Single-node Fragments Research Articles

Clonal fragments of stoloniferous invasive plants benefit more from stolon storage than their congeneric native species

Plants with clonal growth may suffer from great fragmentation risk due to frequent disturbance. Meanwhile, storage capacity of clonal organs (stolon or rhizome) is important for survival and growth of clonal fragments. However, few studies have compared the difference in the regeneration capacity of clonal fragments between invasive clonal plants and congeneric native species. More studies between invasive plants and their congeneric native species are needed to provide insight into traits that contribute to invasiveness. Single-node fragments with stolon internode of different length were used to investigate the effects of stolon storage on survival and growth of three stoloniferous invasive plants (Wedelia trilobata, Alternanthera philoxeroides and Hydrocotyle vulgaris) and their congeneric native species (Wedelia chinensis, Alternanthera sessilis and Hydrocotyle sibthorpioides). Soluble sugar, starch and soluble protein contents of stolon internode per unit length were significantly greater in the three invasive plants than in their congeneric native species. During the experiment, regeneration of clonal fragments was not observed in A. sessilis. With increasing of stolon internode length, accumulative emergence rate of clonal fragments and biomass of their regenerated ramets significantly increased in the other five species. Accumulative emergence rate of clonal fragments and biomass of their regenerated ramets were significantly greater in invasive plant H. vulgaris than in its congeneric native species. A similar pattern was observed in the clonal fragments with stolon internode of long and medium length for Wedelia species pair. In the experiment, regeneration capacity of clonal fragments varied with species and stolon internode length. Clonal fragments of stoloniferous invasive plants benefit more from stolon storage than their congeneric native species. It is suggested that clonal storage may be an important trait for invasiveness of stoloniferous invasive plants. Therefore, intentional fragmentation should be carefully employed to manage stoloniferous invasive plants and avoid the dispersal of generative clonal fragments.

Micropropagation and Composition of Essentials Oils in Garden Thyme (Thymus vulgaris L.)

Thymus vulgaris L. is an important aromatic plant, because of the synthesis and production of its essential oils for the pharmaceutical and cosmetic industries. In this study, we developed a micropropagation protocol for T. vulgaris ‘Słoneczko’ and evaluated the potential of micropropagated plants for essential oil production with industrial application. The seeds were soaked for 10 min in 10% sodium hypochlorite (NaOCl) solution. Then, each seed was put into a 20 ml test tube filled with 5ml of Murashige and Skoog (MS) medium. Half of the cultures were subjected to light intensity which was maintained at 40 µEm−2s−1, and the other half was cultured in the dark. Shoot explants were multiplied in vitro using MS medium supplemented with BAP, 2iP or KIN. The results obtained indicate that the cytokinin which had the most positive impact on plant development at the multiplication stage was 5 mg dm−3 2iP. Single-node fragments of shoots cultured on MS medium without plant growth regulators were transferred to MS medium supplemented with IAA, IBA and NAA at concentrations of 0.2, 0.5, 1 and 2 mgdm−3. The best rooting of shoots was obtained on MS medium supplemented with 2 mgdm−3 IBA. The essential oils obtained by hydrodistillation in Deryng and Clevenger apparatus from in vitro shoot cultures of T. vulgaris L. were analysed using gas chromatography-mass spectrometry (GC-MS). Analysis revealed the presence of 54 components represented mainly by oxygenated monoterpenes (56.81-57.28%) and monoterpene hydrocarbons (31.90-33.72%). Among identified constituents, the most abundant were thymol (33.37-34.05%), γ-terpinene (11.62-11.91%), p-cymene (9.81-10.07%), carvacrol (5.63-5.96%), carvacrol methyl ether (3.86-3.87%) and linalool (3.16-3.36%).

Plant invasiveness is not linked to the capacity of regeneration from small fragments: an experimental test with 39 stoloniferous species

Fragmentation and vegetative regenera- tion from small fragments may contribute to popula- tion expansion, dispersal and establishment of new populations of introduced plants. However, no study has systematically tested whether a high capacity of vegetative regeneration is associated with a high degree of invasiveness. For small single-node frag- ments, the presence of internodes may increase regen- eration capacity because internodes may store carbohydrates and proteins that can be used for regeneration. We conducted an experiment with 39 stoloniferous plant species to examine the regeneration capacity of small, single-node fragments with or without attached stolon internodes. We asked (1) whether the presence of stolon internodes increases regeneration from single-node fragments, (2) whether regeneration capacity differs between native and introduced species in China, and (3) whether regener- ation capacity is positively associated with plant invasiveness at a regional scale (within China) and at a global scale. Most species could regenerate from single-node fragments, and the presence of internodes increased regeneration rate and subsequent growth and/or asexual reproduction. Regeneration capacity varied greatly among species, but showed no relation- ship to invasiveness, either in China or globally. High regeneration capacity from small fragments may contribute to performance of clonal plants in general, but it does not appear to explain differences in invasiveness among stoloniferous clonal species.

Aspects Regarding the In Vitro Culture and Ex Vitro Rooting in Vaccinium macrocarpon Cultivar 'Pilgrim'

Our paper presents aspects regarding in vitro culture initiation in cranberry ( Vaccinium macrocarpon ), cultivar `Pilgrim`, in vitro multiplication and ex vitro acclimation. In order to establish the optimal explant for initiation, several types of explants: single node fragments without leaves, single node fragments with leaves, two-node fragments without leaves, two-node fragments with leaves, multiple node fragments (3-4 nodes with leaves) and 1-1.5 cm long shoot tips were tested on media of the same composition (modified Woody Plant Medium). After testing the explant types, three variants of nutritive media were tested: WPM with three concentrations of 2-Isopentenyladenine: 5, 10 and 20 mg/l in order to induce the proliferation of axillary buds in the initiation phase. In the multiplication phase, several types of culture vessels were tested, as well as the optimal number of inocula/vessel and the influence of growth regulators upon multiplication rate. Among the variants of nutritive media that were tested, modified WPM containing either 1 mg/l zeatin or 5 mg/l 2-Ip presented reasonable proliferation rates and relatively well-developed shoots. In the in vitro layering experiment, 2-Ip at 10 mg/l generated tens of thin shoots/explant. As gelling agents, starch and Plant Agar were tested. Ex vitro acclimation was carried out in Jiffy7 pellets in either covered or uncovered plastic trays and various survival rates (17-92 %) were obtained depending on explant types and culture conditions.

Burial depth and stolon internode length independently affect survival of small clonal fragments.

Disturbance can fragment plant clones into different sizes and unstabilize soils to different degrees, so that clonal fragments of different sizes can be buried in soils at different depths. As a short-term storage organ, solon internode may help fragmented clones of stoloniferous plants to withstand deeper burial in soils. We address (1) whether burial in soils decreases survival and growth of small clonal fragments, and (2) whether increasing internode length increases survival and growth of small fragments under burial. We conducted an experiment with the stoloniferous, invasive herb Alternanthera philoxeroides, in which single-node fragments with stolon internode of 0, 2, 4 and 8 cm were buried in soils at 0, 2, 4 and 8 cm depth, respectively. Increasing burial depth significantly reduced survival of the A. philoxeroides plants and increased root to shoot ratio and total stolon length, but did not change growth measures. Increasing internode length significantly increased survival and growth measures, but there was no interaction effect with burial depth on any traits measured. These results indicate that reserves stored in stolon internodes can contribute to the fitness of the A. philoxeroides plants subject to disturbance. Although burial reduced the regeneration capacity of the A. philoxeroides plants, the species may maintain the fitness by changing biomass allocation and stolon length once it survived the burial. Such responses may play an important role for A. philoxeroides in establishment and invasiveness in frequently disturbed habitats.

Interference between sown grasses and the growth of rhizome of Elymus repens (couch grass)

Rhizome growth of Elymus repens (L.) Gould (couch grass) from single-node fragments on plots sown with six perennial grasses in a surrounding hexagonal mosaic was reduced by a factor of 10, compared with initially bare plots. The location of shoot complexes of E. repens after three seasons indicated that Arrhenatherum elatius and, to lesser extents, Agrostis stolonifera or Dactylis glomerata, prevented couch growth more than Holcus lanatus or Poa trivialis. Strips of sown grass at the edge of arable fields may therefore reduce the spread of couch grass into adjacent crops. Fertiliser application of 32 kg N ha −1 doubled the amount of couch rhizome. Mefluidide and paclobutrazol, plant growth regulators which might be used to manage sown grass, had minor effects on rhizome structure. D. glomerata did not spread from where it was sown and was largely uninvaded by other species.

Colonizing Ability of Ammophila Breviligulata Through Vegetative Regeneration

(1) Plants of Ammophila breviligulata grown from caryopses in a glasshouse allocated about 30% of their biomass to below-ground parts of which 8% were rhizomes bearing dormant buds. No biomass was allocated to sexual reproduction. (2) Plant populations expanded towards a lake by an advancing front of plagiotropic rhizomes. (3) Ice-thrust against the upper beach, violent storm waves and water currents destroyed the lakeward end of the population, fragmenting rhizomes into varying lengths and creating bare areas below the farthest inland reach of waves. (4) Fragmented rhizomes were dispersed by wave action and consequently served as sources of new plants on the driftline. The rhizome fragments occurring in greatest frequency contained two to five nodes. (5) Only a few of the buds on rhizomes growing in situ developed into new shoots. Severing of the rhizome into single-node fragments increased sprouting of buds. However, 76% of the sprouted buds aborted and the shoots failed to emerge from the soil.

Early Development of Johnsongrass

Tillering, flowering, and rhizome formation of johnsongrass(Sorghum halepense(L.) Pers.) started approximately 2 months after planting seeds or single-node rhizome fragments in the warm season. The minimum temperature for rhizome formation was between 15 and 20 C. Inflorescences were produced only from May to November. No causal relationship was found between flowering and rhizome formation. The bud activity of new rhizomes, as assessed by sprouting of single-node fragments, ranged between 48 and 100%. Sprouting was nil at 10 C, slow below 20 C, and maximum at 28 C. Seed germination required a temperature about 10 C higher than rhizome sprouting. While the initial leaf production of seedlings was more rapid than on plants produced from rhizomes, other differences in growth and development between seedlings and rhizome plants were of only limited practical significance.