Number Of Rhizomes Research Articles

Formación in vitro de rizomas en caña flecha (Gynerium sagitatum Aubl.) y recuperación de plantas

La caña flecha Gynerium sagitatum Aubl. (Poaceae) es una especie de gran importancia ambiental, cultural y económica para ciertas comunidades indígenas del Norte de Colombia, empleando su fibra en la fabricación apreciables artesanías. La cosecha de la planta y la no reposición de esta, viene contribuyendo en la disminución de poblaciones naturales de la esta especie. La micropropagación ha emergido como una de las la única posibilidades de producir de forma eficiente material vegetal para el establecimiento de cultivos y restaurar zonas afectadas. Con el fin de mejorar la eficiencia económica del protocolo de micropropagación, estructuras del tipo rizomas fueron inducidas in vitro a partir de explantes consistentes de plantas stablecidas in vitro bajo tres niveles de sacarosa, cuatro de benzilaminopurina – BAP y cuatro de ácido abscísico – ABA en MS con (en mg L-1) myo-inositol (100), tiamine HCL (0,4) y solidificados con Phytagel® (3.000). Los tratamientos (48) fueron distribuidos con un diseño completamente al azar con seis repeticiones por tratamiento. Los cultivos fueron mantenidos durante ocho semanas a 25 °C con 12 h de fotoperíodo (40 μmol fotones m-2 s-1) suministrada con lámparas de luz fría fluorescente. Diferencias estadísticas se observaron con respecto al número de rizomas formados y longitud de los rizomas como efecto de la interacción de los tres factores. La recuperación de las plantas ex vitro ocurrió en mayor número (6,0) cuando los rizomas se desarrollaron en medios suplidos con 263000 µM de sacarosa combinado con 4,44 y 8,88 µM de Benzilaminopurina – BAP. Los resultados evidencian la posibilidad de inducir in vitro rizomes de caña flecha para ser utilizados en conservación y propagación de esta especie.

Respuesta de la Cúrcuma (Curcuma longa L.) a la aplicación de un biofertilizante tratado con un campo magnético

Se evaluó la respuesta del desarrollo y la producción de la cúrcuma (Curcuma longa L.) a la aplicación de una mezcla en solución del bio-fertilizante Multibiol® y agua potable, tratada con una inducción de flujo magnético de 25 mT AC con una frecuencia de 60 Hz. Se utilizó un circuito de recirculación conectado a un solenoide. La solución se aplicó a una concentración de 1:12 durante tres meses a plántulas bajo condiciones de invernadero, en dosis de 0,25 L durante cinco minutos por plántula, cada siete días, obteniendo 10 dosis para todo el experimento. Se establecieron tres tiempos de exposición al flujo (7 ½, 15 y 30 min), además se contó con un testigo recirculado sin el solenoide (T) y un testigo absoluto sin recircular que usó agua potable únicamente (Ta). Se empleó un diseño unifactorial completamente al azar. Los resultados indicaron que la exposición al campo durante 7 ½ minutos generó diferencias estadísticamente significativas (P ≤ 0,05) en las variables de respuesta en comparación con los tratamientos T y Ta, superándolos, respectivamente, en 18 % y 40,1 % para la longitud de la planta; en 80 % y 98 % para el número de rizomas; en 50 % y 500 % para el número de macollos; 73,7 % y 217,4 % para la masa fresca y, finalmente, en un 70,1 % y 186,6 % para la masa seca. Los resultados indican que el riego con bio-fertilizante estimulado magnéticamente puede considerarse como una tecnología complementaria para aumentar la producción de C. longa.

The combined effects of sediment accretion (burial) and nutrient enrichment on the growth and propagation of Phalaris arundinacea

Sediment accretion (burial) and nutrient enrichment occur concurrently in lacustrine wetlands, but the role of these two aspects of sedimentation on macrophyte performance has rarely been examined. Here, we investigated the concurrent effects of sediment accretion and nutrient enrichment on the growth and propagation of Phalaris arundinacea L. using a factorial sediment burial by nutrient addition experimental design. Regardless of burial depth, nutrient addition increased biomass accumulation, shoot mass ratio, the number of rhizomes, and the length of ramets and rhizomes. While burial had little effect on plant growth and propagation, it had an interactive effect with nutrient addition on belowground growth and ramet production. These results indicate that P. arundinacea is tolerant to burial, which allows it to grow in habitats with high sedimentation rates. However, the enhanced growth and propagation of P. arundinacea following sedimentation were primarily related to nutrient enrichment. This suggests that nutrient enrichment of sediments, which occurs in many lacustrine wetlands, increases the risk of invasion by P. arundinacea.

Effect of straw mulch and integrated nitrogen management on yield and quality of turmeric under North Indian plains

The continuous application of nitrogen (N) through chemical source has shown deleterious effect on productivity of turmeric, whereas availability of organic source is very limited to meet the nitrogen requirement. Therefore it was considered worth to study the impact of integration of chemical and organic source of N on productivity of turmeric. A three-year field experiment was conducted at Punjab Agricultural University, Ludhiana, during 2011–12 to 2013–14 to study the response of turmeric to straw mulching and N applied through different combinations of organic manure (FYM) and N-fertilizer (urea). Application of paddy straw as mulch @ 6.25 t ha−1 significantly increased the plant height, number of tillers, mother, primary and secondary rhizomes, rhizome weight and yield of turmeric. The fresh rhizome yield increased by 85.0 and 34.9% during 2011–12 and 2012–13, respectively, due to mulch application over no-mulch. A slight improvement was noticed in curcumin content, however, the difference between mulch and no-mulch treatments was non-significant. Application of 125 kg N/ha through FYM alone, produced the highest rhizome yield during all study years (20.6, 22.36 and 23.17 t/ha during 2011–12, 2012–13 and 2013–14, respectively), which was, however, statistically at par with the application of two-third and half of organic manure along with one-third and half of N through urea, respectively. Nitrogen substitution through urea beyond 50% resulted into reduced growth and fresh rhizome yield. Hence, integration of 50% of N (62.5 kg/ha) through organic manure (FYM) and 50% of N through fertilizer urea enhanced the turmeric yield as compared to 100% N fertilizer alone. Quality parameter in terms of curcumin content did not show any significant differences with the different combinations of integrated nitrogen source.

IDENTIFIKASI VARIETAS TANAMAN KUNYIT MENGGUNAKAN SISTEM PAKAR

In Conjunction with the increasing of plant genetic resources development, the number of accessions of the turmeric plant is also increasing, making it difficult to differentiate between varieties, due to similar appearances. This research aimed to develop an expert system to identify the varieties of turmeric (Turina-1, Turina2, and Turina-3). Knowledge acquisition for building the expert system is performed in conjunction with an expert from the Indonesia Spices and Medicinal Research Institute. The knowledge acquisition process resulted in 13 input variables to describe a variety. The input inference process divides these 13 variables into two types: fuzzy and non-fuzzy. The non-fuzzy variables are: color of flowers, the base of leaf, and the flesh color of the rhizome which were used to decide whether the input description represents a Turina-1, Turina-2, Turina-3 variety or a non-variety. The remaining 10 fuzzy variables are: number of flowers per stem, plant height, number of tillers, leaf length, leaf width, rhizome weight per hill, number of parent rhizome, the number of primary roots, secondary roots and the levels of curcuma, which are used to determine whether the input description represents a Turina-1, Turina-2 or Turina-3 variety, using the Mamdani method for Fuzzy Inference System (FIS). In the testing phase, we used 100 data, which were already labeled according to the decision by the expert. The result shows that the system was able to correctly identify 89 of the input data.

Morphological plasticity in the rhizome system of Solidago gigantea (Asteraceae): Comparison of populations in a wet and a dry habitat

This study was motivated by the fact that although the plasticity of its above-ground organs is obvious in natural conditions and there are many data on the plasticity of Solidago’s rhizome system in glasshouse experiments, there are no data on below-ground plasticity under natural conditions. We compared the morphology of rhizomes in two, contrasting habitats. We found that rhizome system responded to environmental conditions: in the dry habitat, ramets developed more but shorter rhizomes compared to the wet habitat. The decrease in rhizome length can be explained by the decrease in the size of above-ground organs, but the increase of rhizome number cannot. The most important regulating factor of rhizome growth is probably its mechanical restriction by the root biomass of other species.

Effect of salinity on growth of the green alga Caulerpa sertularioides (Bryopsidales, Chlorophyta) under laboratory conditions

Background. Salinity, temperature, nutrients, and light are considered essential parameters to explain growth and distribution of macroalgal assemblages in coastal zones. Goals. In order to evaluate the effect of salinity on the growth properties of Caulerpa sertularioides, we conducted this study under laboratory conditions to find out how salinity affects the distribution of this species in coastal tropical environments. Methods. Five ranges of salinity were used for the experiments (15, 20, 25, 30, and 35 ppt), simulating in situ salinity conditions on the south Pacific Coast of Colombia. The culture was grown in an environmental chamber with controlled temperature and illumination, and a 12:12 photoperiod. The following growth variables were measured weekly: wet biomass, stolon length (cm), number of new fronds and rhizomes. In the experimental cultures, growth (increase in wet biomass and stolon length) was calculated as the relative growth rate (RGR), expressed as a percentage of daily growth. Results. Significant differences (p <0.001) were found between 15 ppt and the remaining treatments (20, 25, 30, and 35 ppt). The highest growth rates were recorded at 25 ppt (4.82 % d-1), while at 15 ppt, whitening and progressive deterioration of C. sertularioides fragments were observed. These results are consistent with the natural habitat of C. sertularioides in Tumaco Bay (Narino, Colombia), where it is found in areas with average salinities of 24 ppt during its annual cycle. Conclusions. The physiological responses obtained in this study will be valuable in exploring possible effects of environmental conditions on the growth and distribution of Caulerpa in tropical estuaries.

Hormone regulation of rhizome development in tall fescue (Festuca arundinacea) associated with proteomic changes controlling respiratory and amino acid metabolism.

Rhizomes are underground stems with meristematic tissues capable of generating shoots and roots. However, mechanisms controlling rhizome formation and growth are yet to be completely understood. The objectives of this study were to investigate whether rhizome development could be regulated by cytokinins (CKs) and gibberellic acids (GAs), and determine underlying mechanisms of regulation of rhizome formation and growth of tall fescue (Festuca arundinacea) by a CK or GA through proteomic and transcript analysis. A rhizomatous genotype of tall fescue ('BR') plants were treated with 6-benzylaminopurine (BAP, a synthetic cytokinin) or GA3 in hydroponic culture in growth chambers. Furthermore, comparative proteomic analysis of two-dimensional electrophoresis and mass spectrometry were performed to investigate proteins and associated metabolic pathways imparting increased rhizome number by BAP and rhizome elongation by GA3 KEY RESULTS: BAP stimulated rhizome formation while GA3 promoted rhizome elongation. Proteomic analysis identified 76 differentially expressed proteins (DEPs) due to BAP treatment and 37 DEPs due to GA3 treatment. Cytokinin-related genes and cell division-related genes were upregulated in the rhizome node by BAP and gibberellin-related and cell growth-related genes in the rhizome by GA3 CONCLUSIONS: Most of the BAP- or GA-responsive DEPs were involved in respiratory metabolism and amino acid metabolism. Transcription analysis demonstrated that genes involved in hormone metabolism, signalling pathways, cell division and cell-wall loosening were upregulated by BAP or GA3 The CK and GA promoted rhizome formation and growth, respectively, by activating metabolic pathways that supply energy and amino acids to support cell division and expansion during rhizome initiation and elongation in tall fescue.

Effects of the Number of Rhizomes and Storage Conditions on Flowering of Curcuma species

Effects of the Number of Rhizomes and Storage Conditions on Flowering of Curcuma species

Effects of different sediment type and burial depth on growth traits and biomass accumulation of Spartina anglica

Soils in salt marsh ecosystems have been undergoing certain changes including those related to sediment types and burial depths due to tidal activity and a variety of biotic factors. The changes in sediment type affect water-retaining properties, permeability and organic content while those in burial depth alter soil humidity, nutrition content, oxygen content, light intensity and temperature. Although many previous studies have focused on the effects of soil properties on plant growth and reproduction, few have explicitly tested the impacts of sediment type and burial depth on plants in salt marsh ecosystems. The exotic species Spartina anglica found in coastal China has been experiencing increased mortality over the past decade, however the mechanism of this mortality remains unclear. This study mainly focused on the effects of sediment type and burial depth on growth traits and biomass accumulation of S. anglica and was conducted under greenhouse conditions. The experiment included two types of sediments with clay and clay-sand mixtures (the volume of 1:1). Furthermore, four treatments were established with burial depths from 0 cm to one quarter of the plant height, one half of the plant height and three quarters of the plant height. Results indicated that clay increased leaf area, number of leaves, number of rhizomes, total length of rhizomes, rhizome mass and aboveground mass, while the clay-sand mixture led to an increase in the number of ramets, total mass, underground mass •研究报告• 1280 生 物 多 样 性 Biodiversity Science 第 24 卷 and root mass. All of the measures, except for leaf area, peaked at one half of the plant height burial treatment among all treatments. Overall, burial depth at one half of the plant height in clay was the most suitable combination for S. anglica. The results indicate that changes in sediment properties and subsequent changes in burial depth for S. anglica may assist with management of its populations over the species range.

Evaluation of different methods of turmeric (Curcuma longa L.) plantation

A study on different methods of turmeric (Curcuma longaL.) planting was carried out at farmers€ field of district Hoshiarpur to evaluate the growth and yield of turmeric. The mean length of turmeric rhizomes for T 1 (planting of turmeric manually at 30cm × 20cm spacing), T 2 (planting of turmeric manually at 45cm × 15cm spacing) and T 3 (planting of turmeric with semi-automatic potato planter at a spacing of 60cm × 15cm) after uprooting was 7.85cm, 7.91cm and 8.20cm, respectively while the mean diameter of turmeric rhizomes for T 1 , T 2 and T 3 after uprooting was 3.05cm, 2.64cm and 3.45cm, respectively. The number of rhizomes per kg for T 1 , T 2 and T 3 were 34, 30 and 24, respectively. The yield of turmeric rhizome was highest (130.0 q/acre) in T 3 which was 17.65 per cent and 8.33 per cent more as compared to T 2 and T 1 , respectively because the rhizomes were grown on ridges and the overall size of rhizomes was bigger.

Nutrient Effects on Belowground Organic Matter in a Minerogenic Salt Marsh, North Inlet, SC

Soil organic matter, roots, rhizomes, and carbon dioxide (CO2) emission rates were examined in minerogenic marshes of the North Inlet Estuary, a system dominated by sediment depositional processes and typical of the Southeast USA. Three marsh sites were sampled: a long-term nutrient enrichment experiment at Goat Island; the high marsh, low marsh, and creekbank of Crab Haul Creek, a fringing marsh that only receives drainage from a forested watershed; and three creekbank locations in Debidue Creek, which receives drainage from a residential and golf course development situated at its headwaters. Goat Island responses to 12 years of nutrient fertilization were an increase in soil organic matter (OM), an increase in number of rhizomes, enlarged rhizome diameters, and increased CO2 emission rates. At soil depths of 10–20 cm, all Debidue creekbank locations had significantly more rhizomes than the reference Crab Haul creekbank. The rhizome diameters at the mid and upper Debidue creekbank locations were significantly larger than the Debidue mouth and reference Crab Haul creekbank. The upper Debidue and the Crab Haul creekbanks had similar soil percent OM, which was significantly greater than the mid Debidue, which was greater than the Debidue mouth. CO2 emission rates at the fertilized Goat Island plots were similar in magnitude to the upper Debidue and significantly greater than the Goat Island control plots and the reference Crab Haul Creek. Inputs of sediment in marshes dominated by depositional processes may buffer the system from adverse effects of nutrient exposure, while increases in soil OM and rhizomes in response to nutrients may contribute to peat formation.

Photoperiod and Temperature Effects on Rhizome Production and Tillering Rate in Tall Fescue [Lolium arundinaceum (Schreb.) Darby.

ABSTRACTTemperature and photoperiod are key factors regulating plant growth and development. The objective of this study was to investigate the effects of temperature and photoperiod on tillering and rhizome formation in tall fescue [Lolium arundinaceum (Schreb.) Darby.]. Different genotypes were selected based on tillering ability and/or rhizome production. Plants were grown in growth chambers with a combination of different photoperiods and day/night temperatures: short photoperiod (9 h) and low temperature (day/night at 15/10°C) (SL), long photoperiod (18 h) and low temperature (LL), short photoperiod and high temperature (day/night at 25/15°C) (SH), and long photoperiod and high temperature (LH). The SL treatment resulted in significant increases in the number of tillers in the experiment and Genotype 1109 produced the maximum number of tillers. The number of rhizomes was increased under LL and LH conditions in three clonal lines. Our results suggested that the responses of tiller and rhizome development to temperature and photoperiod varied with genotypes; in addition, longer photoperiod appeared to promote rhizome formation, regardless of temperature, whereas lower temperature stimulated rapid tiller production in some genotypes of tall fescue. This study will help to determine the performance of tall fescue under the longer/shorter photoperiod and variable temperature conditions in different parts of United States.

Responses of rhizomatous grass Phragmites communis to wind erosion: effects on biomass allocation

The ability of modifying biomass allocation to deal with different environmental stress is an important mechanism for plant population expansion and maintenance in the unstable dune environment where wind erosion persists. However, how biomass is partitioned between horizontal rhizome extension and vertical ramet growth in response to wind erosion has not been fully understood. The objective of this study was to explore how wind erosion affected the relationship between horizontal rhizome extension and vertical ramet growth using a common rhizomatous perennial grass, Phragmites communis. We dug 300 cm × 200 cm, 80 cm deep pits in a garden experiment plot. Clonal fragments of P. communis were planted individually at a depth of 40 cm in these pits for 4 weeks before treatments. Surface sand was gradually removed to the final depth of 0 (control), 10, 20, 30 and 40 cm (maximum sand removal). Ramet emergence time, rhizome-based and tiller-based ramet number, rhizome number and length, biomass of vertically and horizontally oriented structures were monitored at the end of the experiment. With increasing erosion depth, the proportion of tiller-based ramets (in total number of ramets) increased, whereas that of rhizome-based ramets decreased. With increasing erosion depth, the percentage of vertically oriented structures biomass in total biomass increased significantly, whereas that of horizontally oriented structures biomass decreased. The changes in biomass allocation (i.e., more allocation in vertical than horizontal biomass) together with a trade-off in tiller-based and rhizome-based ramets may enable P. communis to make better use of the resources in erosion conditions and maximize plant population expansion and maintenance.

Performance ofCostus speciosus(Koenig) Sm. genotypes under Bastar plateau agro-climatic zone of Chhattisgarh

An experiment was conducted at Jagdalpur, Bastar, Chhattisgarh during Kharif season of 2011 to evaluate the growth and yield performance of different entries of Costus speciosus (Koenig) Sm. commonly called as Kewkand. The experiment was laid out in RBD with three replications and twelve treatments comprising of twelve genotypes. Maximum plant height, number of leaves per plant, inter-nodal length and number of flowering plants per hill was observed in entry IC-542329. The results indicated that maximum number of tillers per hill was observed in entries IC-542327, IC-542328, IC-542330 and IGKK-1. Higher values for leaf length (29.63 cm), leaf width (10.30 cm) and flower length (18.10 cm) were recorded in entry IC-542330. Entry IC-542327 was observed to have maximum flower diameter, number and girth of rhizomes as well as highest total rhizome yield. However, entry IGKK-1 had at par values with entry IC-542327 for length of side rhizomes, number of rhizomes and total rhizome yield. No significant difference among the genotypes was observed for weight of 100 seed weight which ranged from 1.69–1.71g.

Effect of Acute Gamma Irradiation onCurcuma alismatifoliaVarieties and Detection of DNA Polymorphism through SSR Marker

The effects of eight different doses (0, 10, 20, 25, 35, 40, 60, and 100 Gy) of acute gamma irradiation on 44 (three varieties of Curcuma alismatifolia: Chiang Mai Red, Sweet Pink, Kimono Pink, and one Curcuma hybrid (Doi Tung 554) individual plants were investigated. Radiation sensitivity tests revealed that the LD50 values of the varieties were achieved at 21 Gy for Chiang Mai Red, 23 Gy for Sweet Pink, 25 Gy for Kimono Pink, and 28 Gy for Doi Tung 554. From the analysis of variance (ANOVA), significant variations were observed for vegetative traits, flowering development, and rhizome characteristics among the four varieties of Curcuma alismatifolia and dose levels as well as the dose × variety interaction. In irradiated plants, the leaf length, leaf width, inflorescence length, the number of true flowers, the number of pink bracts, number of shoots, plant height, rhizome size, number of storage roots, and number of new rhizomes decreased significantly (P < 0.05) as the radiation dose increased. The cophenetic correlation coefficient (CCC) between genetic dissimilarity matrix estimated from the morphological characters and the UPGMA clustering method was r = 0.93, showing a proof fit. In terms of genetic variation among the acutely irradiated samples, the number of presumed alleles revealed by simple sequence repeats ranged from two to seven alleles with a mean value of 3.1, 4.5, and 5.3 alleles per locus for radiation doses of 0, 10, and 20 Gy, respectively. The average values of the effective number of alleles, Nei's gene diversity, and Shannon's information index were 2.5–3.2, 0.51–0.66, and 0.9–1.3, respectively. The constructed dendrogram grouped the entities into seven clusters. Principal component analysis (PCA) supported the clustering results. Consequently, it was concluded that irradiation with optimum doses of gamma rays efficiently induces mutations in Curcuma alismatifolia varieties.

Propagation in vitro of alstroemeria ligtu hybrid through direct organogenesis from leaf base

ABSTRACT In the present study, multiplication efficiency of Alstroemeria ligtu hybrid was investigated. Bases of the first seedling leaves grown in vitro were used as initial explants. The explants were cultured in the MS media containing 3% sucrose, 0.7% agar at pH 5.8, five N6-benzylaminopurine (BAP) concentrations (0, 0.5, 1, 1.5 and 2 mg·1-1) and three indole-3-butyric acid (IBA) concentrations (0, 0.1 and 0.2 mg·1-1). The cultures were incubated at 21 ± 2 °C under photoperiod 16/8. After three subculturings (3 weeks-long each) the number of rhizome, shoots, buds, leaves, and roots, length of shoots and roots were recorded. Adventitious shoots formed directly on the leaf bases without callus intervention. Their number was affected by BAP concentrations. The highest shoots number, six per explants, was obtained at 1 mg·1-1 BAP and 0.1 mg·1-1 IBA. The shoot length decreased with the increasing concentration of BAP. The highest root number (2.7) was formed on shoots cultured on the MS medium containing 0.5 mg·1-1 α- naphthalene acetic acid, and the highest rhizome number (2.2) was formed on the medium with 0.5 mg·1-1 BAP. In vitro rooted plantlets were able to survive and acclimatize in the greenhouse.

Effects of Summer Nocturnal Warming on Biomass Production of Leymus chinensis in the Songnen Grassland of China: From Bud Bank and Photosynthetic Compensation

AbstractNocturnal warming has various effects on plant biomass production. To understand how biomass production of the dominant grassland species Leymus chinensis responds to summer nocturnal warming in the eastern temperate Eurasian steppes, we simulated summer nocturnal warming (+4 °C) using a phytotron system for 100 days operated based on the variation of diurnal temperatures over the past 12 years in the Songnen Grasslands. Our results show summer nocturnal warming significantly increased above‐ground biomass production of parent and daughter shoots as well as increased below‐ground root and rhizome biomass production; rhizome biomass increased faster than root biomass leading to an increase in the rhizome biomass to root biomass ratio. Nocturnal warming slightly increased the number of daughter shoots per plant, and significantly increased the number of buds in the below‐ground bud bank and the number and length of rhizomes per plant. Also, the dark respiratory and net photosynthetic rates, Jmax, the rate of triosephosphate utilization and chlorophyll fluorescence parameters (ΦPSII and qP) were significantly higher under nocturnal warming conditions. These findings show that nocturnal warming in this ecosystem improves individual biomass accumulation due to photosynthetic compensation, and may enhance the population density and productivity of L. chinensis by increasing bud number in the below‐ground bud bank during the early stage of ecological succession for grasslands dominated by L. chinensis.

Elucidating the Population Dynamics of Japanese Knotweed Using Integral Projection Models

Plant demographic studies coupled with population modeling are crucial components of invasive plant management because they inform managers when in a plant’s life cycle it is most susceptible to control efforts. Providing land managers with appropriate data can be especially challenging when there is limited data on potentially important transitions that occur belowground. For 2 years, we monitored 4 clonal Japanese knotweed ( Polygonum cuspidatum ) infestations for emergence, survival, shoot height until leaf senescence, dry shoot biomass after senescence, and rhizome connections for 424 shoots. We developed an integral projection model using both final autumn shoot height and shoot biomass as predictors of survival between years, growth from year to year, and number of rhizomes produced by a shoot (fecundity). Numbers of new shoots within an infestation (population growth rate λ) were projected to increase 13-233% in a year, with the greatest increase at the most frequently disturbed site. Elasticity analysis revealed population growth at 3 of the 4 sites was primarily due to ramet survival between years and to year-to-year growth in shoot height and shoot biomass. Population growth at the fourth site, the most disturbed, was due to the large production of new rhizomes and associated shoots. In contrast to previous studies, our excavation revealed that most of the shoots were not interconnected, suggesting rhizome production may be limited by the size or age of the plants, resource availability, disturbance frequency, or other factors. Future integration of plant population models with more data on belowground growth structures will clarify the critical stages in Japanese knotweed life cycle and support land managers in their management decisions.

Colonization and infestation ability of Bolboschoenus maritimus Palla in rice paddies of the Camargue, France

Bolboschoenus maritimus is one of the major weed constraints for irrigated rice‐cropping systems in the Camargue, France. This perennial plant propagates mainly through the production of numerous tubers. Observations in both controlled conditions and on‐field studies were used to enhance the level of knowledge of the biology, functioning and infestation dynamics of B. maritimus, with a view to rationalize weed control practices. It was found that B. maritimus displayed a great potential to produce a large number of shoots, rhizomes and tubers. Its propagation in the field plots depended on the initial weed density and its spatial colonization did not show any preferred direction (isotropic). Further observations that were made in the paddy fields showed an interaction between the different cultural practices that were tested and the infestation dynamics of B. maritimus. Efficient control of B. maritimus infestation in the field should make use of the data reported here, based on three levels: (i) prevention of weed stem proliferation during the cropping season with specific herbicides; (ii) elimination of the tubers after the rice crop; and (iii) reduction of the tuber‐germinating ability.