Widespread functional android in Mercurialis annua L. (Euphorbiaceae)

The widespread coexistence of male and monoecious (cosexual) plants in Spanish, Portuguese and Moroccan populations of Mercurialis annua , an annual wind-pollinated ruderal, represents an important case of functional androdioecy, a rare breeding system in plants and animals. In M. annua , both males and cosexes disperse fully competent pollen. Quantitative gender varies discontinuously between males and cosexes, with males producing a mean of 6.09 times as much pollen as cosexes. It appears that gender is determined by a simple developmental switch, with male and cosexual inflorescences differing markedly in morphology: staminate flowers are borne on erect peduncles in males and in tight spiral clusters around a subsessile pistillate flower in cosexes. Males do not differ from cosexes in their biomass, but they are significantly taller, principally as a result of their greater internode lengths. The cosexual inflorescence is strongly protogynous so that outcrossing is favoured in dense stands, but seed-set is assured in cosexes isolated from prospective mates because of their ability to self-fertilize. Males typically occur at frequencies of less than about 30% in androdioecious populations, in accordance with theoretical predictions for functional androdioecy. In the genus Mercurialis , dioecy is the ancestral condition and monoecy and androdioecy, which occur in polyploid populations of M. annua , are derived. I argue here that androdioecy is most likely to evolve in plants (1) from dioecy, (2) in wind-pollinated species, and (3) in species with a colonizing habit. These predictions are also consistent with the limited published data available for other species.     

Different endogenous cytokinins between male and female Mercurialis annua L.

The endogenous pool of cytokinin metabolites during sexual differentiation of Mercurialis annua L. was studied with a computerized gas-chromatography-mass spectrometry system. Certain metabolites were common to both sexes: ribosides (isopentenyl-adenosine, ribosylzeatin) and the nucleotide of I₆-Ade. Zeatin could be detected only in females while its nucleotide was present in males. The results were obtained with differentiating apices and whole plants. The high Z concentration and the low level of its nucleotide are related to the absence of two dominant complementary genes, determining maleness. Study of the regulation of cytokinin metabolism now seems possible.Abbreviations IPA isopentenyl adenosine - I₆-Ade isopentenyl adenine - Z zeatin - RZ ribosylzeatin     

An Approach to the Chemotaxonomic Differentiation of Two European Dog's Mercury Species: Mercurialis annua L. and M. perennis L.

Mercurialis annua and M. perennis are medicinal plants used in complementary medicine. In the present work, analytical methods to allow a chemotaxonomic differentiation of M. annua and M. perennis by means of chemical marker compounds were established. In addition to previously published compounds, the exclusive presence of pyridine‐3‐carbonitrile and nicotinamide in CH₂Cl₂ extracts obtained from the herbal parts of M. annua was demonstrated by GC/MS. Notably, pyridine‐3‐carbonitrile was identified for the first time as a natural product. Further chromatographic separation of the CH₂Cl₂ extracts via polyamide yielded a MeOH fraction exhibiting a broad spectrum of side‐chain saturated n‐alkylresorcinols. While the n‐alkylresorcinol pattern was similar for both plant species, some specific differences were observed for particular n‐alkylresorcinol homologs. Finally, the investigation of H₂O extracts by LC/MS/MS revealed the presence of depside constituents. Whereas, in M. perennis, a mixture of mercurialis acid (=(2R)‐[(E)‐caffeoyl]‐2‐oxoglutarate) and phaselic acid (=(E)‐caffeoyl‐2‐malate) could be detected, in M. annua solely phaselic acid was found. By comparison with synthesized enantiomerically pure (2R)‐ and (2S)‐phaselic acids, the configuration of the depside could be determined as (2S) in M. annua and as (2R) in M. perennis.     

Two's company, three's a crowd: experimental evaluation of the evolutionary maintenance of trioecy in Mercurialis annua (Euphorbiaceae)

Trioecy is an uncommon sexual system in which males, females, and hermaphrodites co-occur as three clearly different gender classes. The evolutionary stability of trioecy is unclear, but would depend on factors such as hermaphroditic sex allocation and rates of outcrossing vs. selfing. Here, trioecious populations of Mercurialis annua are described for the first time. We examined the frequencies of females, males and hermaphrodites across ten natural populations and evaluated the association between the frequency of females and plant densities. Previous studies have shown that selfing rates in this species are density-dependent and are reduced in the presence of males, which produce substantially more pollen than hermaphrodites. Accordingly, we examined the evolutionary stability of trioecy using an experiment in which we (a) indirectly manipulated selfing rates by altering plant densities and the frequency of males in a fully factorial manner across 20 experimental plots and (b) examined the effect of these manipulations on the frequency of the three sex phenotypes in the next generation of plants. In the parental generation, we measured the seed and pollen allocations of hermaphrodites and compared them with allocations by unisexual plants. In natural populations, females occurred at higher frequencies in denser patches, a finding consistent with our expectations. Under our experimental conditions, however, no combination of plant densities and male frequencies was associated with increased frequencies of females. Our results suggest that the factors that regulate female frequencies in trioecious populations of M. annua are independent of those regulating male frequencies (density), and that the stable co-existence of all three sex phenotypes within populations is unlikely.     

DNA markers for sex: Molecular evidence for gender dimorphism in dioecious Mercurialis annua L.

Male specific Random Amplified Polymorphic DNA (RAPD) markers, OPB01-1562 and OPC07-303, were identified and sequenced in dioecious Mercurialis annua. Sequence Characterized Amplified Region (SCAR) primers were designed. Several internal segments of OPB01-1562 were amplified as male specific SCAR markers. These markers were PCR amplified from strong, intermediate and weak male subtypes selected according to their resistance to feminization by cytokinin. Nucleotide sequence of OPB01-1562 isolated from three male subtypes were near identical. The OPB01-1562 and derived SCAR markers were absent in females as well as hexaploid Mercurialis male and monoecious individuals. The gender relationship of the markers was maintained in all ecotypes tested. There were 2 internal fragments of OPB01-1562, which were PCR amplified from all genotypes of diploid and hexaploid Mercurialis. It is argued that identification of gender specific DNA suggests a dimorphic differentiation of the genome of dioecious Mercurialis annua.     

An approach to the chemotaxonomic differentiation of two European dog's mercury species: Mercurialis annua L. and M. perennis L

Mercurialis annua and M. perennis are medicinal plants used in complementary medicine. In the present work, analytical methods to allow a chemotaxonomic differentiation of M. annua and M. perennis by means of chemical marker compounds were established. In addition to previously published compounds, the exclusive presence of pyridine-3-carbonitrile and nicotinamide in CH(2) Cl(2) extracts obtained from the herbal parts of M. annua was demonstrated by GC/MS. Notably, pyridine-3-carbonitrile was identified for the first time as a natural product. Further chromatographic separation of the CH(2) Cl(2) extracts via polyamide yielded a MeOH fraction exhibiting a broad spectrum of side-chain saturated n-alkylresorcinols. While the n-alkylresorcinol pattern was similar for both plant species, some specific differences were observed for particular n-alkylresorcinol homologs. Finally, the investigation of H(2) O extracts by LC/MS/MS revealed the presence of depside constituents. Whereas, in M. perennis, a mixture of mercurialis acid (=(2R)-[(E)-caffeoyl]-2-oxoglutarate) and phaselic acid (=(E)-caffeoyl-2-malate) could be detected, in M. annua solely phaselic acid was found. By comparison with synthesized enantiomerically pure (2R)- and (2S)-phaselic acids, the configuration of the depside could be determined as (2S) in M. annua and as (2R) in M. perennis.     

Responses of carbon acquisition traits to irradiance and light quality in Mercurialis annua (Euphorbiaceae): evidence for weak integration of plastic responses

It is often suggested that traits will be integrated, either because of pleiotropy or because natural selection may favor suites of integrated traits. Plant responses to different environments can provide evidence of such integration. We grew Mercurialis annua plants in high-density stands in high irradiance, in neutral shade, and in high red to far-red (R:FR) shade, resulting in environments of high irradiance, low R:FR; low irradiance, low R:FR; and low irradiance, high R:FR. We measured gas exchange, leaf morphology, stem elongation, and biomass traits and tested the prediction that traits within each functional group would show higher trait integration, as evidenced by high correlations among traits within environments, higher correlations of trait plasticity, and lower plasticity of trait correlations. Overall, we found evidence of only moderate integration for some groups of traits. Functionally related groups of traits, or pairs of traits, could be strongly integrated by one criterion but weakly integrated by another of the criteria. Stem elongation traits, though often observed to be strongly integrated in other taxa, showed little evidence of integration. Internode traits exhibited a novel pattern of responses to low R:FR, with increased elongation of the hypocotyl, decreased elongation of the first internode, and no change in the second internode. We propose that these responses to light are more likely to be the result of natural selection than the consequence of constraints imposed by pleiotropy.     

Isolation and localization by histoimmunology of isoperoxidases specific for male flowers of the dioecious species Mercurialis annua L.

Specific anodic isoperoxidases of male flowers of the dioecious plant Mercurialis annua were extracted, partially purified, and injected into rabbits. The serum against these specific peroxidases was used after absorption to localize these male isoenzymes during flower development by means of histoimmunology. (Indirect immunoperoxidase method). The peroxidases were characteristic of microsporogenesis and tapetum differentiation. Their synthesis started at an early stage of male organogenesis. They were not observed in other sites of peroxidase activity of male flowers (tunica, endothecium, filament, vascular anatomy) or in female flowers (embryo sac or nucellus). I propose that these isoenzymes constitute an early and specific marker of male organogenesis in higher plants.     

Phytohormone control of translatable RNA populations in sexual organogenesis of the dioecious plant Mercurialis annua L. (2n = 16)

A cell-free translation system was programmed with total, poly(A), non poly(A) and polysomal RNAs from male and female flowers of this plant with separated sexes. The peptide patterns obtained reflected differences in corresponding translatable RNAs. In total RNA products, three peptides were specific for males, two for females. One of the two male-specific polypeptides of high molecular weight was obtained from poly(A) RNAs and a female-specific one from non poly(A) RNAs. Differences between peptides common to both sexes reflected different concentrations of corresponding messengers. Similar results were obtained with polysomal RNAs. The male-specific RNAs were depending on high endogenous auxin concentrations while the female on active cytokinins. Cytokinin feminization of males induced the female-specific RNAs showing cytokinin action at pretranslational stages. Phytohormone roles are discussed.     

小桐子花的性别与开花时间的相互关系

通过对小桐子(Jatropha curcas L.)花序上小花的开花顺序和小花性别的观察,发现其聚伞花序中心花的性别与其开花时间相关联,同时还和周围其它小花的性别有很大的相关性.中心花若在整个花序开花的第一天开放,仅有23.2%的可能是雌花;若在第二天及以后开放,有85%以上的可能为雌花.而中心花的性别又与其它花的性别相关,中心花如为雌花,那么聚伞花序上的其它小花有80%的可能性为雌花;但中心花若为雄花,那么整个聚伞花序上将不会再有雌花.研究小桐子的开花行为及性别控制规律,对于进一步人工调控小桐子花的性别表达,提高小桐子的产量、培育高产稳产品种,具有重要的应用价值.     

Hybridization, polyploidy, and the evolution of sexual systems in Mercurialis (Euphorbiaceae)

Hybridization and polyploidy are widely believed to be important sources of evolutionary novelty in plant evolution. Both can lead to novel gene combinations and/or novel patterns of gene expression, which in turn provide the variation on which natural selection can act. Here, we use nuclear and plastid gene trees, in conjunction with morphological data and genome size measurements, to show that both processes have been important in shaping the evolution of the angiosperm genus Mercurialis, particularly a clade of annual lineages that shows exceptional variation in the sexual system. Our results indicate that hexaploid populations of M. annua, in which the rare sexual system androdioecy is common (the occurrence of males and hermaphrodites) is of allopolyploid origin involving hybridization between an autotetraploid lineage of M. annua and the related diploid species M. huetii. We discuss the possibility that androdioecy may have evolved as a result of hybridization between dioecious M. huetii and monoecious tetraploid M. annua, an event that brought together the genes for specialist males with those for hermaphrodites.     

Molecular Markers in the Identification of Some Early Flowering Curcuma L. (Zingiberaceae) Species

In this paper, isozymes have been used for the first time astools to aid identification of someCurcuma L. species that arestill taxonomically confused. These markers were employed toconfirm the taxonomic identification and to distinguish thetaxa analysed; the results were used to describe the relationshipwithin the early-flowering group. Twenty-one isozymes were initiallytested; out of these, eight isozymes showed reliable polymorphismto distinguish between the taxa analysed. Patterns from isozymedata were analysed using cluster analysis and UPGMA to producea dendrogram depicting the degree of relationship among thespecies. Copyright 1999 Annals of Botany Company Curcuma, Zingiberaceae, isozymes, species identification.     

白背叶(大戟科)性系统和传粉生物学研究

为探讨野桐属(Mallotus)雌雄异株的进化和传粉机制,对白背叶(Mallotus apelta)野生居群的性系统和传粉生物学进行了研究。结果表明,所调查的白背叶居群均由雌性(F)、雄性(M)和少数两性(B)个体组成,平均性比为1：0.66：0.18(F：M：B);3种性别植株的基径大小差异不显著;雌株与两性植株的单花胚珠数、单果结籽数和自然结实率无显著差异;雄株与两性植株的花粉萌发率、花粉组织化学和花粉微形态特征也无显著差异,但雄株的单花花粉量是两性植株的1.26~1.63倍,且差异显著;雌株的异交结实率为96.67%,两性植株的异交结实率为76.00%,两者差异显著,说明居群内雌株的潜在种子生产力明显高于两性植株;野外观察到雄株和两性植株上的雄花具有访花者而雌株没有;雌株经套网处理后结实率超过30%而套袋处理不结实。这些表明白背叶具典型的亚雌雄异株性系统,雌株和雄株的适合度均高于两性植株;雌株以风媒传粉结实,两性植株可能兼有风媒和虫媒传粉特征。     

Pollination biology of Harrisia portoricensis (Cactaceae), an endangered Caribbean species

Traits associated with self-pollination are common features of island plant communities. In this work, we studied the pollination biology and the breeding system of Harrisia portoricensis, an island columnar cactus, to test for the presence of inbreeding and inbreeding depression. For H. portoricensis, which bears flowers with typical outcrossing morphology, the results from 322 h of direct observations and videotaping showed that visits to flowers by animals were uncommon. Controlled pollinations demonstrated that H. portoricensis has a partially self-compatible breeding system that it is not autogamous and thus requires an external mechanism for the movement of pollen to set fruit. We detected differences in seed size, seed mass, germination success, and multiplicative fitness estimates between self- and cross-pollination treatments. We found that progeny resulting from natural and self-pollination treatments showed signs of inbreeding depression compared with progeny resulting from cross-pollination; however, the magnitude of the inbreeding depression was less than 50%. Our combined results suggest that for this species an endogamous breeding system should be favored by natural selection.     

Population Size,Pollination and Breeding System of Silene stockenii Chater (Caryophyllaceae), an Annual Gynodioecious Species of Southern Spain

The distribution area, phenology, sex polymorphism, floral characteristics and breeding system of Silene stockenii (Caryophyllaceae), a narrowly endemic annual species of southern Spain, were studied. Only five populations were found in a total area of 2 ha. Silene stockenii is a gynodioecious species with fully female, fully hermaphrodite and intermediate plants bearing hermaphrodite, male-sterile, and partially male-sterile flowers. Male-sterile flowers are typically smaller than hermaphrodites. Nectar production was significantly higher in hermaphrodite plants and during the female phase of hermaphrodite flowers. The red flowers appear during the spring (March-May) and are pollinated by long-tongued Bombyliidae. Hand pollinations revealed that the species is self-compatible; however, natural self-pollination is rare due to marked protandry. Hand pollination significantly increased the number of seeds per fruit and seed set, indicating limited pollination in the field. In controlled pollinations female plants of S. stockenii produced higher seed set than hermaphrodite plants, but in freely pollinated plants fruit set and seed production was similar in both morphs, indicating that pollinators do not discriminate in favour of hermaphrodite plants.     

Phytochemical Analysis,Biological Activity,and Secretory Structures of Stachys annua (L.) L. subsp. annua (Lamiaceae) from Central Italy

Stachys annua subsp. annua, well‐known in central Italy as ‘stregona annuale’, is an annual, small, slightly‐scented herb, commonly found in fields and uncultivated areas in almost all regions of Italy. In folk medicine, its aerial parts were used as anti‐catarrhal, febrifuge, tonic, and vulnerary. In the present work, the chemical composition of the flowering aerial parts was studied. The hydrodistilled volatile oil, analysed by GC/MS, showed sesquiterpenoids as the major fraction (42.5%); phytol (9.8%), germacrene D (9.2%), and spathulenol (8.5%) were the most abundant constituents. The volatile oil was assayed for antioxidant and cytotoxic activity by DPPH, ABTS, FRAP, and MTT methods. The cytotoxicity results against HCT116, A375, and MDA‐MB 231 human tumor cell lines were significant, with IC₅₀ values of 23.5, 37.2, and 41.5 μg/ml, respectively, whereas the antioxidant power was negligible. The EtOH extract was composed mainly of three glycosidic flavonoids, namely 7‐{[2‐O‐(6‐O‐acetyl‐β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐5,8‐dihydroxy‐2‐(4‐methoxyphenyl)‐4H‐1‐benzopyran‐4‐one ( 1 ), 7‐{[6‐O‐acetyl‐2‐O‐(6‐O‐acetyl‐β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐2‐(3,4‐dihydroxyphenyl)‐5,8‐dihydroxy‐4H‐1‐benzopyran‐4‐one ( 2 ), and 7‐{[6‐O‐acetyl‐2‐O‐(β‐D ‐allopyranosyl)‐β‐D ‐glucopyranosyl]oxy}‐2‐(3‐hydroxy‐4‐methoxyphenyl)‐5,8‐dihydroxy‐4H‐1‐benzopyran‐4‐one ( 3 ). On the contrary, iridoids, considered chemotaxonomic markers of the genus Stachys, were absent in this species. Finally, the morphological and histochemical survey showed that glandular trichomes were composed of two main types, i.e. peltate type A and capitate types B and C giving positive response for both lipids and polyphenols.     

Flowering and Pollination of Philodendron melinonii (Araceae) in French Guiana

Abstract: The pollination ecology of Philodendron melinonii was studied at two locations in French Guiana. Inflorescences of P. melinonii were regularly visited by Cyclocephala colasi, a scarab beetle also found in inflorescences of P. solimoesense in the same area. The flowering cycle lasted two days and the inflorescence exhibited features typical for beetle pollination (e.g., floral chamber, food rewards, flower heating). The flowering process is well synchronized with the night activity of Cyclocephala visitors. The spadix temperature was measured during the entire flowering cycle in the field in French Guiana and in greenhouse conditions at the Montreal Botanical Garden. Both measurements gave a similar temperature pattern with a two hour delay at the Botanical Garden. The spadix warmed up twice during the flowering period and its temperature was not significantly different from that of ambient air between the two peaks. These two temperature peaks are also well synchronized with the arrival and departure of the beetles on two consecutive nights.     

青藏高原高山植物麻花艽的传粉生态学研究

对青藏高原东部麻花艽 (Gentiana straminea)海北居群的传粉生态学进行了 3a连续的观察和实验。试验表明自然去雄、人工自交和杂交处理均结实 ,而人工去雄套袋和自然套袋不结实。麻花艽自交亲合 ,但必须依赖传粉媒介才能完成授粉过程 ,不存在无融合生殖。野外捕捉到 14种访花昆虫 ,它们分别属于 2个纲 ,7个目 ,8个科。观察和分析了各种昆虫的访花行为后 ,认为苏氏熊蜂 (Bombus sushikini)是麻花艽有效而稳定的传粉者。测量表明麻花艽花蜜通道的深度和苏氏熊蜂的舌长基本吻合。苏氏熊蜂的访花频率在 10 :0 0～ 12 :0 0 ,13:0 0～ 15 :0 0和 16 :0 0～ 18:0 0时间段没有差别 ,单花的访花频率为 0 .0 0 5次 / (花· min)。和其它高山植物相比 ,青藏高原高山植物麻花艽的访花频率较高。熊蜂传粉和高频率的访花维持了麻花艽在极端寒旱的青藏高原环境下的有性生殖。此外 ,高频率的访花对于维持该地区高山植物的生殖保障具有重要的现实意义 ,但是否具有普遍性 ,还有待研究更多的高山代表类群。