Stolon Production Research Articles

Seasonal Changes in Morphology and Physiology of Roughstalk Bluegrass

ABSTRACTRoughstalk bluegrass (Poa trivialis L.) (RBG) is a weed in many turf settings because it often thins, goes dormant, or dies with increasing summer temperatures. Morphology and physiology of RBG are not well understood. Our objective was to describe morphological differences and physiological changes in shoots and stolons of RBG and creeping bentgrass (Agrostis stolonifera L.) (CBG) during the growing season in Indiana. The study evaluated three grasses (‘L93’ CBG and ‘Laser’ and ‘Pulsar’ RBG) over nine harvests from field plots between April and October of 2008 and 2009. Turf quality and percent cover were consistently higher for CBG compared to RBG. However, mild summer temperatures in 2008 and 2009 likely resulted in minimal separation between RBG cultivars. Stolon production began in May for RBG and CBG after planting in August of the previous year. Specific stolon dry weights (mg cm−1) of RBG doubled compared to L93 during peak summer stress in August. Total nonstructural carbohydrate (TNC) concentration of RBG shoots decreased 26% while TNC in stolons remained unchanged. Additionally, protein and amino acid concentrations increased in stolons and decreased in shoots of RBG during summer stress, further supporting our hypothesis that stolons act as storage organs during high temperatures. Conserving protein and carbohydrates in stolons at the expense of shoots until high temperature stress subsides may be a stress tolerance mechanism of RBG.

Reproductive Versatility and the Epigenetic Control of Female Gametogenesis

Each year, plants and animals perform the task of repopulating the planet through patterns of courtship and mating that have a unifying and compelling logic: the production of offspring. Although life of nearly all organisms is organized around sex and breeding, Darwinian thinking focused more on the struggle for existence than on evolutionary significance of this frantic race to reproduce. In Darwin's own words, "We do not know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements. The whole subject is hidden in darkness…" (Darwin 1862). In plants, a major consequence of this search for survival is the evolution of a multitude of reproductive alternatives that have intrigued botanists, geneticists, and evolutionary biologists for more than 100 years. Because sexually derived genetic diversity is interpreted as essential for adaptation, it is often thought that sex is necessary for the perpetuation of a species; however, many organisms--including several hundred families of flowering plants--are going efficiently about propagating their kind without bothering with meiosis and mating. Whereas many plants can undergo vegetative propagation, through the production of stolons, bulbs, or rhizomes, for example, many others have developed methods to produce an embryo from a single cell whose nucleus is not formed by the fusion of two gametes, offering a direct developmental and evolutionary challenge to sexual reproduction. Recent evidence suggests that epigenetic mechanisms that control transcriptional silencing of DNA repetitive elements and heterochromatin are crucial for the acquisition of cell identity in the ovule, opening the possibility that the developmental distinction between sexual development and apomixis might have evolved as an adaptive response to evolutionary forces that modulate structural variation and reproductive versatility in flowering plants.

Mixed-Mating Strategies and their Sensitivity to Abiotic Variation in Viola Lanceolata L. (Violaceae)~!2010-04-09~!2010-06-08~!2010-09-15~!

Mating-system expression is sensitive to environmental conditions, and can be an important determinant of lifetime fitness because progeny that are produced via outcrossing vs. selfing may differ in quality. We quantified sexual and asexual reproduction in Viola lanceolata, a regionally threatened species, across populations that varied in disturbance history and across microsites that differed in percent soil moisture, irradiance, and temperature. In V. lanceolata, reproduction can occur sexually through facultatively outcrossing chasmogamous (CH) flowers and obligately selfing cleistogamous (CL) flowers in addition to asexually via stolons. The frequency of individuals producing CH and CL flowers differed among sites as did the frequency of vegetative reproduction. Interestingly, sites also differed in fruit maturation success, with ~33, 100, and 16% of the CH fruits matured in the oldest, intermediate, and most-recently disturbed populations respectively. Analogous site differences in CL fruit maturation were observed. Cleistagamous, but not CH, reproduction was also dependent on percent soil moisture. The observed differences in fruit maturation success likely lead to variable rates of outcrossed vs. self-fertilized seed production; as a consequence, populations are likely to differ in genetic structure and in relative dependence on chasmogamy vs. cleiostogamy for population growth. Finally, CL flower and stolon production were negatively correlated, suggesting a tradeoff between sexual and asexual reproduction that might affect population growth.

Growth-promotion of strawberry plants inoculated with Azospirillum brasilense

Azospirillum brasilense (strains REC3, RLC1, PEC5) were root inoculated in strawberry plants of the cultivars 'Milsei', 'Selva' and 'Camarosa' to assess plant growth-promoting effects. The bacteria were able to pro- mote plant growth (expressed as root length, root area, and dry weight of root and shoot), depending on the genotypes of plants and bacteria used, whereas the stolon production (3-4) depended only on the strawberry cultivar. To explain whether root exudates plays any role on the growth-pro- motion observed herein, total protein and sugar were determined, and chemotaxis properties were evaluated. The strains showed positive chemotaxis toward the root exu- dates, being influenced by the total sugars content, sug- gesting that the latter plays an important role in the chemotaxis effect and may contribute to enhance the root capacity to recruit azospirilla from rhizosphere, thus improving the growth-promoting effect exerted by these bacteria.

Evaluation of Zoysiagrass Genotypes for Shade Tolerance

Establishing turfgrass in shaded environments can create a unique maintenance challenge. Shading reduces zoysiagrass (Zoysia spp.) photosynthesis and results in reduced turfgrass aesthetic quality. Zoysiagrass is a warm-season, perennial turfgrass that forms a dense, uniform turf through the production of rhizomes and stolons. It has demonstrated good tolerance to growth in reduced light intensity environments. Greenhouse experiments were conducted in 2006 and 2007 to evaluate the relative difference in growth response to three light intensities (0%, 50%, and 90% shade) among six zoysiagrass genotypes under artificial shade conditions. Percent change in zoysiagrass plug diameter decreased as shade level increased 6 and 12 weeks after planting (WAP) regardless of year or genotype. ‘Diamond’ and ‘Shadow Turf’ exhibited the greatest percent change in plug diameter 12 WAP (60% to 69%) followed by the remaining zoysiagrass genotypes (21% to 56%) when grown under 50% shade, regardless of year. In 2006, no zoysiagrass genotype maintained acceptable turfgrass quality (6 or greater) 12 WAP when grown under 50% shade. However, ‘Diamond’ and ‘Shadow Turf’ exhibited acceptable turfgrass quality ratings (7.0 and 6.3) 12 WAP in 2007, whereas all other genotypes exhibited unacceptable turfgrass quality ratings (5.0 to 5.7). In 2006, ‘Shadow Turf’ zoysiagrass exhibited the greatest percent increase in plug diameter (21%) followed by ‘DALZ 0501’ (15%) and ‘Diamond’ (5%) 12 WAP when grown under 90% shade. All other zoysiagrass genotypes exhibited decreases in plug diameter (31% to 87%). In 2007, ‘Shadow Turf’ and ‘Diamond’ exhibited the greatest percent change in plug diameter (11%) followed by ‘DALZ 0501’ (7%) 12 WAP when grown under 90% shade. All other zoysiagrass genotypes exhibited decreases in plug diameter (17% to 38%). Turfgrass quality declined as shade level increased 6 and 12 WAP regardless of year or genotype. ‘Shadow Turf’ and ‘Diamond’ exhibited the highest turfgrass quality ratings (4.7 and 3.7, respectively, in 2006 and 5.3 in 2007) 12 WAP when grown under 90% shade. Proper zoysiagrass cultivar selection may improve turfgrass growth and quality under low light intensity while increasing turfgrass options for shaded environments.

Synchronization of tuber formation in potato grown in vitro by cell division synchronization in axillary meristems of stem explants

Optimization of in vitro tuberization (formation and growth of stolons and microtubers) by synchronization of cell divisions in axillary meristems of initial stem explants induced by low nonfreezing temperatures was studied in potato (Solanum tuberosum L., cv. Lugovskoi) plants. The proportion of simultaneously dividing cells in axillary meristems of stem explants subjected to 2-h cold treatment at 4°C was in 2.6 times greater than in control material (without chilling). The analysis of growth of stolons and microtubers produced from the explants exposed to cold showed that synchronization of cell divisions in the meristems of initial explants resulted in synchronization of stolon and microtuber formation and production of microtubers of identical physiological age.

The Biology of Invasive Alien Plants in Canada. 10. Nymphoides peltata (S. G. Gmel.) Kuntze

The freshwater aquatic species Nymphoides peltata has been introduced to Canada as an ornamental plant and has been found at sites in Newfoundland, Nova Scotia, Quebec, Ontario and British Columbia. It is currently available through the aquatic nursery trade in Canada and the United States. It may be considered as adventive in Canada since populations readily expand beyond the site of planting, but there is no evidence as yet that it is fully naturalized. In the United States it has naturalized in still or slow-moving waters at widely scattered locations where it replaces native plant communities, changes ecological processes and interferes with human navigation and recreational activities. The short rhizomes over-winter under Canadian conditions, even when complete water drainage results in freezing of the substratum. In its native range, the species has two floral morphs (i.e., is distylous) with a weak incompatibility system, but North American populations usually consist of a single flower morph. A population at Ottawa, ON, has monomorphic flowers with characteristics overlapping between the two Eurasian morphs and has been observed to produce large numbers of viable seeds. Seeds germinate in the spring either on the substratum in shallow water or at the water surface. Seedlings germinating at the water surface may float for several weeks prior to sinking and establishing on the substratum in shallow water. Vigorous stolon production promotes rapid colonization, and vegetative dispersal is readily accomplished through fragmentation of stolons and stems. Key words: Nymphoides peltata, yellow floating-heart, Menyanthaceae, faux nénuphar, NYPPE, weed biology

Biology and Control of Creeping Rivergrass (Echinochloa polystachya) in Rice

Rice was planted at 78 kg/ha with different densities of creeping rivergrass. Creeping rivergrass at stand densities (SD) of 10,000 to 70,000 stolon segments/ha produced 5.4 to 6 stolons per introduced segment; however, 130,000 through 520,000 SD produced 1.4 to 2.1 stolons per segment. Stolon production was 60,000 plants/ha and increased to 760,000 stolons/ha at planting densities of 10,000 to 520,000/ha, respectively. The 260,000 and 520,000 SD produced similar stolon lengths of 217 and 318 km/ha; however, stolon length was less at lower SD. Total node production was 290,000 nodes per ha with an average of 29 nodes per segment in the 10,000 SD and 5.4 to 9.8 nodes per segment with 70,000 or greater SD. Total biomass increased as SD increased. Creeping rivergrass shoot emergence from soil was 31, 63, 44, and 25% for segments planted at 0, 1.3, 2.5, and 5 cm deep, respectively. In a greenhouse study, glyphosate at 1,260 g ai/ha controlled creeping rivergrass 91% and biomass production was 19% of the nontr...

Enhancing Native Grass Productivity by Cocultivating With Endophyte-Laden Calli

The influence native endophytes have on grass establishment and productivity was evaluated by cocultivating Bouteloua eriopoda (Torr.) Torr. (black grama) or Sporobolus cryptandrus (Torr.) Gray (sand dropseed) seedlings with endophyte-laden calli from three of four native grass and shrub species: Atriplex canescens (Pursh) Nutt. (fourwing saltbush), S. cryptandrus, Sporobolus airoides (Torr.) Torr. (alkali sacaton), and B. eriopoda in vitro. Following cocultivation, grass seedlings were hardened and transferred to three replicate field plots, each containing 16 grass plants of a single species that had been cocultivated with a single callus species. Plant establishment rates, heights, crown diameters, aboveground biomass, seed yields, and seed quality were compared. In B. eriopoda (black grama), significant increases in plant biomass were not observed. However, early plant heights and crown diameters, establishment rates, and stolon production were higher in some callus treatments. In S. cryptandrus (sand dropseed), all variables were positively influenced by one or more of the endophyte treatments. Biomass increases ranged from 2.5- to threefold over untreated plants, and harvested seed increased 5.9-fold in plants treated with endophytes from A. canescens (fourwing saltbush). Seed quality, determined by purity, germination rates, and tetrazolium assays, did not differ across endophyte treatments for either grass. There is evidence that endophyte transfer is responsible for the altered vigor of treated plants.

Strawberry production from transplants fumigated with methyl bromide alternatives

Research aimed at finding alternatives to methyl bromide has tended to focus on strawberries, since this crop is the largest methyl bromide consumer in Spain, pre-plant soil fumigation with methyl bromide, or with mixtures of methyl bromide and chloropicrin, are standard practices for controlling soil-borne diseases. Methyl bromide, however, has been phased out due to its environmental risks except for critical use exemptions. Soil fumigants were evaluated as alternatives for methyl bromide soil fumigation at two high-elevation strawberry nurseries in Spain. Strawberry plants produced at high elevation nurseries were evaluated for fruit yield at two commercial fruit production sites. All fumigation treatments had higher stolon production than plants grown in non-fumigated soil. The results indicate that pre-plant soil treatment with chloropicrin alone or 1,3-dichloropropene plus 35% chloropicrin could be potential alternatives to methyl bromide for soil treatment at high-elevation strawberry nurseries in Spain.

Clonal performance of perennial Oryza sativa/ O. rufipogon selections and their combining ability with O. sativa cultivars for survival, stolon production and yield

In Southeast Asia, upland rice ( Oryza sativa) is an annual crop typically grown for subsistence on hilly lands that are at risk for soil erosion. If perennial cultivars of upland rice were developed, they would provide farmers with an inexpensive tool to produce a preferred food while conserving soil. O. rufipogon, the undomesticated progenitor of O. sativa, includes perennial and stoloniferous forms. To evaluate the feasibility of developing perennial cultivars by combining genes of O. sativa and O. rufipogon, four trials were conducted in an upland field at IRRI: O. sativa/ O. rufipogon F 1 clone and cutting height trial, F 2 family trial, and two O. sativa/stoloniferous-selection factorial mating design trials. Plants were established at the beginning of the rainy season, then subjected to a 6-month dry season and evaluated for survival after 1 year. Of the 2101 cultivar control plants, only three IR47686-1-4-B individuals survived and none produced stolons. The 18 F 1 clones, which were selected from previous trials with less drought stress, ranged in survival from 4.4 to 91.4%. Cutting height at harvest did not affect survival. Survival among the F 2 families ranged from 9.4 to 31.9%. Segregation for stolon presence did not differ from a 3:1 ratio for five of the six F 2 families, suggesting the effect of a single dominant gene. Average yields per plant for the F 2 families were 1/3 to 1/9 of yields for the cultivars. However, by crossing the F 1s to cultivars, yield potential was almost fully recovered. For the full-sib families of the factorial trials, survival ranged from 0.0 to 48.6%. Azucena and IR47686-1-4-B, both japonica cultivars, exhibited greater general combining ability for survival relative to the six other cultivar parents. Thus, the process of developing perennial cultivars of rice should include screening annual cultivars to identify those with the best combining ability for survival. To develop cultivars of perennial upland rice, drought avoidance and/or tolerance from annual upland cultivars must be combined with the capacity for perennial growth from wild perennial species. The frequency of stolonifereous testcross progeny was lower than expected and was affected by the O. sativa parent. Thus, additional genes likely affected stolon penetrance and expression. Analyses of covariance indicated that stolons improved the likelihood of survival for progenies of the factorial trials but the effect was small ( b < 0.1), and that yield (g/plant) had a small negative effect on percent survival ( b = −0.13 to −0.32). This study demonstrated that it was possible to introgress genes for perennial growth from wild O. rufipogon accessions into domesticated O. sativa. Additionally, strategies for developing perennial cultivars of upland rice were improved.

The relative importance of sexual and clonal reproduction for population growth in the long‐lived alpine plant Geum reptans

Summary Demographic studies in natural habitats are important for understanding the life history and mechanisms of population persistence of particular species. For plants living in high‐alpine habitats, it is of significant importance to what extent sexual or clonal reproduction contribute to population growth, but respective data are scarce. We studied the demography of Geum reptans, an alpine plant which reproduces by seeds and by vegetative rosettes formed at the ends of above‐ground stolons. In three consecutive years, growth, survival, and reproduction were measured in two populations with 579 and 301 individuals, respectively. The two resulting transition matrices per population were used to calculate population growth rates (λ) and elasticities, and to perform stochastic simulations to assess the relative importance of sexual vs. clonal reproduction for population growth. Population growth rates (λ) varied from 0.999 to 1.074 among years and populations. The frequency of seed and stolon production was relatively constant over the years. However, there was interannual variation in seed germination (0.7–2.4%) and in establishment of clonal offspring (53–74%). Elasticity analysis showed that changes in the survival of adults had the largest effect on λ, confirming the importance of longevity and persistence in the life history of G. reptans. Stochastic simulations showed that in G. reptans, independently of location and year, both sexual and clonal reproduction did not significantly differ in their contribution to the population growth rate λ. Establishment from seeds contributes to population growth particularly in favourable years, while the more regularly occurring reproduction by clonal offspring may ensure population growth in less favourable years. Sexual reproduction in clonal plants is frequently explained by the short‐ and long‐term benefits of genetic variation and the need for dispersal and colonization, for which seeds are better suited than vegetative organs. Our results, however, show the importance of sexual reproduction in a clonal plant for local dynamics as well, and prove the power of matrix models to evaluate the relative contributions of the two reproductive modes.

Private Strawberry Breeders in California

Private Strawberry Breeders in California

Fitness Implications of Clonal Integration and Leaf Dynamics in a Stoloniferous Herb, Nelsonia canescens (Lam.) Spreng (Nelsoniaceae)

Very little has been published on the life-history significance of clonal plants inhabiting southern African savanna environments. This study investigated the fitness implications of clonal integration, resprouting behaviour and growth phenology in a stoloniferous herb, Nelsonia canescens (blue pussyleaf) at a savanna site in Zambia, central Africa. Census data on growth and survival were obtained regularly on permanently marked ramets over a 4-year period, from 2001 to 2005, and analyzed to assess how physiological integration and module demography contribute to fitness in Nelsonia. Above ground and below ground growth occurred during the dry and rainy seasons, respectively. Dry season growth was characterized by resprouting and production of stolons that bore small pubescent leaves with high mortality (30–80% month−1). Deep roots and high leaf turnover appear to contribute to sustained growth during the dry season when topsoil moisture and nutrient availability are low. The interaction between maximum temperature and precipitation explained a significant proportion (59%, p<0.01) of the monthly variation in leaf size and increasing evapo-transpiration levels appeared to trigger the shift in leaf size from a large wet season type to a small dry season one. During the dry season Nelsonia resprouted from dormant buds buried at the time of root development in daughter ramets in the rainy season. Temporal integration significantly (p<0.05) enhanced survival of daughter ramets. However, daughter ramets with severed mother–daughter ramet inter-connectors experienced high initial mortality that was caused by both early stolon severing and drought stress during the root development phase. The majority of ramets lived for 5–10 months and 25% were still alive at the age of 3.5 years. The study showed that although the growth phenology of Nelsonia has serious ecological implications for accessing scarce resources during the dry season, the species utilizes a number of strategies to overcome resource limitations in a seasonally heterogenous environment.

Variation of sexual and clonal reproduction in the alpine Geum reptans in contrasting altitudes and successional stages

We studied the relative proportion of sexual vs. clonal reproduction in 20 populations of the alpine pioneer plant Geum reptans in response to altitude (low and high) and succession (early and late). Additionally, the proportion of life-cycle stages, the proportion of reproducing adults, seed size, and seed number per flower head were determined. With increasing plant size, the probability of producing both flower heads and stolons increased (P > 0.001). Individuals of all size classes tended to produce more flower heads than stolons. Stolon production was more frequent only if plants reproduced by one reproductive mode (P > 0.05). The significant difference among populations in sexual reproduction and of seed number per flower head was not explained by habitat type. However, clonal reproduction was higher in populations at low and high altitude compared to populations at intermediate altitude (P > 0.05). High altitude populations were characterised by a tendency of small plants to decline and an increase in the proportion of large plants (P > 0.05) whereas the proportion of reproducing adults did not change with altitude. This indicates not only lower recruitment but also, that after successful establishment, growth and reproduction in G. reptans are not generally restricted, even above 2850 m. Our results suggest that variation in the proportion of sexual and clonal reproduction in G. reptans is probably more shaped by individual, i.e. plastic responses to local environmental conditions than by environmental gradients.

PHOTOPERIOD AND STOCK PLANT AGE EFFECTS ON SHOOT, STOLON, AND RHIZOME FORMATION RESPONSE FROM LEAF CUTTINGS OF ACHIMENES

Leaf cuttings of three cultivars of Achimenes, ‘A09’, ‘A16’, and ‘A23’ were taken from stock plants of different ages and photoperiod treatments to determine the effects of these environmental treatments on subsequent growth and development. The cuttings were planted and placed in either long days (LD, 16 hours) or short days (SD, 8 hours) at 20°C in growth chambers. Stock plant leaf age had significant effect on rhizome, shoot, and stolon initiation. Old leaf tissue had a greater propensity to initiate rhizomes, 2 times more than that of young tissue. Young tissue responded with the production of shoots and stolons, 25 and 3.5 times more, respectively, than that of old tissue. Rhizome response was also promoted when leaf cuttings received a LD stock plant photoperiod followed by a SD propagation photoperiod.

Effect of Prohexidione-Ca and Mepiquat Chloride on Stolon Production and Yield of Florida Grown Strawberry (Fragaria × ananassaDuch)

Abstract Removal of stolons from strawberry plants in Florida's annual winter production system incurs significant costs to growers. Mepiquat chloride (Ponnax®) and prohexidione-calcium (Apogee®) were evaluated for the ability to reduce stolon production of strawberries grown under annual production techniques. Two rates of mepiquat chloride (170.6 and 273.5 g ai/ha) and two rates of prohexidione-calcium (113.8 and 227.6 g ai/ha) were applied three times at two week intervals beginning 4 weeks after establishment. Significant control of stolon production was achieved with both rates of prohexidione-calcium compared to mepiquat chloride and untreated controls. However, significant reductions in yields were associated with prohexidione-calcium. Application of mepiquat chloride at 273.5 g ai/ha increased fruit yield during the month of January above all other treatments.

Effects of soil nutrient heterogeneity on the growth of plants under the various distributions and levels of nutrients in Zoysia japonica Steud.

AbstractAn experiment was carried out to analyze the effects of soil nitrogen heterogeneity in containers on the growth of a clonal plant of Zoysia japonica Steud. The overall soil nitrogen supply in the containers, their distribution and their interactions significantly affected the dry matter production of Zoysia japonica plants. Dry matter production in Zoysia japonica was benefited from heterogeneous nitrogen distributions when the overall soil nitrogen supply in the containers was relatively low. When the overall soil nitrogen was relatively high, stolon production was substantially higher in homogeneous soil nutrients. In heterogeneous distributions of nutrients, the positions of rich soil bands close to the initial Zoysia ramets positively affected the stolon production. The earlier Zoysia clones acquired abundant nitrogen from rich soil bands, the more they increased dry matter production in low nitrogen levels.

Nitrogen load and irradiance affect morphology, photosynthesis and growth of Caulerpa prolifera (Bryopsidales: Chlorophyta)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 298:101-114 (2005) - doi:10.3354/meps298101 Nitrogen load and irradiance affect morphology, photosynthesis and growth of Caulerpa prolifera (Bryopsidales: Chlorophyta) Erik-jan Malta1,2,*, Daniela G. Ferreira1,3, Juan J. Vergara1, J. Lucas Pérez-Lloréns1 1Departamento de Biología, Área de Ecología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510 Puerto Real (Cádiz), Spain2Present address: ALGAE-Marine Plant Ecology Research group, Centre of Marine Sciences, Universidade do Algarve,Campus de Gambelas, 8005-139 Faro, Portugal3Present address: Department of Biology, University of the Azores, Rua São Gonçalo, 9504-539 Ponta Delgada, Portugal *Email: emalta@ualg.pt ABSTRACT: The effect of nitrogen (N) load and irradiance on morphology, growth and photosynthetic performance was studied in the green macroalga Caulerpa prolifera (Forsskål) J.V. Lamouroux from the Gulf of Cádiz (south Spain). Constant growth rates were obtained for thalli growing at different N loads, which could be fitted to tissue N using the Droop equation, rendering a maximum growth rate of 0.09 d–1, a minimum tissue N level of 1.71% dry weight (DW) and a critical tissue N of 5.2% DW. N limitation had no effects on Fv/Fm (maximum quantum yield of chlorophyll a fluorescence). Stolon production was significantly highest at low N loads; a reverse trend was observed for assimilator production. In a second experiment, algae were subjected to combinations of high and low N loads (HN and LN) and irradiance (HL and LL) levels. Highest growth rates were observed in the HNLL treatment, whereas the reverse combination rendered the lowest growth rate. High irradiance and high N load both led to increased biomass allocation to assimilators; at low N, the bulk of the biomass (>75% in the HLLN treatment) was allocated to the stolons. HN had a positive effect on Fv/Fm, and HL had a negative effect. HL algae had a higher capacity for non-photochemical quenching. Despite its prolific nature, C. prolifera should be characterised as a slow-growing, but highly nitrophilic alga which has the capacity to forage for nutrients by allocating biomass to the stolons. KEY WORDS: Caulerpa prolifera · Clonal growth · Morphology · Nitrogen foraging · Growth rate · Photosynthesis Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 298. Online publication date: August 15, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Patterning a multi-headed mutant in Hydractinia: enhancement of head formation and its phenotypic normalization.

In a mutant strain of Hydractinia (Cnidaria: Hydrozoa), the polyps develop ectopic supernumerary tentacles and heads (hypostomes) after an initial phase of wild-type growth. In order to elucidate the molecular mechanisms implicated in the development of aberrant phenotypes, we tried to enhance or suppress the expressivity of this hypomorphic mutation by exposing subclones to factors supposedly influencing pattern formation. Upon iterated treatment with alsterpaullone, an inhibitor of GSK-3, the formation of additional, ectopic head structures and the budding of new polyps were dramatically accelerated and enhanced. The endogenous stolon-inducing factor (SIF) had opposite effects by reducing head forming potential while increasing stolon-forming potential. SIF could be used to rescue extremely aberrant phenotypes. In these mutant colonies, long polyps with multiple heads eventually detach from stolons and lose the ability to regenerate stolons. Upon exposure to SIF, such free-floating multi-headed polyps resumed production of stolons and acquired wild-type morphology. We conclude that a canonical WNT signaling cascade is involved in patterning the body axis of polyps and in the initiation of budding, and that SIF counteracts this signaling system.