipping in different NAA concentrations (0.0, 250, 500 ppm) or induced for 6 days in root induction medium (MS) with 3.0 mg/L NAA, then shoots were transferred onto containers containing 200 ml of peatmoss, perlite, or peatmoss: perlite mixture (1:1, v/v). Results of the first experiment showed that best rooting was obtained with NAA, followed by IBA. In the second experiment, dark treatments improved rooting percentage and root length. NAA was superior to IBA in root number. Higher IBA and NAA (3.0 mg/L) concentrations gave the best rooting. In the third experiment, induced shoots transferred to perlite gave better root number and rooting percentage followed by peatmoss: perlite mixture. Regardless of rooting medium, insignificant differences between 250 and 500 ppm NAA in root number and rooting percentage were obtained. In the quick dip method, NAA was superior to the in vitro root induction method. The highest rooting percentage (86.7%) was obtained with perlite at either 250 or 500 ppm, replacing by that the traditional in vitro rooting and obtaining plantlets that are more ready to grow under in vivo conditions.
The effects of woody plant medium (WPM) with various formulations and concentrations of Cu+2 on in vitro rooting and subsequent shoot growth of microcuttings of a Betu pubescens × papyrzfera (birch) clone were monitored for 28 days. Adventitious root initiation and elongation were reduced in magnitude and slowed in development by moderate to high Cu (as CuSO4·5H2O) concentrations, with near zero root regeneration occurring at 157 μm Cu. Shoot growth was also inhibited by 157 μM Cu as cupric sulfate. Copper-toxicity symptoms (senescent leaves, necrotic stems, and bulbous and stunted roots) were significantly increased by moderate to high levels (≥ 79 μm) of Cu as cupric sulfate. Microcuttings responded differently to Cu+2 applied as cupric chloride (CuCl2·2H2O). Root initiation, root elongation, and root branching were increased by moderate concentrations of Cu as cupric chloride. Shoot growth was slightly stimulated by cupric chloride at moderate levels. No significant increase in Cu-toxicity symptoms was observed at concentrations up to 157 μm Cu as cupric chloride. Cupric acetate [Cu(CH3 COO);H2O] and cupric carbonate [CuCO3·Cu(OH)2] produced more severe Cu-toxicity symptoms than cupric sulfate. Root regeneration and shoot growth were inhibited and increased Cu-toxicity symptoms were apparent even with low concentrations (39 μm) of Cu as cupric acetate or cupric carbonate. There was little or no effect on root regeneration when the Cu+2 in cupric sulfate was replaced by different cations, i.e., magnesium sulfate (MgSO4·7H2O), calcium sulfate (CaSO4·2H2O), and sulfuric acid (H2SO4), a result suggesting that the observed responses could be attributed to the Cu+2 concentration. Changes in media pH did not correspond to Cu-toxicity symptoms or alterations in root or shoot growth by the Cu compounds.
Differences were observed in microcutting harvests from 5 shoot tip explant sequential recultures of the hardy deciduous azalea (Rhododendron spp.) accessions 800374, 620014, and 800057. In general microcutting production increased and then declined over reculture times in a nearly bell-shaped curve for all 3 clones tested. Maximum numbers of usable microcuttings were harvested in the 3rd and 4th recultures. Productivity varied among the 3 clones, with accession 800374 the most prolific and accession 800057 the least. The microcutting height was the same for all 5 recultures of accessions 800374 and 620014, whereas, in accession 800057 the height declined from the 1st through the 5th reculture. The microcutting quality rating was similar throughout all recultures of accessions 800374 and 620014, but accession 800057 produced higher quality microcuttings in the 3rd reculture than in the 5th reculture. Rooting of microcuttings in soilless medium increased from the 1st to the 5th reculture for all 3 clones, reaching more than 97% for the last 2 harvests.
This work was carried out in the Tissue Culture Laboratory of Embrapa Temperate Climate aiming to maximize the protocol for in vitro culture of potato cv. Baronesa. The treatments consisted of multiplication of microcuttings with one, two, or three buds with/without leaves and originated from different regions of the shoot: apical, middle, or basal. Each treatment was repeated five times with each replication composed of five explants that were inoculated in 250-ml flasks with 40 ml of the medium containing MS salts and vitamins added to: sucrose (30 g·L-1), myo-inositol (100 mg·L-1), agar (6 g·L-1). The pH was adjusted to 5.6 before autoclaving. After inoculation, the flasks remained in a growth room at 25 ± 2 °C, 16-h photoperiod, and 19 μmol·m-2·s-1 light intensity provided by cool-white fluorescents lamps. Observations were done every 5 days. Final evaluation was performed after 30 days. It was observed that basal microcuttings provided longer shoots and that microcuttings with leaves bore the best ones. This kind of explant also favored a higher number of shoots, axilary buds, and better multiplication rate. The presence of leaves in the microcutting is important when basal explants are used once it can improve the number of axillary buds and the rate of multiplication. The higher the number of buds in the microcutting the lower the rate of multiplication. The in vitro multiplication of potato could be improved by using one-leaf bud basal microcutting.
Sphagnum peat (peat) media (adjusted to pH 4.0, 4.6, 5.5, 6.6, and 7.4 with ground dolomitic limestone) and unadulterated peat (pH 3.6) were tested for their effectiveness on rooting of hardy deciduous azalea (Rhododendron sp.) microcuttings in high-humidity chambers. Rooting of more than 90% occurred in media with pH 4.0, 4.6, and 5.5; however, a) shoot height and quality rating and b) root length and quality rating were superior at pH 4.0. Clonal differences in rooting percentages were found for 3 clones of azalea microcuttings rooted in 5 soilless mixtures. A mixture including equal parts (v/v) of peat and either sphagnum, vermiculite, or perlite, or a combination of 2 peat : 1 vermiculite : 1 perlite (by volume) increased rooting percentages over peat alone for all 3 azalea clones examined.
The potato cultivar Cristal recently released by the CPACT/EMBRAPA Breeding Program has high dry matter and low reduce sugars. These are desirable characteristics as industry processing is concerned. Nevertheless, this is a recalcitrant cultivar. The meristem culture is difficult to establish along with a very low multiplication rate. The aim of this work was to improve the multiplication rate for this cultivar. Two-bud microcuttings derived from apical, mid, and basal regions were inoculated in test tubes with 10 ml MS culture media and vitamins as follows; myo-inositol (100 mg·L–1); sucrose (10 g·L–1). No growth regulator was added. All treatments were placed in a growth room in a 16-hour photoperiod; 25 ± 2°C and 2000 lux. One month later, although it was observed that the final growth was more pronounced for basal microcuttings, no difference could be detected for number of shoots and multiplication rate. It was concluded that it makes no difference whatsoever kind of microcutting is used to start the micropropagation process.