An unusual homostyle inHedyotis caerulea (Rubiaceae)

Hedyotis caerulea, a spring flowering herb widely distributed in eastern North America, has distylous flowers that differ by a number of morphological and physiological traits. The presence of a strong incompatibility system is indicated by the fact that intramorph crosses or self-pollinations produced little or no seed and intermorph crosses produced copious seed. An unusual homostyle was located that had most floral characters intermediate between pin and thrum flowers, although its pollen size was that of pin. The homostyle was only moderately self-compatible, and its pollen did not behave as pin pollen on thrum stigmas. It appears that, despite their intermediate position and morphology, the homostyle stigmas were fundamentally pin. Although the exceptional rarity of the homostyle suggests that it is an inadaptive failure, workers should watch for its further occurrence since additional study of it may provide insights into the genetic and physiological basis of heterostyly in theRubiaceae.     

茜草科二型花柱植物滇丁香传粉精确性研究

异型花柱是一种受遗传因素控制的花型多态性现象,其适应意义在于提高不同花型间传粉精确性,从而促进异交。为检验二型花柱植物滇丁香（Luculia pinceana）是如何促进异交并确定有效传粉者的类型,实验统计自然种群中长、短柱型的植株数量,测量花部特征,统计自然种群植株柱头上的型间花粉落置的数量和比例,比较型内、型间花粉的萌发率以及花粉管长度,比较不同人工授粉处理结实情况,观察传粉昆虫类型并测量虫体特征。结果表明（1）滇丁香自然居群中长、短柱型植株的数量没有显著性差异。长柱型的筒深、筒直径、开口直径、雄蕊长和柱头长均显著小于短柱型,而长柱型的叶片长和宽、雌蕊长、花药体积、花粉粒体积、柱头厚均显著大于短柱型。（2）自然种群植株柱头上型间花粉所占比例显著低于型内花粉的比例。（3）型间授粉的花粉萌发率以及花粉管长度均大于型内授粉和混合授粉。（4）型间授粉的结实率显著高于型内授粉的结实率,型内授粉具有一定的结实。（5）夜行性长喙条背天蛾（Cechenena lineosa）是滇丁香的有效传粉者,其吻长和滇丁香的花筒深相适应。本研究表明二型花柱植物滇丁香主要是通过与其花部特征相匹配的长喙天蛾实现有效的传粉,通过促进型间花粉的萌发和花粉管的伸长而有利于型间授粉结实,提高传粉精确性。     

The origin ofSenecio vulgaris (Asteraceae)

Senecio vulgaris L. (2n = 40) is suggested to be of autotetraploid origin fromS. vernalis Waldst. & Kit. (2n = 20). This conclusion is based on results obtained from experimental hybridisations and cytological observations, and the consideration of morphological affinities, patterns of geographical distribution and hybrid formation under natural conditions. The morphological differences between the two species are related to a difference in the breeding system. WhilstS. vernalis is self-incompatible,S. vulgaris is self-compatible and strongly self-pollinating. Equally, other self-pollinating taxa traditionally associated withS. vulgaris are shown to have evolved independently from outbreeding relatives. Within a narrow frame of relationship, annual weeds have evolved in different cytotaxonomic circumstances.     

Bottleneck-induced dissolution of self-incompatibility and breeding system consequences in Aster furcatus (Asteraceae)

Aster furcatus is a rare species with extremely limited genetic variation at isozyme loci. We utilized crossing experiments and seed set data obtained from natural populations to verify that there is also little allelic variation at the self-incompatibility (S) locus. Seed set in several populations was limited by a low number of S-alleles. Associated with a low number of S-alleles in populations was the dissolution of the incompatibility system, manifest by individual variation in self-compatibility, and by complex dominance relationships among S-alleles. Plant self-compatibility was correlated with mean number of ovules per inflorescence. Thus, self-compatibility appeared to be under partial environmental influence. Computer simulations revealed that the shapes of seed set distribution curves of modeled self-incompatible plant populations depend on the number of incompatibility alleles in the populations. By varying the number of S-alleles in modeled populations, we generated seed set distribution curves similar to those of natural populations. Genetic bottlenecks reduce the number of S-alleles and the proportion of compatible matings in populations of multiallelic self-incompatible species. Self-compatible genotypes are at a selective advantage in populations that lack a sufficient number of S-alleles to produce compatible crosses. Aster furcatus appears to be evolving self-compatibility as a result of bottleneck-induced losses of S-alleles.     

Sexual reproduction and crossing barriers in white pines: the case between <Emphasis Type="Italic">Pinus lambertiana</Emphasis> (sugar pine) and <Emphasis Type="Italic">P. monticola</Emphasis> (western white pine)

The sexual reproductive process in Pinus lambertiana has not been completely described, and previous attempts to generate hybrids with Pinus monticola and other North American pines have not been successful. The nature of incompatibility barriers between P. lambertiana and P. monticola is unknown. This needs to be understood if strategies are to be developed to overcome the said barriers. In this paper, development on interspecific crosses is compared with that on intraspecific crosses on the same parent trees. Pollen grains of both species germinated on the nucellus of both species within a week after pollination. Seed cone receptivity in P. lambertiana came approximately 2 weeks after receptivity in P. monticola, and this delay was perpetuated throughout ovule development in the first year of the reproductive process. Development of the second-year seed cones proceeded more gradually in P. lambertiana. However, seed cones reached maturity only for P. monticola x P. lambertiana. In both crosses, the barriers to hybridization occurred during the second year of the reproductive process. With the P. lambertiana as the seed parent, it was manifested through the failure of the megaspores at the free-nuclear stage to resume development. When P. monticola was used as the seed parent, the male and female gametes failed to fuse. Our results clearly show that the barriers to hybridization in these species occur before or at fertilization. However, the exact mechanisms behind these are still unknown. Based on the results of this study, we present several strategies to bypass the developmental barriers and possibly produce hybrid progenies.     

Crossing and selfing experiments in theOrnithogalum umbellatum/augustifolium complex

The fertility relationships ofOrnithogalum umbellatum, O. angustifolium and 9 related taxa were studied.O. umbellatum andO. angustifolium, which are not interfertile, are both recognized as a comparium. Pollination of five species belonging to theO. umbellatum/angustifolium polyploid complex, i.e.O. umbellatum, O. angustifolium, O. baeticum, O. monticolum andO. algeriense, resulted in a moderate seed set. However, the seeds obtained after these interspecific crosses did not germinate. Six related species, i.e.O. exscapum, O. nivale, O. comosum, O. collinum, O. gussonei andO. woronowii showed a very low seed set after being crossed. One exception occurs:O. nivale ×O. exscapum. The seed set was also low after the complex species had been crossed with some related species, but there was one exception: both reciprocal crosses betweenO. monticolum andO. woronowii yielded some viable seeds. No other interspecific crosses gave rise to viable seeds. Bulbil-producing species have a lower seed set after self-pollination than species which do not produce bulbils.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex IV.—Previous contributions: (I–III):Raamsdonk (1982, 1985a, 1985b).     

Density and reproductive success in wild populations of Diplotaxis erucoides (Brassicaceae)

Summary One possible consequence of low population density, particularly in self-incompatible plants, is reproductive failure. I surveyed seed set per flower in two populations of the self-incompatible annual Diplotaxis erucoides (Brassicaceae) in Jerusalem, Israel. Widely spaced plants had lower fruit set and fewer seeds per filled silique than did plants growing close to conspecific neighbors. Such density-dependent reproductive success could help explain the maintanence of spatial patchiness in plant populations, and could also have implications for population dynamics of rare species.     

Pollen tube expression of pseudo-self-compatibility (PSC) inPetunia hybrida

Summary AnS _1.1 self-incompatible (SI) petunia plant which showed atypical seed set was found in an I₇ population. This plant showed a strong SI reaction when selfed but produced varying amounts of seed when used as the seed parent in crosses with unrelated individuals homozygous for the sameS allele. Reciprocal crosses yielded no seed indicating that the reaction was a stylar response. Self seed obtained by high temperature treatments produced 18 plants, all of which exhibited the parental characteristics, the ability to reject self pollen but accept, to varying degrees, pollen bearing the sameS allele from unrelated plants. Several petunias homozygous forS ₁, and exhibiting various levels of PSC as determined by self seed set, progeny tests and temperature treatments, were used as pollen parents. The mean seed set of these crosses produced a ranking of the pollen parents which reflected the PSC levels obtained by other methods. The behavior of the F₁ and F₂ populations suggests that the pollen discriminating ability may be a simply inherited, dominant character in these plants. The styles of these unusual petunias illustrate the participation of the pollen tube in determining PSC.Scientific Journal Series Paper Number 10.479 of the Minnesota Agricultural Experiment Station     

Distyly and sequential pollinators of Psychotria nuda (Rubiaceae) in the Atlantic rain forest, Brazil

Reciprocal herkogamy is known to promote intermorph-pollination in distylous species, which are generally self- and intramorph-incompatible. Legitimate crossing rates are also influenced by pollinator foraging strategy, which determines most of the pollen flow in natural populations. This study reports on the floral morphology, compatibility relations and pollination biology of Psychotria nuda (Cham. and Schltdl.) Wawra in the Atlantic rain forest, southeastern Brazil, based on floral measurements, hand-pollination experiments and focal observation of floral visitors. It was found that P. nuda does not present an exactly reciprocal herkogamy, however, this morphological trait in P. nuda is as good as in most of Rubiaceae. Reproductive experiments showed compatibility relations similar to those frequently observed in distylous species. The hummingbirds Ramphodon naevius and females of Thalurania glaucopis were the main pollinators of P. nuda, presenting the traplining foraging strategy, which seems to maximize intermorph crosses in P. nuda flowers. These hummingbirds pollinated P. nuda flowers sequentially throughout the flowering period.     

COMPARATIVE FECUNDITY AND POPULATION COMPOSITION OF HETEROSTYLOUS AND NON-HETEROSTYLOUS SPECIES OF VILLARSIA (MENYANTHACEAE) IN WESTERN AUSTRALIA

Several species of Villarsia in Western Australia are distylous, but their floral morphology is variable and mostly differs from the expected positional relationships of stigmas and anthers. Villarsia albiflora is non-heterostylous but self-incompatible. In the distylous V. calthifolia, V. capitata, and V. lasiosperma, morph ratios were 1:1, but in some populations of V. parnassiifolia the short morph was present in excess. Ovule production per flower of the two morphs of the distylous species varied between populations, but within most populations was equal. In nine populations of the distylous species, percentage seed-set of Longs and Shorts was equal. In the five populations of the distylous species in which percentage seed-set differed between the morphs, seed-set of Longs exceeded that of Shorts. In four populations of V. parnassiifolia with Shorts in excess, percentage seed-set of the two morphs was equal; in a fifth, that of Longs exceeded that of Shorts. Percent seed-set of V. albiflora did not differ from that of the distylous species and remained constant during the flowering season despite a substantial decrease in ovule production during this period. This study demonstrated no reproductive advantage of distyly over monomorphism in the species studied.     

腺柄凤仙花，中国凤仙花属一新归化种

报道了我国漠河城郊发现的凤仙花科凤仙花属新归化种：腺柄凤仙花(Impatiens glandulifera Royle)。腺柄凤仙花原产于印度及西喜马拉雅山脉,是一种具有高度入侵性的一年生草本植物,已经入侵欧洲和北美的许多地区,目前发现已经归化于黑龙江省大兴安岭地区漠河市。调访得知该种至少于两年前人为引入种植,种植1 a后即可通过种子在周边繁殖大量个体。报道了腺柄凤仙花的形态特征、地理分布、生物学特征、传播途径、入侵潜力及危害和防治措施,以期为外来入侵物种的鉴定与防治提供数据支持。     

How selfing and intra- and interspecific crossing influence seed set, morphology and ploidy level in Euphrasia: An experimental study of species occurring in the Alps of Switzerland

Annual alpine species rely on selfing rather than on cross-pollination for successful reproduction. However, insect visits may occasionally cause cross-pollination not only within but also between closely related species. The aim of this study was to investigate four species of Euphrasia for their efficiency in spontaneous selfing and their success in intra- and interspecific crossing. We used the seed sets that followed spontaneous selfing and artificial cross- and selfpollination to measure the breeding success. We compared the morphological characters of species and hybrids and determined their ploidy level using flow cytometry. We verified the hybridogenous origin of plants resulting from interspecific crosses using RAPD banding patterns. While spontaneous seed set was high in the two small-flowered species, seed set in the large-flowered species was small and affected by external circumstances. We obtained F1 and F2 hybrids from interspecific crosses of two diploid species and detected polyploid individuals in both generations.     

Pollen morphology inLinum sect.Macrantholinum

Pollen of the two distylous species which make upLinum sect.Macrantholinum differs from that of other distylous species in the genus in being multiporate and in having much more modest differences in exine sculpturing between grains from long- and short-styled plants. Pollen morphology does not help in relating the two species to others in the genus but does support their retention in a separate section.     

Heterostyly in species ofNarcissus (Amaryllidaceae) andHugonia (Linaceae) and other disputed cases

The hypothesis ofHenriques andFernandes that several Iberian species ofNarcissus (Amaryllidaceae) are tristylous is reconsidered. Contrary to the opinion ofBateman and most subsequent authors, we believe that the available evidence indicates that some populations ofN. triandrus andN. fernandesii, at least, are tristylous; other populations ofN. triandrus are distylous.Hugonia cf.penicillanthemum (Linaceae) from new Caledonia is distylous, but it remains possible that other species ofHugonia are tristylous. The disputed occurrence of heterostyly in S. African species ofBauhinia (Leguminosae),Cleome (Capparaceae) andAneilema (Commelinaceae), and inAgelaea (Connaraceae) is discussed.     

Cross-incompatibility between two sympatric polyploid Solanum species

Summary Preliminary results from a large number of reciprocal crosses between the closely related sympatric species S. gourlayi Hawkes (2n=4x=48) and S. oplocense Hawkes (2n=6x=72) indicated that they are difficult to hybridize. Pollen-pistil incompatibility barriers were detected via fluorescent microscopy. The cross incompatibility reaction occurred at three sites in 6x×4x crosses; on the stigma, in the first one-third of the style, and in the first two-thirds of the style. In the reciprocal 4x×6x crosses the incompatibility reaction invariably occurred in the ovary. Backcrosses of interspecific pentaploid hybrids (that were occasionally formed) to both parental populations were fully compatible, partially compatible, and fully incompatible with three sites of cross-incompatibility reaction similar to those observed in 6x×4x crosses, respectively. Both polyploid species were found to be selfcompatible, whereas their F1 hybrids were found to be self-incompatible. An hypothesis based on interactions of dominant cross-incompatibility (CI) genes in pistils and dominant specific complementary genes in pollen grains is postulated to explain these observations. The cross-incompatibility system that appears to be operating in nature between 4x S. gourlayi and 6x S. oplocense provides a way for gene exchange between sympatric populations without threatening the identity of either species.     

Compatibility studies in three wild species of Lycopersicon

A study was made on the self-compatibility in L. hirsutum (LH), L. pennellii (LP) and L. chilense (LC) and on cross-compatibility or preferable unilateral compatibility between these wild species and L. esculentum (LE). From the results of various test crosses and selfings and of cytological research and fruit and seed setting as well it was concluded that the material used is compatible but it differed in the degree of the expression. The highest self- and cross-compatibility was found in LP where number of seed, their viability and also pollen tube growth was similar to LE. Differences between LC and LH in self-compatibility and the congruity with LE were very small on the basis of pollen tube elongation but relatively fewer number of fruit and seed were obtained in the cross LE × LC than from the combination of LE × LH. In the reciprocal crosses when wild species were used as the pistillate parent, no seed were obtained as fertilization was prevented.     

Immunocytochemical distribution of polygalacturonase and pectins in styles of distylous and homostylous Turneraceae

Distyly is a plant breeding system in which two self-incompatible, but cross-compatible, floral morphs occur within populations. The morphs differ in having a reciprocal arrangement of styles and anthers. Little or nothing is known of the proteins involved in self-incompatibility for any distylous species. Here we show that a 35 kDa putative polygalacturonase is specific to the transmitting tissue of short-styled plants of five species in series Turnera. The polygalacturonase was not detected in styles of long-styled plants, or in styles of five homostylous self-compatible species in this series of the genus. It is also absent from two X-ray generated mutants and a spontaneous somatic homostylous mutant that arose on a short-styled plant and whose style does possess this polygalacturonase. Three more distantly related species in the Turneraceae were investigated. Turnera weddelliana (series Salicifoliae) does possess the polygalacturonase; however, T. diffusa (series Microphyllae), and Piriqueta caroliniana, showed no evidence of possessing this polygalacturonase using immunocytochemistry. Polygalacturonase assays revealed activity in styles of long- and short-styled plants, but showed no activity of the 35 kDa style polygalacturonase. The distribution of pectins in styles and pollen tubes revealed no difference between the long- and short-styled morphs. Methyl-esterified pectins occur throughout the style tissues, except in the transmitting tissue. The transmitting tissue possesses unesterified pectins that could provide a substrate for polygalacturonase activity. We propose that the style polygalacturonase might act in a complementary manner, allowing pollen of long-styled plants to grow through short styles or, alternatively, oligogalacturonide products of polygalacturonase activity might play a role in signalling compatible responses.     

Pollination and breeding system of Melochia tomentosa L. (Malvaceae), a keystone floral resource in the Brazilian Caatinga

The main goals of the present paper were to investigate the floral biology and the breeding system of Melochia tomentosa in a semi-arid region in Brazil, comparing the role of Apis mellifera with other native pollinators, and to discuss the importance of this plant species as a floral resource for the local fauna in maintaining different guilds of specialized pollinators in the Caatinga. M. tomentosa is very common in Caatinga areas and blooms year-round with two flowering peaks, one in the wet and another in the dry period. The pink, bright-colored flowers are distylous and both morphs are homogamous. The trichomatic nectary is located on the inner surface of the connate sepals, and the nectar (ca. 7 μl) is accumulated in the space between the corolla and the calyx. Nectar sugar concentration reaches an average of 28%. The results of controlled pollination experiments show that M. tomentosa is self-incompatible. Pollen viability varies from 94% to 98%. In spite of being visited by several pollen vectors, flower attributes of M. tomentosa point to melittophily, and A. mellifera was the most frequent visitor and the principal pollinator. Although honeybees are exotic, severely competing with native pollinators, they are important together with other native bees, like Centris and Xylocopa species, for the fruit set of M. tomentosa. This species represents a keystone floral resource favoring the maintenance of many species of bees, butterflies and hummingbirds through the year in this deciduous tropical dry forest.     

The evolutionary significance of multigermicity in the genusSpinacia (Chenopodiaceae)

The presence of multigerm seedballs in the chenopodiacious genusSpinacia is noted. In the wild, colonising, and weedy dioecious species,S. turkestanica andS. tetrandra, the distribution of a multigerm seedball could effectively overcome the problem posed by isolation of the sexes. The hypothesis is tested assessing the extent of intra-seedball progeny hybridisations and seed production in the two wild species. The success in seed production by intra-seedball progeny crosses suggests that the distribution of such seedball progeny groups permits not only a percentage survival under isolation of these dioecious plants, but also the colonisation of areas outside that of the parent populations.     

Dimorphic exine sculpturing in two distylous species ofDyerophytum (Plumbaginaceae)

Light and SEM observations on the pollen ofDyerophytum africanum andD. indicum have revealed marked differences in exine features. These distylous species also have dimorphic pollen. In the short-styled individuals of both species, the sexine and nexine are of equal thickness, and the clava-like sexinous processes are short without marked projections. In the long-styled individuals, the sexine is thicker than the nexine, the clavae are higher than broad with an apical spinule. Pollen size and apertures are identical in both morphs. — Palynological evidence is presented for relationships betweenDyerophytum andCeratostigma, Plumbago andAegialitis. Moreover, the genusDyerophytum exhibits pollen morphological similarities with some species ofLinum (Linaceae).