Factors influencing direct shoot regeneration from leaves,petioles,and plantlet roots of triploid hybrid Populus sect.Tacamahaca

Since the generation of full-sib artificial triploid families, rapid clone establishment and genetic improvements have been needed. Here, we report an in vitro method of direct shoot regeneration of a triploid hybrid poplar[(Populus simonii × P. nigra 'Italica')×(P. × 'popularis')]. Using different randomized block designs, we selected one triploid to evaluate the explant type, optimal concentrations of plant growth regulators and agar, and culture time under light or dark conditions over 60 days. The highest rate of shoot induction, 80.0%, was obtained using Murashige and Skoog(MS) medium supplemented with 0.2 mg/L benzyladenine, 0.04 mg/L naphthaleneacetic acid(NAA), and 5.5 g/L agar for the first 30 days in the dark,then 3 g/L agar for the next 30 days in light. This last medium yielded the best rate of shoot induction(6.32 shoots/explant). These three media were also used to evaluate the influence of the genotypes of the parents and hybrid triploids on regeneration. Two parents and three of the four full-sib triploids were regenerated successfully;different genotypes and explant types significantly affected the rate of shoot induction and average number of shoots.Leaves but not petioles were a suitable explant. One genotype produced the highest rate of shoot induction of 96.67%.Half-strength MS medium supplemented with 0.2 mg/L indole butyric acid and 0.04 mg/L NAA was the most effective for rooting; rooting rate was 96.67%, survival rate of transplants was 73.33%, and rooting frequency surpassed 85% for each genotype. Overall, this in vitro regeneration system will be useful for the propagation and genetic modification of triploid poplars.     

Effects of Thidiazuron, basal medium and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis

The effect of Thidiazuron (TDZ), basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus alba×P. berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba×P. berolinensis. Stems of Populus alba×P. berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L-1 NAA (naphthaleneacetic acid), and 0.1, 0.3, 0.5 and 1.0 mg·L-1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium (WPM) and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that different concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ (0.1 mg·L-1) resulted in more adventitious shoot regeneration and higher concentration of TDZ (>0.1 mg·L-1) inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.     

Adventitious shoot regeneration of Platanus acerifolia Willd. facilitated by Timentin, an antibiotic for suppression of Agrobacterium tumefaciens in genetic transformation

The effects of Timentin and cefotaxime (Cef) on shoot regeneration of the London plane tree (Platanus acerifolia Willd.) and their use for the suppression of Agrobacterium tumefaciens in Agrobacterium-mediated genetic transformation were compared. Shoot regeneration was significantly reduced on the media with Cef at concentrations from 100 to 500 mg·L–1. Timentin showed negative effect on plant regeneration at concentrations of 100 and 500 mg·L–1; however, 300 mg·L–1 Timentin was shown to facilitate shoot r...     

Direct shoot organogenesis from leaf explants of Embelia ribes Burm. f.: a vulnerable medicinal plant

An efficient system was developed for direct plant regeneration from in vitro-derived leaf explants of Embelia ribes Burm. f., a vulnerable medicinal woody climber of the Western Ghats of India. The in vitro procedure involved three steps that included induction of shoot initials from leaf tissue, regeneration and elongation of shoots from the shoot initials, and rooting of shoots. The induction of shoot initials was achieved on Murashige and Skoog (MS) solid medium supplemented with different concentrations of thidiazuron (TDZ). The best medium for shoot induction was MS with 0.272 μM TDZ. Numerous shoot primordia developed within 2–3 weeks on the leaf margin as well as on the midrib region, without any callus phase. In the second step, the shoot clumps separated from the leaf explant on transfer to MS basal medium, resulting in the differentiation of 90% of the shoot initials into well-developed shoots. The 2- to 3-cm-long shoots rooted on half-strength MS basal medium supplemented with 4.90 μM indole-3-butyric acid (IBA) and 3% (w/v) sucrose in the third stage. The rooted plants could be established in soil with 70% success. This protocol could be utilized for in vitro propagation and conservation of this important threatened medicinal plant.     

Establishment of Efficient Regeneration System of Populus×euramericana cl.‘Bofeng’

Compared with the species of Leuce section,the difficulty in plant regeneration during tissue culture for the species of Aigeiros section is a key limiting factor for their application in genetic engineering of forest trees.In this study,the plant growth regulators combination,copper concentration,light intensity,and the selection pressures of kanamycin were investigated using leaves of Populus×euramericana cl.’Bofeng’ as explants,and a stable and high efficient regeneration system was established.Using this system,both the shoot regeneration rate and rooting rate were up to 100%,and the average number of differentiated shoots in each leaf explant was up to 20,and the survival rate of seedlings reached 98%.The optimal selection pressure of kanamycin in shoot inducement for leaf-explant was 40 mg·L^-1,and the optimal selection pressure of kanamycin in root inducement of adventitious bud was 20 mg·L^-1.The authors also found that differentiation rate of adventitious buds of P.×euramericana cl.’Bofeng’ could be significantly promoted by increased copper concentration,and this is the first report about the key role of copper（Cu） in explant regeneration of Poplars.This regeneration system with high frequency which was established by the authors was as good as that of species of Leuce section,and it provides a good technological platform for genetic engineering of forest tree which uses the species of Aigeiros section as model materials.     

Assessment of factors affecting in vitro shoot regeneration from axillary bud explant of Camptotheca acuminata

Axillary buds from 3-yr.-old seedlings of Camptotheca acuminata in the greenhouse were cultured on the different basal media with different concentrations of growth regulators for shoot regeneration for studying the effects of different basal media, different concentrations of growth regulators (BA or TDZ), sucrose, agar and pH value on shoot regeneration from axillary bud. The results showed that B5 and WPM media were the optimal basal media and the optimal phyotohormone was BA of 1.0 mg/L or TDZ of 0.1 mg/L; The concentrations of sucrose of 30g/L and agar of 6g/L were most suitable for the shoot regeneration; pH value from 5.8 to 6.6 were broadly effective, but the best at pH 5.8.     

Effects of Thidiazuron,basal medium and light quality on adventitious shoot regeneration from <Emphasis Type="Italic">in vitro</Emphasis> cultured stem of <Emphasis Type="Italic">Populus alba</Emphasis>×<Emphasis Type="Italic">P. berolinensis</Emphasis>

The effect of Thidiazuron （TDZ）, basal media and light quality on adventitious shoot regeneration from in vitro cultured stem of Populus albaxP berolinensis were determined to establish a high efficiency shoot regeneration system from stem explants of P. alba~P berolinensis. Stems ofPopulus alba~P berolinensis were collected from cultured shoots in vitro derived from dormancy buds of 3-year-old seedlings. The stem explants were cultured on MS medium containing 0.02-mg·L-1NAA （naphthaleneacetic acid）, and 0.1, 0.3, 0.5 and 1.0 mg·L-1 concentrations of TDZ to determine the effect of TDZ on shoot regeneration. Three basal media, i.e. MS, woody plant medium （WPM） and B5, were used to test their influences of different media on adventitious shoot regeneration. Green, red, blue and yellow plastic films in comparison with florescent light as control were used to observe their effects on shoot regeneration. The results showed that differ- ent concentrations of TDZ had an evident influence on shoot regeneration. Lower concentration of TDZ （0.1 mg·L-1） resulted in more ad- ventitious shoot regeneration and higher concentration of TDZ （〉0.1 mg·L-1） inhibited shoot regeneration. Among different media, MS medium exhibited a high efficiency for shoot regeneration, followed by WPM medium, while B5 medium inhibited shoot regeneration. Normal light and yellow light exhibited better effects on shoot regeneration, compared with other light.     

Establishment of high frequency shoot regeneration system in Himalayan poplar (Populus ciliata Wall. ex Royle) from petiole explants using Thidiazuron cytokinin as plant growth regulator

Populus species are important resources for industry and in scientific study on biological and agricul-tural systems. Our objective was to enhance the frequency of plant regeneration in Himalayan popla...     

Micropropagation of Eucalyptus grandis × E.urophylla AEC 224 clone

Genetic transformation systems require protocols that allow regenerating transgenic plants from transformed tissues. This study aimed to establish a protocol for indirect organogenesis in leaf explants of a Eucalyptus grandis × E. urophylla AEC 224 clone. During callogenesis stage, several concentrations of NAA and then NAA or 2,4-D combined with TDZ were tested in JADS culture medium for 30 days, followed by subculture of the explants in the regeneration medium, containing 5.0μM BA and 0.5μM NAA for another 30 days. In these media,the explant oxidation rate was high(95 %). Thus, in order to reduce oxidation, different culture media were compared: WPM, MS, JADS and modified QL, followed by explant transfer onto regeneration medium. The highest percentage of regeneration and the lowest oxidation rate were achieved on WPM medium. Then, NAA and 2,4-Dwere tested in combination with TDZ and also TDZ and BA combined with NAA in WPM medium. The most efficient culture media in terms of shoot regeneration were WPM supplemented with 0.25μM TDZ and 0.1μM NAA during 30 days for callus induction and then with 5.0μM BA and 0.5μM NAA for another 30 days. This protocol yielded a regeneration rate of 43 %, with a low oxidation of tissues. A rooting experiment was conducted using half strength MS medium and comparing three concentrations of IBA(2.46, 4.90 and 7.35μM). The highest rooting percentage(35 %) was obtained on medium containing2.46μM IBA. Once the shoots were rooted, acclimatization in a greenhouse was not challenging and plant survival reached 100 %.     

Effects of antibiotics on plantlet regeneration via organogenesis in Populus euphratica

Four antibiotics, kanamycin, geneticin, carbenicillin and cefotaxime,were evaluated for their effect on the regeneration of adventitious buds, shoot differentiation, rooting from regenerated shoots of Populus euphratica as well as on their control of Agrobacterium -mediated transformations. Results showed that the optimum concentration ranges of kanamycin and geneticin were 15-20 and 10-15 mg·L-1 at the stage of transgenic plantlet selection. The inhibitory effects of cefotaxime and carbenicillin varied among different genotypes of Agrobacterium. The inhibition of cefotaxime on Agrobacterium C58 was stronger than that of carbenicillin. The optimum concentration of cefotaxime was 100 mg·L-1. Cefotaxime and carbenicillin had similar effects on Agrobacterium LBA4404 and their optimum concentrations were both 150 mg·L-1.     

Micropropagation of yellow mangosteen: a valuable endemic tree of India

We developed a method for in vitro regeneration of Garcinia xanthochymus(yellow mangosteen) from matured seed segments. Multiple shoots were induced on woody plant(WP) medium supplemented with cytokinins.An average of 11 shoots per explant were regenerated from mature seed segments on WP medium containing 20 μM 6-benzylaminopurine. Histological analysis revealed that hypodermal cells of seed segments were initially involved in active division, which later developed into meristemoids, subsequently leading to the formation of shoot buds.Shoot elongation was achieved by repeated subculturing of seed explants in shoot regeneration medium. Rooting of shoots was achieved on WP medium supplemented with indole-3-butyric acid or a-naphthalene acetic acid. Plantlets were transplanted to pots containing soil: compost(1:1) and survival rate was 90%.     

Coppicing ability of dry miombo woodland species harvested for traditional charcoal production in Zambia:a win–win strategy for sustaining rural livelihoods and recovering a woodland ecosystem

The miombo woodland is one of the most extensive woodlands in Africa, supporting livelihoods based on biomass fuel for millions of rural people. However, there are growing concerns about the sustainability of harvesting for biomass fuel(mainly charcoal). Thus, the aim of this study was to examine whether regeneration by coppice is a viable option for sustainably managing miombo woodlands for biomass fuel production. We tested the hypotheses that(1) species, stump diameter, stump height and time since cutting significantly affect the number of sprouts per cut stump(coppice density) and mean sprout height(shoot vigour) and(2) higher coppice density reduces shoot vigour due to competition among coppice shoots in a given stump. In an inventory in areas that were harvested for charcoal production by the local people, 369 stumps of 11 species were recorded with mean coppice stumps ranged from 6 to 84. The mean coppice density ranged from 5 to 8 shoots per stump while the mean height of coppice shoots ranged from 46 to 118 cm with marked interspecific variations. Stump size was significantly and positively correlated with coppice density for some of the species, but not with shoot vigour for the majority of the species. However, shoot vigour was significantly positively correlated to time since cutting of trees for nearly half of the species. Coppice density had a significant negative correlation with shoot vigour for two species, and a positive correlation for one species. In conclusion, the results provide evidence about the importance of coppice management as a win–win strategy for sustaining charcoal-based rural livelihoods and recovering the miombo woodland ecosystem.     

A modified Murashige and Skoog media for efficient multipleshoot induction in G. arborea Roxb.

This paper reports on the effect of various micropropagation factors of Gmelina arborea Roxb. through multiple shoot induction. Factors like the source and age of explants, plant growth regulators （PGRs）, media composition, and carbon source affected multiple shoot-ing in the present study. Among all the explants used, only shoot tips derived from one, two, and three week old seedlings could form multiple shoots. Besides, the formation of multiple shoots depended on the con-centration and combination of PGRs. Among all the PGRs, BAP （6-benzylaminopurine） alone gave the highest regeneration efficiency. Simi-larly, IBA （Indole-3-butyric acid） was the most efficient PGR in inducing root formation in the microshoots. Media composition and carbon source also affected the regeneration efficiency. MS （Murashige and Skoog medium） proved to be the best media for regeneration followed by B5, SH （Schenk and Hilderbrandt medium） and WPM （Woody plant medium） in that order. Similarly, among sugars, only sucrose and glucose sup-ported induction of microshoots. Based on this study we recommend the use of glucose in place of sucrose in MS medium for maximum regenera-tion efficiency.     

The forecast of fire impact on Pinus sylvestris renewal in southwestern Siberia

Simulation of fire impact on forest floor renewal in pine forests was based on predictions for 2100 by the Canadian Climate Centre for increase in temperatures of by4.5℃ and total precipitation by 14% in the West Siberian pre-forest-steppes and empirical regression relationships between them and the degree of burnt forest floor,as well as amount of Pinus sylvestris L.regeneration.It was predicted that by 2100,pine regeneration on fire prone sites under the canopy of the dominant forest type will increase by 29-54% compared to the 1980 s but on adjacent open sites,regeneration will decrease twice as much.This means that the regeneration potential and pine population stability in pre-forest-steppes will become as poor as it is today.     

Shoot drying and its cause in Calamus simplicifolius at Nanmeiling, Hainan, China

Many stems are subject to shoot drying in the plantations of Calamus simplicifolius Wei at the Nanmeiling Base of the Forestry Bu- reau of Baisha County, Hainan Province. As a palm, stems of C. simpli- cifolius stop growing and later die if the shoots are dry. Generally, shoot drying means reduced cane production and reduced profit for a rattan plantation. We aimed to quantify the incidence of shoot drying and de- termine its reason. We sampled eight 20 m × 20 m plots in the C. simpli- cifolius plantations. In each plot, we counted stems and categorized them as drying shoot or normal shoot, and mother stem or sucker stem. We measured stem length and categorized them as drying shoot and normal shoot for mother stems. We cut open each shoot-drying stem to deter- mine the cause of drying from drying part to fresh part. The frequency of mother stems (259 stem·ha -1 ), was significantly lower than sucker stems (588 stem·ha -1 ). The percentage of shoot drying was 33.8% for mother stems, not significantly higher than that for sucker stems (18.9%). The mother shoot stems were significantly shorter if they were drying than if normal. 80% of stems with a drying shoot were hollow within the leaf sheath, whereas 10% hosted lively mature larvae (one larvae per shoot) and 10% hosted several lively young larvae. Mature larvae were identi- fied as the Red Palm Weevil, Rhynchophorus ferrugineus Oliver. To confirm the present of the weevil, three pheromone traps for the weevil were set up in the plantations and adult weevils were trapped on the nextday and identified as the Red Palm Weevil. We conclude that shoot dry- ing of C. simplicifolius is probably caused by the Red Palm Weevil.     

Influences of antibiotics on plantlet regeneration via organogenesis in Ioblolly pine （Pinus taeda L.）

Three antibiotics ampicillin, carbenicillin, and cefotaxime were evaluated for their effects on induction, growth, and differentiation of organogenic calli, as well as rooting of regenerated shoots of three Ioblolly pine (Pinus taeda L.) genotypes. Of the antibiotics administered, cefotaxime maximally increased the frequency of callus formation and growth rate of organogeni ccalli, carbenicillin maximally increased the frequency of shoot regeneration and the average number of adventitious shoots per piece of organogenic callus, ampicUlin maximally decreased the rooting frequency of regenerated shoots and mean number of roots per regenerated shoot, in comparison with antibiotic-free media. Compared with the control, ampicillin minimally increased the frequency of callus formation, cefotaxime minimally increased the frequency of shoot regeneration, and carbenicillin minimally decreased the rooting frequency of regenerated shoots in three Ioblolly pine genotypes tested. All three antibiotics increased the frequencies of callus formation and shoot regeneration, and reduced the rooting frequency ot regenerated shoots suggested that the establishment of an efficient Agrobacterium tumefaciens-mediated transformation protocol for stable integration of foreign genes into Ioblolly pine need to select a suitable antibiotic. This investigation could be useful for optimizing genetic transformation of conifers.     

In vitro regeneration of Populus tomentosa from petioles

A reliable in vitro regeneration procedure for Populus tomentosa is a prerequisite for its trait improvement through genetic transformation. We established a systematic protocol for indirect regeneration of P. tomentosa using in vitro petioles of Chinese poplar cultivar ‘fasta-3'. A high frequency of callus induction([97 %) was obtained from isolated petioles cultured on the modified 1/2MS basal medium supplemented with 0.5 mg/L ZT and 1.0 mg/L NAA, and the tested calli were subsequently plated on1/2MS basal medium supplemented with 0.25 mg/L BA,0.25 mg/L ZT, 0.25 mg/L NAA, 0.01 mg/L TDZ, and0.5 mg/L KT for efficient regeneration of shoots after being cultured for 6 weeks. The regenerated shoots were vigorously rooted on the tested media supplemented with 1.0 mg/L IBA and 0.5 mg/L NAA. These results can facilitate genetic transformation of P. tomentosa for trait improvements in future.     

Regeneration status of riparian tree species in two sites that differ in land-use in the Okavango Delta,Botswana

Human communities from the Okavango Delta benefit from the services and goods provided by the wetland ecosystem through its riparian vegetation.These include food and timber products used for the construction of shelter and canoes.Despite the importance of riparian tree species in the Delta,their regeneration structure is currently unknown.For riparian trees to be managed sustainably,information on the current regeneration status of the trees under different land uses is needed.The Moremi game reserve(protected area) and Seronga(communal area) were selected for this study on the regeneration of riparian tree species of Croton megalobotrys Mull.Arg,Philenoptera violacea(Klotzsch) Schrire,Senegalia nigrescens(Acacia nigrescens) Oliv and Diospyros mespiliformis Hochst.ex A.Dc.The height of each individual tree was estimated in randomly selected 30 plots(15 from each site) of 20 9 50 m for assignment to five regeneration classes:0–0.5,0.5–1,1–2,2–4 and 4 m.Linear regression was used to infer regeneration status of each species.An independent-sample Student's t test was used to determine any significance differences in seedling density/ha and sapling density/ha between different sites at p0.05.Diospyros mespiliformis populations had an unstable regeneration structure in both sites,while P.violacea regeneration was stable regardless of land-use type.Croton megalobotrys and S.nigrescens had an unstable regeneration pattern in Seronga,while in Moremi it was stable;thus,the regeneration structure of C.megalobotrys and S.nigrescens is affected by land-use.This result implies that intervention is needed to conserve the two species in Seronga where the current land-use appears to be incompatible with regeneration;D.mespiliformis also needs to be conserved in both Moremi and Seronga.     

Effects of gaps on regeneration of woody plants: a meta-analysis

Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.