Regeneration of <Emphasis Type="Italic">Melia volkensii</Emphasis> Gürke (Meliaceae) through direct somatic embryogenesis

Experiments were conducted to study plant regeneration through direct somatic embryogenesis using mature zygotic embryo and cotyledonary explants from seeds of Melia volkensii stored for <3 and >12 months. Explants were cultured on Murashige and Skoog (MS) medium supplemented with BAP, NAA and 2,4-D (0.5, 1.0 and 2.0 mg l⁻¹) alone, and BAP (0.5, 1.0, 2.0 and 4.0 mg l⁻¹) in combination with 2,4-D or NAA (0.2 and 0.5 mg l⁻¹). After 4 weeks in culture, up to 60% of cotyledonary explants from the seeds stored for <3 months produced direct somatic embryos on BAP (0.5–4.0 mg l⁻¹) in combination with 2,4-D (0.2 mg l⁻¹). The number of somatic embryos ranged from 5 to 14 per explant in BAP (0.5 mg l⁻¹) and 2,4-D (0.2 mg l⁻¹) combination. Only 20% of cotyledonary explants from seeds stored for >12 months produced somatic embryos. Mature zygotic embryos failed to produce any somatic embryos. Subcultures of somatic embryos from cotyledonary explants of seeds stored for <3 months formed clusters of shootlets on semi solid MS and 1/2 MS media. After 6 weeks of subculture on multiplication MS media augmented with BAP (0.5 mg l⁻¹) and IAA (0.2 mg l⁻¹), 70% of the shoot tips formed 4–7 shoots per explant. Up to 33% of the multiplied shoots were rooted in MS medium supplemented with 2.0 mg l⁻¹ IBA. Plantlets developed normally into seedlings in the greenhouse.     

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 an in vitro plant regeneration protocol for Casuarina cunninghamiana Miq. via indirect organogenesis

An in vitro plant regeneration protocol via indirect organogenesis from morphogenetic callus was established for Casuarina cunninghamiana Miq. Effects of plant growth regulator NAA (naphthaleneacetic acid) and BAP (6-benzylaminopurine), sucrose and AgNO₃ on callus induction, adventitious bud differentiation and shoot development were examined. Explants used were epicotyl fragments from 45-day-old seedlings. The largest callus (4.29 mm in diameter) was obtained after 1 month on a basic culture medium consisting of Murashige and Skoog ? macro- and full strength micro- elements, Nitsch and Nitsch vitamins, supplemented with 0.54 μM NAA, 3.30 μM BAP, and 30 g L⁻¹ sucrose. The calli were subcultured in the same medium above for 2 months. They were then cultured for another 2 months for adventitious bud differentiation and shoot development. The highest mean adventitious bud differentiation, number of shoots formed per callus and number of shoots ≥2 cm long per callus (47.50%, 27.38 and 4.75, respectively) were achieved on the above medium modified with NAA at 0.27 μM and supplemented with AgNO₃ 1 mg L⁻¹. Shoots were successfully rooted without plant growth regulator and the rooted plantlets survived and grew normally. This protocol for in vitro plant regeneration provides a tool not only for vegetative propagation but also for plant genetic transformation and gene function studies of C. cunninghamiana.     

In vitro propagation of a medicinal plant: Tripterygium wilfordii Hook f.

In this study a reliable protocol was developed for the establishment of commercial in vitro cultures of Tripterygium wilfordii Hook f.. Juvenile shoots from one-year-old elite plants were used as the source of explants. New axillary shoots were obtained after 30 days of culture on a MS medium supplemented with BAP (2.0 mg·L^–1) and NAA (0.1 mg·L^–1). The optimal multiplication medium was a modified MS medium supplemented with BAP (1.0 mg·L^–1) and NAA (0.1 mg·L^–1). This yielded a multiplication rate of 2.4 for each subculture. Slightly more than 92% of shoots rooted when cultured on a modified MS medium containing IBA (0.2 mg·L^–1) and acti-vated charcoal (0.5 mg·L^–1). Activated charcoal promoted both a strong and a high rooting rate during the rooting phase. Plantlets were transferred to pots for a short acclimatization stage in a greenhouse where 95% of the plantlets survived. This highly reproduci-ble procedure can be adopted for large-scale propagation of T. wilfordii.     

Thidiazuron-induced somatic embryos,their multiplication,maturation, and conversion in <Emphasis Type="Italic">Cinnamomum pauciflorum</Emphasis> Nees (Lauraceae)

Thidiazuron (TDZ) induced somatic embryogenesis from immature zygotic embryos in Cinnamomum pauciflorum Nees while 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BA) or picloram only induced callus and/or adventitious buds. The highest induction frequency for somatic embryogenesis was achieved with MS medium (Murashige and Skoog in Physiol Plant 15:473–497 1962) supplemented with 2.5 μM TDZ using torpedo-shaped embryos (3–5 mm in length) as explants. In addition, induction medium was supplemented with 0.8 g l⁻¹ casein, 0.4 g l⁻¹ glutamine, and 10 g l⁻¹ sucrose. Somatic embryos (SEs) initiated from root tips or hypocotyls without callus formation. SEs were maintained and multiplied via secondary somatic embryogenesis. Embryo maintenance medium was similar to induction medium except that TDZ was reduced to 0.5 μM. Secondary embryogenesis was enhanced by supplementation of 5 g l⁻¹ activated charcoal in the culture. The best medium for embryo maturation was MS medium containing 30 g l⁻¹ sucrose and 5 g l⁻¹ Phytagel without plant growth regulators. A typical mature SE consisted of two large cotyledons and a short embryo proper. Approximately 82% of selected mature SEs were able to germinate and 63% could convert into plantlets on germination medium that was composed of half strength MS medium salts, 10 g l⁻¹ sucrose, 3 g l⁻¹ Phytagel, and 5 g l⁻¹ activated charcoal.     

An efficient method for clonal propagation and in vitro establishment of softwood shoots from epicormic buds of teak (Tectona grandis L.)

Softwood shoots were produced from 40 cm long stem segments placed horizontally in flat trays containing sterilized sand under natural light or shade conditions for subsequent rooting and micropropagation studies in teak (Tectona grandis L.). Higher number of shoots (6.17) per log was produced under natural light as compared to shade conditions. Forcing was also better in natural light as compared to shade in terms of shoot length, number of nodes or leaves. For rooting, 2–4 cm long softwood shoots were excised and treated with either indole-3-butyric acid (IBA) or α-naphthyl acetic acid (NAA) at 0, 1000, 2000 or 3000 μmol·L^–1 each or with combinations (1000 + 1000, 2000 + 2000 or 3000 + 3000 μmol·L^–1) and then placed in flat trays containing autoclaved sand at 25 ± 2ºC in 16 h photoperiod at 35 µmol·m^–2·s^–1. After 28 days, softwood cuttings treated with IBA + NAA (3000 + 3000 μmol·L–1) had highest rooting percentage (89.3%) with 5.5 mean roots. Shoot apex and nodal explants of softwood cuttings were pretreated with 0.1% (w/v) ascorbic acid, boric acid, activated charcoal, citric acid, glutamine or polyvinylpolypyrollidone (PVP) for 24 h to remove phenolic compounds before surface disinfestation. Glutamine (Gl) and PVP were equally effective resulting in 60% establishment of shoot apices on MS medium supplemented with 10 μmol·L–1 6-benzylaminopurine (BAP) + 5 μmol·L–1 NAA. Using shoot apices, highest (42.80) number of multiple shoots with 54.33 mm shoot length were obtained on MS + BAP (8.8 μmol·L–1) + IBA (2 μmol·L–1) after 45 days. Shoots were successfully rooted and acclimatized to greenhouse     

Micropropagation of Vitex negundo L. and Random Amplified Polymorphic DNA Analysis of Micropropagated Plants

A micropropagation protocol was established for a medicinal plant Vitex negundo. Genetic stability of micropropagated plants was investigated. Multiple shoots were induced from nodal explants cultured on Murashige and Skoog (MS) medium with 0.53 μM naphthalene acetic acid (NAA) and 11.0 μM benzyl aminopurine (BAP) along with additives (ascorbic acid, 283.9 μM; citric acid, 130.1 μM; and arginine, 143.6 μM). Shoots were further multiplied by repeated transfer of the mother explant. The shoots were further multiplied on MS medium + 0.57 μM indole-3-acetic acid (IAA) and 6.6 μM BAP. The micropropagated shoots were pulse treated with 122.5 μM indole-3-butyric acid (IBA), in liquid MS medium and then transferred to autoclaved soilrite. These rooted ex vitro. Shoots were also rooted in vitro on a half-strength MS medium + 2.45 μM IBA. The survival rate of in vitro rooted plantlets was poor during hardening compared to ex vitro rooted plantlets. About 95% of the ex vitro rooted, hardened plantlets survived in the field. Genetic stability of micropropagated plants was tested by using 25 random amplified polymorphic DNA primers. The cloned plants exhibited no variation in banding pattern in comparison with the mother plant.     

Micropropagation and callus culture of <Emphasis Type="Italic">Saussurea laniceps</Emphasis>, an alpine medicinal plant

Cottonhead windhairdaisy (Saussurea laniceps Hand.-Mazz.) is one of the most famous and important medicinal herbs in China. Illegal collection from wild populations is increasingly threatening the present environment of S. laniceps. Establishment of an efficient method for micropropagation is the best way to change its endangered situation. When mature seeds of S. laniceps were cultured on hormone-free MS medium, plantlets were formed from germinated seeds in 7–10 d. Then 0.5 cm × 0.5 cm leaf explants were transplanted to MS medium supplemented with 1-naphthalene-acetic acid (NAA)/2,4-D and benzyladenine (BA)/KT and callus was achieved 10 d after transfer. Shoot bud regeneration occurred from callus cultured on MS medium supplemented with different growth regulators 20 d after culturing. The regeneration percentages varied with the different components of plant growth regulators. The percent regeneration from callus pretreated at low temperature of 5°C increased significantly compared with those incubated at 23/20°C directly. Optimal regeneration was observed with explants on media supplemented with 1.5 mg&#8226;L^–1 BA plus 0.2 mg&#8226;L^-1 NAA. In the presence of 0.2 mg&#8226;L^–1 NAA in half-strength MS, 78% of the shoots formed roots. Plantlets from explants showed 63% survival after acclimatization.     

Micropropagation of Anogeissus latifolia (Roxb. Ex DC.) Wall,ex Guill. & Perr.- A Tree of Fragile Ecosystems

Abstract

A micropropagation process was developed for Anogeissus latifolia-a tree of fragile ecosystems. Multiple shoots were regenerated from cotyledonary node and epicotyl explants on Murashige and Skoog's (MS) medium containing 0.1 mgl^-1 indole-3-acetic acid (IAA) + 1.5 mgl ^-l 6-benzylaminopurine (BAP) + additives (25 mgl ^-l each of adenine sulphate, L-arginine, ascorbic-, citric acids and 1.0 mM L-asparagine) + 200 μM Fe-EDTA (ferric-ethylenediaminetetraacetic acid) salt. The shoots differentiated in vitro were subcultured and repeatedly transferred onto fresh medium but with 1.0 mgl^-1 of BAP to achieve 4-5 fold rate of shoot multiplication. After every 4th week of culture, from each culture bottle 8-10 shoots could be harvested for rooting. The shoots produced in culture were rooted in vitro on half strength MS medium with 1.0 mgl ^-l either of IBA (indolebutyric acid) or NAA (naphthaleneacetic acid). The shoots were pulse treated with combination (100 mgl ^-l each) of IBA and NOA (2-naphthoxy acetic acid) rooted ex vitro. The ex vitro root induction method is highly efficient and plantlets so generated could be acclimatized and pot transferred. The process developed can be used for large scale production of plants of A.     

青钱柳子叶不定根的发生机制

本文以青钱柳子叶为材料,WPM为基本培养基,研究不同质量浓度的外源ABA和IBA对子叶不定根发生的影响,并对不定根发生与内源激素的变化关系进行探讨.结果表明:添加0.5～5 mg·L~(-1) IBA,对子叶不定根发生均有不同程度的促进作用,以1.5 mg·L~(-1)效果最佳,诱导生根率、平均生根条数和根长均达最大,生根率可达到100%;而添加0.01～0.5 mg·L~(-1) ABA和不加激素的对照没有不定根的发生.内源激素的动态测定表明IAA对不定根的发生起关键性作用,根原基的启动需要较高的内源IAA,而不定根的形成与根的伸长需要相对较低的内源IAA水平.较高的IAA/ABA,IAA/GA_3比值有利于不定根的发生,能较好反映出生根过程中内源激素间的平衡需求,GA_3可能不是影响不定根发生的关键因素.研究结果为青钱柳生根诱导及其机制的研究提供依据.     

Micropropagation of Vegetable Rennet (Withania coagulans [Stocks] Dunal)—A Critically Endangered Medicinal Plant

Withania coagulans (Stocks) Dunal (Solanaceae), popularly called vegetable rennet, is a critically endangered and highly valued medicinal plant. Overexploitation and reproductive failure forced the plant species toward the verge of complete extinction. We describe here the development of a simple, rapid, and cost effective in vitro micropropagation system for W. coagulans for mass-scale production of true-to-type plantlets using nodal shoot segments. Exactly 95.5 ± 0.34% explants responded within 8–10 days (d) and produced multiple shoot buds (4.1 ± 0.10 shoots of 2.95 ± 0.15 cm length) on 0.8% agar-gelled Murashige and Skoog's (MS) basal medium supplemented with 8.88 μM 6-benzylaminopurine (BAP), 0.57 μM indole-3-acetic acid (IAA), and additives (100 mg L^?1 L-ascorbic acid, 25 mg L^?1 each citric acid, adenine sulphate, and L-arginine). The shoots in cultures were multiplied by repeated transfer on MS medium with 4.44 μM BAP, 0.57 μM IAA, and additives. Further cultures were multiplied on a large-scale through the subculturing of shoot clumps differentiated in vitro, on MS medium supplemented with 1.11 μM BAP, 0.57 μM IAA, and additives. Maximum number (19.1 ± 0.28) of healthy (6.15 ± 0.25 cm) and viable shoots differentiated on this medium. The microshoots were rooted both in vitro and ex vitro. Exactly 67.3 ± 1.01% microshoots rooted in vitro within 25–30 d on agar-gelled half-strength MS salts supplemented with 29.52 μM indole-3-butyric acid (IBA) and 200 mg L^?1 of activated charcoal (AC). Alternatively, 73.8 ± 0.65% cloned shoots rooted on sterile soilrite (soilless compost and soil conditioner) under ex vitro conditions after pulse treatment with 2.46 mM IBA for 300 s. The clones of W. coagulans were hardened in a greenhouse within 40–45 d by slow and gradual exposure of plantlets from high relative humidity (RH; 70–80%) and low (26 ± 2°C) temperature to low RH (40–50%) and high (34 ± 2°C) temperature. The hardened plantlets were transferred to soil and stored in agro-net house with more than 90% survival rate. Replacement of pure and laboratory grade sucrose with commercial grade sugar, use of less expensive commercial grade agar-agar in culture medium, higher rate of shoot proliferation, single step ex vitro rooting, and hardening of plantlets in the greenhouse are advantageous features of the protocol. The micropropagation protocol defined here is reproducible, easy to follow, and would be helpful in large-scale restoration programs through true-to-type mass-multiplication of W. coagulans.     

An Efficient Micropropagation Protocol for High-Frequency Plantlet Regeneration from Liquid Culture of Nodal Tissues in a Medicinal Plant,Turnera ulmifolia L.

A highly efficient, stable, and cost-effective micropropagation protocol for the conservation of a medicinal plant Turnera ulmifolia L. was established from nodal tissues via multiple axillary shoot proliferation on using Murashige and Skoog’s (MS) liquid nutrient medium. To begin with, nodal explants were placed on agar gelled medium amended with 2.0 mg L^?1 6-benzylaminopurine (BAP) and 0.1 mg L^?1 indole-3 acetic acid (IAA) for shoot induction. Subsequently, elongation of regenerated shoots could be possible on liquid MS medium supplemented with 0.5 mg L^?1 BAP and Kin (kinetin) each along with 0.1 mg L^?1 IAA where high frequency of regeneration in terms of number of shoots (47.2 shoots/explant) was achieved. Furthermore, long and healthy shoots (4?5 cm in length) were rooted on agar gelled half-strength of MS medium supplemented with 2.0 mg L^?1 indole-3 butyric acid (IBA). Finally, in vitro regenerated plantlets were gradually acclimatized in the greenhouse and transferred to the field successfully.     

Caulogenic callus induction and adventitious bud formation from embryos of long-term stored seeds ofPicea jezoensis

Caulogenic calli with a high differentiation potency were induced from mature embryos ofPicea jezoensis seeds stored over a long time, for 29 years, resulting in the active formation of adventitious buds. Embryos began to induce calli within 3 weeks of cultivating on LP medium containing 3 μM BAP and 1 μM 2,4-D. Then, the calli proliferated and transformed into caulogenic calli with bud primordia in 8 weeks. The caulogenic calli increased actively with the addition of 500 mg/l ofl-glutamine in the medium. Furthermore, caulogenic calli, induced on LP medium containingl-glutamine, resulted in the formation of adventitious buds, which elongated after transferring the calli into LP medium with 0.1 μM BAP, but withoutl-glutamine. It appears that the number of adventitious buds and the process of shoot elongation are influenced by the kind of nitrogen contained in the medium for callus induction. A part of this study was presented at the 107th Annual Meeting of the Japanese Forestry Society (1996).     

Micropropagation of Selected Genotype of Aloe vera L.—An Ancient Plant for Modern Industry

Aloe vera Linn. (Syn. Aloe barbadensis Mill; Gwar-patha in Hindi) belongs to family Liliaceae. The plant, for its medicinal properties, has commercial value. Some of the genotypes of Aloe vera are consumed as a vegetable and processed to make curry and other edible products. We report here on the development of an efficient method for rapid clonal propagation by shoot proliferation from axillary meristem(s) of selected germplasm of Aloe vera. Explants were pretreated with 0.1% aqueous solution of both streptomycin and bavistin separately, each for 15 min. These were surface sterilized with 0.1% aqueous solution of mercuric chloride (HgCl₂) for 4–5 min and washed several times with autoclaved water. These were kept in a chilled, sterile antioxidant (200.0 mg L^?1 of ascorbic acid, 50.0 mg L^?1 of citric acid, and 25.0 mg L^?1 of polyvinylpyrrolidone; PVP) solution and cultured on semi-solid Murashige and Skoog's (MS) medium. The bud explants produced multiple (10.3 ± 0.675/explant) shoots on MS medium containing 13.32 μM of 6-Benzylaminopurine (BAP) and 100.0 mg L^?1 of ascorbic acid, 50.0 mg L^?1 each of citric acid and PVP, with 25.0 mg L^?1 each of arginine and adenine sulphate as additives. The shoots were further multiplied by (a) repeated transfer to fresh MS medium with additives + 13.32 μM BAP, and (b) subculturing on MS medium with a lower (4.44 μM) concentration of BAP. On MS medium containing 4.44 μM of BAP and additives, a maximum number (27.8 ± 0.63) of shoots were produced. In liquid MS medium with 4.44 μM of BAP, the rate of shoot multiplication increased and the vigor of the shoots improved. One hundred percent of the cloned shoots rooted under in vitro conditions on hormone-free half-strength MS salts containing 200.0 mg L^?1 of activated charcoal at 32 ± 2°C. The cloned shoots treated with 2.46 mM of indole-3-butyric acid (IBA) or 2.473 mM of β-naphthoxyacetic acid (NOA) for 5 min rooted under ex vitro conditions in the greenhouse. The rooted plants were hardened in the greenhouse and stored under an agro-net house. The cloned plants were transferred under different field conditions at various sites in Western Rajasthan. These plants grew normally. The higher rate of shoot multiplication and easier approach of direct rooting and hardening make this method superior to the methods previously reported on cloning/tissue culture of Aloe species. From a single shoot bud, approximately 5000 plants can be produced within 180 days.     

Stimulation of in vitro organogenesis from epicotyl explants and successive micropropagation round in Cassia angustifolia Vahl.: an important source of sennosides

This report describes a protocol for the in vitro shoot induction and plant regeneration from epicotyl explants of Cassia angustifolia on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA), Kinetin and 2-iP (0.5–10.0 μM). MS medium supplemented with BA (5.0 μM) was the most effective in inducing adventitious shoots and growth. The highest rate of shoot multiplication was achieved on MS medium supplemented with BA (5.0 μM) and Indole-3-acetic acid (IAA, 1.0 μM). The nodal segments excised from the shoots regenerated from BA (5.0 μM) and IAA (1.0 μM) were used as explants for next three round of micropropagation. The number of shoots significantly increased at successive round of micropropagation. For rooting, MS medium supplemented with 2.0 μM indole-3-butyric acid proved to be better than that supplemented with IAA or α-naphthalene acetic acid. The in vitro raised plantlets with well developed shoot and roots were successfully established in earthen pots containing garden soil and were grown in greenhouse. About 52 plants (85 %) survived out of 60 plants transferred in garden soil.     

无患子硬枝扦插进程插穗内源激素和多酚类物质含量变化

为了解无患子硬枝扦插生根机制,以1年生无患子硬枝作为扦插材料,在扦插第0—80天调查愈伤组织发育和根系形成情况,测定插穗的腋芽(嫩叶)以及基部2cm长度的韧皮部内源激素和多酚类物质的含量。结果表明,无患子硬枝扦插第10天开始出现愈伤组织,第50天愈伤率达到最高值83.33%;第40天开始出现生根插穗,生根率为6.67%,随后不定根数量迅速增加,第70天生根率达到86.67%,此时平均有5.33条。之后生根数量不变,根系仍然在生长,且扦插后根系效果指数持续增高。插穗韧皮部内源激素含量变化较复杂。整体来看,高含量赤霉素(GA3)抑制愈伤组织和不定根形成,且在根原基发生期和不定根形成关键期达到峰值,在不定根速生期持续下降;高含量生长素(IAA)促进不定根的形成,且在扦插后第20天,即根原基发生期,达到峰值(92.7μg/g);玉米素核苷(ZR)对无患子硬枝扦插过程的生理作用较复杂,低含量的ZR有利于根原基的发生和不定根速生,但高含量的ZR促进不定根形成。韧皮部ZR/IAA在扦插后第20—40天呈下降趋势,第40—60天快速上升,促进不定根生长;GA3/IAA整体呈现抛物线形下降趋势,特别是在根原基发生期和不定根速生期,下降速率更快,以促进不定根的生长。无患子硬枝插穗生根进程中,多数多酚类物质对愈伤组织形成、根原基发生及不定根形成有极显著抑制作用,没食子酸抑制效果稍弱;插穗内多种激素和多酚类物质的含量均发生了变化,且对插穗生根产生重大影响。总之,插穗根原基发生和不定根形成等关键时期,IAA含量升高,GA3、ZR以及多酚类物质含量降低,植物体内多种内源物质此消彼长,达到动态平衡,共同促进插穗生根。     

Biomass of fine and small roots in two Japanese black pine stands of different ages

The biomass and the spatial distribution of fine and small roots were studied in two Japanese black pine (Pinus thunbergii Parl.) stands growing on a sandy soil. More biomass of fine and small roots was found in the 17-year-old than in the 40-year-old stand. There were 62 g m⁻² of fine roots and 56 g m⁻² of small roots in the older stand, which represented mean values of 608 g for fine and 552 g for small roots per tree, respectively. In the younger stand, a total of 85 g m⁻² of fine roots and 66 g m⁻² of small roots were determined, representing a mean of 238 g for fine and 186 g for small roots per tree, respectively. Fine and small root biomasses decreased linearly with a soil depth of 0–50 cm in the older stand. In the younger stand, the fine and small roots developed only up to a depth of 30 cm. Horizontal distributions (with regard to distance from a tree) of both root groups were homogeneous. A positive correlation in the amount of biomass of fine and small roots per m² relative to tree size was found. Fine and small root biomasses increased consistently from April to July in both stands. The results also indicated earlier growth activity of the fine roots than small roots at the beginning of the growing season. The seasonal increases in fine and small root biomasses were slightly higher in the younger stand than the older stand.     

Root distribution of Senna siamea grown on a series of derived-savanna-zone soils in Togo, West Africa

Although crucial for assessing the functioning of alley cropping systems, quantitative information related to the hedgerow tree root distribution remains scarce. Soil mapping and destructive soil sampling was used to assess the impact of soil profile features on selected root characteristics of Senna siamea hedgerows, growing in alley cropping systems in three sites (Glidji, Amoutchou, and Sarakawa) representative for the derived savanna of Togo, West Africa. While the soil profiles in Glidji and Sarakawa contained a clay accumulation horizon, the Amoutchou profile was sandy up to 1 m. The number of small roots (diameter < 2 mm), quantified on a soil profile wall, decreased with depth in all sites. For most soil depths, the abundance of small roots tended to be higher near the tree base, e.g., ranging from 5.3 dm⁻² in Amoutchou to 21.4 dm⁻² in Glidji for the 0–20 cm layer, than in the middle of the alley, e.g., ranging from 3.1 dm⁻² in Amoutchou to 13.8 dm⁻² in Glidji for the 0–20 cm layer. Root length density (RLD) of the 0–10 cm and 10–20 cm layers was significantly higher in Glidji than in Amoutchou (P < 0.05) and in Sarakawa (P = 0.08). Differences in RLD between sites were not significant for layers below 30 cm. For each layer, root weight densities (RWD) were similar in all sites, e.g., ranging from 0.44 mg cm⁻³ in Amoutchou to 0.64 mg cm⁻³ in Glidji in the 0–10 cm layer, indicating that the roots in the Glidji topsoil had a smaller overall diameter than in Amoutchou. In Amoutchou, the relative RLD was lower than in Glidji or Sarakawa for the top 40 cm of soil, while the inverse was observed for the layers between 50 and 100 cm deep and this was related to the sandy soil profile in Amoutchou. Another consequence of the sandy profile was the larger tap root diameter below 50 cm in Amoutchou compared to Sarakawa. For all sites, significant (P < 0.001) linear regressions were observedbetween RLD's, RWD's, and the abundance of small roots, although the variation explained by the regression equations was highest for the relationship between RLD and RWD. The potential of the hedgerows to recover nutrients leached beyond the reach of food crops or the safety-net efficiency was evaluated for the tree sites. This revised version was published online in June 2006 with corrections to the Cover Date.     

Organic matter contribution to soil fertility improvement and maintenance in red Alder （Alnus rubra） silvopastoral systems

An investigation was conducted to quantify fine roots and roots nodules over the four seasons in forestry and agroforestry alder (Alnus rubra) stands in North Wales. Soil samples collected in each season were excavated at three sampling points (0.30 m, 0.57 m and 1.00 m distance from the base of each tree) from nine trees of the agroforestry and forestry plots. Result showed that the density of live fine root had significant differences in between seasons and treatments (P ＜ 0.001). The mean weight density of live fine root over the four seasons in agroforestry and forestry was 0.27±0.01 kg·m-3 and 0.54±0.03 kg·m-3, respectively. Weight density of dead root in each system remained constant throughout the year. The mean weight density of dead root was also significantly different (P ＜ 0.01) between forestry and agroforestry systems. Weight density of live and dead root nodule was both constant throughout the year and between the different sampling distances. The mean weight densities of live and dead root nodule over the four seasons were 0.09±0.03 kg·m-3 and 0.05±0.03 kg·m-3 in agroforestry and 0.08±0.02 kg·m-3 and 0.03±0.01 kg·m-3 in the forestry plots, respectively.     

Cultural factors influencing adventitious shoot and plantlet formation from slash pine cotyledons

Cultural factors affecting in vitro shoot and subsequent plantlet formation of slash pine (Pinus elliotti Engelm.) cotyledons were investigated. Basal media composition, N⁶-benzylaminopurine (BAP) concentration and exposure time significantly influenced bud induction in cotyledons cultured under a continuous photoperiod of 35–40 mol m^–2 s^–1 at 24 ± 1 °C. The largest number of adventitious shoots was obtained after 28 days exposure to 66 M BAP-supplemented modified Gresshoff and Doy 1 (GD1) medium. Relatively high frequencies of large shoots were obtained after a 14-day exposure to 22 M BAP-supplemented Brown and Lawrence (BL) or 66 M BAP-supplemented GD1. Adventitious shoots derived from 21- or 28-day exposures to BAP developed more slowly and were smaller in size than those derived from a 14-day exposure to the cytokinin. Shoot differentiation and subsequent growth were also influenced by basal media, media concentration, and presence of activated charcoal in the medium. The percentage of cotyledons forming shoots was highest on half-strength GD1 medium containing activated charcoal. Rooting was achieved in vitro under a continuous photoperiod of 60–70 mol M^–2 S^–1. Roots were formed when excised shoots were planted on GD 1/2 medium supplemented with 2.68 M 1^–1 a-napthaleneacetic acid (NAA) with or without BAP for 14 days. The proposed technique of slash pine propagation using cotyledon explants can produce up to 100 seedlings per embryo.