Number Of Capitula Research Articles

Mapping the genomic regions encoding biomass-related traits in Cynara cardunculus L

Cynara cardunculus, a member of the Asteraceae family, comprises the three taxa var. scolymus (globe artichoke), var. altilis (cultivated cardoon) and the ancestral var. sylvestris (wild cardoon). The substantial quantities of lignocellulosic biomass produced by these plants (up to 30.0 t/ha year−1 dry matter by the cultivated cardoon) can be used either as a source of bioenergy and/or as raw material for paper pulp production. Here, genotyping-by-sequencing to an F1 population derived from a cross between a globe artichoke (C3) and a cultivated cardoon (ALT) genotypes has been used to perform a genome-wide linkage analysis, leading to the elaboration of a pair of highly dense genetic maps, each derived from one of the two highly heterozygous parental genotypes. In both maps, the number of linkage groups (17) matched the species’ haploid chromosome number. The F1 population was phenotyped over two seasons with respect to plant height, stem number, capitulum number, leaf and stem fresh weight, and the dry weight of the whole plant, the leaves, the stems, the capitula and the achenes. The phenotypic data were combined with the linkage maps to identify 81 quantitative trait loci, of which 50 were placed on the C3 map and 31 on the ALT map. The loci were scattered over 13 linkage groups, and were clustered within 27 genomic regions, 22 of which harboured two or more QTL. Ten of these regions were specific to the C3 map and six to the ALT map, while the other 11 were represented on both maps. The 27 regions harboured in all 1960 genes, 83% of which could be functionally annotated. An enrichment for certain gene ontology terms was noted for the gene content of the genomic regions harbouring loci influencing seed yield and the number/weight of stems.

Association Mapping for Important Agronomic Traits in Safflower (Carthamus tinctorius L.) Core Collection Using Microsatellite Markers.

Carthamus tinctorius L. (safflower) is an important oilseed crop producing seed oil rich in unsaturated fatty acids. Scarcity of identified marker-trait associations is a major limitation toward development of successful marker-assisted breeding programs in safflower. In the present study, a safflower panel (CartAP) comprising 124 accessions derived from two core collections was assayed for its suitability for association mapping. Genotyping of CartAP using microsatellite markers revealed significant genetic diversity indicated by Shannon information index (H = 0.7537) and Nei's expected heterozygosity (I = 0.4432). In Principal Coordinate Analysis, the CartAP accessions were distributed homogeneously in all quadrants indicating their diverse nature. Distance-based Neighbor Joining analysis did not delineate the CartAP accessions in consonance with their geographical origin. Bayesian analysis of population structure of CartAP demonstrated the unstructured nature of the association panel. Kinship analysis at population (Gij) and individual level (Fij) revealed absence of or weak relatedness between the CartAP accessions. The above parameters established the suitability of CartAP for association mapping. We performed association mapping using phenotypic data for eight traits of agronomic value (viz., seed oil content, oleic acid, linoleic acid, plant height, number of primary branches, number of capitula per plant, 100-seed weight and days to 50% flowering) available for two growing seasons (2011–2012 and 2012–2013) through General Linear Model and Mixed Linear Model. Our study identified ninety-six significant marker-trait associations (MTAs; P < 0.05) of which, several MTAs with correlation coefficient (R2) > 10% were consistently represented in both models and in both seasons for traits viz., oil content, oleic acid content, linoleic acid content and number of primary branches. Several MTAs with high R2-values were detected either in a majority or in some environments (models and/or seasons). Many MTAs were also common between traits (viz., oleic/linoleic acid content; plant height/days to 50% flowering; number of primary branches/number of capitula per plant) that showed positive or negative correlation in their phenotypic values. The marker-trait associations identified in this study will facilitate marker-assisted breeding and identification of genetic determinants of trait variability.

Effects of altitude on the reproductive characteristics of Saussurea przewalskii at the eastern margin of the Tibetan Plateau, China.

The paper studied the effects of altitude on reproductive characteristics in 12 populations of Saussurea przewalskii at the eastern Qinhai-Tibetan Plateau, China. The results showed that the size, reproductive organ biomass, vegetative organ biomass, capitulum number, and seed number of individual plant decreased with the increasing altitude, and the capitulum mass and hundred-grain mass increased continuously. S. przewalskii could ensure its reproduction by reducing plant body size to decrease resource consumption, and increasing the allocation of limit resources to flower biomass. In order to ensure sexual reproduction, the reproductive allocation of the plants increased with increasing the altitude. There was a trade-off between capitulum number and capitulum mass, and between seed number and hundred-grain mass, which allowed the plants to maximize their fitness under stressful conditions.

Genetic diversity analysis in selected germplasm lines of safflower (Carthamus tinctorius L.)

In the present study, a total of 155 genotypes along with five checks ‘A-1, PBNS-12, AKS-207, PKV Pink, Bhima ’were assessed to study the genetic diversity among the genotypes. These genotypes were grouped into eleven clusters based on the measurements of genetic divergence obtained by means of Mahalanobis distance (D2) and in the grouping by Tocher optimization method. The average inter cluster distance was maximum between clusters VI and IX (7037.21) followed by clusters III and IX (6895.24), clusters IX and XI (6756.33), clusters IX and X (5760.02), clusters VII and IX (5724.53) which indicated that the genotypes included in these clusters may give high heterotic responses and thus better segregants. The present study projected the importance of GMU-4502, GMU-4934, GMU-4507 as parents for higher heterosis in F1 and potential transgressive segregants in subsequent generations as they have least mean values for days to 50% flowering, days to maturity whereas high mean values of GMU-4839, GMU-4934, GMU-40, GMU-5032, GMU-2969, GMU-5663 and GMU-3740 for characters viz. plant height, number of primary branch per plant, number of capitula per plant, volume weight, 100-seed weight, seed yield per plant and oil content respectively suggest their further improvement in respect to these yield attributing characters.

Distribution, competitive ability, and seed production of Bidens frondosa L. in the Middle Urals

The distribution, plant size and biomass allocation, leaf traits, and seed production of the invasive Bidens frondosa L. plant in the Middle Urals were studied. This species was found in disturbed riverside habitats in the upper stream of the Iset’ River in habitats extending approximately 100 km (from the city of Aramil’ to the city of Kamensk-Ural’sky). Comparative analysis showed that the B. frondosa plant was 35% taller than the native species of the genus Bidens. The dry mass of the B. frondosa plant exceeded the biomass of B. tripartita and B. radiata by 1.5 and 4.9 times, respectively. The large size and biomass of B. frondosa indicated a higher competitive ability of this species than the native species of the genus Bidens. Given the same leaf thickness in the three studied species, the smaller leaf density (LD) of B. frondosa determined a lower (by 1.2 times) dry leaf mass per unit area (LMA) than that of B. tripartita and B. radiata. These structural features of B. frondosa leaves contributed to the optimization of gas exchange processes within a leaf and made it possible to develop a greater assimilation area per unit plant weight (the leaf area ratio (LAR)), which should provide a high growth rate of this species. Analysis of seed production parameters showed that the number of capitula per plant increased in the series B. radiata–B. tripartita–B. frondosa; however, the number of achenes per capitulum and per plant decreased in this sequence. The mass of 100 achenes was 1.6 and 2.3 times higher in B. frondosa than in B. tripartita and B. radiata, respectively. On the whole, the frequent occurrence of B. frondosa in the extended area (approximately 100 km) in the upper stream of the Iset’ River and the values of production parameters (the size and weight of plants and the mass and number of seeds) indicate a successful naturalization of this species in the Middle Urals.

Sensory analysis and postharvest of potted gerbera based on fertilization

The cultivation of gerberas as cut flowers has been broadly studied. With the purpose of assess the production and visual quality of potted gerberas conducted with different fertilizations, the experiment was performed in a greenhouse located at UNIOESTE – Campus of Cascavel – Parana - Brazil. The experimental design was done in randomized blocks with four repetitions and five treatments. The treatments were defined based on the fertilization source: mineral (NPK) or organic. The organic fertilizations were obtained with the dilution of four organic composts derived from the composting process of agro-industrial wastes in water. The agro-industrial waste, used in different percentages in each treatment, were: grains pre-cleaning residues (corn meal and wheat husk); hatchery waste; flotation sludge; cellulose casing (sausage covering); solid fraction of pig slurry (Piglet Producer Unit) and truck washing; coal and ash remaining from boiler; poultry litter and sugarcane bagasse. The growth parameters were evaluated at the commercialization phase (plant height and diameter, stem height, capitulum number, and capitulum and stem diameter) and sensory analysis through trait and preference assessment tests. The use of liquid organic fertilizers are a feasible alternative to substitute conventional mineral fertilization. Farmers should observe EC values and K, Ca, Mg ratio for better quality assurance according to the results obtained in T5 . The T5 (Boiler remaining ash + Hatchery residue) has a larger amount of boiler remaining ash, whereas the chemical elements in mineral form are already readily available to the plants, this fact may have contributed to better visual development of plants grown in this treatment.

Production and response toAzospirillum brasilenseinoculation in two globe artichoke hybrids

The implementation of the Municipal Ordinance No6425 in Junin, Buenos Aires, Argentina (34°28'5S; 60°52'W) will impose a restriction to continue the current production practices by defining a “buffer area”. In this context it would be interesting to evaluate non-traditional crops for this zone and the implementation of sustainable practices. The aim of this work was to study the productive feasibility of two globe artichoke hybrids and their response to Azospirillum brasilense inoculation. The trial essay was carried out in the Experimental Field of Universidad Nacional del Noroeste de la Provincia de Buenos Aires (UNNOBA). Two commercial seed propagated hybrids were used: 'Opal' and 'Madrigal'. Transplant was performed on June 27, 2014. Both hybrids were drenched with a formulation of Azospirillum brasilense strain AZ39 (50 cm3 plant-1, 1×10(7) cfu mL-1) provided by the PGPR working group from Universidad Nacional de Lujan. Non-inoculated plants were used as control. The experimental design was a split plot with 12 replications, with hybrids in the main plot and inoculation treatments in the subplot. Yield, average capitulum weight and number of capitula were recorded and analyses of variance were conducted. Yield was significantly influenced by the hybrid (2.90 kg plant-1 for 'Opal', 4.40 kg plant-1 for 'Madrigal'), as well as by inoculation treatment (3.4 kg plant-1 for control, 3.9 kg plant-1 for treated plants), without significant effect of interaction. Capitula per plant were significantly modified by the hybrid, with a mean of 21 for 'Opal' and 35 for 'Madrigal', while the average capitulum weight was influenced by the interaction of both treatments, with no significant differences attributable to the inoculation in 'Opal' (average weight of 137 g) and a significant increase on capitulum weight in inoculated plants of 'Madrigal' (136 vs. 120 g).

Traditional grazing regimes promote biodiversity and increase nectar production in Tibetan alpine meadows

Pastoralists claim that traditional management practices involving light to moderate grazing ensure sustainable yield and promote the multifunctional services provided by rangeland ecosystems. Nectar production is a key ecosystem function crucial to successful apiculture and to the sustainability of services provided by pollinators in the Tibetan alpine rangeland. Here, we evaluated whether traditional (light to moderate) grazing promotes plant biodiversity and nectar production at the level of individual plants and at the level of an entire community. We compared plant species diversity and nectar production of the dominant nectariferous species (Saussurea nigrescens) at the individual plant level and at the community level in ungrazed, lightly grazed, moderately grazed, and heavily grazed plots in each of three Tibetan alpine meadow sites. Individual nectar production was quantified as nectar volume×floret number per capitulum×capitulum per plant. Community nectar production was calculated as individual nectar production×the number of flowering plants per 1.0m2 plot. We found that nectar production at the floret, individual, and community levels was significantly higher in lightly and moderately grazed plots compared to heavily grazed or ungrazed plots. This somewhat counterintuitive observation (particularly with regard to ungrazed plots) resulted from the fact that light and moderate grazing increased floret and capitulum number, and the number of flowering individuals per plot as a result of lowered competition for light. Moreover, species richness was significantly correlated with nectar production (as a result of light to moderate grazing) both at the individual level and at the community level. These results support the traditional view that light to moderate grazing not only promotes plant biodiversity but also ensures a sustainable yield in nectar production (and forage). Thus, traditional grazing management practices are more “eco-friendly” compared to recent and widespread practices involving either grazing exclusion or overgrazing in the Tibetan rangelands examined in this study.

Variation in reproductive investment and floret gender ratios in two gynodioecious mat daisies (Raoulia, Asteraceae)

ABSTRACTWidespread species could be expected to demonstrate greater among-population variation in reproductive traits than species with limited distributions. We investigated variability in floret gender and capitula number in populations of two gynomonoecious mat daisies, the widespread Raoulia australis and the alpine specialist Raoulia hectori in Central Otago, lower South Island. Gynomonoecy (female and hermaphrodite florets in a capitulum) is common in the daisy family Asteraceae. Varying gender ratios within capitula could allow for plasticity in reproductive investment in relation to environment and life-history stage. We found that the ratio of female to hermaphrodite florets within capitula did not vary significantly among populations or with plant size for either Raoulia species. Instead, the number of capitula produced varied among populations within species, independent of plant size, and showed different patterns in relationship to plant size between the two species. Smaller plants of the alpine specialist R. hectori consistently showed a proportionally greater allocation to reproduction than larger plants, whereas the relationship between plant size and reproductive allocation varied markedly among populations of R. australis. These results suggest that allocation to capitula may be a key component of reproduction in Raoulia species, and is potentially responsive to environment and life-history stage. However, as our study included few populations and did not follow through to seed production, this hypothesis requires further testing. Moreover, our values for floret gender ratios differed from standard species descriptions, so broader geographic variation in floret gender ratios may still exist.

Characters Associations and Path Analysis in Safflower (&lt;i&gt;Carthamus tinctorious&lt;/i&gt;) Accessions

Safflower as a potential oil crops which can be used as an alternative to the existing widely cultivated oil crops in Ethiopia needs seed yield improvement which inturn relies on its component characters. Examining character association and their interrelationships is helpful in selecting the breeding material for improving the complex trait such as seed yield. A study was carried out during 2012 cropping season to determine the associations of characters and partition of this association into direct and indirect effects on seed yield of safflower. Correlation coefficient analysis showed that seed yield recorded significant positive association with days to flowering (0.190), plant height (0.234), number of capitula (0.172), number of seed per plant (0.834) and hundred seed weight (0.197). The highest positive direct effect was revealed by number of seed per plant (0.89) followed by hundred seed weight (0.106) as depicted by path coefficient analysis. This study showed that number of seed per plant is the most important yield component followed by seed weight. Therefore, this suggests that direct selection based on these characters would be effective for the improvement of safflower.

Evaluating the Contribution of Ionic and Agronomic Components toward Salinity Tolerance in Safflower

Safflower (Carthamus tinctorius L.) is a versatile crop species that is well adapted to arid and semiarid conditions. Limited information is available on the response of safflower genotypes to salinity stress under field conditions. The objective of this study was to investigate the effects of field salinity on seed yield, yield components, and leaf ionic concentrations in different safflower genotypes. A 2‐yr field experiment was conducted in normal (E1) and saline (E2) field conditions using 64 safflower genotypes. Plant height, number of capitula per plant, number of seeds per capitulum, 1000‐seed weight, seed yield, biological yield, and harvest index were determined in this study. Leaf concentrations of Na+ and K+ were also measured and the K+/Na+ ratio calculated. Results indicated that under salinity all the traits significantly decreased except tissue Na+ content and harvest index. Linear regression and genotype‐by‐traits analyses revealed a strong inverse association between leaf Na+ concentration and salinity tolerance. Results of stepwise multiple regression analysis showed that plant height, number of capitula per plant, biological yield, harvest index, and leaf Na+ content were the strongest predictors of seed yield, collectively explaining 97% of the variation in seed yield under saline conditions. Therefore, the only ionic predictor of salinity tolerance in the regression model, leaf Na+ concentration, can be suggested as an effective indirect screening criterion for salinity tolerance in safflower. The mechanisms of Na+ homoeostasis, including Na+‐specific transport or K+/Na+ co‐transport, could also be explored using the most contrasting genotypes with respect to salinity stress.

Comparison of seven colchicine-induced tetraploid clones with their original diploid clones in purple coneflower (Echinacea purpurea L.)

Seven clones of colchicine-induced tetraploid purple coneflower (Echinacea purpurea L.) plants were grown on a farm for comparison with their corresponding original diploid plants. In the first year of cultivation, the plant height, number of capitula, and inflorescence (branched flower stalk) were significantly reduced in all of the tetraploid plants, while the length-to-width leaf ratio, pollen size, and root thickness were significantly increased. Although the tetraploid plants had larger seeds, most of the seeds of tetraploid plants were not fully filled and the naked seeds (i.e., seeds observed without the outer seed coat) were noticeably smaller than those of the diploid plants. In the second year of cultivation, the phenological stages were markedly delayed in the tetraploid plants; the number of capitula increased much more in tetraploid plants than in diploid plants. Among the seven tetraploid clones, two yielded significantly higher plant biomass and higher cichoric acid content per gram dry weight as well as per plant. The results of the present experiments indicate that some effects of tetraploidization of diploid E. purpurea are genotype-dependent, suggesting that the tetraploidization of more genotypes of the diploid is needed to breed better tetraploid varieties.

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae.

Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows. A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7°C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8°C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology. Six years of experimental warming resulted in reductions in nectar volume per floret (64·7% of control), floret number per capitulum (8·7%) and capitulum number per plant (32·5%), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90% in nectar production per unit area. The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant-pollinator interactions and plant reproduction via induction of allocation shifts for plants growing in communities subject to asymmetric warming.

Evaluation of Four Sunflower Hybrids (Helianthus annuus) under Three Irrigation Regimes and Two Doses of Fertilization on Flower Production

Flower production is an income source for farming families. However, their productivity has been limited due to the lack of information on technical managements of crop species. In Mexico, 21,129 hectares are planted every year, with an annual production of 83,000 tons of flowers for decoration, and a total production value of 6,097 million Mexican pesos. In order to design agronomic management practices for sunflower production in the state of Campeche, three factors were evaluated: 1) sunflower hybrids, 2) time of irrigation and 3) fertilization doses, with four (hybrids: “Sunbright”, “Prado Red Shade”, “Full Sun” and “GH-382”), three (soil moisture tension at the start of irrigation of -10, -35 and -60 kPa), and two (Fertilization formulas: 60-50-0, and 30-25-0) levels, respectively using a sub split plot arrangement nested in a complete random block design with three replicates. Response variables evaluated were: plant height (PH), stem diameter (SD), leaf width (LW), leaf length (LL), distance between nodes (DN), number of inflorescences (NF), inner diameter (IDF), external diameter (EDF) and capitulum weight (CW). Irrigation affected PH, SD, LL, IDF, EDF, and CW. In all these variables, the highest values were found when irrigation was conducted at the lowest moisture tension (-10 kPa). Likewise, in all those variables significant effect of hybrids were found, which confirms that the morphology of flowers is defined by genetic factors. Specifically, hybrid “Full Sun” had significantly higher PH, SD, and DN compared to the rest of the hybrids. “Full Sun” and “Sunbright” had the highest values for PH and LL. “Full Sun” and “GH 382” had significantly higher IDF and EDF. “Prado Red Shade” had significantly lower PH, SD, LL, CW and higher NF. Fertilization only had significant effects on LW, DN and CW. In conclusion, irrigation improves morphological characteristics of sunflower plants. If the farmer’s objective is to produce larger flowers, then hybrids “Fun Sun” and “GH 382” are recommended. However, if the objective is to produce small flowers, hybrids “Sunbright” and “Prado Red Shade” are recommended. The latter is also suitable to produce a larger number of capitula.

Evaluation of recurrent selection derived lines in safflower (Carthamus tinctorius L.)

The present study was undertaken; to evaluate the response of recurrent selection derived lines by the testing of (C 3 ) derived lines for genetic variability, genetic advance and heritability and to assess the effect of selection on other quantitative traits. The 16 half-sib families were selected from 3 rd cycle of recurrent selection were grown for evaluation in Randomized Block Design in Rabi 2009 -10 along with check varieties Bhima and A 1 . The expected genetic advance expressed as per cent of population mean at 10 per cent was high for seed yield per plot (48.84) followed by seed yield per plant (28.88). The expected genetic advance per cent over Bhima at 10 per cent selection intensity was high for seed yield per plot (28.27) followed by seed yield per plant (22.78). In safflower seed yield per plant was positively and significantly correlated with days to maturity, number of capitula per plant, number of seeds per capitulum and 100 seed weight. Days to maturity and seed yield per plant had exhibited significant and positive correlation. Two halfsib families were identified for testing in preliminary yield evaluation trial.

Changes in flowering resource allocation of Saussurea dzeurensis with elevations

Aims Our objective is to study the effect of elevation on the reproductive allocation and sexual allocation of Saussurea dzeurensis during the flowering season. Methods We used the field investigation method and dry mass method to evaluate morphological characteristics of S. dzeurensis at different elevations. Important findings Elevation had a significant impact on the biomass and resource allocation of S. dzeurensis; reproductive allocation and male allocation were positively correlated with elevation, but vegetative allocation and female allocation were negatively correlated with elevation; there was a trade-off of resource allocation between capitulum number and mass, between reproductive allocation and vegetative allocation, and between male allocation and female allocation; When resources were limiting, the resource input of every structure of S. dzeurensis was balanced by increasing reproductive allocation and sexual allocation so that the plant can adapt to the stressful environment and have high rate of reproductive success.

Zu unbeachteten Quellen und zur Kapitelzählung der Regula Donati (Ergänzendes zu CSEL 98)

Summary – In the 7th century, Donatus, bishop of Besan on, wrote a rule for nuns based on the Regula Benedicti, the Regula Caesarii ad virgines and the Regulae Columbani. This article discusses previously unnoticed allusions to late antique authors in Donatus’ openingletter, which shed light on Donatus’ erudition and his skilful use of prefatory-topoi for his captatio benevolentiae. The second part of this article deals with the lost index of contents and the manifold problems concerning the number of Capitula of Donatus’ Regula.

Influence of achene heteromorphism on life-cycle traits in the annual weed gallant soldier (Galinsoga parviflora Cav.)

Galinsoga parviflora (gallant soldier), Asteraceae, produces two morphologically distinct achenes in a single capitulum: peripheral and central. The morphological, phenological and generative reproduction traits of the progeny derived from peripheral and central achenes that were cultivated in greenhouse conditions were analyzed. Differences between the progeny of various morph types were manifested at different stages of life. The plants of both morph types developed at a similar rate and they entered key phenological phases at the same time except for the flowering stage. The average height of the studied plants was similar on the same days of the experiment. The study showed that plants from peripheral achenes realize the generative reproduction in other pattern than plants from central achenes. The plants from central achenes produce more capitula per plant at the beginning of the fruiting stage, whereas plants from peripheral seeds achieve the highest number of capitula per plant at later stages. Finally, on day 130 of the experiment, the number of capitula per plant of both morphs equalized. At the early fruiting stage, the number of achenes per capitulum of plants from the two morphs did not differ significantly. The number of achenes within one capitulum decreases with plant age in both populations, but the rate of that decline is greater in the progeny of peripheral seeds. The number of peripheral achenes per capitulum in plants from both achene types decreases at a comparable rate. In contrast, the number of central achenes is reduced at a faster rate in plants germinated from peripheral achenes. After day 83, the individuals from peripheral diaspores intensified their reproductive effort; they produced more capitula but with fewer number of achenes than in individuals from central diaspores. On day 130, the number of dispores per plant of the two morphs equalized. The changes of fecundity of peripheral and central progeny with the age of the plant (at different stages of the life cycle of a single plant) contribute to an intensive seed rain throughout the fruiting period. By producing a large number of less fertile capitula with a stable number of peripheral achenes, plants derived from peripheral achenes are able to supply a higher share of peripheral achenes than if they would produce fewer but more fertile capitula. This strategy increases the pool of peripheral achenes.

Comparison of Flowering Phenology of Two Kinds of Sandy Semi-shrub of Artemisia L. in the Horqin Sandy Land

The flowering phenology of Artemisia wudanica and A. halodendron were investigated at four levels( capitulum,inflorescence branches,individual and population) in the Horqin Sandy Land. The results showed that:(1) At the population level,the initial time of flowering of A.wudanica was18th June,which was9d earlier than A.halodendron,the durations were 19 d and 16 d,respectively,and the overlapping flowering period was 10 d in two species. At the individual level,the initial time of flowering was 7 d earlier and the duration was 2 d longer in A.wudanica than in A. halodendron;( 2) The number of capitulum on secondary inflorescence branches was less and duration was longer in A. wudanica than in A. halodendron. The flowering frequency of two species were all singlepeak type,the highest frequency of flowering duration time at the secondary inflorescence branch were all 8 d,followed by 9 d; for the capitulum,the higher frequency were all 5 d,4 d,6 d and the highest one was 5 d;( 3) The first flowering position was near the base of secondary inflorescence branches in A. halodendron,the highest frequency was the second and the third one from the base,being 12. 7% and 11. 9%,respectively. However,the capitulum on the top of secondary inflorescence branches was the first blossom in A. wudanica,the frequency was up to 56. 3%;( 4) The flowering amplitude curve of two species all showed a single peak curve,A. wudanica reached its peak on the 9th day after flowering,and A. halodendron was on the 6th day. The similarity of these two species' flowering phenology reflected their phylogenetic relationship and adaptability to environment. The differences,especially the first flowering position,indicated the genetic differences in long-term evolution of two species.

Host Impact and Specificity of Tortoise Beetle (Cassida rubiginosa) on Canada Thistle (Cirsium arvense) in Iran

This study determined the potential of the tortoise beetle (Coleoptera: Chrysomelidae) to control Canada thistle (Asteraceae) in Iran. Genetic analysis of the tortoise beetle, based on mitochondrial DNA, confirmed the presence of the species in Iran. A field experiment using five insect densities (0 to 20 larvae plant−1) showed a positive correlation between the number of larvae transferred and impact. Feeding by 20 larvae reduced total biomass of Canada thistle by 78% and the number of capitula by 94%. More important, when grown in competition with wheat, four and eight egg batches (corresponding to approximately 12 and 24 larvae) per Canada thistle plant increased wheat ear weight by 46 and 82%, respectively. Host range studies with 22 crop and 21 weed species using no-choice and multiple-choice tests under laboratory and field conditions and parallel data from a field survey showed that joint feeding and oviposition were restricted to Canada thistle and a few other weed species. Limited feeding, without oviposition, was recorded on an additional seven weed species but also on safflower (10 to 15% reduction in biomass), and common sunflower (&lt; 10%); the latter only under no-choice conditions. The growing period of either crop species, however, does not coincide with the feeding period of the tortoise beetle in the field. Findings indicate that the tortoise beetle is a promising biological control agent for Canada thistle in arable crops and grasslands in Iran. Other complementary methods will likely be needed to prevent substantial yield losses.