Cloning and expression of flavonol synthase from Petunia hybrida

Flavonols are important co-pigments in flower colour and are also essential for pollen tube growth. In petunia, flavonol synthesis is controlled by the Fl locus. Flavonol synthase (FLS) belongs to the 2-oxoglutarate-dependent dioxygenase family. Dioxygenase gene fragments were amplified by PCR on cDNA made from FlFl and flfl flowers using degenerate primers designed from conserved dioxygenase sequences. A petunia petal cDNA library was screened for clones that hybridized more strongly to the Fl PCR products than the fl PCR products. A full-length cDNA clone identified by this screening exhibited FLS activity when expressed in yeast. FLS gene expression is developmentally regulated during flower development. Antisense expression of an FLS cDNA clone in petunia markedly reduced flavonol synthesis in petals. RFLP mapping showed that the FLS gene is linked to Fl , suggesting that Fl is the structural gene for FLS.     

Density and seed set in a self-compatible forb, Penstemon digitalis (Plantaginaceae), with multiple pollinators

Seed production may be limited because flowers do not get enough suitable pollen or because plants lack the resources to make seeds. We used replicated plantings to test factors that influence effects of bumblebee behavior on pollen limitation, as measured by the difference in seed set between hand- and naturally pollinated flowers, of Penstemon digitalis in patches of four to 41 flowering individuals. Seed set per flower was 376% higher in the largest as compared with the smallest Penstemon patches. This positive density dependence reflects activity of long-tongued bees, which (1) have higher effective density as patch size increases, (2) visit greater proportions of plants as patch size increases, and (3) visit smaller proportions of flowers per visited plant as patch size increases. Our results suggest that economics of flight and maneuverability of large, long-tongued bumblebees lead them to transfer more pollen between than within Penstemon plants in large patches. Density of smaller, short-tongued bumblebees was not positively associated with Penstemon seed set, but these bees may be important pollinators at low plant densities. Our experimental system indicates a clear positive relationship between activity of effective pollinators and seed set in a species capable of pollinating itself.     

Foliar macronutrients (N,P, K,Ca and Mg) in lime (Tilia spp.)

Summary The effect of sampling technique upon the measurement of variation in nutrient (N, P, K, Ca and Mg) concentration was examined. Sampling and analytical precision over two years were indicated by coefficients of variation which ranged from 5.7 to 14.0 per cent for sampling error and 4.3 to 16.1 per cent for analytical error. Concentration of N, P and K in the leaves was found to be independent of sampling height. Ca and Mg concentrations, however, decreased with increased height on the crown. The differences in concentration between the bottom and top of the crown were 15 and 19 per cent for Ca and Mg respectively. The nutrient concentrations of samples taken from basal coppice shoots were significantly different from those in the true crown. Nutrient concentration was independent of aspect. Leaf area varied throghout the season, but the largest leaves were always at the base of the crown and the smallest at the top.     

No evidence for a role of pollinator discrimination in causing selection on flower size through female reproduction

The preference for certain floral phenotypes by flower visiting animals may fuel the evolution of floral traits because variation in flower visitation rates may lead to fitness variation within a population. Here, I examine the importance of flower size for pollinator visitation rate, seed set, and seed mass in two alpine populations of the insect-pollinated herb Ranunculus acris L. during two seasons. There was no pollen limitation of seed set or mass. Pollinators discriminated strongly against flowers experimentally reduced in size. Despite this, there were no signs of any significant impact of flower size on female reproductive success. The results show that although pollinators discriminate strongly among floral phenotypes, this may not always result in female fitness differences within a population because seed set or mass is not limited by pollen availability alone. Probably abiotic environmental constraints prevent plants with high pollinator visitation from capitalizing on the high pollen deposition.     

Variation in magnesium and nitrogen content in seeds of antelope bitterbrush (Purshia tridentata, Rosaceae)

One-hundred and sixty-three seeds from 38 shrubs of antelope bitterbrush (Purshia tridentata) from four different sites were individually analyzed for N and Mg content. Seed nutrient content has previously been shown to affect seedling growth, competitive ability, and adult biomass and seed production, though estimations of nutrient concentration in seeds have always been based on bulk samples of more than one seed. The results from antelope bitterbrush show that individual seeds vary in N and Mg content (coefficient of variation = 15.9 and 10.1%, respectively), with most of the variation being attributable to seed size (over 70%). Larger seeds not only had greater absolute quantities of N and Mg, but also a greater concentration of N. Differences between seeds from the same shrub explained the second largest amount of variation (over 20%), while differences between shrubs and site of growth, though significant, accounted for much less of the variation (just over 5%). Soil N and Mg were not closely related to seed N or Mg at a site, suggesting that decisions on how much N or Mg to allocate to seeds are not entirely based on supply. Shrubs that were browsed most intensively the winter prior to seed production had seeds with higher concentrations of Mg. Differences in seed mineral content between shrubs suggest the possibility for natural selection to operate, though research to determine heritability of this character will be necessary to confirm how much of the observed variation is attributable to plasticity in seed filling.     

POLLINATION IN FLORAL SCENT MORPHS OF POLEMONIUM VISCOSUM: A MECHANISM FOR DISRUPTIVE SELECTION ON FLOWER SIZE

Plants of Polemonium viscosum have flowers that are either sweet or skunky in scent. The two morphs are preferentially pollinated by insects of strongly contrasting body size: bumblebee queens specialize on sweet flowers, flies on skunky ones. In this study 13 characters were examined in plant specimens from five populations to identify major components of intraspecific variation in flower and inflorescence morphology and test their correlation with floral scent. Factor analysis identified four major axes of morphological variation. The first explained 22% of the variance among specimens and correlated strongly with four flower size characters: sepal length, corolla tube length, corolla lobe width, and corolla lobe length. Floral scent morphs differed significantly in the multivariate representation of flower size defined by these characters. Sweet flowers had wider corolla lobes, longer corolla tubes, and longer sepals than skunky ones. Corolla lobe width accounted for the greatest amount of intermorph divergence. Divergence in flower size between morphs was maintained in mixed populations at four locations in alpine Colorado, with corollas of sweet flowers significantly broader or more flared than those of skunky flowers. Patterns of pollen receipt suggest that this difference is adaptive. In the sweet morph, pollination intensity and purity increased significantly with corolla flare. Conversely, in the skunky morph, corolla flare had little influence on pollination intensity and had a strong negative effect on purity. These findings suggest that selection for effective pollination should favor intraspecific divergence in flower size in Polemonium viscosum.     

The relationship of the female reproductive success of Eucalyptus globulus to the endogenous properties of the flower

Low capsule and seed set is a major factor limiting seed production in Eucalyptus globulus seed orchards. Controlled pollination studies showed that the reproductive success (number of seeds produced per flower pollinated) was primarily determined by the female. We aimed to identify the factors contributing to the differences in reproductive success between female genotypes in terms of the physical and anatomical properties of the flower. We studied pairs of genotypes of high and low reproductive success from each of three races (Furneaux Group, Strzelecki Ranges and Western Otways) growing in a seed orchard. Controlled pollinations were performed on six females and along with flower physical measurements, pollen tube growth and seed set were assessed. Overall tree reproductive success was positively correlated with flower size, ovule numbers, style size, cross-sectional area of conductive tissue within the style (all of which were inter-correlated) and the proportion of pollen tubes reaching the bottom of the style. Significant positive correlations of reproductive success and flower physical properties between different ramets of the same genotypes across seasons suggests a genetic basis to the variation observed. The majority of pollen tube attrition occurred within the first millimetre of the cut style and appeared to be associated with differences in style physiology. When examined as pairs within races the difference in reproductive success for the Western Otways pair was simply explained by differences in flower size and the number of ovules per flower. Physical features did not differ significantly for the Strzelecki Ranges pair, but the proportion of pollen tubes reaching the bottom of the style was lower in the less reproductively successful genotype, suggesting an endogenous physiological constraint to pollen tube growth. The difference in reproductive success between the females from the Furneaux Group was associated with a combination of these factors.     

Influence of flower functionality and pollination system on the pollen size-pistil length relationship

Twenty-five biotically pollinated plants of the Chaco Serrano Forest (Córdoba, Argentina) were studied in order to analyze whether ‘flower functionality’ is related to the relationship between pollen size and pistil length. Because flower functionality may act on the respective mean values of pollen size and pistil length rather than on intraspecific variation in these traits, we expected (1) a high positive correlation between pollen size and pistil length in a set of sympatric species, independent of their degree of pollination specialization or generalization; and (2) no interspecific correlation between the coefficients of variation (CVs) of those traits. On the other hand, on the assumption that pollinators are influencing the variation in floral traits (e.g. in pistil length) we expected lower mean phenotypic variation of pollen size and pistil length in pollination-specialist plants than in pollination-generalist ones. A positive correlation between pollen size and pistil length was found for the set of species, but not between the CVs of these traits. This trend was maintained when pollination-specialist plants were analyzed separately, but no statistical significance was obtained for the correlation in pollination-generalist plants. Contrary to our expectations, pollination-specialist plants did not show less mean intraspecific variation in floral traits than pollination-generalist plants. Therefore, the relationship between pollen size and pistil length among species suggests that the pollination system may be of less importance as a selective force than flower functionality.     

ASEXUAL DEVELOPMENTAL PATTERNS OF THE DIATOM STAURONEIS ANCEPS IN CULTURE123

During several months under controlled growth conditions, cell division in the diatom Stauroneis anceps resulted in a gradual decrease in length as predicted by the Macdonald-Pfitzer hypothesis. Cells of a clone decreased in average length from 35 to 17 μ. The smallest cell observed measured 12 μ. Cells longer than 26 μ typically had capitate ends. As the cells became shorter, there was a gradual decrease in this capitate configuration with the smallest cells being oval in outline. The estimated increment of size reduction due to cell division in the clone was 0.1 μ per division. This value is dependent on the assumption of random division. Populations with cells less than 28 μ in length showed an increase in valve aberrations, but these cells continued to reproduce. A cell 13 μ long and similar to the smallest specimen of the clone was observed from a core sample with fossil specimens of S. anceps.     

Sexual reproduction and variation in floral morphology in an ephemeral vernal lily,Eyythronium americanum

Summary In a riparian population of Erythronium americanum (Liliaceae) in central New Jersey, experimentally self-pollinated plant produced markedly fewer fruit and fewer seeds per fruit than hand-outcrossed and open pollinated plants, even though differences were not evident between pollen tubes that penetrated stigmas from self or foreign pollen. This weak self-compatibility and a positive relation between the percentage of seeds set by outcrossed plants and the distance between pollen donor and recipient plants indicate that this population could be susceptible to inbreeding depression.Limited resources for seed development apparently constrained maximal seed production, based on low seed set (40.6%) by hand-pollinated plants and positive correlations for these plants between plant size and the number and size of seeds set. In contrast, naturally-pollinated plants set a smaller proportion of their ovules, suggesting that limited pollinator service reduced the quantity of seeds produced in this population. Free-foraging bees usually removed more than half of the available pollen in a single visit, so that individual plants probably have few opportunities to disseminate their pollen.Even though sexually reproductive ramets produce only a single flower per year, less than a third of variation in floral morphology is associated with variation in plant size. Within the flower, the sizes of some closely associated structures, such as the style and ovary, and the anthers and filaments, vary essentially independently of one another. Production of nectar and pollen, the ultimate attractors of pollinating insects, was positively correlated with flower size.     

Does cholinesterase participate in the intercellular interactions in pollen-pistil system?

Hydrolysis of acetylthiocholine and butyrylthiocholine has been observed in aqueous extracts from petunia pollen and pistils. The reproductive organs of self-compatible clone showed a higher rate of choline ester hydrolysis than those of self-incompatible clone. The highest rate of acetylthiocholine hydrolysis blocked by the cholinesterase inhibitors (physostigmine and neostigmine) was characteristic for the pollen of self-compatible clone. The incomplete (25 - 40 %) inhibition of hydrolysis in pistil extracts of self-compatible clone suggests the presence of unspecific esterases. The eight-fold lower hydrolysis was observed in the pistils of self-incompatible clone as compared to the pistils of compatible clone; neostigmine completely blocked this low hydrolytic activity. The treatment of flower buds with physostigmine and neostigmine (10-5 - 10-3 M) decreased the seed production by 10 - 20 % in compatible clone. When the surfaces of pistil stigmae were treated with physostigmine and neostigmine (10-5 - 10-3 M) before pollination, the seed formation was inhibited by 95 % after both self- and cross-pollination. This revised version was published online in July 2006 with corrections to the Cover Date.     

A model for seed size variation among plants

Summary I developed a model for seed size variation among plants assuming that the pollen captured per flower depends on both the allocation to pollen capture mechanisms per flower and the number of flowers on each plant. I showed that the optimal seed size increases with (1) the total resource allocation to reproduction, (2) decreasing outcross pollen availability, (3) decreasing probability of seedling establishment and (4) decreasing selfing rate. However, optimal seed size does not depend on the total resource allocation if the total number of pollen grains captured by a plant increases linearly with its flower number. In addition, the optimal seed size is not always positively correlated with the optimal resource allocation to pollen capture mechanisms per flower. I discussed implications of the results for seasonal decline in seed size and seed size variations among populations, such as alutitudinal variation.     

Pollen Morphology of the Subtribe Hyoscyaminae (Solanaceae)

The pollen morphology of 12 species representing 6 genera was examined under the light; scanning and transmission electron microscope. According to form of aperture; sculpture and structure of exine; the palynological relationships among the 6 genera are discussed. 1. Scopolia Jacq. (plate 1:1-4) Pollen grains subspheroidal or irregular; 43.7-49.6 μ in diameter; nonaperturate; Exine about 1.2-1.5μ thick; verrucate; with verrucae unequal in size; spinulose or granular. Stratification indistinct; with no columella layer visible under TEM. 2. Anisodus Link et Otto (plate 1: 5-12) Pollen grains subspheroidal; 43.4-48.7 μ in diameter; nonaperturate. Exine 1.5-1.8 μ thick; verrucate; with verrucae unequal in size; spinulose or smooth. Stratification indistinct under TEM. 3. Atropanthe Pascher (plate 2: 1-4) Pollen grains subspheroidai or spheroidal; triangular-circular in polar view; oblong in equatorial view; 47.2-49.3 μ ×39.8-47 μ; 3-colpate; colpi wide or narrow; colpus membranes finely granular. Exine with irregular short-stick sculpture; 2.3μ thick; distinctly 2-layered; columella layer clearly visible; sexine thicker than nexine under TEM. 4. Przewalskia Maxim. (plate 2: 5-8) Pollen grains subspheroidal; triangular-circular in polar view; oblong in equatorial view; 39.2-40.3 μ × 36.4-42.8 μ ; tricolporate; ora lalongate; colpus membranes granular. Exine reticulate; 2-layered; 2u thick; columella layer distinct; sexine and nexine equal in thickness under TEM. 5. Physochlaina G. Don (plate 2: 9-12; plate 3: 1-12) Pollen grains polymorphic; usually subspheroidal; 36.5-39.4μ in diameter; aperture varying from nonaperturate (P. macrophylla); 3-4 rugose (P. physaloides) to 3-colporate (P. praealta). Exine 1.5-2μ thick; reticulate; smooth or with spinulose or verrucous processes under SEM; distinctly 2-layered; or without stratification; columella layer differentiated or not. 6. Hyoscyamus Linn. (plate 4: 1-9) Pollen grains subspheroidal; circular-triangular in polar view; oval in equatorial view; 39.9-41.8 μ × 38.7-4.2 μ; tricolporate. Ora orbicular; colpus membranes finely granular or with striate processes. Exine reticulate or striate-rugulate; 2-2.3μ thick; distinctly 2-layered; columella layer developed. The dendrogram (Fig. 1) indicates probable phylogenetic relationships among the sixgenera in the subtribe Hyoscyaminae.     

Does the morphological fit between flowers and pollinators affect pollen deposition? An experimental test in a buzz‐pollinated species with anther dimorphism

Some pollination systems, such as buzz‐pollination, are associated with floral morphologies that require a close physical interaction between floral sexual organs and insect visitors. In these systems, a pollinator's size relative to the flower may be an important feature determining whether the visitor touches both male and female sexual organs and thus transfers pollen between plants efficiently. To date, few studies have addressed whether in fact the “fit” between flower and pollinator influences pollen transfer, particularly among buzz‐pollinated species. Here we use Solanum rostratum, a buzz‐pollinated plant with dimorphic anthers and mirror‐image flowers, to investigate whether the morphological fit between the pollinator's body and floral morphology influences pollen deposition. We hypothesized that when the size of the pollinator matches the separation between the sexual organs in a flower, more pollen should be transferred to the stigma than when the visitor is either too small or too big relative to the flower. To test this hypothesis, we exposed flowers of S. rostratum with varying levels of separation between sexual organs, to bumblebees (Bombus terrestris) of different sizes. We recorded the number of visits received, pollen deposition, and fruit and seed production. We found higher pollen deposition when bees were the same size or bigger than the separation between anther and stigma within a flower. We found a similar, but not statistically significant pattern for fruit set. In contrast, seed set was more likely to occur when the size of the flower exceeded the size of the bee, suggesting that other postpollination processes may be important in translating pollen receipt to seed set. Our results suggest that the fit between flower and pollinator significantly influences pollen deposition in this buzz‐pollinated species. We speculate that in buzz‐pollinated species where floral morphology and pollinators interact closely, variation in the visitor's size may determine whether it acts mainly as a pollinator or as a pollen thief (i.e., removing pollen rewards but contributing little to pollen deposition and fertilization).     

水蓼花大小在花序和个体上的变化及其与数量权衡关系研究

探讨一年生植物水蓼花大小在花序上和个体上的变化及花大小与花数量的权衡关系。在54株植物个体上随机选取一花序,在花序的基部、中部和顶部各选取1～2朵花,花大小(生物量)以基部最大(0.851mg),顶部最小(0.715mg),可能是由结构效应引起的。在每个体上随机采集4～20朵花,以其均值表示植物个体的花大小,花大小不随植物个体大小变化而变化。花朵展示和总花数均随个体增大而增加。在控制植物个体大小(地上部分营养器官生物量)后,没有发现花朵展示或花数量与花大小之间的权衡关系,表明个体资源水平的差异可能掩盖了花数量与大小间的权衡关系。     

Genetic constraints on floral evolution in a sexually dimorphic plant revealed by artificial selection

Sexual dimorphism is one of the most widespread and recognizable patterns of phenotypic variation in the biotic world. Sexual dimorphism in floral display is striking in the dioecious plant Silene latifolia, with males making many, small flowers compared to females. We investigated this dimorphism via artificial selection on two populations to determine whether genetic variation exists within populations for flower size and the extent of the between-sex correlation, whether a flower size and number trade-off exists within each sex, and whether pollen and ovule production vary with flower size. We selected for decreased flower size (calyx width) in females and increased flower size in males and measured the response to selection in size and correlated responses in flower dry mass, flower number, and pollen or ovule number per flower. Four bouts of selection in each of two selection programs were performed, for a total of three selection lines to decrease size, three to increase it, and two control lines. Flower size always significantly responded to selection and we always found a significant correlated response in the sex not under selection. Selection decreased but did not eliminate the sexual dimorphism in flower dry mass and number. A negative relationship between flower size and number within each sex was revealed. Whereas ovule number showed a significant correlated response to selection on flower size, pollen number did not. Our results indicate that although substantial additive genetic variation for flower size exists, the high between-sex genetic correlation would likely constrain flower size from becoming more sexually dimorphic. Furthermore, floral display within each sex is constrained by a flower size and number trade-off. Given this trade-off and lack of variation in pollen production with flower size, we suggest that sexual dimorphism evolved via sexual selection to increase flower number in males but not females.     

中国壳斗科栎亚科花粉形态研究

本文应用光学显微镜与扫描电子显微镜观察了壳斗科所属栎亚科2属26种2变种的花粉形态,并以本科其它属一些代表种作对比,试图从孢粉学方面为栎亚科的系统分类提供依据。 花粉外壁纹饰在扫描电镜下可分三种类型,即水青冈型(含水青冈属),栎型(含栎属和三棱栎属),栗型(含栗属、锥属和柯属),花粉的类型与植物形态分类的三个亚科一致。 栎亚科的花粉外壁纹饰在扫描电镜下为颗粒聚集成的种种形状。栎属可区分为四种类型,即颗粒状、颗粒——蠕虫状、聚颗粒及芽孢状,其中类型一、二、三为常绿种类,类型四为落叶种类。花粉纹饰在常绿与落叶种类之间有较明显的差异,而青冈亚属和栎亚属之间却没有界线。因此,栎属仍以包含两个亚属为宜。三棱栎属花粉纹饰则介于栎属的类型二与三之间。     

The influence of plant and corolla size on pollen deposition and seed set in Geranium sanguineum (Geraniaceae)

In a coastal grassland area the influence of plant and corolla size on insect visitation rate, pollen deposition on stigmas and seed set was measured in a natural population of Geranium sanguineum. Visits by bumble bees, the primal pollinators, were significantly affected by plant size measured as the number of flowers, and differences in visit rates among plants were explained by size differences among these. On average, larger plants had bigger corollas. The mean corolla area affected pollen deposition positively whereas deposition did neither affect seed set (number per flower) nor seed weight. Insects reaction to corolla size was dependent on plant size, and thus we found the effect of corolla size on pollen deposition to decline with plant size. Instead pollen deposition per plant seemed to be correlated to overall floral display. We argued that resource status of the individual plants could explain corolla size and seed set variation. The finding of some plant setting seeds while other plant with comparable size did not set any seeds could not be explained satisfactory by resource limitation.     

Evolution of floral display in Eichhornia paniculata (Pontederiaceae): direct and correlated responses to selection on flower size and number

Trade-offs between flower size and number seem likely to influence the evolution of floral display and are an important assumption of several theoretical models. We assessed floral trade-offs by imposing two generations of selection on flower size and number in a greenhouse population of bee-pollinated Eichhornia paniculata. We established a control line and two replicate selection lines of 100 plants each for large flowers (S+), small flowers (S-), and many flowers per inflorescence (N+). We compared realized heritabilities and genetic correlations with estimates based on restricted-maximum-likelihood (REML) analysis of pedigrees. Responses to selection confirmed REML heritability estimates (flower size, h2 = 0.48; daily flower number, h2 = 0.10; total flower number, h2 = 0.23). Differences in nectar, pollen, and ovule production between S+ and S- lines supported an overall divergence in investment per flower. Both realized and REML estimates of the genetic correlation between daily and total flower number were r = 1.0. However, correlated responses to selection were inconsistent in their support of a trade-off. In both S- lines, correlated increases in flower number indicated a genetic correlation of r = -0.6 between flower size and number. In contrast, correlated responses in N+ and S+ lines were not significant, although flower size decreased in one N+ line. In addition, REML estimates of genetic correlations between flower size and number were positive, and did not differ from zero when variation in leaf area and age at first flowering were taken into account. These results likely reflect the combined effects of variation in genes controlling the resources available for flowering and genes with opposing effects on flower size and number. Our results suggest that the short-term evolution of floral display is not necessarily constrained by trade-offs between flower size and number, as is often assumed.     

加拿大一枝黄花对土壤营养元素吸收与转运特征

选择临海沿江镇加拿大一枝黄花重度入侵区域,分别收集植物与土壤样品,研究加拿大一枝黄花对土壤中7种营养元素的吸收、转运特征。研究结果表明：7种营养元素在植物组织中的平均含量排序为：Zn〉K〉Ca〉N〉Mg〉P〉Mn。而且不同器官对同一种元素的积累存在显著差异,总体规律表现为叶和花蕾积累元素最多,其次是枝条和根状茎,根和茎则积累最少。地上器官对各元素的转移能力表现出明显差异,但各器官均对氮素有较强的转运能力,转运因子均明显高于1。地下器官（根和根状茎）对氮素有较高的富集能力,富集因子同样明显高于1。7种元素在加拿大一枝黄花不同器官的吸收转运存在着一定的促进或者拮抗作用。在花蕾、枝条和根中,磷吸收分别与Mg、Mn和Zn吸收呈现显著负相关;在花蕾中,氮的吸收和Mn的吸收呈现显著正相关;在不同器官里,K、Ca、Mg、Zn和Mn吸收之间多呈现正相关。