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Karim H. Al-Juboory and David J. Williams

Shoot tip explants of Algerian Ivy Heder a canariensis were cultured on MS basal medium supplemented with a combination of salt strength and NAA and IBA. More roots per explant developed on full salt strength medium combined with NAA. The most roots per explant were obtained with a combination of IBA and 1/4 MS salt. There was an inverse relationship between an increase in IBA or NAA concentration and root length and number. Shoots proliferated better on full MS salt combined with NAA and IBA. The highest level of NAA (40 uM) and 0.1 uM TDZ produced the most shoots and roots, the longest roots, the highest rooting percentage, the largest plants with the most leaves and the best callus quality per explant. The leaves from in vitro were cultured on MS medium with varying levels of Thidiazuron (TDZ) and NAA in the presence of light produced the highest number of roots.

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Enaksha R. Wickremesinhe and Richard N. Arteca

Fast growing callus was derived from Cephalotaxus harringtonia stem explants placed on MS basal salt medium with B-5 vitamins, 3% sucrose, 1 μM kinetin and 4.5 μM 2,4-D. Callus placed on basal medium with 10 μM kinetin and 0.45 μM 2,4-D turned green and organogenesis was observed upon subculture onto basal medium without hormones. Shoots were excised and placed on 1/2 strength MS salts and 10% sucrose for further shoot development. During the process of organogenesis, we also observed the differentiation of roots. Rapidly growing root cultures were established by culturing them under a 24 hour light regime of 35 μM/m2/s. Two grams of root tip explants cultured on B-5 medium with 2% sucrose were capable of producing an average of 24 grams of roots within 11 days. A 20-fold increase in fresh weight was achieved within 3 weeks when 15 grams of these roots were cultured in a 3 liter air-sparged bioreactor. C. harringtonia contains a number of alkaloids that exhibit cytotoxicity and are being evaluated as chemotherapeutic agents. We are currently in the process of establishing growth characteristics for these roots and assaying roots for the presence of these alkaloids. All cultures were grown under a 12 hour light regime unless otherwise stated.

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Sven E. Svenson

Rooting and growth of Verbena cuttings (Verbena × hybrids Voss) were measured to determine response to foliar-applied benzylaminopurine (BA). There was no rooting response to BA application when visible nodal roots were present at the base of the cutting. There was no response to 30, 100, or 300 mg BA/liter applied to the foliage 48 or 96 hours after excision from the stock plant. Rooting-zone dry mass, total cutting dry mass, and number of roots were increased by 30 mg BA/liter applied immediately after excision when there were no visible nodal roots at the base of the cuttings. Foliar application of BA at 10 or 30 mg·liter-1 increased lateral bud elongation of subsequently rooted shoots by 20% and 49%, respectively. Application of BA during cutting propagation to enhance subsequent lateral bud elongation does not appear to inhibit rooting in Verbena stem cuttings. Chemical name used: 6-benzylaminopurine (BA).

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A. A. De Hertogh and M. Tilley

Almost all Amaryllis (Hippeastrum) forced in the U.S. and Canada by either homeowners or commercial forcers are grown overseas. In order to comply with USDA/APHIS plant quarantine regulations, all bulbs must be free of soil. Thus, they are washed once or twice prior to packing and shipping. As a result of this treatment, the bulbs arrive with only basal roots and no secondary roots. Therefore, over the past year, 2 hand made mixes and 7 commercially prepared mixes were evaluated using 2 cultivars each of Swaziland- and Dutch-grown bulbs. The effects of these media on forcing characteristics, e.g. total plant height, leaf length, flower number, etc. were examined. Also, the influence of the various media on basal root growth and formation of new secondary roots was measured. The results of these 2 studies will be presented.

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Paul G. Thompson, J. C. Schneider, Boyett Graves, and B. K. Kim

Twenty-four half-sib sweetpotato families were field tested for freedom from injury by sweetpotato weevil and other soil inhabiting, injurious insects (WDS). Three pairs of adult male and female weevils were applied to the crown of each plant at the beginning of storage root enlargement. Naturally occurring numbers of WDS were high enough for considerable injury from those insects. WDS injury free roots ranged from 19% in Centennial, the suceptible control, to 57% in Regal, the resistant control. The highest family mean for percent non-injured by WDS was 55%. Weevil injury free roots ranged from 67% in Centennial to 90% in Regal with 3 families producing mean weevil non-injured roots of 89%. The genetic correlation between weevil injury free and WDS injury free roots was 0.69 ± 0.28. That estimate is preliminary and based on data from one environment. Evaluations will be repeated in 1994 for estimates of GXE to derive genetic correlation estimates with less environmental interactions.

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C.C. Pasian, F. Varela Ramirez, and S. Nameth

Evaluation of disease severity in root systems is usually subjective, based on observation and categorization into an arbitrary scale of several categories. Results obtained using this approach can vary according to the observer's experience. A new, simple method for evaluating and quantifying the root severity index (RSI) was developed. This method consists of surrounding the root pan with a transparent film and tracing all roots with a marker. On a second transparency, only healthy roots are traced. Lengths of both healthy and diseased roots are measured with a root length/area meter (Dias II). The method of peripheral root-ball root tracings was evaluated with poinsettias infected with Pythium ultimum (Trow.). Results indicated that it was as effective as the traditional method of determining RSI for total and peripheral roots.

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Jean-Pierre Prive and M.I.N. Zhang

2,3,5-triphenyltetrazolium chloride (TTC) staining and electrical impedance (?) analyses of apple roots (Malus domestica Borkh. `Beautiful Arcade') taken in late March from either the field or from 3C refrigerated storage (cold-stored). LT50 levels using TTC were much lower than those found using electrical impedance. No loss of viability in the roots was detectable using TTC staining until a freeze–thaw stress of –9C whereas? analysis detected changes in cell viability after a freeze–thaw stress of only –3C. With increasing cold stress, two parameters: extracellular electrical resistance (Ro) and time constant?, decreased linearly for cold-stored roots and exponentially for field roots. Impedance analysis also revealed that the values for both extracellular Ro and total tissue electrical resistance (R?) for the field roots were approximately 5 and 8 times lower, respectively, than in the cold-stored roots. It is believed that the smaller Ro and R? values obtained from the field roots were due to natural in-field freeze–thaw cycling prior to the controlled stress tests in the laboratory. Based on the analyses of winter hardiness using the two methods, the impedance technique? provided the physiological information not only about the hardiness level, but also about freeze–thaw history prior to the hardiness assessment.

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David Graper and Will Healy

Non flowering Alstroemeria `Regina' plants were divided into aerial components: stems and apical and basal leaves or underground components: rhizome, storage roots, stele and fibrous roots. Samples were collected from distal and proximal ends of the rhizome to allow comparisons between structures of different ages. Ethanol soluble sugars were extracted and measured using HPLC. Starch was degraded to glucose using amyloglucosidase and measured.

There were no age differences in the starch, total soluble sugar (TSUGAR) or total soluble carbohydrates (TCHO) in the rhizome or aerial portions of the plant. There was a preferential partitioning of starch, sucrose, TSUGAR and TCHO to underground plant parts. The storage roots were the primary sink for the stored carbohydrates. Stems contained large concentration of glucose while fructose was found in storage roots and old stems. Sucrose was found primarily in old steles and storage roots. Starch was partitioned almost exclusively into the storage roots with no difference due to age of the storage root. Up to 42% of the TCHO in the old storage roots was composed of a carbohydrate which co-chromatogramed with melezitose using HPLC.

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D.D. Douds Jr., G. Bécard, P.E. Pfeffer, L.W. Doner, T.J. Dymant, and W.M. Kayser

A vesicular–arbuscular mycorrhizal fungus in a peat-based medium significantly increased survival, callus development, and rooting percentage of Sciadopitys verticillata cuttings over noninoculated cuttings. The presence of a nurse host plant for the mycorrhizal fungi to colonize in the absence of S. verticillata roots decreased survival and rooting percentage, but not callus development, relative to the fungus without the nurse host. Among plants that did produce roots, however, there were no significant differences among treatments for root number, weight, or length per cutting.

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A.R. Talaie and M. Ramazani Malakroodi

Propagation testing of semi-hardwood olive cuttings was conducted to ensure adequate production to meet Iranian needs. `Clonavis', `Sevillana', and `Manzanilla' were selected to investigate their rooting situations. Three variables (cultivar, differential concentrations of IBA, and vertical cut in the basal end of the cuttings) were considered in a randomized complete-block factorial design test with four replications with 10 cuttings in each treatment. Cuttings 10 to 15 cm long and 0.5 to 1.5 cm in diameter were taken from each cultivar. IBA (0, 2000, 3000, and 4000 ppm) was used in two vertical cuts in basal end of half of the cuttings. Statistical analysis of the rooting capability differed for the three cultivars. `Sevillana' and `Clovanis' rooted better than `Manzanilla'. IBA at 3000 ppm resulted in the highest rooting percentage in all cultivars. The maximum number of roots was obtained with IBA at 4000 ppm in roots that had the basal cuts. Basal end cuts affected considerably the rooting percentage and number of roots, but had no effect on increased root length.