The Vegetative Growth of Lycopodiella cernua (L.) Pic. Ser. and its Importance in the Generic Determination of the Species

The growth pattern of Lycopodiella cernua is described fromspecimens growing wild in Ghana. Vegetative propagation is bymeans of runner-like shoots rather than by horizontal creepingaxes as is usually quoted. Its growth is therefore orthotropic.Stem anatomy is shown to be consistently radially symmetricthroughout the plant which is consistent with orthotropism.The differing ideas of taxonomists in dealing with this speciesare discussed in relation to this new concept of orthotropismand radial symmetry. Lycopodiella cernua (L.) Pic.Ser., vegetative propagation, orthotropism, pteridophyta     

The effects of storage condition on starch metabolism and regeneration potentials of twin-scales and inflorescence stem explants of <Emphasis Type="Italic">Narcissus tazetta</Emphasis>

Summary The natural propagation rate of Narcissus is very slow. In vitro micropropagation of Narcissus is more efficient than conventional propagation for rapidly building up aseptic stocks of varieties, especially for the establishment of new cvs. and the production of pathogen-free stock material. In the present study, Narcissus tazetta cv. ‘Ziva’ bulbs were used as the source of mother plants. The bulbs were kept at 30°C in a dark chamber until the start of the experiments. Prior to explant preparation, the bulbs were subjected to a cold treatment at 15°C in the dark for 6 wk to break dormancy. Twin-scales and inflorescence stem discs were isolated from aseptic bulb parts and were used as the initial explants. The polar orientation affected the regeneration of the inflorescence stem. Storage duration at 30°C followed by cold treatment were found to affect starch levels, adenosine diphosphate glucose pyrophosphorylase (AGPase) activities, and regeneration potentials. Starch levels were reduced significantly during a 10 mo. storage period at 30°C in both twin-scales and inflorescence stem disc explants. Regeneration was followed by an efficient acclimatization system with 98–99% survival. More than 500 highly uniform young bulbs were propagated from one mother bulb in a 12 mo. period.     

<Emphasis Type="Italic">Mayaca fluviatilis</Emphasis> Aubl.: an ornamental aquatic with invasive potential in Sri Lanka

The ornamental aquatic plant industry in Sri Lanka has grown substantially during the last decade and there is a renewed demand for several exotic species. Mayaca fluviatilis, a submerged plant used in aquaria, is not recorded as a naturally occurring plant in Sri Lanka. However, recent studies recorded it in the wet zone of Sri Lanka and certain countries have recognized it as a problematic plant. The knowledge of the mode of propagation of invasive species is vital in the management of biological invasions. Therefore, the present study was conducted to investigate the propagation ability of vegetative parts of M. fluviatilis. A field survey was conducted in the wet zone of Sri Lanka, and populations of M. fluviatilis were monitored between 2006 and 2009. The propagation ability of different maturity stages of stem cuttings (terminal, middle and basal) were investigated, and terminal stem cuttings with five different lengths (2, 4, 6, 8 and 10 cm) were used to investigate the propagation ability of fragmented vegetative parts. Terminal shoots showed the highest survival rates and significantly high (P < 0.05) shoot and root lengths compared to middle and basal parts of the stem cuttings. In the other experiment with terminal stem cuttings with different lengths, all the stem fragments were capable of developing into a new plant. Increasing lengths of fragments was significantly related to the number of roots. Nevertheless, as even the 2-cm fragment was capable of developing into a new plant, removal of even the smallest fragments is necessary to control this plant. Submerged plants can spread easily through fragmentation and manual removal will likely increase its spread. Nevertheless, it is considered as effective for small infestations. Therefore, repeated removal of plant parts can be suggested as an ecologically sound management approach to prevent further spread of M. fluviatilis since it is in the early stage of establishment.     

Complementary patterns of stiffness in stem and leaf sheaths of Triticale

The variation in the stiffness of stem and leaf sheaths along the shoot axis of Triticale (Triticosecale W., cv. Jago) was examined, using an ultrasonic method, at two stages of development, (i) at the stage of high stem mechanical instability when upper internodes are forming (heading), and (ii) at milk maturity when development of strengthening tissues is completed (three weeks after anthesis). The squared velocity of low-frequency longitudinal pulse waves was used as a measure of the specific modulus of elasticity, averaged over the whole cross section of the structures and related to the unit density of the material. Structural material of varying effective stiffness was found to be utilized along leaf sheaths with a pattern complementary to that in growing stems. The stiffness increased basipetally along leaf sheaths in the direction of increasing flexibility of internodes. Maximum values of the specific modulus of elasticity in particular leaf sheaths were enhanced acropetally, ensuring the stronger mechanical protection of those meristematic zones which were actively elongating and were located at the upper internodes. The stiffest material present in leaf sheaths covered only those stem sections which could be the most critical for plant safety during stem elongation. This characteristic and very regular pattern of stiffness alteration along the shoot axis was structurally determined as it remained similar after air drying the specimens. It is concluded that adaptation of cereals to withstand environmental loads is realized not only on morphological and anatomical levels but is also reflected in a specific heterogeneity in the material properties of the cell walls which support the plant.This research was supported by the Ministry of Agriculture, Poland (Project CPBR 10.1 C 29).     

Clonal propagation,encapsulation and reintroduction of <Emphasis Type="Italic">Ipsea malabarica</Emphasis> (Reichb. f.) J. D. Hook., an endangered orchid

Summary Rapid clonal propagation and encapsulation of in vitro-formed bulbs of Ipsea malabarica (Reichb. f.) J. D. Hook., an endemic and endangered orchid of the Western Ghats of Kerala, and its reintroduction to the natural habitat were accomplished. Rhizome segments of Ipsea cultured on half-strength Murashige and Skoog (MS) medium supplemented with 6.97 μM kinetin induced the highest number of shoots, at the rate of four shoots per explant within 50 d. Transfer of the isolated shoots increased the rate of shoot multiplication to more than 10 shoots. Subsequent culture enhanced the number of shoots. No decline of shoot multiplication was observed up to the 10th subculture. Shoots developed bulbs during culture which developed into rhizomes. Sucrose at 6–8% reduced the time for the development of bulbs and rhizomes. Roots were developed from the base of the developed shoots as well as from the bulbs. Isolation and culture of bulbs also developed 5–10 shoots within 50 d. Encapsulated in vitro-formed bulbs cultured either on hormone-free halfstrength MS or 6.97 μM kinetin-supplemented medium facilitated 100% conversion. As a step to conservation in situ, 50 plantlets were reintroduced into their natural habitat, i.e. at Vellarimala (at 1300 m height) of the Western Ghats of Kerala, and flowered normally. Development of more than 40 000 plantlets starting from a single explant is possible within 250 d. This threatened endemic orchid stands to benefit greatly from the established protocol and will hopefully curtail the threat of extinction.     

The types of bioreactors used for shoots and embryos

Plant regenerated organs such as shoots, bulbs, microtubers, corms, embryos, etc. have been successfully proliferated in the bioreactor. The use of a bioreactor leads to the development of technology suitable for large scale plant propagation. The basic construction and characteristics of various types of bioreactor systems are reviewed in relation to shoot and embryo cultures. A pilot scale 500 liter bioreactor system was applied to the production of large scale Stevia rebaudiana shoots.Abbreviations DW dry weight - EC electrical conductivity - FW fresh weight - ORP oxidation-reduction potential     

新疆列当的种类、分布及其防治技术研究进展

列当是一种根寄生种子植物,是我国进境植物检疫对象,同时也是我国的内检对象。新疆是我国列当发生面积最大、危害最重和种类最多的地区,对新疆的主要经济作物,如加工番茄、向日葵、甜瓜等已造成严重危害。在新疆文献记载的列当种类有18种,常见的有埃及列当、大麻列当、向日葵列当和弯管列当,并已广泛分布于新疆各县、市、团场。列当的防治技术主要包括检疫、田间管理、轮作等,但目前的防治效果均不理想。本文通过对新疆列当的相关文献搜集、整理分析,总结了目前新疆列当的种类、分布情况,以及综合防治技术,为今后列当的研究和防治提供参考。     

Shoot dynamics of the giant grass Gynerium sagittatum in Peruvian Amazon floodplains,a clonal plant that does show self-thinning

The giant rhizomatous grass Gynerium sagittatum is an early successional species that forms dense monocultures in Peruvian Amazon floodplains. We studied the shoot population structures by recording shoot densities and shoot heights. Leaf areas and stem volumes were allometrically estimated. Stands of two varieties of G. sagittatum were examined that differ in height and in the degree of shoot branching. In stands of increasing age, marked decreases in shoot densities were accompanied with an increase in mean shoot size. Self-thinning was indicated by the negative correlation between log stem volume per unit ground area and log shoot density, significant at least for one of the two varieties. The difference in thinning slope between the varieties could be largely accounted for by their different shoot geometry, as was revealed by calculations based on the allometric model of Weller (1987b). The relationship between log leaf area per shoot and log shoot density was significantly negative with slopes close to –1. Shoot size inequalities decreased with increasing mean stem volume per shoot, probably as a result of density-dependent mortality of the smaller shoots. All of these results accord with expectations for shoot self-thining. Gynerium sagittatum is the first clear example of a clonal plant species that exhibits self-thining in natural monospecific stands. It is argued that self-thinning occurs in this giant tropical grass because its shoots are perennial and do not experience seasonal die-back (periodic density-independent mortality), in contrast to many of the clonal plant species that have been studies so far.     

Shoot Anatomy of Three Bulbous Species of Oxalis

The shoots of Oxalis latifolia, O. corymbosa and O. oxypteraare comprised of underground bulbs which send out stolons withapical and lateral bulbs. The external scales of the bulbs formthe base of the leaves; an adnation of the stipules to the petioleoccurs as well. In O. oxyptera the bulb shows primitive charactersand can be considered a rhizome-shaped bulb. Incipient secondarygrowth and schizo-lysigenous secretory cavities are described.An ascending evolutionary sequence of O. oxyptera, O. latifoliaand O. corymbosa is proposed based on the vegetative system. Oxalis spp., Oxalidaceae, shoot anatomy, bulb, stolons     

Solute fluxes from tobacco to the parasitic angiosperm Orobanche cernua and the influence of infection on host carbon and nitrogen relations

Orobanche species are holoparasites which are very efficient sinks for host-derived solutes. Here, we report the use of direct measurements of xylem sap solute concentrations and water fluxes, together with a modelling procedure to calculate element fluxes within an association between Orobanche cernua and its tobacco host. Infection of tobacco by the parasite markedly influenced carbon acquisition and partitioning; net fixation of carbon was 20% higher in infected tobacco compared with controls. Orobanche cernua caused a 84% increase in net carbon flux moving downward from the tobacco shoot and 73% of this carbon was intercepted by the parasite, almost entirely through the phloem (>99%). Further, the parasite also exerted a large impact on the nitrogen relations of the plant, notably nitrate uptake was stimulated and the amino acid content of xylem sap was lower. The parasite also relied heavily on host phloem for the supply of other resources, with only 5 to 15% of N, and 16% of K, 23% of Na, 63% of Mg and 13% of S being derived from the xylem. Thus, we provide quantitative information on the phloem dependency of the parasite and show that host carbon and nitrogen metabolism is stimulated as a consequence of infection.     

A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

In vitro propagation of the medicinal herbs Ocimum americanum L. syn. O. canum Sims. (hoary basil) and Ocimum sanctum L. (holy basil)

A procedure is outlined for in vitro propagation of two medicinal herbs, Ocimum americanum L. syn. O. canum Sims (hoary basil) and Ocimum sanctum L. (holy basil), using axillary shoot buds. Multiple shoot formation was induced from shoot bud explants of both species on Murashige and Skoog medium (MS) supplemented with benzyladenine (BA). The optimum BA concentrations for shoot proliferation were 0.25 mg/l for O. americanum and 1.0 mg/l for O. sanctum. Incorporation of 0.5 mg/l gibberellic acid (GA₃) along with BA in the culture medium resulted in a marked increase in the frequency of axillary branching as well as multiple shoot formation. Shoot buds collected between September through December were most responsive in culture. Shoots of O. americanum were rooted on half-strength MS supplemented with 1.0 mg/l indole-3-butyric acid (IBA), whereas O. sanctum rooted best on medium with 1.0 mg/l naphthaleneacetic acid (NAA). The plantlets were hardened off and successfully established in natural soil, where they grew and matured normally.Abbreviations BA N⁶-benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - MS Murashige and Skoog (1962) medium - NAA 1-naphthaleneacetic acid     

Differences in Shoot Size and Allometry between Two Evergreen Broad-Leaved Shrubs, Aucuba japonica Varieties in Two Contrasting Snowfall Habitats

Aucuba japonica , an evergreen broad-leaved shrub. Aucuba Japonica var. borealis is widely distributed in heavy snowfall areas in Japan and is covered, shaded and physically pressured by snow for more than four months of the year. On the other hand, var. japonica is widely distributed in light snowfall areas. The sizes of new shoots and leaves were significantly different between the two varieties with different critical shoot sizes for flowering. The average new shoot dry mass of var. borealis was about one third of that of var. japonica. Despite the differences in growing conditions and shoot size, no significant differences were observed in the allometry of their shoot organs between the two varieties. Large new shoots had thicker and longer stems per biomass than small shoots because of their larger pith volume. The large shoots showed higher efficiency of stem growth per invested biomass and had a higher rate of annual height increase than small shoots. When the size of new shoot rapidly increased from year to year, i.e. the plants are growing well, initiation of flowering was postponed and vegetative growth continued. Small new shoots were tolerant of low productivity conditions but traded vertical growth for an increase in matter allocation to leaves. Received 8 July 1999/ Accepted in revised form 1 September 2000     

Notizen zur Morphologie,Lebensdauer und Ökologie einiger kubanischer Monocotylen-Sippen

Field investigations show Tillandsia excelsa Griseb. (Bromeliaceae) to be a monocarpic perennial. The deceased, reflexed stem leaves of Copernicia torreana León (Arecaceae) which reach down to the ground are of ecological importance (protection against heat and drought). Oncidium usneoides Lindl. (Orchidaceae) is a terrestrial stoloniferous plant without bulbs.     

Seedling establishment,underground kinetics,and clonal reiteration: How do Potentilla inclinata and Inula ensifolia get their multifunctional subterranean systems?

The development of a seedling into an adult plant comprises various underground processes. Time-lapse photography (TLP) makes them visible. This is documented for Potentilla inclinata (Rosaceae) and Inula ensifolia (Asteraceae).After germination, P. inclinata develops a taproot system. Contraction phenomena pull the basal part of the shoot at least 10 mm into the soil. Later, several adventitious roots are generated, and thus the root system changes to a fibrous one. This is followed by cloning without separation of the ramets.Seedlings of I. ensifolia develop a weak primary root. At an early stage, adventitious roots are formed at the leaf rosette. This fibrous root system exerts a strong pulling effect on the shoot. After one vegetation period the basis of the rosette is approx. 30 mm under the soil surface. Cloning includes the formation of many new horizontal shoots, which conquer new sites.These two examples show three functional steps common in the developmental progress of subterranean systems: (I) establishment of the seedling, (II) innovation and survival of the young plant, and (III) reiteration (cloning and dispersal). However, to accomplish these basic development steps the diversity of subterranean systems is enhanced by different organographical components.Furthermore, the development of subterranean systems is a dynamic process consisting of two kinetic processes: the vertical movement during seedling establishment, which brings the innovation buds to a safe soil position, and the horizontal movement during dispersal, which conquers new sites.     

Bacterial inhibition of Orobanche aegyptiaca and Orobanche cernua radical elongation

The ability of different bacteria to inhibit Orobanche radical elongation was examined. Seeds of Orobanche aegyptiaca Pers. and O. cernua Loefl. were induced to germinate with the Growth Regulator GR24 in the presence or absence of test bacterium. Radical lengths were estimated microscopically on a scale relative to seed length (0–5 seed lengths) after 5 days of incubation at 25°C. The results indicated that Pseudomonas aeruginosa QUBC1, P. fluorescens QUBC3, Bacillus atrophaeus QUBC16, and B. subtilis QUBC18 significantly inhibited radical elongation (P≤0.01) of both O. aegyptiaca and O. cernua relative to control radicals, whereas Microbacterium hydrocarbonoxydans QUBC11 and Ochrobactrum anthropi QUBC13 showed less inhibitory effects. Other bacterial isolates had no inhibitory effects. Bacterial isolates were identified using the universal method in addition to morphological and biochemical features. The establishment of the inhibitory effect of the most promising isolates, B. atrophaeus QUBC16 and P. aeruginosa QUBC1 on radical elongation of both Orobanche spp. is a step towards utilizing such bacteria as biocontrol agents against O. aegyptiaca, O. cernua, and potentially other Orobanche species.     

Micropropagation of lily (Lilium longiflorum) via in vitro stem node and pseudo-bulblet culture

A protocol for micropropagation of Lilium longiflorum using pseudo-bulblets from in vitro shoot-tip-derived stem nodes was developed. Shoot tips from stems of dormant bulbs were cultured on one-half Murashige and Skoog (MS) medium. Stems from plantlets derived from the shoot tips were cut into nodal segments, which were then cultured on one-half MS medium supplemented with 1 μm 6-benzyladenine (BA). Pseudo-bulblets formed on each node after 1 month. An average of 32 pseudo-bulblets were formed on all nodes of the plantlet. Pseudo-bulblets gave rise to multiple shoots when cultured on one-half MS medium supplemented with 2.3 μm BA. Shoots were rooted on one-half MS medium containing 1.1 μm α-naphthaleneacetic acid. A continuous system of propagation by multiplication of pseudo-bulblets with no dormancy period was developed. The 80 flowering plants produced from shoot tip culture were acclimatized in the greenhouse for 3 months and then grown in the experimental garden for 8 months. Received: 29 October 1997 / Revision received: 28 April 1998 / Accepted: 3 May 1998