The pollination ecology of Paraboea rufescens (Gesneriaceae): a buzz-pollinated tropical herb with mirror-image flowers

BACKGROUND AND AIMS: Gesneriaceae is a pantropical plant family with over 3000 species. A great variety of pollination mechanisms have been reported for the neotropical members of the family, but the details of buzz-pollination and enantiostyly for the family have not been described. We investigated the floral biology and pollination ecology of Paraboea rufescens in Xishuangbanna, south-west China, considering three aspects: (1) the type of enantiostyly exhibited; (2) whether the species is self-compatible; and (3) whether pollinator behaviour could enhance the precision of pollen transfer between flowers of contrasting stylar orientation. METHODS: Flowering phenology was monitored once a month during vegetative growth, and once a week during flowering both in the field and under cultivation. Pollination manipulations and pollinator observation in the field were conducted. KEY RESULTS: Anthesis occurred early during the morning, and flowers remained open for 1-5 d, depending on weather conditions. Controlled pollinations revealed that P. rufescens is self-compatible, and exhibited inbreeding depression in seed set. Plants were pollinator limited in natural populations. The similar stylar deflection among flowers within a plant limits autonomous self-pollination as well as pollination between flowers. Two species of bumble bees (Bombus spp.), Amegila malaccensis and Nomia sp. effectively pollinated P. rufescens. These pollinators visited flowers in search of pollen with almost the same frequency. None of the pollinators appeared to discriminate between left- or right-handed flowers. CONCLUSIONS: Paraboea rufescens exhibits monomorphic enantiostylous flowers and a buzz-pollination syndrome. Floral morphology in P. rufescens and pollinator foraging behaviour seems likely to reduce self-pollination and pollinations between flowers of the same stylar deflection.     

花、基因、禾本科

进化发育生物学的一个重要任务就是揭示形态多样性的分子基础,该领域的研究包含形态、形态发育相关基因和形态所属类群等三个要素。花/花序是进化发育生物学研究的首要对象,系统发育重建和个体发育剖析的结合将促进认知花的形态进化。发育相关基因的进化表现为等位基因遗传或表观遗传的突变,基因家族生与死的进化,不同基因组拥有独特的基因。运用形态学或序列分析方法很大程度揭示了禾本科植物花进化过程中的基因进化。试从学科问题、思路方法以及具体例子介绍植物进化发育生物学。     

野葛花醇提物中异黄酮含量及其抗氧化活性测定

以葛花苷为标准品,对野葛花醇提物的氯仿、乙酸乙酯、正丁醇萃取物及水溶物4部分中的异黄酮含量进行测定,并采用DPPH·法对各萃取物进行自由基清除实验.结果显示,(1)氯仿、乙酸乙酯、正丁醇萃取物及水溶物4部分的异黄酮含量分别为35.27%、53.42%、52.13%和2.34%.(2)抗氧化实验显示, 4 部分清除DPPH·的IC50值分别为252、49、197和344 μg/mL.(3)相关性分析表明,野葛花醇提物各萃取部分的抗氧化活性主要来自于其中含有的异黄酮类化合物.研究表明野葛花醇提物的乙酸乙酯和正丁醇萃取部分异黄酮含量较高;氯仿、乙酸乙酯、正丁醇萃取物及水溶物4部分对DPPH自由基均有一定的清除作用,其中以乙酸乙酯萃取物的效果最佳;表明异黄酮是一种天然的抗氧化剂,具有较强的抗氧化作用.     

四川攀西地区南亚热带观赏花卉引试种初报

本文报道四川攀西地区引进的53科143个观赏花卉品种的引种试种情况。结果表明,所引进的品种在攀西地区均表现为适应性较强,可望成为今后该地区发展观赏花卉的主导品种。     

Colonization of Female Watermelon Blossoms by Acidovorax avenae ssp. citrulli and the Relationship between Blossom Inoculum Dosage and Seed Infestation

The aim of this work was to investigate the ability of Acidovorax avenae ssp. citrulli, the causal agent of bacterial fruit blotch of cucurbits (BFB), to colonize female watermelon blossoms, and to explore the relationship between blossom inoculum dosage and seed infestation. Under greenhouse conditions A. avenae ssp. citrulli colonized stigmas and styles of female watermelon blossoms reaching populations of ≈10⁷ to 10⁸ colony‐forming units (CFU) per blossom for 96 h after inoculation. Acidovorax avenae ssp. citrulli growth on stigmas was slower than that of Pseudomonas syringae Cit7, a non‐pathogenic, foliar epiphyte of tomato. While pollination reduced growth of A. avenae ssp. citrulli, but P. syringae Cit7 was unaffected. Both bacteria colonized style tissues but bacterial growth in the style was significantly less than the stigma. Blossom inoculation with ≈1 × 10³A. avenae ssp. citrulli CFU/blossom led to 36–55% infested seedlots within symptomless fruits. On average 14% of the seedlings produced from these seedlots displayed BFB symptoms. There was a strong positive correlation between A. avenae ssp. citrulli inoculum concentration applied to blossoms and the percentage of infested seedlots, as determined by the seedling grow‐out assay (R² = 0.94). However, this relationship was weaker when seedlot infestation was determined by a polymerase chain reaction‐based assay (R² = 0.34). There was also a strong positive linear relationship between A. avenae ssp. citrulli blossom inoculum dose and the mean percentage of BFB‐infected seedlings (R² = 0.99) produced in seedling grow‐out assays. These data support the hypothesis that blossom colonization might be involved in seed infestation under field conditions.     

Flowers and fruits prolong survival of drosophila pupal parasitoids

Adult parasitoids often feed on sugar sources for survival and to fuel energy. Therefore, the provision of sugar sources, such as nectar from flowers, can enhance biological control. We assessed whether Pachycrepoideus vindemmiae and Trichopria drosophilae, two pupal parasitoids of Drosophila spp., can profit from different sugar sources. In a laboratory experiment, we offered honey, cornflower and buckwheat flowers, crushed and Drosophila suzukii-infested blueberries as well as hosts together with honey. In both parasitoid species, all food sources significantly prolonged the lifespan of females compared to the control. The flowers prolonged the lifespan in both species threefold or fourfold, in P. vindemmiae from a mean of 6 to 28 days, in T. drosophilae from 13 to 49 days. Infested and damaged blueberries also enhanced mean survival in both species. When fed honey, the presence of hosts slightly decreased lifespan in P. vindemmiae and strongly decreased it in T. drosophilae. Our results suggest that the parasitoids can utilize the fruits they encounter during host search. Flowers could enhance their biological control function even further, as long as they do not benefit the pest.     

The ecology and evolution of pollen odors

The literature is reviewed and new evidence presented that pollen produces odors, which serve multiple functions in pollination and defense. Pollen odor, which originates from pollenkitt, comprises volatiles that belong to the same chemical classes found in flower scents, that are in species-specific mixtures, and that contrast with odors of other floral parts. Pollen can also take up volatiles from surrounding floral odors, but this adsorption is selective and varies among species. Pollen odors are more pronounced in insect- than bird- or wind-pollinated plants, suggesting that volatile emission evolved in part under selection to attract pollinators. Pollen-feeding insects can perceive pollen odor and use it to discriminate between different pollen types and host plants. Pollen odor influences bee foraging, including the location of pollen sources, discrimination of flowers with different amounts of pollen, and hostplant recognition by pollen-specialist species. In the few wind-pollinated plants studied, odors of male flowers or pollen are comparatively high in -methyl alcohols and ketones; these volatiles may serve in pollen defense, with some known to repel insects. Pollen odor often includes chemicals with documented defense activity, which is probably aimed mainly at nonpollinator pollen-feeding insects and pathogens; an involvement in pollen allelopathy is also possible. Pollen volatiles comprise chemically diverse compounds that may play multiple roles, and their emission in pollen odor undoubtedly evolved under the principle, and often conflicting, selective pressures to both protect the male gametophyte and increase its dispersal by animals.     

高黎贡山花卉资源与赏花旅游初探

高黎贡山有完整的生物气候垂直带谱自然景观,多种植被类型和丰富的植物资源,目前已知有种子植物2门210科1086属4303种及变种,其中有较高观赏价值的花卉达62科320属1053种,是我国花卉资源最丰富的地区之一。高黎贡山花卉资源具有种类丰富,名花众多;珍稀,濒危植物多;植物区系成分复杂,起源古老,特有植物多;垂直分布明显,四季花卉不断;形态各异,色彩绚丽等特点,是开展赏花旅游的理想地方,笔者设计3条赏花旅游线中;（1）百花岭景区;（2）大蒿坪景区;（3）大塘大树杜鹃景区。为高黎贡山开展赏花旅游提供思路。     

Gymnosperm Orthologues of Class B Floral Homeotic Genes and Their Impact on Understanding Flower Origin

Class B floral homeotic genes play a key role in specifying the identity of male reproductive organs (stamens) and petals during the development of flowers. Recently, close relatives (orthologues) of these genes have been found in diverse gymnosperms, the sister group of the flowering plants (angiosperms). The fact that such genes have not been found so far, despite considerable efforts, in mosses, ferns or algae, has been taken as evidence to suggest that B genes originated 300–400 million years ago in a lineage that led to extant seed plants. Gymnosperms do not develop petals, and their male reproductive organs deviate considerably from angiosperm stamens. So what is the function of gymnosperm B genes? Recent experiments revealed that B genes from diverse extant gymnosperms are exclusively expressed in male reproductive organs (microsporophylls). At least for some of these genes it has been shown that they can partially substitute for the Arabidopsis B genes AP3 and PI in ectopic expression experiments, or even partially substitute these genes in different class B floral organ identity gene mutants. This functional complementation, however, is restricted to male organ development. These findings strongly suggest that gymnosperm and angiosperm B genes have highly related interaction partners and equivalent functions in the male organs of their different host species. It seems likely that in extant gymnosperms B genes have a function in specifying male reproductive organs. This function was probably established already in the most recent common ancestor of extant gymnosperms and angiosperms (seed plants) 300 million years ago and thus represents the ancestral function of seed plant B genes, from which other functions (e.g., in specifying petal identity) might have been derived. This suggests that the B gene function is part of an ancestral sex determination system in which B gene expression specifies male reproductive organ development, while the absence of B gene expression leads to the formation of female reproductive organs. Such a simple switch mechanism suggests that B genes might have played a central role during the origin of flowers. In the out-of-male and out-of-female hypotheses changes in B gene expression led to the origin of hermaphroditic flower precursors out of male or female gymnosperm reproductive cones, respectively. We compare these hypotheses with other recent molecular hypotheses on the origin of flowers, in which C/D and FLORICAULA/LEAFY-like genes is given a more prominent role, and we suggest how these hypotheses might be tested in the future.