Micropropagation of Rollinia mucosa (JACQ.) baill

Summary A protocol for in vitro propagation of Rollinia mucosa, an important medicinal plant, was developed. The presence of 500 mg l⁻¹ polyvinylpyrrolidone (PVP) during explant excision was important to avoid browning. Axillary buds, adventitious buds, and shoot cluster proliferation were achieved from epicotyl and hypocotyl explants from nursery-grown seedlings. The highest direct organogenesis percentage from hypocotyl explants was obtained upon culture of explants on Murashige and Skoog medium supplemented with 2.2 μM benzyladenine (BA) plus 2.32 μM kinetin. Epicotyl explants display highest regeneration frequency on a medium containing 8.8 μM BA and 0.54 μM naphthaleneacetic acid. Gibberellic acid was necessary for shoot elongation. Root induction was observed when shoots were pretreated with activated charcoal for 7 d in the dark before culture on Woody Plant Medium supplemented with 49.21 μM indolebutyric acid for 10 d. Root development was observed when 20 g l⁻¹ sucrose was used. Rooted plantlets were acclimatized and grown in the greenhouse.     

Population dynamics ofGlaux maritima (L.) along a distributional cline

Population fluctuations ofGlaux maritima, along a transect on a Baltle sea shore meadow, were recorded between 1979 and 1983. A bimodal distribution in numbers along the transect reflects the variation in factors regulating numbers: The two maintenance systems of the species, vegetative propagation and sexual reproduction play different roles. Vegetative propagation is fast and responds quickly to variations in the environment. The seeds germinate in strongly fluctuating temperatures which are triggered by disturbances such as flooding, damaging the vegetation.     

Pay attention to membrane tension: Mechanobiology of the cell surface

The cell surface is a mechanobiological unit that encompasses the plasma membrane, its interacting proteins, and the complex underlying cytoskeleton. Recently, attention has been directed to the mechanics of the plasma membrane, and in particular membrane tension, which has been linked to diverse cellular processes such as cell migration and membrane trafficking. However, how tension across the plasma membrane is regulated and propagated is still not completely understood. Here, we review recent efforts to study the interplay between membrane tension and the cytoskeletal machinery and how they control cell form and function. We focus on factors that have been proposed to affect the propagation of membrane tension and as such could determine whether it can act as a global or local regulator of cell behavior. Finally, we discuss the limitations of the available tool kit as new approaches that reveal its dynamics in cells are needed to decipher how membrane tension regulates diverse cellular processes.     

云南山楂茎尖的离体培养及其无性系快速繁殖

用云南山楂(Crataegus scabrifolia(Franch.)Rehd.)成年树茎尖和实生芽两种不同发育阶段的材料为外殖体,诱导它们休眠芽萌动,丛生芽条并诱导芽条生根。实验结果如下:1.以成年态的云南山楂侧芽为外植体,培养在附加IAA 0.1—0.5mg/l+6-BA 1-2mg/l的MS培养基上可诱导芽的萌发;将芽继代培养在附加0.5—1mg/l 6-BA的SH或MS培养基上,40天后芽数增殖4—6倍;将芽条截下置于1/2MS培养基上,附加不同浓度的IAA或IBA,可得到50—80％的生根率。2.以实生芽为外殖体,在相同条件下,则20天后芽数增殖便可获4—6倍;98％以上生根。结果表明:云南山楂的幼年态要比成年态易脱分化和再分化。     

Effects of continuous nitrogen application and nitrogen preconditioning on nodulation and growth ofCeanothus griseus varhorizontalis

Rooted cuttings ofCeanothus griseus varhorizontalis were irrigated with 0, 10, 20, 50, 75 or 100ppm nitrogen as NH₄NO₃ for eight weeks prior to inoculation with infectiveFrankia. After inoculation, half of the plants for each treatment nitrogen level continued to be irrigated with the preconditioning nitrogen level and half were given no more supplemental nitrogen. For plants continuously receiving nitrogen, nodule initiation (nodule number) was inversely correlated with increasing supplemental nitrogen levels, and suppressed above 50 ppm N. Leaf nitrogen above 2% in continuous-N plants correlated with greatly reduced or suppressed nodulation. Plants maintained after inoculation without supplemental nitrogen showed influence of the prior nitrogen treatment on nodulation. Preconditioning at 50 ppm and above greatly reduced the number of nodules formed. The evidence suggests that stored internal nitrogen can regulate nodulation.Plant biomass accumulated maximally when nodulation was suppressed, at 75 and 100 ppm supplemental N applied continuously. Internode elongation during the nodulation period occurred only on nodulated plants, or in the presence of supplemental N (10 ppm and above).     

In vitro propagation of green-foliaged Dracaena fragrans Ker.

Callus tissue was induced in young stem segments cultured on MS based media supplemented with 0.25–0.5 mg l^-1 2, 4-D. Shoots were differentiated on media containing 0.5–1.0 mg l^-1 BA and 0.5–2.0 mg l^-1 IBA or 0.1–0.2 mg l^-1 NAA. The same media were suitable for shoot multiplication. Shoot elongation and rooting were strongly inhibited by BA and stimulated by auxins IBA and NAA. Medium containing 0.5 mg l^-1 IBA was optimal for rooting. Root elongation was stimulated by light and inhibited in darkness. Transfer of rooted plantlets to outdoor conditions was feasible and special hardening procedures were not required. Among more than 5000 plants produced by this procedure only 9 off-type plants with variegated leaves were found.     

Nauclea diderrichii: rooting of stem cuttings,clonal variation in shoot dominance,and branch plagiotropism

Summary Nauclea diderrichii (De Wild, and Th. Dur.) Merill (Rubiaceae), an indigenous hardwood of West Africa, is increasingly being grown commercially. This study investigates the potential for vegetative propagation and clonal selection, and raises some fundamental questions about the physiology of apical dominance and of plagiotropism. Rooting ability was high, with up to 100% rooting in 2–4 weeks, when different Indole-3-butyric acid (IBA) concentrations and leaf areas were tested. Auxin applications greatly increased the numbers of roots per cutting. The decapitation of unbranched plants revealed clonal variation in apical dominance and also in the establishment of outright dominance by the two shoots formed from the outgrowth of the axillary buds of the opposite leaves at the top node. Regression analysis of the Dominance Ratio (length of dominant: length of the sub-dominant shoot at the time of achieving dominance) against overall lateral bud activity (r = 0.82), showed that when the two top shoots co-dominate they provide a more powerful source of Correlative Inhibition than when one of the top shoots dominates the other. The imposition of plagiotropism in the axillary bud occurred over a period of a few days as the terminal and axillary buds emerged from the stipule. Growth of accessory buds on intact plants and debranched cuttings was orthotropic. These results are discussed with regard to the role of the leaf in root formation and the understanding of dominance relationships, branching and crown development in trees.     

Effects of auxins and cytokinins on epigenetic instability of callus-propagated Kalanchoe blossfeldiana Poelln.

A main problem in the vegetative propagation of ornamental plants in vitro is the epigenetic instability of cells removed from their organized environment. With calluses of leaf explants of Kalanchoe blossfeldiana Poelln., cv. Yucatan, the role of plant growth regulators (PGRs) in the occurrence of fasciation was studied.In various combinations of auxins and cytokinins, the auxin 2,4-D (2,4-dichlorophenoxyacetic acid) gave only deformed, inseparable shoot primordia. The most rapid callus induction with regeneration of well-developed sprouts was obtained with the natural IAA (indoleacetic acid) and Z (zeatin).As a first symptom of fasciation, aberration in decussate phyllotaxis can be observed. At increasing concentrations of IAA + Z, this symptom gradually decreased but fasciation proper increased. The optimum concentration was at 1 M for both PGRs. Reduction of exposure to the PGRs from six to three weeks reduced the epigenetic instability.     

In vitro tuberization in white yam (Dioscorea rotundata Poir)

Nodal cuttings of white yam were induced to produce microtubers on a MS-revised medium supplemented with various concentrations of sucrose, 20 mgl^–1 L-cysteine, 0.5 mgl^–1 kinetin and 0.7% agar. The frequency of tuberization was affected by the daylength, which is optimal at 12 and 16 h of light depending on the sucrose concentration. The microtubers were planted in a seed bed and grown to maturity. The importance of in vitro tuberization of yam as a means of international germplasm distribution or exchange as well as for the propagation of planting material is discussed.     

湖北贝母单鳞片砂培繁殖研究

本文针对湖北贝母生产中存在繁殖系数低的问题,研究了单鳞片砂培繁殖对提高鳞茎繁殖率的效果和原理。试验结果表明:1.单鳞片繁殖率为对照种鳞茎的5—9倍,2.低温(2—10℃)预处理4—8周和暗条件培养,能有效地提高子球形成率,促使子球迅速长大,3.植物激素(6-BA、KT、2,4-D)处理,有利于促进鳞片不定芽原基的分化,繁殖率为种茎繁殖的9—11倍;4.单鳞片繁殖的小鳞茎主要发生在鳞片基部的茎盘上,还可发生在鳞片的远轴面上,但不发生在近轴面。