Shoot tips and stem nodes of Asclepias erosa Torr., cultured on a modified (0.5 × major salts) Murashige and Skoog (MS) medium containing 0.54 µm (0.1 mg/liter) NAA and 44.4 µm (10 mg/liter) BA, produced multiple shoots in 5 weeks. Subcultures of the individual shoots on the same medium produced 5-12 new shoots 4 weeks later. Rooting of the resultant shoots was best accomplished by preculturing them for 48 hr on MS medium containing 246 or 492 µm (50 or 100 mg/liter) IB A prior to subculturing for 4 weeks on MS medium devoid of growth regulators. The rooted cultures were established successfully in soil. Chemical names used. NAA: 1-naphthaleneacetic acid. BA:N-(phenylmethyl)-lH-purin-6-amine. IBA: lH-indole-3-butanoic acid.
Inflorescence explants of Liriope muscari Bailey ‘ Variegata’ and Ophiopogon jaburan Lodd. ‘Variegatus’ produced multiple shoots in vitro on a modified Murashige and Skoog medium via callus. In subsequent studies with L. muscari‘ Variegata’, there was no difference in floret and scape explant growth, while rhizome and modified root explants were either contaminated or failed to grow. Distal floret explants produced more shoots than proximal explants but there were no significant positional differences in scape explants. In liquid culture 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.5 mg/liter promoted the greatest fresh weight and shoot and root length. Benzylamino purine (BA) at 0.1 mg/liter increased the number of shoots while decreasing the number of roots. Agitation of liquid cultures increased callus fresh weight.
Many wetland plant species used for aquascaping and wetland revegetation projects are collected from donor wetland sites for planting elsewhere. Increased demand for wetland plants has lead to over-collection and subsequent environmental damage to these donor sites. Micropropagation provides an ecologically sound alternative to field collection and allows for production of under utilized wetland species and genotypes that are either slow-growing or difficult to propagate using conventional methods. Sagittaria latifolia Willd. (Duck-potato), a rhizomatous herbaceous wetland species, was established in vitro from surface-sterilized lateral and terminal rhizome shoot-tips cultured in liquid basal medium consisting of half-strength Murashige and Skoog mineral salts, 0.56 mM myo-inositol and 1.2 μM thiamine supplemented with 87.6 mM sucrose. Prior to multiplication, responsive Stage I cultures were indexed for cultivable bacteria and fungi. Shoot multiplication occurred in vitro through formation of multiple node rhizomes bearing terminal shoots. Duck-potato exhibited a high sensitivity to relatively low benzyladenine (BA) levels. Maximum rhizome and shoot production occurred from single shoot explants initially cultured on agar-solidified BM supplemented with 4.0 μM BA for 28 days. However, repeated subculture on BM supplemented with greater than 2.5 μM BA resulted in increased mortality, reduction in multiplication rate, or production of dormant corms. Consistent shoot multiplication (four to five shoots/explant) was possible in the presence of 1.5 μM BA. Maximum (100%) acclimatization and rooting was attained by direct sticking of Stage II microcuttings in soilless growing medium contained in 38 cell plugs. Production of salable plants bearing multiple rhizomes was possible within 6 weeks post-transplant. Preliminary observations indicate that corm formation in Sagittaria latifolia may be mediated by photoperiod.
A study was conducted with Prunus × incamp `Okame' to evaluate the effects of a pot-in-pot production system compared to a conventional above-ground system and cyclic irrigation on plant growth and water loss. Plants were grown in #7 (26-L) containers with a 8:1 pinebark:sand (v/v) substrate. Cyclic irrigation provided the same total volume of water, but was applied one, three, or four times per day. Final plant height and stem diameter, shoot and root dry weight, total biomass, and root:shoot ratio were all increased for plants grown pot-in-pot compared to above-ground. Multiple irrigation cycles increased stem diameter, shoot dry weight, and total biomass, compared to a single irrigation application. Multiple irrigation cycles decreased the root:shoot ratio. Evapotranspiration was influenced by production system, irrigation, and date. Amount of water lost as leachate was influenced by irrigation and date. Cyclic irrigation resulted in a two-fold decrease in leachate volume. Soluble salts and nitrate-nitrogen in the leachate were influenced by an interaction between production system, irrigation, and date.
It has been previously demonstrated that thidiazuron (TDZ) enhanced the regeneration and multiple shoot proliferation of vinifera grape cultivars. To determine the effect of TDZ on the multiplication of hybrid grapes, in vitro nodal segments from cultivars Chancellor, Leon Millot, and Valiant were cultured on MS medium supplemented with 0, 0.01, 0.05, 0.1, 0.5, and 1.0 mg TDZ/liter. After 1 month, the higher percentage of rooted shoots was obtained from the explants cultured in medium containing the lowest concentration of TDZ (0.01 mg–liter–1) independent of the genotype. Multiple shoot proliferation was favored by high concentrations of TDZ (0.5 and 1.0 mg–liter–1). An average of 0.39 and 0.39 shoots, respectively, was obtained from `Chancellor' cultures, 0.56 and 0.59 from `Leon Millot', and 1.93 and 2.38 from `Valiant'. Vitrification and teratological structures were observed in all the cultures of the three genotypes, but less vitrification occurred in `Valiant' plantlets.
In vitro cultures were used to study the development of axillary bud and stolon tip explants of cultivated strawberry (Fragaria × ananassa Duch.). Explants cultured on Murashige-Skoog basal media containing kinetin at 1, 5, or 10 mg/liter developed into leafy shoots. Low concentration of kinetin (1 mg/liter) promoted the development of both types of explants into single shoots while higher concentration (10 mg/liter) promoted production of multiple leafy shoots developing from axillary buds of the earlier formed leafy shoots. NAA at 1 mg/liter promoted callus growth from both types of explants. Axillary bud explants developed into stolons when cultured on media containing gibberellic acid (GA3) at 5, 10 or 20 mg/liter. Stolon apices developed into leafy shoots while the second axillary stolon buds of the tips were inhibited when the explants were cultured on GA3-containing media. Combinations of GA3 and kinetin induced the development of axillary bud explants into structures intermediate in form between those of stolons and leafy shoots. Stolon apices and stolon axillary buds at the stolon tips developed into leafy shoots and continuing stolons, respectively, when the explants were cultured on a kinetin-containing medium for one week, and then transferred onto a GA3-containing medium. Thus, the developmental pathway of axillary strawberry buds was shown to be responsive to a balance between GA and cytokinins following removal from apical dominance.
Under typical South African growing conditions, `Fuji' apple (Malus domestica Borkh.) trees are characterized by strong apical dominance during the first few years after planting. This, together with the current lack of suitable precocious rootstocks and the tip-bearing habit, causes willowy “blind wood” growth with few flowering positions, and delays bearing until the third leaf when a crop of less than 10 tons/hectare can be realized. Promalin (GA4+7 and benzyladenine, Abbott Laboratories) was used in combination with apical meristem defoliation and Agral or Armoblen as surfactant/penetrant to induce sylleptic shoot growth in an effort to increase tree complexity (i.e., branching) without having to resort to pruning, which is dwarfing and delays bearing. The treatments were tested on `Fuji' grafts, 1-year old trees and 2-year old trees in the 1993–1994, 1994–1995, and 1995–1996 seasons, respectively. Concentrations tested were 0, 500, 750, or 1000 ppm, as single or multiple applications in spring. In all trials, randomized, complete block designs were used. Control trees had few, if any, sylleptic shoots or spurs, whereas Promalin in combination with leaf removal or in combination with Armoblen caused significant sylleptic growth to occur. Generally, multiple applications spaced fortnightly, gave best results. Sylleptic shoots were ≈15 cm long, terminated in a reproductive bud, and did not influence the length of the “mother” shoot or the trunk circumference. Based on these results, a combination of multiple applications of 500 ppm Promalin with Armoblen as penetrant, and no leaf removal, is being tested semi-commercially this season.
Hypericum perforatum L. (St. John's Wort) has an extensive history as an important medicinal herb used for the treatment of neurological and depressive disorders (Linde et al., 1996). The objective of this study was to establish an in vitro tissue culture protocol for St. John's Wort. Nodal segments, axillary buds, and leaf disc explants produced multiple shoots and callus on Murashige and Skoog minimal organics medium supplemented with combinations of indoleacetic acid (IAA; 0.57, 2.85, 5.71 μm) and benzylaminopurine (BA; 2.22, 4.44, 8.88 μm). Shoot production occurred on all combinations of IAA/BA tested and was significantly less in treatments without hormones. Callus production was higher on treatments containing 2.85 μm IAA + 4.44 μm BA, or 5.71 μm IAA + 8.88 μm BA. Shoots transferred to hormone-free medium at 8 weeks formed roots by 12 weeks. A micropropagation protocol was established for St. John's Wort using mature plants as the explant source.
Prohexadione-Ca (BAS 12511W or Apogee™ Plant Growth Regulator) acts within a plant by blocking the biosynthesis of growth-active gibberellin. The result is decreased cell and shoot elongation; thus, vegetative growth in apple trees can be reduced. Air blast applications of prohexadione calcium were made in the Spring 1998 in commercial orchards. Application rate was 125 ppm a.i. applied twice beginning at 5 to 12 cm of new shoot growth. Reduction of shoot growth averaged 45% across locations. As a result of reduced vegetative growth, dormant pruning was reduced. In total, significant benefits to the grower included reduced pruning costs in addition to other positive effects such as improved light penetration and enhanced resistance to some pathogens. Research will continue with the effect of prohexadione-Ca on pruning in multiple year studies.
Grand crinum Lily is an ornamental plant which is considered to be one of the architect's favorite accent. plants and one that bloom most of the year. A protocol for plant propagation from inflorescence is described. Explants were excised from inflorescence at the primordial stage. and cultured on Murashige and Skoog medium (MS: alone or supplemented with benzyladenine 4.4 or 13.3 uM benzyladenine (BA) and 0.5 uM naphthaleneacetic acid (NAA) and incubated for four weeks. Explants cultured on BA-containing media produced white flower-like structures on the receptacle which produced multiple shoots after additional four weeks on a fresh medium containing 4.4 uM BA and 0.05 uM NAA. Shoots were transferred to a fresh medium for further growth during which the basal stem reached 3 to 5 mm diameter. At this stage shoots, with or without roots, were transferred to soil, without acclimatization, and normal plants were established in soil.