Axillary shoot proliferation of blue honeysuckle

Callus cultures of Ajuga reptans flowers produced a complex mixture of cyanidin- and delphinidin-based pigments, of which more than 90% were acylated. The anthocyanin composition varied little during one growth period. During a time span of 5 years no new anthocyanin classes appeared. Quantitative differences in anthocyanin composition between the callus lines and during a 5 year time span were more pronounced. In general, the accumulation of delphinidin-based anthocyanins decreased. The percentage of acylated anthocyanins was stable in time. The accumulation of metabolically evolved anthocyanins (5′-substituted and acylated) decreased during passage from solid culture to liquid culture. The accumulation of acylated anthocyanins was influenced by the type of aeration in liquid cultures. This revised version was published online in June 2006 with corrections to the Cover Date.     

SHORT INTERNODES-like genes regulate shoot growth and xylem proliferation in Populus

? Genes controlling plant growth and form are of considerable interest, because they affect survival and productivity traits, and are largely unknown or poorly characterized. The SHORT INTERNODES(SHI) gene is one of a 10-member SHI-RELATED SEQUENCE (SRS) gene family in Arabidopsis that includes important developmental regulators. ? Using comparative sequence analysis of the SRS gene families in poplar and Arabidopsis, we identified two poplar proteins that are most similar to SHI and its closely related gene STYLISH1 (STY1). The two poplar genes are very similar in sequence and expression and are therefore probably paralogs with redundant functions. ? RNAi suppression of the two Populus genes enhanced shoot and root growth, whereas the overexpression of Arabidopsis SHI in poplar reduced internode and petiole length. The suppression of the two genes increased fiber length and the proportion of xylem tissue, mainly through increased xylem cell proliferation. The transgenic modifications were also associated with significant changes in the concentrations of gibberellins and cytokinin. ? We conclude that Populus SHI-RELATED SEQUENCE (SRS) genes play an important role in the regulation of vegetative growth, including wood formation, and thus could be useful tools for the modification of biomass productivity, wood quality or plant form.     

The Initiation and Development of Secondary Xylem in Axillary Branches of Populus deltoides

The initiation of secondary xylem in elongating axillary branchesof Populus deltoides Bartr. ex Marsh. is independent of thatin the main stem. Although secondary xylem differentiates acropetallyin the main stem, it does not differentiate from the stem intothe axillary branch. Secondary xylem is usually initiated ininternode 4 (occasionally 3) of the axillary branch, and fromthis site it develops both acropetally in the elongating branchand basipetally toward the main stem. Secondary vessel differentiationalways precedes fibre differentiation. Although secondary xylemdifferentiates in internodes that have ceased elongation, itdifferentiates first in traces of the vascular cylinder servingrapidly expanding and maturing foliage leaves. As younger leaveson the branch expand and mature, secondary xylem differentiatesin their traces eventually producing a complete secondary vascularcylinder. Scale leaves do not initiate secondary xylem independentlyin their traces; they are activated by adjacent traces in thevascular cylinder serving foliage leaves. Once established,the primary-secondary vascular transition zone advances acropetallyin a branch just as it does in the main stem. Populus deltoides Bartr. ex Marsh., cottonwood, axillary branches, secondary xylem, plastochron index, post-dormancy development, xylem.     

In vitro shoot regeneration of Populus deltoides: effect of cytokinin and genotype

Treatment differences were observed in the in vitro adventitious shoot regeneration response from internodal explants of three genotypes of Populus deltoides cultured on media supplemented with five concentrations each of the cytokinins 6-benzyladenine, 2-isopentyladenine, and zeatin. For each of the three genotypes, the greatest number of shoots were consistently regenerated on media containing the cytokinin zeatin. Tissue necrosis resulted when explants from any of the three genotypes were cultured on media supplemented with 6-benzyladenine. A zeatin concentration by genotype interaction was also observed. Genotypic differences in shoot regeneration were observed for 16 genotypes of Populus deltoides when cultured on medium supplemented with 0.5 mgL^–1 zeatin. Six genotypes were highly recalcitrant and failed to regenerate shoots. The percent of explants regenerating was greater than 50% for four genotypes.Abbreviations WNA modified Woody Plant Media - BA N⁶-benzyladenine - 2-iP 2-isopentenyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IBA indole-3-butyric acid - MS Murashige Skoog (1962) medium - NAA 1-naphthaleneacetic acid - PAR photosynthetically active radiation Journal Series No. 8938, Agricultural Research Division, University of Nebraska     

The influence of ethylene on proliferation and growth of rose shoot cultures

Ethylene accumulation in four different rose in vitro culture containers was evaluated. Multiplication rate was the highest, and axes most elongated, in the two containers where ethylene accumulation was limited. Pulse treatments of ethylene at various concentrations enhanced proliferation depending on concentration (5 ppm generally was the most favourable) and time of application, while reducing elongation of the shoots. An ethylene trap in the flask atmospheres of the cultures reduced rose shoot proliferation rate but increased elongation of the axes. Inhibitors of ethylene biosynthesis, aminoethoxyvinylglycine (AVG) and cobalt chloride (CoCl₂), increased multiplication rate by providing a higher number of axes of a suitable size for subculture. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) had a beneficial effect on multiplication rate, although reducing longitudinal growth of the axes.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - BA benzyladenine - GA₃ gibberellic acid - IBA indolyl-3-butyric acid     

Phloroglucinol enhances growth and rate of axillary shoot proliferation in potato shoot tip cultures in vitro

Efficacy of phloroglucinol in promoting growth and development of in vitro-derived shoot tips was studied in six potato (Solanum tuberosum L.) genotypes. Different concentrations of phloroglucinol (0, 0.08, 0.4, 0.8, 1.2 and 1.6 mM) were tested in combination with either 0.1 or 0.2 M sucrose in shoot tip proliferation medium based on MS (Murashige and Skoog, 1962) medium supplemented with 5.8 μM GA₃ (gibberellic acid), 1.1 μM BA (N⁶-benzyladenine) and 8.39 μM D-calcium pantothenate. Phloroglucinol fostered multiple shoot formation, promoted axillary shoot proliferation in terms of shoot tip fresh weight and shoot length, and stimulated root formation on the shoot tips. There was significant phloroglucinol × sucrose interaction for number of shoots developed per shoot tip, shoot tip fresh weight and number of roots induced per shoot tip. The beneficial effect of phloroglucinol on shoot tip survival was conspicuous only in genotypes that showed poor survival in the control proliferation medium. There were significant differences in response between the two sucrose levels with regard to shoot tip fresh weight and number of roots per shoot tip. Phloroglucinol in combination with 0.2 M sucrose induced maximum number of roots per shoot tip. Optimum shoot tip growth was fostered in medium containing 0.8 mM phloroglucinol and 0.2 M sucrose. High frequency multiple shoot formation in this medium ensures a faster rate of potato shoot tip multiplication within a limited time and space. This revised version was published online in June 2006 with corrections to the Cover Date.     

Anthocyanin, bisabolol and phenylammonialyase activity in cell cultures of Populus deltoides

Phenolics, anthocyanin and alpha-bisabolol production from poplar (Populus delotides) in tissue culture was determined. A number of phenolic acids were identified by HPLC. PAL activity in response to phytohormones, cells growth and anthocyanin production showed a positive correlation. A component, alpha-bisabolol, was identified using gas chromatography and UV spectroscopy. In vitro production of said metabolites was influenced by phytohormones.     

Direct shoot organogenesis from leaf explants of Populus deltoides and changes in selected enzymatic activities

The direct shoot organogenesis was achieved from leaf explant of two commercially important clones of Populus deltoides on MS medium enriched with 15 mg/l adenine sulphate, 5 mg/l Ascorbic acid, 250 mg/l (NH4)2SO4 (referred to as PD1 medium) supplemented with 2.5 µM each of 6-benzylaminopurine and indole-3-acetic acid. Higher shoot organogenic potential was recorded from the explants of clone ‘G48’ as compared to clone ‘L34’. The age of leaf explant also affected the shoot organogenic potential, and maximum shoot organogenesis was recorded in case of 5th leaf from the top of microshoot. Histological studies revealed altered cell division resulting in the formation of meristematic pockets after 5 days of culture, these meristematic pockets grew into dome protuberances by 10th day. Organized shoots were visible after 15 days of culture. A clear three phases of shoot organogenesis viz induction (0–4 days), initiation and organization (4–10 days) and growth (11–16 days onwards) were observed. Marked variation in the activity of enzymes such as catalase, peroxidase, polyphenol oxidase and acid phosphatase was observed during these phases. The activity of these enzymes was found to increase in cultures grown on the medium resulting in shoot organogenesis during shoot development (after 7 days of culture).     

Factors affecting shoot proliferation and vitrification inDigitalis obscura cultures

Summary Variations of composition and consistency of the culture medium and time of exposure to growth regulators were assayed to optimize normal caulogenic response ofDigitalis obscura hypocotyls cultured in vitro. The effects of the culture conditions on physiologic changes related to vitrification of the regenerated plants were also investigated. Liquid medium increased the bud-forming capacity of the explants but induced buds failed to develop into shoots and showed symptoms of vitrification. On agar-solidified media, maximum multiplication rates were achieved with 0.7% agar. Increasing agar concentration reduced vitrification but lowered the propagation rate. Changes in the strength of the macronutrients of Murashige and Skoog did not significantly affect the bud-forming capacity of the explants. In contrast, a drastic inhibitory effect on both bud formation and shoot elongation was produced when NH₄NO₃ was omitted. Reduction of NH₄NO₃ to one-half or one-fourth of the level of the original formulation not only increased the bud-forming capacity ofD. obscura hypocotyls but also resulted in less vitrification. Modifications of time and method of exposure to growth regulators neither improved the multiplication rates nor overcame vitrification. Cardenolide content was lower in vitrified than in normal cultures and coincided with an overall reduction of photosynthetic pigments, lignin, and dry matter.     

Genome Fingerprinting Analysis in Populus deltoides

The appraisal of cultivar authenticity is a problem that needs to be settled in agricultural and forestry activities. AFLP is a novel, reliable and effective technique in DNA fingerprint. 42 clones of Populus deltoides Mash. were fingerprinted with the technique. AFLP technique can be widely used in the practical cultivar identification.     

Empirical Models for Xylogenesis in Populus deltoides

Empirical quantitative models were constructed for Populus deltoidesdescribing temporal and spatial changes in vessel characteristicsof metaxylem, both within individual central leaf traces andwithin all central leaf traces considered as a morphologicalunit at a given transverse level in the stem (the central tracesympodia). Similar models were constructed for secondary vesselcharacteristics. The growth processes of the stem segment throughwhich the vasculature extended were incorporated in these modelsto illustrate how a functional vascular system is maintainedin the stem as a whole. The central trace sympodia representedthe integrals of the temporal and spatial functions for individualcentral leaf traces. Metaxylem vessel production ceased in individualleaf traces two plastochrons before the cessation was reflectedin the central trace sympodia because of the integrative natureof the sympodial complex. A functional continuum of developmentwas apparent between metaxylem vessels of the central tracesympodia and secondary vessels of the stem. The transition betweenmetaxylem and secondary xylem production in the central tracesympodia corresponded with cessation of leaf and internode elongation. Populus deltoides Bartr. ex Marsh., cottonwood, primary xylem, secondary xylem, primary-secondary vascular transition, leaf growth, xylogenesis     

Multiple shoot regeneration from root organ cultures of Populus alba x P. grandidentata

Excised roots of various ages from Crandon and Hansen clones of Populus alba x P. grandidentata were tested for their regeneration capacity. Sixty-day-old excised roots that contained root tips were found to be most suitable. The highest number of shoots (an average of 111 shoots/root segment with Crandon and 98 with Hansen) was obtained by adding 22M and 14M zeatin to the medium, respectively. The two clones of hybrid poplar responded similarly to growth regulator treatments; however, the number of shoots produced was greater from the root organs derived from Crandon clones. Regenerated shoots were rooted in basal Woody Plant Medium without any growth regulators. Successful transplantation into soil and growth was achieved with all plants.     

美洲黑杨不同无性系对分月扇舟蛾幼虫生长和食物利用的影响

本文研究了不同的美洲黑杨无性系对分月扇舟蛾Clostera anastomosis L.幼虫生长的影响。结果表明,抗性水平不同的无性系影响分月扇舟蛾幼虫体重、相对生长率、食物利用率和转化率。抗性较强的89-3号无性系对幼虫的生长有抑制作用,幼虫取食后,其食物利用率和转化率在第2天有显著下降,但随后表现不明显;而感性较强的74-4号无性系有一定的促进作用,幼虫取食后,其食物利用率和转化率都显著提高。     

Defoliation effects on isoprene emission from Populus deltoides

Isoprene emission from plants is one of the principal ways in which plant processes alter atmospheric chemistry. Despite the importance of this process, few long-term controls over basal emission rates have been identified. Stress-induced changes in carbon allocation within the entire plant, such as those produced by defoliation, have not been examined as potential mechanisms that may control isoprene production and emission. Eastern cottonwood (Populus deltoides) saplings were partially defoliated and physiological and growth responses were measured from undamaged and damaged leaves 7 days following damage. Defoliation reduced isoprene emission from undamaged and damaged leaves on partially defoliated plants. Photosynthetic rates and leaf carbon and nitrogen pools were unaffected by damage. Photosynthetic rate and isoprene emission were highly correlated in undamaged leaves on undamaged plants and damaged leaves on partially defoliated plants. There was no correlation between photosynthetic rate and isoprene emission in undamaged leaves on partially defoliated plants. Isoprene emission was also highly correlated with the number of source leaves on the apical shoot in damage treatments. Increased carbon export from source leaves in response to defoliation may have depleted the amount of carbon available for isoprene synthesis, decreasing isoprene emission. These results suggest that while isoprene emission is controlled at the leaf level in undamaged plants, emission from leaves on damaged plants is controlled by whole-branch allocation patterns. Received: 12 May 1998 / Accepted: 9 November 1998     

Response to increasing rates of boron and NaCl on shoot proliferation and chemical composition of in vitro kiwifruit shoot cultures

The in vitro response of kiwifruit (Actinidia deliciosa) to increasing concentrations of boron (B) and NaCl in the culture medium was studied. Kiwifruit shoot cultures were grown in vitro for 12 weeks on an MS medium containing two B concentrations (0.1 and 2 mM) combined with five NaCl concentrations (0, 10, 20, 40 and 80 mM). Kiwifruit produced the longest shoots with 2 mM B when NaCl concentration was 0--20 mM. More shoots were produced with 2 mM B for all NaCl treatments. More shoots were produced with 2 mM B and 10 and 20 mM NaCl. High B concentrations in the culture medium significantly increased shoot proliferation. Explants exhibited a moderate chlorotic appearance with 40 mM NaCl and shoots died with 80 mM NaCl. With 2 mM B, the B concentration of explants was 5--9X greater for the various NaCl treatments compared to the control. Increasing the NaCl concentration from 10 to 80 mM, resulted in higher Na and Cl concentrations in explants for all B treatments, while K and Ca concentrations decreased. Phosphorus concentration in the explants was significantly increased by increasing the NaCl concentration reaching a maximum value at 80 mM NaCl for the two B concentrations.     

Morphactin-kinetin interaction on growth and shoot formation in tobacco callus cultures

Pith-derived calluses of Nicotiana tabacum L. cv. Wisconsinno. 38 were inoculated on an RM-1964 medium containing variousconcentrations of a morphactin, chlorflurenol (CFl) and kinetin(KIN). An addition of KIN (0.1–2 mg/liter) alone was effectivefor shoot formation from the calluses, but a high dose (10 mg/liter)resulted in the inhibition of growth and in no differentiation.The inhibitory effect of a high dose of KIN was counteractedwith CFl. Three combinations of KIN and CFl; CFl (0.1 mg/liter)$KIN(2.0 mg/liter); CFl (0.1 mg/liter)$KIN (10.0 mg/liter) and CFl(1.0 mg/liter) $KIN (2.0 mg/liter), were successful for 100%shoot redifferentiation in inoculated calluses. An appropriatebalance between CFl and KIN seems to be involved in shoot formation.The present results can best be interpreted by assuming thatCFl acts as an auxin in cultured tissues. (Received January 16, 1975; )     

Population genomics of the eastern cottonwood (Populus deltoides)

Despite its economic importance as a bioenergy crop and key role in riparian ecosystems, little is known about genetic diversity and adaptation of the eastern cottonwood (Populus deltoides). Here, we report the first population genomics study for this species, conducted on a sample of 425 unrelated individuals collected in 13 states of the southeastern United States. The trees were genotyped by targeted resequencing of 18,153 genes and 23,835 intergenic regions, followed by the identification of single nucleotide polymorphisms (SNPs). This natural P. deltoides population showed low levels of subpopulation differentiation (F_ST = 0.022–0.106), high genetic diversity (θ_W = 0.00100, π = 0.00170), a large effective population size (N_e ≈ 32,900), and low to moderate levels of linkage disequilibrium. Additionally, genomewide scans for selection (Tajima's D), subpopulation differentiation (X^TX), and environmental association analyses with eleven climate variables carried out with two different methods (LFMM and BAYENV2) identified genes putatively involved in local adaptation. Interestingly, many of these genes were also identified as adaptation candidates in another poplar species, Populus trichocarpa, indicating possible convergent evolution. This study constitutes the first assessment of genetic diversity and local adaptation in P. deltoides throughout the southern part of its range, information we expect to be of use to guide management and breeding strategies for this species in future, especially in the face of climate change.     

Influence of benzimidazole on callus growth and shoot formation on callus cultures

The influence of benzimidazole on callus growth and shoot formationin vitro was examined. At concentrations of 8.5 x 10^–4mMto 8.5 x 10^–1mM benzimidazole failed to stimulate callusgrowth or shoot formation. Concentrations of 0.85 mM and 1.7mM inhibited kinetin-dependent callus growth while lower concentrationswere without effect. It may be inferred that benzimidazole hasno cell division properties such as is associated with the cytokinins,though it mimics, in appearance, cytokinins actions in severalphysiological processes. (Received August 12, 1975; )