Average Number Of Inflorescences Research Articles

An agro-environmental mowing regime favors the number of inflorescences and flower-visiting insects but not ground beetles of herbaceous boundaries of arable fields

Herbaceous boundaries adjacent to arable fields can deliver ecosystem services not sufficiently provided at the field scale, as well as disservices such as increased weed pressure. The levels of services and disservices depend on the management regime implemented in these boundaries. Our study was conducted in Western France, where herbaceous boundaries of many arable fields constitute the road verge, and various mowing regimes were tested for conservation purposes. Until now, most studies of the influence of mowing regimes focused on one taxonomic group and documented contrasting results depending on the environmental context. This study aimed to compare the influence of two mowing regimes on road verges by evaluating different taxonomic groups that could potentially deliver services or disservices to adjacent arable fields. The mowing regimes used were a standard and an agro-environmental regime, the latter being characterized by one late mowing, a high mowing height and biomass removal. We monitored, during two consecutive years, seven road verges and their adjacent arable fields. Each road verge was divided into two zones of equal length, characterized by a different mowing regime. Communities of plants, flower-visiting insects and ground beetles were sampled in herbaceous boundaries and/or arable fields in the period between the mass-flowering of oilseed rape and sunflower crops. In zones where the agro-environmental mowing regime had been implemented, the average number of inflorescences and flower-visiting insects within boundaries were higher than under the standard mowing regime. However, between the two mowing regimes, no differences in weed cover within arable fields and the average number of ground beetles within boundaries and arable fields were observed. To conclude, our study suggests that in our particular environmental context, an agro-environmental mowing regime could promote pollination in adjacent arable fields without increasing weed pressure within the field.

The Effect of Light Intensity and Temperature on Flowering and Morphology of Potted Red Firespike

Red firespike (Odontonema strictum) is a tropical flowering plant that was selected as a potential flowering potted plant for its attractive red floral spikes. The objective of this study was to evaluate how light intensity, photoperiod, and temperature affect the growth and flowering of firespike. In Experiment 1, plants were grown under 0%, 45%, or 65% shade and two photoperiod conditions; long-day (LD = ≥14 h) and short-day (SD = 9 h), for 16 weeks. Plants grown under 45% shade + LD were tallest at 35.9 cm, while plants grown under 65% shade + SD were shortest at 22.8 cm. During the finishing stage, the number of inflorescences increased when plants were grown under 45% shade + SD, 45% shade + LD, and no shade, with 6, 7, and 9 inflorescences, respectively. In addition, the first open flower was observed in the 0% shade group (control) 92 days after starting the experiment. The time to first open flower increased when the plants were grown under 65% shade, either under SD or LD. In Experiment 2, plants were grown in controlled environment growth chambers with average daily temperatures of 15, 25, or 35 °C and an irradiance of 200 µmol·m−2·s−1 for 9 h per day. Plants grown at 25 °C were the tallest and had the largest leaf area. Plants grown at 15 and 35 °C had 28% and 22% less leaf area, respectively. The average number of inflorescences in plants grown at 25 °C was 1.6, while no inflorescence development was observed in plants grown at 15 or 35 °C by the termination of the experiment. There were no differences between plant growth index or branch number in response to temperature. Under the experimental conditions tested, the most rapid and uniform flowering of firespike occurred when plants were grown under no shade or at 25 °C.

Population Structure and Site Characteristics of the Rare Shasta Snow-Wreath (Neviusia cliftonii)

The Shasta snow-wreath (Neviusia cliftonii Shevock, Ertter & D.W. Taylor; Rosaceae) is a rare shrub, endemic to areas near Shasta Lake in the eastern Klamath Range of northern California, USA. Since discovery in 1992, the number of known populations has increased from 3 to 33. Shasta snow-wreath is a thicket-forming shrub, thought to reproduce primarily vegetatively, where individual stems (ramets) arise from the root system. We provide the first descriptions of demography and site characteristics using data collected in eight populations of Shasta snow-wreath. We established permanently-marked transects and recorded the number of ramets, individual stem heights, and the number of inflorescences in 2011, 2012, and 2013. We also characterized sites by tree canopy, shrub components, fuels, vegetation, and ground cover. Using the number of ramets recorded and the total population area, we estimated the number of ramets in each population (‘ramet population size'). Ramet population size ranged from 716 to 18,641 (mean = 5467), and the average maximum stem height ranged from 50 to 159 cm (mean = 104 cm). Larger ramet population size and taller stems were both associated with less tree cover. The two largest ramet population sizes were found at the two highest elevations and most west-facing sites. The average number of inflorescences per stem over three years ranged from 0.08 to 4.91 (mean = 2.76) and showed an increase with elevation. How Shasta snow-wreath will respond to succession or disturbances is unknown, but the negative relationship of ramet population size and canopy cover indicates that fire may have been important for influencing the population size historically. Continued monitoring of the studied populations, and the addition of more populations to the monitoring program, would be useful for detecting demographic changes and for better understanding the factors that govern Shasta snow-wreath.

Índices de crecimiento en plantas de mora (<i>Rubus alpinus</i> Macfad) bajo diferentes sistemas de poda

El cultivo de mora en Colombia es un renglón importante para el desarrollo económico de medianos y pequeños productores. Las plantas de Rubus alpinus son arbustos semierectos, con tallos de seis metros o más, en cada uno se forman cerca de 50 hojas y 20 panículas, por tanto, las actividades de poda son labores indispensables en este cultivo y tienen el propósito de renovar las ramas productivas. En este sentido, el establecimiento de índices fisiológicos y de las curvas de crecimiento en estas plantas manejadas bajo diferentes sistemas de poda, permitirá plantear propuestas para el manejo agronómico de esta especie. En el presente ensayo se utilizaron plantas de dos años de edad, tutoradas en T, se marcaron 48 tallos bajo diferentes sistemas de poda (testigo: sin podar; poda corta: tallo a 1,6 m de longitud; poda larga: tallo a 2,6 m de longitud), se midió longitud de los tallos, y se registró el número de hojas y panículas aparecidas a través del tiempo, se graficó el comportamiento de las variables respecto a los días después de brotación (ddb). Se establecieron las curvas y tasas de crecimiento mediante análisis funcional. Como resultado se obtuvo que los modelos logísticos fueron los mejor ajustados para la descripción del crecimiento de esta especie, la máxima longitud del tallo se presentó a los 231 ddb con 535 cm, la tasa relativa de crecimiento (TRC) del tallo disminuyó gradualmente, la tasa absoluta de crecimiento (TAC) del tallo así como el número de hojas y panículas disminuyeron con tiempo. El número máximo de hojas fue de 55 a los 231 ddb, la floración en todos los sistemas de poda inició a los 126 ddb aproximadamente, el número de inflorescencias en promedio fue de 18 en plantas sin poda, con poda corta tuvo un valor de 10 y 21 con poda larga. Los resultados mostraron que la poda es un factor determinante en el desarrollo fisiológico y productivo en esta especie de mora.

Response of Six Begonia Species to Fertilizer Concentration and Substrate pH

Begonia albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, B. holtonis, B. foliosa var. miniata and B. 'Fuchsifoliosa' are conserved at the Ornamental Plant Germplasm Center (OPGC), in Columbus Ohio as a source of germplasm for breeders and researchers. No cultural information for these species is available. Our objective was to evaluate the response of the above mentioned species to different fertilizer concentrations and substrate pH levels. Rooted cuttings were transplanted into plastic containers using a soilless mix. One of five concentrations ranging from 20 to 600 mg·L -1 N of 17-5-17 water soluble fertilizer were applied in irrigation water for 12 weeks. We found significant responses to the fertilizer concentrations and differences among species on weekly measured substrate EC, shoot length, leaf area, dry weight, average number of inflorescences, and SPAD readings. Growth parameters and visual observations were used to determine optimal fertilizer concentration. High quality B. albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, and B. holtonis plants were obtained with 200 to 300 mg·L -1 N. On the other hand, low fertilizer concentration was found to be better for B. foliosa var. miniata and B. 'Fuchsifoliosa' in order to avoid high salt stress causing plant death. Seven different pH ranges of the peat-based substrates were obtained by adding different rate of dolomitic hydrated lime ranging from 1.0 to 2.6 kg·m 3 . pH was monitored weekly and maintained accordingly by adding flowable lime or a diluted sulfuric acid solution. The inflorescence number and SPAD readings were significantly different among six species, but there was no significant effect of substrate pH. Significant interaction between species and substrate pH was found in shoot length, leaf area, and dry weight. Substrate pH between 5.6 and 6.0 was found to be adequate for B. albopicta, B. echinosepala var. elongatifolia and B. holtonis. B. foliosa var. miniata plant mortality was observed when grown at a substrate pH below 5.2. The information presented in this work will be useful to OPGC personnel in the maintenance of these species at their facilities, as well as to begonia breeders and collectors.

Rodent pollination in Protea nana

Floral morphology, late winter flowering time and a distinct yeasty odour in Protea nana suggest that it is adapted for rodent pollination. To test this hypothesis, rodents were trapped in a stand of P. nana, examined for presence of pollen (on their noses and in their scats) and then observed in the laboratory for pollination behaviour. Inflorescences were placed in wire and shade-cloth exclosures and seed-set compared to controls in the field. Otomys irroratus, Aethomys namaquensis, Rhabdomys pumilio and Myomyscus ( Praomys) verreauxi were captured and all tested positive for the presence of protea pollen. All, except O. irroratus, displayed legitimate pollination of P. nana. Myomyscus verreauxi was regarded as the most competent pollinator as it displayed superior climbing ability in comparison to the other rodent species. R. pumilio sometimes displayed highly destructive behaviour of P. nana inflorescences and is the likely explanation for the observed 20% reduction in average number of inflorescences per plant over a two month period. Seeds per inflorescence were lowest in shade-cloth covered inflorescences (total pollinator exclusion), but not significantly lower in wire exclosures which provided access for insects. A high percentage of sugar (29.4% by weight) in the nectar of P. nana is similar to known rodent pollinated species. We conclude that P. nana is at least partially rodent pollinated.

Auxin Synthesis-Encoding Transgene Enhances Grape Fecundity

Grape (Vitis vinifera) yield is largely dependent on the fecundity of the cultivar. The average number of inflorescences per shoot (i.e. shoot fruitfulness) is a trait related to fecundity of each grapevine. Berry number and weight per bunch are other features affecting grape yield. An ovule-specific auxin-synthesizing (DefH9-iaaM) transgene that increases the indole-3-acetic acid content of grape transgenic berries was transformed into cultivars Silcora and Thompson Seedless, which differ in the average number of inflorescences per shoots. Thompson Seedless naturally has very low shoot fruitfulness, whereas Silcora has medium shoot fruitfulness. The average number of inflorescences per shoot in DefH9-iaaM Thompson Seedless was doubled compared to its wild-type control. Berry number per bunch was increased in both transgenic cultivars. The quality and nutritional value of transgenic berries were substantially equivalent to their control fruits. The data presented indicate that auxin enhances fecundity in grapes, thus enabling to increase yield with lower production costs.

Reproduction in the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

This study investigates the reproductive periodicity and reproductive output of the seagrass Zostera novazelandica on two intertidal reefs. Peak numbers of flowering shoots occurred during March (late summer) of two years at both sites and no flowering shoots occurred during the winter months of July to September. There were greater numbers of flowering shoots in seagrass patches in the low intertidal zone (up to an average of 55 per 0.1 m2) compared to the middle (up to 20 per 0.1 m2) and upper (up to 9 per 0.1 m2) zones, and about three times greater reproductive output in patches associated with tidepools compared to those not bordering tidepools. The average number of inflorescences per shoot was 3.1 (±0.25) at one site vs 1.2 (±0.08) at the other, and showed a progressive decrease from the lower shore to the upper shore. Patches associated with tidepools had twice the number of inflorescences per shoot (2.8 ± 0.24) than patches not bordering tidepools (1.5 ± 0.16). The number of flowering shoots was highly correlated with leaf width, leaf length, and ramet density, while the leaf-area index decreased from the lower shore to the upper shore. The reproductive effort of plants, as measured by the percent biomass invested in flowering shoots during peak reproduction, was significantly different between sites, tidepool associations, and shore level. For all the variables measured, there was considerable spatial variation, with significant interaction terms between most factors investigated. In laboratory experiments, more inflorescences were produced at light intensities of 30 and 300 μE m−2 s−1 than at 100 μE m−2 s−1. At a salinity of 17‰, 1.5 × the number of flowers was produced than at 33‰, while none was formed at 70‰. Plants cultured at 5 °C had about three times the number of inflorescences than those at 15 °C, while none was formed at 25 °C.

ON THE MEASUREMENT OF NATURAL AND SEXUAL SELECTION: APPLICATIONS.

In this paper, we use measures of selection developed by quantitative geneticists and some new results (Arnold and Wade, 1984) to analyze multiple episodes of selection in natural populations of amphibians, reptiles, and insects. These examples show how different methods of data collection influence the potential for relating field observations to formal evolutionary theory. We adhere to the Darwinian tradition of distinguishing between natural and sexual selection (Darwin, 1859, 1871; Ghiselin, 1974). We view sexual selection as selection arising from variance in mating success and natural selection as arising from variance in other components of fitness. The justification for this formal distinction is developed by Wade (1979), Lande (1980), Wade and Arnold (1980), Arnold and Houck (1982) and Arnold (1 983 a). (We define mating success as the number of mates that bear progeny given survival of the mating organsim to sexual maturity. We do not equate mating success with mere copulatory success.) The utility of the distinction between sexual and natural selection is that the two forms of selection may often act in opposite directions on particular characters (Darwin, 1859, 1871). While we find the distinction between these two forms of selection useful, the difference is not crucial to our analysis. The essential point is that the recognition of selection episodes permits analysis of selection that may change in magnitude and direction during the life cycle. Defining Fitness Components. -The key first step in the analysis of data is to define multiplicative components of fitness so that selection can be partitioned into parts corresponding to these components or episodes of selection. Using an animal example, if the number of offspring zygotes is taken as total fitness, we can define the following components of fitness: viability (survivorship to sexual maturity), mating success (the number of mates) and fertility per mate (the average number of zygotes produced per mate). These components of fitness are defined so that their product gives total fitness. As a second example, consider the components of fitness in a plant in which yield (seeds/plant) is taken as the measure of total fitness (Primack and Antonovics, 1981). We might define the following components of fitness: number of stems per plant, average number of inflorescences per stem, average number of seed capsules per inflorescence, and average number of seeds per capsule. Again, these four fitness components are defined so that their product gives total fitness. We will need to measure each component of fitness and each character on each individual in order to partition selection into parts corresponding to the separate episodes of selection or to the separate components of fitness. Thus in the animal example, we need to measure the viability, mating success and fertility of each individual. With this accomplished we can estimate the separate forces of viability, sexual and fertility selection on each phenotypic character. In addition we can calculate the opportunities of selection corresponding to these three episodes and covariances between the different kinds of selection. In the plant example, we might begin with the intuition that larger plants have a greater yield. Using our methodology we can reword and extend this intuition. We can not only test the proposition of